AndroidのSQLiteでCRUDを作成できない

Question

私は、ローカルデータベースにハイスコアを保持するゲームを作ろうとしており、最後のスコアがdbのスコアよりも大きい場合にはそれを更新します。しかし、私が理解できなかった小さな問題があります。 dbから値を取得できず、cursor.getCount（）は常に0を返します。私は、dbが作成されたばかりの、最初のハイスコアの初期値を0にします。事前に

package com.example.recepinanc.countdowntimer; 
 

 
import android.content.ContentValues; 
 
import android.content.Context; 
 
import android.database.Cursor; 
 
import android.database.DatabaseErrorHandler; 
 
import android.database.sqlite.SQLiteDatabase; 
 
import android.database.sqlite.SQLiteOpenHelper; 
 
import android.util.Log; 
 

 
/** 
 
* Created by recepinanc on 29/03/16. 
 
*/ 
 

 
public class DBHelper extends SQLiteOpenHelper { 
 

 
    private static String DATABASE_NAME = "database_name"; 
 
    private static String TABLE_NAME = "table_name"; 
 
    private static String PLAYER_NAME = "player_name"; 
 
    private static String PLAYER_HIGHSCORE = "player_high_score"; 
 
    private static String PLAYER_ID = "player_id"; 
 

 
    private static String CREATE_PLAYER_TABLE = "CREATE TABLE " + TABLE_NAME + "(" + PLAYER_ID + " INTEGER PRIMARY KEY, " + PLAYER_NAME + " TEXT, " + PLAYER_HIGHSCORE + " INTEGER DEFAULT 0)"; 
 

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

 
    public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler) { 
 
     super(context, name, factory, version, errorHandler); 
 
    } 
 

 
    public DBHelper(Context context) { 
 
     super(context, DATABASE_NAME, null, 1); 
 
    } 
 

 
    @Override 
 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
 
     db.execSQL("DROP TABLE IF EXIST " + CREATE_PLAYER_TABLE); 
 
     onCreate(db); 
 
    } 
 

 
    public void insertHighScore(int score) { 
 
     SQLiteDatabase db = this.getWritableDatabase(); 
 
     ContentValues values = new ContentValues(); 
 
     values.put(PLAYER_HIGHSCORE, score); 
 

 
     db.insert(TABLE_NAME, null, values); 
 
     db.close(); 
 
    } 
 

 
    public int getHighScore() { 
 

 
     SQLiteDatabase db = this.getReadableDatabase(); 
 
     Cursor cursor = db.query(TABLE_NAME, new String[]{PLAYER_HIGHSCORE}, null, null, null, null, null); 
 

 
     if (cursor != null) { 
 
      cursor.moveToFirst(); 
 
      Log.i("Get Count : ", cursor.getCount() + ""); 
 
     } 
 

 
     return cursor.getInt(2); 
 
    } 
 

 
    public void updateHighScore(int newHighScore) { 
 
     SQLiteDatabase db = this.getWritableDatabase(); 
 
     db.execSQL("UPDATE " + TABLE_NAME + " SET " + PLAYER_HIGHSCORE + "=" + newHighScore + " WHERE " + PLAYER_ID + "=1"); 
 
     Log.i("UPDATE","UPDATED !"); 
 
     db.close(); 
 
    } 
 
}

public class GameOver extends Activity { 
 

 
    DBHelper dbhelper; 
 
    static int highScore; 
 

 
    TextView best; 
 
    ImageView repeat; 
 

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

 
     dbhelper = new DBHelper(getApplicationContext()); 
 
     highScore = dbhelper.getHighScore(); 
 

 
     repeat = (ImageView) findViewById(R.id.play_again); 
 
     best = (TextView) findViewById(R.id.best_score_tv); 
 
     best.setText(dbhelper.getHighScore()+""); 
 

 
     int score = getIntent().getIntExtra(MainActivity.CLICK_COUNTS, 0); 
 

 
     dbhelper.insertHighScore(score); 
 

 
     if (score > highScore) { 
 
      dbhelper.updateHighScore(score); 
 
      Log.i("HighScoreNew", dbhelper.getHighScore() + ""); 
 
     } 
 

 
     repeat.setOnClickListener(new View.OnClickListener() { 
 
      @Override 
 
      public void onClick(View v) { 
 
       Intent intent = new Intent(GameOver.this, MainActivity.class); 
 
       startActivity(intent); 
 
       finish(); 
 
      } 
 
     }); 
 
     TextView clickCountTextView = (TextView) findViewById(R.id.clickCounts_TextView); 
 
     clickCountTextView.setText(score + ""); 
 
    } 
 
}

ありがとう：

は、ここに私のコードです！

Answer 1

最初に取引を開始し、それを成功とマークして終了する必要があります。挿入方法の例を以下に示します。

try { 
     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues values = new ContentValues(); 
     db.beginTransaction(); 
     values.put(PLAYER_HIGHSCORE, score); 
     db.insert(TABLE_NAME, null, values); 
     db.setTransactionSuccessful(); 
    } 
finally { 
     db.endTransaction(); 
    }