安卓工作室 : Bitmap to ImageView Error

Question

我在将位图附加到 ImageView 时遇到问题。这是我得到的错误:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: accelerometer.example.com.accgame, PID: 25897
...
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setImageBitmap(android.graphics.Bitmap)' on a null object reference

我知道这是一个空指针异常，但我不知道为什么 getResources() 返回 null... 这是我的构造函数类:

public SimulationView(Context context) {
    super(context);
    mXOrigin = 50;
    mYOrigin = 50;

    mHorizontalBound = 100;
    mVerticalBound = 100;

    //Sensor Manager
    sensorManager = (SensorManager)context.getSystemService(SENSOR_SERVICE);

    Bitmap ball = BitmapFactory.decodeResource(getResources(), R.drawable.ball);
    iBall.setImageBitmap(ball);

    mBitmap = Bitmap.createScaledBitmap(ball, BALL_SIZE, BALL_SIZE, true);
    Bitmap basket = BitmapFactory.decodeResource(getResources(), R.drawable.basket);
    mBasket = Bitmap.createScaledBitmap(basket, BASKET_SIZE, BASKET_SIZE, true);
    BitmapFactory.Options opts = new BitmapFactory.Options();
    opts.inDither = true;
    opts.inPreferredConfig = Bitmap.Config.RGB_565;
    mField = BitmapFactory.decodeResource(getResources(), R.drawable.field, opts);

    WindowManager mWindowManager = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
    mDisplay = mWindowManager.getDefaultDisplay();
}

基本上错误突出显示行 iBall.setImageBitmap(ball);

就图像本身而言，我确保将其放在 drawables 文件夹中。这是一个 .jpg 文件，我也将它缩小了很多。

Answer 1

在 OnCreate() 方法中初始化 iBall

iBall = (ImageView)findViewById(R.id.image);