从SQLite数据库检索数据时Android应用程序崩溃

Question

This is the retriver method:

public Cursor getData(String subj) {

    String selectQuery = "SELECT " + subj + " FROM " + TABLE_PRIMEIRO;
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    if(cursor != null){
        cursor.moveToFirst();
    }
    return cursor;
}

This is how I'm displaying it in a TextView:

        Cursor cursor = db.getData("columnname");
        cursor.moveToFirst();
        String dataget = cursor.getString(cursor.getColumnIndex("columnname"));
        if (dataget!= null){
            textView1.setText(dataget);
        }

The app is made for API 23+, this code works fine on the API 23 emulator and on my own cellphone (which has Android 7.1) but it does not work on other cellphones. (Android 7.0 and 6.0).

Answer 1

Fixed it by changing:

    Cursor cursor = db.getData("columnname");
    cursor.moveToFirst();
    String dataget = cursor.getString(cursor.getColumnIndex("columnname"));
    if (dataget!= null){
        textView1.setText(dataget);
    }

To:

    Cursor cursor = db.getData("columnname");
    cursor.moveToFirst();
    if (cursor.moveToFirst()){
        String dataget = cursor.getString(cursor.getColumnIndex("columnname"));
        if (dataget!= null){
        textView1.setText(dataget);
        }
    }