java - 奇怪的目录没有提供任何解释

Question

最近开始收到一个相当奇怪的目录，它不能很好地描述出了什么问题。

我把它贴在这里:http://pastie.org/9415113

第 55 行:

        DebugCarTxt = (EditText) findViewById(R.id.DebugCar);

        // you should  instantiate 'DatabaseHandler'  here
        DatabaseHandler db = new DatabaseHandler(this); // "this" refer to the context
        Car cars = db.getCurrentCar();

        db.createCar(new Car(cars.get_id(),cars.get_address(),cars.get_postcode(),cars.get_image()));
//this is line 55       String rows= "id : "+ cars.get_id()+ " address : "+cars.get_address() + "postcode : "+cars.get_postcode()+" image : "+cars.get_image();

这是我的 getCurrentCar() {}；

public Car getCurrentCar() {

    SQLiteDatabase db       =   getWritableDatabase();
    String sql              = "SELECT " + KEY_ID + "," + KEY_IMAGE + " FROM " + TABLE_CARS + " ORDER BY RANDOM() LIMIT 1";
    Cursor cursor           =   db.rawQuery(sql, new String[] {});
    Car car = null;

    try {
        if (cursor.moveToFirst()) {
            car = new Car(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3));
        }
    }
    finally {
        if (cursor != null && !cursor.isClosed()) {
            cursor.close();
        }
            db.close();
    }
    return car;
}

我是否正确地假设它调用 null 因为数据库中没有任何内容？

Answer 1

您获得的值之一设置为 null。

<小时/>

编辑:我的错，我相信汽车是空的。 您应该检查是否有任何值设置为空:

if(car == null) { //and etc for other get method.
    //Use Logs here to print error on logcat.
}

这应该有助于识别哪个值为空。

日志信息:http://developer.android.com/reference/android/util/Log.html