Question

我正在尝试从我的视图中的Asynctask中绘制多个矩形。在我的MainActivity中，我将View调用如下：

public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        View bouncingBallView = new BouncingBallView2(this);
        setContentView(bouncingBallView);
        bouncingBallView.setBackgroundColor(Color.BLACK);
    }
}

然后在我的BouncingBallView我创建画布：

public class BouncingBallView2 extends View {
    private Box box;

    final BouncingBallView2 context = this;
    private AsyncTask<Void, Void, Void> task;


    // Constructor
    public BouncingBallView2(Context context) {
        super(context);

        box = new Box(Color.BLACK);  // ARGB


        task=new PackagesPosition();
        task.execute();
    }

    // Called back to draw the view. Also called after invalidate().
    @Override
    protected void onDraw(Canvas canvas) {
        // Draw the components
        box.draw(canvas);


        invalidate();  // Force a re-draw
    }

    // Called back when the view is first created or its size changes.
    @Override
    public void onSizeChanged(int w, int h, int oldW, int oldH) {

        box.set(0, 0, w, h);

    }

如您所见，我调用了AsyncTask类，它也在BouncingBall中。 AsyncTask会获得一个包含每个框四个值的框列表：x,y,width,height。

框类的工作原理如下：

public class Box {
    int xMin, xMax, yMin, yMax;
    private Paint paint;  // paint style and color
    private Rect bounds;


    public Box(int color) {
        paint = new Paint();
        paint.setColor(color);
        bounds = new Rect();

    }

    public void set(int x, int y, int width, int height) {
        xMin = x;
        xMax = x + width - 1;
        yMin = y;
        yMax = y + height - 1;
        // The box's bounds do not change unless the view's size changes
        bounds.set(xMin, yMin, xMax, yMax);
    }


    public void draw(Canvas canvas) {
        canvas.drawRect(bounds, paint);


    }
}

我不知道如何从AsyncTask添加一个框，因为我无法直接访问Canvas，你知道我该怎么办？任何帮助都会非常感激

Answer 1

我认为最简单的方法是通过Box类的构造函数注入画布。我个人不会在View之外画画。我建议您在BouncingBallView2内移动您的绘画，并添加一个从AsyncTask调用的方法。此方法将控制动画序列并在视图上执行invalidate()。

从另一个班级

1 个答案: