모르니까 검색할거야

1.sharedPreferences

-적은양의 원시데이터

-key와 value의 형태

-저장 후 필요할 때 언제든지 가져올 수 있다.

-onPause()에 저장하는 것이 좋다.

Room

-SQLite에 대한 추상화 레이어를 제공하여 원활한 데이터베이스 액세스를 지원하는 동시에 SQLite를 완벽히 활용한다.

-관련 데이터 캐싱

-사용자가 오프라인 상태인 동안에도 사용자가 여전히 콘텐츠를 탐색할 수 있다.

-기기가 다시 온라인 상태가 되면 사용자가 시작한 콘텐츠 변경사항이 서버에 동기화한다.

room을 사용한 간단한 어플을 사용 후 직접적으로 개발하는 앱에 넣어볼 계획이다.

데이터베이스 class

package com.gohool.sqiteexample;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

import java.util.ArrayList;

//데이터베이스
public class DBHelper extends SQLiteOpenHelper {


    //버전
    private static final int DB_VERSION = 1;
    //db이름
    private static final String DB_NAME = "dw.db";

    //생성자
    public DBHelper(@Nullable Context context) {
        super(context,DB_NAME,null,DB_VERSION);
    }



    @Override
    public void onCreate(SQLiteDatabase db) { //데이터베이스가 생성됐을때 호출/ AUTOINCREMENT: 하나하나씩 값이 올라감 id++
        // 데이터베이스 -> 테이블 -> 컬럼 -> 값
        db.execSQL("CREATE TABLE IF NOT EXISTS ToDoList (id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT NOT NULL, content TEXT NOT NULL, writeDate TEXT NOT NULL)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        onCreate(db);
    }

    //SELECT문 (조회)
    public ArrayList<ToDoItem> getToDoList() { //ArrayList<ToDoItem>데이터형식의 메소드
      ArrayList<ToDoItem> toDoItems = new ArrayList<>();

      SQLiteDatabase db = getReadableDatabase();
      Cursor cursor = db.rawQuery("SELECT * FROM ToDoList ORDER BY writeDate DESC", null); //cursor : 가르키다
      if(cursor.getCount() != 0) { //데이터가 있으면
          while (cursor.moveToNext()){ //다음 데이터가 없을때까지
              int id = cursor.getInt(cursor.getColumnIndex("id")); //cursor가 가르켜 가져옴 / 데이터를 변수에 넣어줄거임
              String title = cursor.getString(cursor.getColumnIndex("title"));
              String content = cursor.getString(cursor.getColumnIndex("content"));
              String writeDate = cursor.getString(cursor.getColumnIndex("writeDate"));


              ToDoItem toDoItem = new ToDoItem();
              toDoItem.setId(id);
              toDoItem.setTitle(title);
              toDoItem.setContent(content);
              toDoItem.setWriteDate(writeDate);
              toDoItems.add(toDoItem); // 리스트에 추가해줌


          }
      }
      cursor.close(); //종료
      return  toDoItems;
    }


    // INSERT문 (삽입) / id값 넣지않음 알아서 입력됨 /
    public void InsertTodo(String _title, String _content, String _writeDate){
        SQLiteDatabase db = getWritableDatabase(); // 쓰기가능
        db.execSQL("INSERT INTO ToDoList (title, content, writeDate) VALUES('" + _title + "', '" + _content + "' , '" + _writeDate + "');"); // sql문
    }

    //UPDATE 문(수정)
    public void UpdateToDo(String _title, String _content, String _writeDate, String _beforeDate){
        SQLiteDatabase db = getWritableDatabase();
        db.execSQL("UPDATE ToDoList SET title= '" + _title + "', content = '" + _content + "',  writeDate = '" + _writeDate + "' WHERE writeDate= '" + _beforeDate + "'");
    }

    //DELETE 문(삭제)
    public void DeleteToDo(String _beforeDate){
        SQLiteDatabase db = getWritableDatabase();
        db.execSQL("DELETE FROM ToDoList WHERE writeDate = '" + _beforeDate + "' "); //id만 지우면 됨
    }

}

gradle

dependencies {

    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'com.google.android.material:material:1.2.1'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}

android.defaultConfig.vectorDrawables.useSupportLibrary = true

사용할 아이템들 class

package com.gohool.sqiteexample;

public class ToDoItem {
    private int id;
    private String title;
    private String content;
    private String writeDate;

    public ToDoItem() {
    }


    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public String getWriteDate() {
        return writeDate;
    }

    public void setWriteDate(String writeDate) {
        this.writeDate = writeDate;
    }
}

manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.gohool.sqiteexample">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar"> //테마
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

팝업창 xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:layout_marginStart="32dp"
        android:layout_marginTop="32dp"
        android:layout_marginEnd="32dp"
        android:layout_marginBottom="32dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/dialog_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginTop="16dp"
            android:text="게시글 제목"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <!-- singleLines, maxLines : 초과입력시에도 한줄로 고정 -->

        <TextView
            android:id="@+id/dialog_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginTop="16dp"
            android:text="게시글 내용"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/edit_title" />

        <EditText
            android:id="@+id/edit_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:ems="10"
            android:inputType="textPersonName"
            android:maxLines="1"
            android:singleLine="true"
            app:layout_constraintStart_toStartOf="@+id/dialog_title"
            app:layout_constraintTop_toBottomOf="@+id/dialog_title" />

        <EditText
            android:id="@+id/edit_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:ems="10"
            android:inputType="textPersonName"
            android:maxLines="1"
            android:singleLine="true"
            app:layout_constraintStart_toStartOf="@+id/dialog_content"
            app:layout_constraintTop_toBottomOf="@+id/dialog_content" />

        <Button
            android:id="@+id/dialog_btn"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="16dp"
            android:layout_marginEnd="16dp"
            android:layout_marginBottom="8dp"
            android:background="@color/design_default_color_secondary"
            android:text="확인"
            android:textColor="@color/white"
            android:textSize="18sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

itemlist.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="8dp"
        android:text="제목"
        android:textColor="#070505"
        android:textSize="24dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_content"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginBottom="8dp"
        android:text="내용"
        android:textColor="#070505"
        android:textSize="20dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="@+id/tv_title"
        app:layout_constraintTop_toBottomOf="@+id/tv_title" />

    <TextView
        android:id="@+id/tv_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="16dp"
        android:text="작성날짜"
        android:textColor="#070505"
        android:textSize="16dp"
        app:layout_constraintBottom_toBottomOf="@+id/tv_content"
        app:layout_constraintEnd_toEndOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

activitymain. xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/add_btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="25dp"
        android:layout_marginBottom="25dp"
        android:clickable="true"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:srcCompat="@drawable/ic_baseline_add_circle_outline_24" />

        <!--app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"

        tools:listitem="@layout/item_list" : 미리보기
        -->

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/re_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginBottom="16dp"
        tools:listitem="@layout/item_list"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

CustomAdapter . class

package com.gohool.sqiteexample;

import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {

    private ArrayList<ToDoItem> mToDoItems; // m:전역변수
    private Context mcontext;
    private DBHelper mDBhelper;

    public CustomAdapter(ArrayList<ToDoItem> mToDoItems, Context mcontext) {
        this.mToDoItems = mToDoItems;
        this.mcontext = mcontext;
        mDBhelper = new DBHelper(mcontext); //

    }

    @NonNull
    @Override
    public CustomAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View holder = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_list, parent, false);

        return new ViewHolder(holder);
    }

    @Override
    public void onBindViewHolder(@NonNull CustomAdapter.ViewHolder holder, int position) {

        holder.tv_title.setText(mToDoItems.get(position).getTitle());
        holder.tv_content.setText(mToDoItems.get(position).getContent());
        holder.tv_date.setText(mToDoItems.get(position).getWriteDate());

    }

    @Override
    public int getItemCount() {
        return mToDoItems.size();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        //item_list.xml
        private TextView tv_title;
        private TextView tv_content;
        private TextView tv_date;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);

            tv_title = (TextView) itemView.findViewById(R.id.tv_title);
            tv_content = (TextView) itemView.findViewById(R.id.tv_content);
            tv_date = (TextView) itemView.findViewById(R.id.tv_date);


            itemView.setOnClickListener(new View.OnClickListener() { //객체 하나
                @Override
                public void onClick(View v) {
                    int curPos = getAdapterPosition(); //클릭한  위치값 가져오기
                    ToDoItem toDoItem = mToDoItems.get(curPos);


                    String[] strChoiceItems = {"수정하기", "삭제하기"}; //0, 1
                    AlertDialog.Builder builder = new AlertDialog.Builder(mcontext);
                    builder.setTitle("원하는 작업을 선택해주세요");
                    builder.setItems(strChoiceItems, new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialogInterface, int position) {
                            if(position == 0) { //수정하기 / 팝업창
                                Dialog dialog = new Dialog(mcontext, android.R.style.Theme_Material_Light_Dialog); //팝업창
                                dialog.setContentView(R.layout.dialog_edit);
                                EditText edit_title = dialog.findViewById(R.id.edit_title);
                                EditText edit_content = dialog.findViewById(R.id.edit_content);
                                Button dialog_btn = dialog.findViewById(R.id.dialog_btn);

                                edit_title.setText(toDoItem.getTitle()); //수정시 내용 가져오기
                                edit_content.setText(toDoItem.getContent());

                                edit_title.setSelection(edit_title.getText().length()); //수정시 커서 마지막에 놓기


                                dialog_btn.setOnClickListener(new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        //db 업데이트
                                        String title = edit_title.getText().toString();
                                        String content = edit_content.getText().toString();
                                        String currentTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()); //현재시간 받아오기
                                        String beforeTime = toDoItem.getWriteDate(); //등록되었던 시간

                                        mDBhelper.UpdateToDo(title, content,currentTime,beforeTime); //db에 넣기

                                        //UI 업데이트
                                        toDoItem.setTitle(title);;
                                        toDoItem.setContent(content);
                                        toDoItem.setWriteDate(currentTime);
                                        notifyItemChanged(curPos, toDoItem); //현재 객체, 갱신
                                        dialog.dismiss(); //끔
                                        Toast.makeText(mcontext, "수정이 완료 되었습니다.", Toast.LENGTH_SHORT).show();
                                    }
                                });
                                dialog.show(); //필수

                            } else if(position == 1){ //삭제하기
                                // db 테이블 삭제
                                String beforeTime = toDoItem.getWriteDate(); //등록되었던 시간
                                mDBhelper.DeleteToDo(beforeTime);
                                //UI 삭제
                                mToDoItems.remove(curPos);
                                notifyItemRemoved(curPos);
                                Toast.makeText(mcontext, "삭제가 완료되었습니다.", Toast.LENGTH_SHORT).show();


                            }
                        }
                    });
                    builder.show();
                }
            });
        }
    }
    // 액티비티에서 호출되는 함수이며, 현재 어댑터에 새로운 게시글 아이템을 전달받아 추가하는 목적
    public void addItem(ToDoItem _item){
        mToDoItems.add(0, _item); // 0번째에 추가됨
        notifyItemInserted(0); //새로고침
    }

}

mainactivity , java

package com.gohool.sqiteexample;

import android.app.Dialog;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.RecyclerView;

import com.google.android.material.floatingactionbutton.FloatingActionButton;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private RecyclerView mrecyclerView;
    private FloatingActionButton madd_btn;
    private ArrayList<ToDoItem> mtoDoItems;
    private DBHelper mdbHelper;
    private CustomAdapter mAdapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        setInit();

    }

    private void setInit() {
        mdbHelper = new DBHelper(this);
        mrecyclerView = findViewById(R.id.re_view);
        madd_btn = findViewById(R.id.add_btn);
        mtoDoItems = new ArrayList<>();

        loadRecentDB(); //실행시, 이전에 DB가 존재한다면 LOAD해옴


        madd_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Dialog dialog = new Dialog(MainActivity.this, android.R.style.Theme_Material_Light_Dialog); //팝업창
                dialog.setContentView(R.layout.dialog_edit);

                //팝업창 정의
                EditText edit_title = dialog.findViewById(R.id.edit_title);
                EditText edit_content = dialog.findViewById(R.id.edit_content);
                Button dialog_btn = dialog.findViewById(R.id.dialog_btn);
                dialog_btn.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        //데이터베이스에 삽입
                        String currentTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()); //현재시간 받아오기
                        mdbHelper.InsertTodo(edit_title.getText().toString(), edit_content.getText().toString(),currentTime); //db에 넣기

                        //UI에 삽입
                        ToDoItem item = new ToDoItem();
                        item.setTitle(edit_title.getText().toString());
                        item.setContent(edit_content.getText().toString());
                        item.setWriteDate(currentTime);

                        mAdapter.addItem(item); //객체를 넘겨줌(한 세트)
                        mrecyclerView.smoothScrollToPosition(0); //데이터가 올라갈때마다 ListView가 쫒아올라가서 이쁘게 해줌
                        dialog.dismiss();
                        Toast.makeText(MainActivity.this, "정상적으로 추가되었습니다.", Toast.LENGTH_SHORT).show();



                    }
                });
                dialog.show(); //필수

            }
        });

    }

    private void loadRecentDB() {
        //저장된 db가져옴
        mtoDoItems = mdbHelper.getToDoList();
        if(mAdapter == null){
            mAdapter = new CustomAdapter(mtoDoItems, this);
            mrecyclerView.setHasFixedSize(true); //성능 강화
            mrecyclerView.setAdapter(mAdapter);
        }
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'com.google.android.material:material:1.2.0-alpha01'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}

//implementation 'com.google.android.material:material:1.2.0-alpha01' 추가

// main xml


<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tab_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toTopOf="@+id/const_vp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Monday" />

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Tuesday" />

        <com.google.android.material.tabs.TabItem
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Wednesday" />
    </com.google.android.material.tabs.TabLayout>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/const_vp"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/tab_layout"
        app:layout_constraintVertical_bias="0.425">

        <androidx.viewpager.widget.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

//fragment xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="다원프로젝트 3"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

// fragment. class



package com.gohool.viewpager;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class Fragment1 extends Fragment {

    private View view;


    //fragment가 주기적으로 변경됨에 따라 상태저장이 필요함
    public static Fragment1 newInstance(){
        Fragment1 fragment1 = new Fragment1();
        return fragment1;
    }


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment1,container,false);

        return view;
    }
}

//adapter . class



package com.gohool.viewpager;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;

public class PagerAdapter extends FragmentPagerAdapter {
    public PagerAdapter(@NonNull FragmentManager fm) {
        super(fm);
    }


//프래그먼트 교체를 보여주는 처리를 구현한 곳
    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0:
                return Fragment1.newInstance(); //화면을 띄어주기 위해 어뎁터에서 인식을 할 수 있게
            case 1:
                return Fragment2.newInstance();
            case 2:
                return Fragment3.newInstance();
            default:
                return null;
        }
    }

    //뷰페이지 개수
    @Override
    public int getCount() {
        return 3;
    }

    //각 뷰페이지의 이름
    @Nullable
    @Override
    public CharSequence getPageTitle(int position) {
        switch (position){
            case 0:
                return "Monday";
            case 1:
                return "tuesday";
            case 2:
                return "friday";
            default:
                return null;
        }
    }
}

// main activity . java



package com.gohool.viewpager;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.FragmentPagerAdapter;
import androidx.viewpager.widget.ViewPager;

import com.google.android.material.tabs.TabLayout;

public class MainActivity extends AppCompatActivity {

    private FragmentPagerAdapter fragmentPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);



        //뷰페이저 세팅
        ViewPager viewPager = findViewById(R.id.viewPager);
        PagerAdapter fragmentPagerAdapter = new PagerAdapter(getSupportFragmentManager());

        TabLayout tabLayout = findViewById(R.id.tab_layout);
        viewPager.setAdapter(fragmentPagerAdapter); //연동
        tabLayout.setupWithViewPager(viewPager);
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.2.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'gun0912.ted:tedpermission:2.0.0'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}

특정 상황에서 권한이 필요하기 때문에, tedpermission을 쓰면 쉽게 권한 창을 만들 수 있다.

//res. xml. file_paths

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path
        name="my_images"
        path="Android/data/com.com.gohool.cameraexample/files/Pictures"/>

</paths>

//manifest


<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.gohool.cameraexample">

    <!--카메라 권한 -->
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.CameraExample">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>


        <!--추가 -->
        <provider
            android:authorities="com.gohool.cameraexample"
            android:name="androidx.core.content.FileProvider"
            android:exported="false"
            android:grantUriPermissions="true">

            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths"/>

        </provider>
    </application>

</manifest>

//activity main . xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1">

        <ImageView
            android:id="@+id/result"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </LinearLayout>

    <LinearLayout
        android:gravity="center"
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/btnCapture"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="촬영"/>

    </LinearLayout>



</LinearLayout>

// activity main .java


package com.gohool.cameraexample;

import android.Manifest;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.media.ExifInterface;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.FileProvider;

import com.gun0912.tedpermission.PermissionListener;
import com.gun0912.tedpermission.TedPermission;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_IMAGE_CAPTURE = 672;
    private String imageFilePath;
    private Uri photoUri;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //권한 체크
        TedPermission.with(getApplicationContext())
                .setPermissionListener(permissionListener)
                .setRationaleMessage("카메라 권한이 필요합니다.") //카메라권한 열때 사용자에게 보여주는 메세지
                .setDeniedMessage("카메라 권한을 거부하셨습니다.")
                .setPermissions(Manifest.permission.WRITE_EXTERNAL_STORAGE,Manifest.permission.CAMERA) //manifest에 추가한 권한
                .check();

        findViewById(R.id.btnCapture).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                if(intent.resolveActivity(getPackageManager()) != null){
                    File photoFile = null; //파일쓰기시에는 항상 try catch문 필요
                    try {
                        photoFile = createImageFile();
                    }catch (IOException e){

                    }
                    if(photoFile != null){
                        photoUri = FileProvider.getUriForFile(getApplicationContext(), getPackageName(),photoFile);
                        intent.putExtra(MediaStore.EXTRA_OUTPUT,photoUri);
                        startActivityForResult(intent, REQUEST_IMAGE_CAPTURE);
                    }
                }
            }
        });

    }

    private File createImageFile() throws IOException{ //년원일분초 시간단위로 생성 후 저장
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "TEST_" + timeStamp + "_";
        File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
        File image = File.createTempFile(
                imageFileName,
                ".jpg",
                storageDir
        );

        imageFilePath = image.getAbsolutePath();
        return image;

    }

    //forresult
    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            Bitmap bitmap = BitmapFactory.decodeFile(imageFilePath);
            ExifInterface exifInterface = null;

            try {
                exifInterface = new ExifInterface(imageFilePath);
            } catch (IOException e) {
                e.printStackTrace();
            }

            int exifOrientation;
            int exifDegree;

            if (exifInterface != null) {
                exifOrientation = exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
                exifDegree = exifOrientationToDegree(exifOrientation);

            } else {
                exifDegree = 0;
            }
            ((ImageView) findViewById(R.id.result)).setImageBitmap(rotate(bitmap, exifDegree));
        }


    }
    private Bitmap rotate(Bitmap bitmap, float degree){
        Matrix matrix = new Matrix();
        matrix.postRotate(degree);
        return Bitmap.createBitmap(bitmap,0,0,bitmap.getWidth(),bitmap.getHeight(),matrix,true);
    }


    private int exifOrientationToDegree(int exifOrientation) { //촬영중 화면 돌아갈때
        if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_90) {
            return 90;
        } else if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_180) {
            return 180;
        } else if (exifOrientation == ExifInterface.ORIENTATION_ROTATE_270) {
            return 270;
        }
        return 0;
    }

    PermissionListener permissionListener = new PermissionListener() {
        @Override
        public void onPermissionGranted() { //권한 허용에대한 액션
            Toast.makeText(getApplicationContext(), "권한이 허용됨", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onPermissionDenied(ArrayList<String> deniedPermissions) {
            Toast.makeText(getApplicationContext(), "권한이 거부됨", Toast.LENGTH_SHORT).show();
        }
    };
}

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <shape>
            <solid android:color="#F06292" />
            <corners android:radius="10dp"/>
        </shape>
    </item>
    <item android:state_pressed="false">
        <shape>
            <solid android:color="#64B5F6" />
            <corners android:radius="10dp"/>
        </shape>
    </item>



</selector>

버튼이 눌러진 경우와 버튼이 떼진 경우의 background 칼러를 변경해주기 위함

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" android:drawable="@mipmap/ic_launcher_round">

    </item>
    <item android:state_pressed="false" android:drawable="@mipmap/ic_launcher">

    </item>



</selector>

이미지가 눌러진 경우와 이미지를 버튼이 떼진 경우의 background 칼러를 변경해주기 위함

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/selector_btn"
        android:text="다원프로젝트"
        android:textColor="#ffffff"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2"
        app:layout_constraintVertical_bias="0.304" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="188dp"
        android:background="@drawable/selector_image"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

package com.gohool.twobackbutton;

import android.os.Bundle;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private long backBtnTime = 0; //int보다 긴 자료형 형태

    @Override
    public void onBackPressed() {
        long curTime = System.currentTimeMillis(); //현재시간
        long gapTime = curTime - backBtnTime;

        if(0 <= gapTime && 2000 >= gapTime){ //2초안에 한번 더 누르게 되면 종료
            super.onBackPressed();
        }else {
            backBtnTime = curTime;
            Toast.makeText(this, "한번 더 누르면 종료 됩니다.", Toast.LENGTH_SHORT).show();
        }


    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);



    }
}

이번에는 github 라이브러리를 이용한 로딩화면 만들어볼것이다.

구글에 android loading animation github라고 검색 후 

여기

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:gravity="center"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.github.ybq.android.spinkit.SpinKitView
        android:id="@+id/spin_kit"
        style="@style/SpinKitView.Large.DoubleBounce"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        app:SpinKit_Color="@color/black" />


</LinearLayout>

그대로 받아서 넣고, 실행 해보았다.

package com.gohool.dropdownmenu;

import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private Spinner spinner;
    private TextView result;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        spinner = (Spinner) findViewById(R.id.spinner); //드롭다운메뉴
        result = (TextView) findViewById(R.id.result);

        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                result.setText(parent.getItemAtPosition(position).toString()); //포지션에 있는 값을 가져와야하니 string으로 변환
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });


    }
}

array.xml이라는 xml파일을 만들어준다.

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="text">
        <item>다원프로젝트</item>
        <item>눈</item>
        <item>코</item>
        <item>발</item>
        <item>다리</item>

    </string-array>
</resources>

entries를 사용해 array에 있는 name="text"를 가져와 넣어줄것이다.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Spinner
        android:id="@+id/spinner"

        android:layout_width="150dp"
        android:layout_height="40dp"
        android:entries="@array/text">
    </Spinner>

    <TextView
        android:id="@+id/result"
        android:text="드롭다운결과"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

</LinearLayout>