Android Studio ToDoListアプリ制作(動画有り)

今回はToDoListアプリを制作しました。
YouTubeに作っている動画をアップしています。
https://www.youtube.com/watch?v=HyNPhjL53QY&list=PLhg2PHSq8bjiV6wEal7OVfNEfi520OAza

strings.xml

<resources>
    <string name="app_name">ToDoListApp</string>
    <string name="lbl_title">タイトル：</string>
    <string name="lbl_content">内容：</string>
    <string name="btn_input_register">登録</string>
    <string name="toast_register">登録しました</string>
    <string name="toast_failed">登録出来ませんでした</string>

    <string name="hint_title">タイトルを入力してください</string>
    <string name="hint_content">内容を入力してください</string>
    <string name="btn_input_to_list">一覧画面へ</string>
    <string name="lbl_empty">表示するTODOはありません</string>

    <string name="btn_update">更新</string>
    <string name="toast_update">更新しました</string>

    <string name="btn_delete">削除</string>
    <string name="toast_delete">削除しました</string>
</resources>

list_row.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:id="@+id/list_row"></TextView>

</LinearLayout>

ToDoOpenHelper.java

package com.example.todolistapp.helper;

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

public class ToDoOpenHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "DATABASE";
    public static final int VERSION = 1;
    public static final String CREATE_TABLE = "CREATE TABLE 'ToDoList' ('_id' INTEGER PRIMARY KEY AUTOINCREMENT , 'title' TEXT , 'content' TEXT);";

    public ToDoOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE);
    }

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

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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="wrap_content"
        android:orientation="horizontal">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lbl_title"></TextView>

        <EditText
            android:id="@+id/edit_title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/hint_title"></EditText>

    </LinearLayout>

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

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lbl_content"></TextView>

        <EditText
            android:id="@+id/edit_content"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/hint_content"></EditText>

    </LinearLayout>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="register"
        android:text="@string/btn_input_register"></Button>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="toList"
        android:text="@string/btn_input_to_list"></Button>

</LinearLayout>

MainActivity.java

package com.example.todolistapp;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentProviderClient;
import android.content.ContentValues;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import com.example.todolistapp.helper.ToDoOpenHelper;

public class MainActivity extends AppCompatActivity {

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

    public void toList(View view) {
        Intent intent = new Intent(MainActivity.this, ListActivity.class);
        startActivity(intent);
    }

    public void register(View view) {
        EditText editTitle = findViewById(R.id.edit_title);
        EditText editContent = findViewById(R.id.edit_content);

        SQLiteDatabase database = null;

        try {
            ToDoOpenHelper helper = new ToDoOpenHelper(MainActivity.this);
            database = helper.getWritableDatabase();

            ContentValues contentValues = new ContentValues();
            contentValues.put("title", editTitle.getText().toString());
            contentValues.put("content", editContent.getText().toString());

            database.insert("ToDoList", null, contentValues);
        } catch (Exception e) {
            Toast.makeText(MainActivity.this, R.string.toast_failed, Toast.LENGTH_LONG).show();
        } finally {
            database.close();
        }
        Toast.makeText(MainActivity.this, R.string.toast_register, Toast.LENGTH_LONG).show();
    }
}

activity_list.xml

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

    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@android:id/list"></ListView>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@android:id/empty"
        android:text="@string/lbl_empty"></TextView>

</LinearLayout>

ListActivity.java

package com.example.todolistapp;


import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.CursorAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;

import com.example.todolistapp.helper.ToDoOpenHelper;

public class ListActivity extends android.app.ListActivity {
    Cursor cursor;

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

    @Override
    protected void onResume() {
        super.onResume();
        SQLiteDatabase database = null;
        try{
            SQLiteOpenHelper helper = new ToDoOpenHelper(ListActivity.this);
            database = helper.getReadableDatabase();

            cursor = database.query("ToDoList",null,null,null,null,null,null);
            SimpleCursorAdapter adapter = new SimpleCursorAdapter(
                                                   ListActivity.this,
                                                   R.layout.list_row,
                                                   cursor,
                                                   new String[]{"title"},
                                                   new int[]{R.id.list_row},
                                                   CursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
            setListAdapter(adapter);
        }catch (Exception e){
            Log.e("エラー",e.getMessage(),e);
        }finally {
            database.close();
        }
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        Intent intent = new Intent(ListActivity.this,ContentActivity.class);
        intent.putExtra("id",id);
        startActivity(intent);
    }

    @Override
    protected void onStop() {
        super.onStop();
        if(cursor != null || !cursor.isClosed()){
            cursor.close();
        }
    }
}

activity_content.xml

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

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

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lbl_title"></TextView>

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/text_title"></EditText>
    </LinearLayout>

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

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lbl_content"></TextView>

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/text_content"></EditText>
    </LinearLayout>

    <LinearLayout
        android:layout_gravity="right"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:layout_marginRight="12dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="update"
            android:text="@string/btn_update"></Button>

        <Button
            android:layout_marginRight="12dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="delete"
            android:text="@string/btn_delete"></Button>

    </LinearLayout>

</LinearLayout>

ContentActivity.java

package com.example.todolistapp;

import androidx.appcompat.app.AppCompatActivity;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import com.example.todolistapp.helper.ToDoOpenHelper;

public class ContentActivity extends AppCompatActivity {

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

    @Override
    protected void onResume() {
        super.onResume();
        Long id = getIntent().getLongExtra("id", 0L);

        SQLiteOpenHelper helper = null;
        SQLiteDatabase database = null;
        Cursor cursor = null;

        try {
            helper = new ToDoOpenHelper(ContentActivity.this);
            database = helper.getReadableDatabase();

            cursor = database.query(
                           "ToDoList", 
                           null, 
                           "_id=?", 
                           new String[]{String.valueOf(id)}, 
                           null, 
                           null, 
                           null);
            if (cursor.moveToFirst()) {
                int columnIndex = cursor.getColumnIndex("title");
                String strTitle = cursor.getString(columnIndex);
                columnIndex = cursor.getColumnIndex("content");
                String strContent = cursor.getString(columnIndex);

                EditText titleView = findViewById(R.id.text_title);
                EditText contentView = findViewById(R.id.text_content);

                titleView.setText(strTitle);
                contentView.setText(strContent);
            }
        } catch (Exception e) {
            Log.e("エラー", e.getMessage(), e);
        } finally {
            cursor.close();
            database.close();
        }
    }

    public void update(View view) {
        SQLiteOpenHelper helperUpdate = null;
        SQLiteDatabase databaseUpdate = null;

        String title = ((EditText) findViewById(R.id.text_title)).getText().toString();
        String content = ((EditText) findViewById(R.id.text_content)).getText().toString();

        try {
            helperUpdate = new ToDoOpenHelper(ContentActivity.this);
            databaseUpdate = helperUpdate.getWritableDatabase();

            ContentValues contentValues = new ContentValues();
            contentValues.put("title", title);
            contentValues.put("content", content);

            int updateCount = databaseUpdate.update(
                           "ToDoList", 
                           contentValues, 
                           "_id=?", 
                           new String[]{String.valueOf(getIntent().getLongExtra("id", 0L))});

            if (updateCount == 1) {
                Toast.makeText(ContentActivity.this, R.string.toast_update, Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(ContentActivity.this, R.string.toast_failed, Toast.LENGTH_LONG).show();
            }
            finish();
        } catch (Exception e) {
            Log.e("エラー", e.getMessage(), e);
        } finally {
            databaseUpdate.close();
        }
    }

    public void delete(View view) {

        SQLiteOpenHelper helperDelete = null;
        SQLiteDatabase databaseDelete = null;

        try {
            helperDelete = new ToDoOpenHelper(ContentActivity.this);
            databaseDelete = helperDelete.getWritableDatabase();

            int deleteCount = databaseDelete.delete(
                           "ToDoList", 
                           "_id=?", 
                           new String[]{String.valueOf(getIntent().getLongExtra("id", 0L))});

            if (deleteCount == 1) {
                Toast.makeText(ContentActivity.this, R.string.toast_delete, Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(ContentActivity.this, R.string.toast_failed, Toast.LENGTH_LONG).show();
            }
            finish();
        } catch (Exception e) {
            Log.e("エラー", e.getMessage(), e);
        } finally {
            databaseDelete.close();
        }

    }
}

YouTubeに作っている動画をアップしています。
https://www.youtube.com/watch?v=HyNPhjL53QY&list=PLhg2PHSq8bjiV6wEal7OVfNEfi520OAza
以上。