AS Room編②解説part3～Roomを使って、登録したデータを別のActivityに表示する～

MainActivity.java

package com.example.databasedemo6;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.sql.Timestamp;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    static AppDatabase db;　・・・・・・・・・・・・・・・・・・・・・①


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


        TextView showData = findViewById(R.id.showData);
        Button registerBtn = findViewById(R.id.registerBtn);
        db = AppDatabaseSingleton.getInstance(getApplicationContext());
        registerBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new DataStoreAsyncTask(db,showData).execute();
            }
        });

        Button nextBtn = findViewById(R.id.nextBtn);
        nextBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                startActivity(new Intent(MainActivity.this,SubActivity.class));
            }
        });
    }

    public class DataStoreAsyncTask extends AsyncTask<Void,Void,Integer> {
        private AppDatabase db;
        private TextView textView;
        StringBuilder sb;

        public DataStoreAsyncTask(AppDatabase db,TextView textView) {
            this.db= db;
            this.textView =textView;
        }

        @Override
        protected Integer doInBackground(Void... voids) {
            UserDao userDao = db.userDao();
            EditText editName = findViewById(R.id.editName);
            userDao.insert(new User(editName.getText().toString()));
            sb = new StringBuilder();
            List<User> atList = userDao.getAll();
            for(User user: atList){
                sb.append(user.getName()).append("\n");
            }
            return 0;
        }

        protected  void onPostExecute(Integer code){
            textView.setText(sb.toString());

        }
    }
}

SubActivity.java

package com.example.databasedemo6;

import androidx.appcompat.app.AppCompatActivity;

import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.TextView;

import java.util.List;

public class SubActivity extends AppCompatActivity {

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

        TextView subView = findViewById(R.id.subView);

        new DataStoreAsyncTask(MainActivity.db,subView).execute();

    }

    public class DataStoreAsyncTask extends AsyncTask<Void,Void,Integer> {　　　・・・・②
        private AppDatabase db;
        private TextView textView;
        StringBuilder sb;

        public DataStoreAsyncTask(AppDatabase db,TextView textView) {
            this.db= db;
            this.textView =textView;
        }

        @Override
        protected Integer doInBackground(Void... voids) {
            UserDao userDao = db.userDao();
            sb = new StringBuilder();
            List<User> atList = userDao.getAll();
            for(User user: atList){
                sb.append(user.getName()).append("\n");
            }
            return 0;
        }

        protected  void onPostExecute(Integer code){
            textView.setText(sb.toString());

        }
    }
}

User.java

package com.example.databasedemo6;

import androidx.annotation.NonNull;
import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.PrimaryKey;

@Entity(tableName ="users")
public class User {
    @PrimaryKey(autoGenerate = true)
    @NonNull
    @ColumnInfo(name = "id")
    private int id;

    @ColumnInfo(name = "name")
    private String name;

    public User(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

UserDao(インターフェース）

これまでと同じですがあげときます

package com.example.databasedemo6;

import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.Query;

import java.util.List;

@Dao
public interface UserDao {
    @Insert
    void insertAll(User... users);

    @Insert
    void insert(User user);

    @Delete
    void delete(User user);

    @Query("SELECT * FROM users")
    List<User> getAll();
}

AppDatabase.java

これまでと同じですがあげときます

package com.example.databasedemo6;

import androidx.room.Database;
import androidx.room.RoomDatabase;

@Database(entities = {User.class},version = 1,exportSchema = false)
public abstract class AppDatabase extends RoomDatabase {
    public abstract UserDao userDao();
}

AppDatabaseSingleton.java

これまでと同じですがあげときます

package com.example.databasedemo6;
import android.content.Context;

import androidx.room.Room;

public class AppDatabaseSingleton {
    private static AppDatabase instance = null;

    static AppDatabase getInstance(Context context){
        instance = Room.databaseBuilder(context,AppDatabase.class,"db-name").build();
        return instance;
    }
}

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"
    tools:context=".MainActivity"
    android:gravity="center_horizontal"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="名前："/>
    <EditText
        android:id="@+id/editName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <Button
        android:id="@+id/registerBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="登録"/>
    <TextView
        android:id="@+id/showData"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <Button
        android:id="@+id/nextBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="一覧のみ表示"/>

</LinearLayout>

activity_sub.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"
    tools:context=".SubActivity">
    <TextView
        android:id="@+id/subView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

あとは、build.gradle(Module)へ下記追記

def room_version = "2.2.6"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"

dependencies {
    def room_version = "2.2.6"
    implementation "androidx.room:room-runtime:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"

    implementation 'androidx.appcompat:appcompat:1.5.1'
    implementation 'com.google.android.material:material:1.7.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.4'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.0'
}