如何計算表中的記錄並將值存入活動？

Question

我想在我的DBHandler類

public int getPointsCount() { 
     String countQuery = "SELECT * FROM " + TABLE_STUDENTS; 
     SQLiteDatabase db = this.getReadableDatabase(); 
     Cursor cursor = db.rawQuery(countQuery, null); 
     cursor.close(); 
     return cursor.getCount(); 
    } 

使用此代碼，我用在主要活動按鈕這一呼籲，但它會導致我的應用程序崩潰，當我按一下按鈕

callButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
      int cn = countStudents(); 
       studentNumberText.setText(cn); 
      } 
     }); 

public int countStudents(){ 
     DBHandler dbHandler = new DBHandler(this, null, null, 1); 
     int c = dbHandler.getPointsCount(); 
     return c; 
    } 

Answer 1

通過調用這個方法從tablename.http

public int gettablecount(){ 
    Cursor mCount= db.rawQuery("select count(*) from TABLENAME ", null); 
    mCount.moveToFirst(); 
    int count= mCount.getInt(0); 
    mCount.close(); 
    return count; 
}