从另一个 Class 借鉴 Canvas

Question

我正在尝试从视图中的 Asynctask 绘制多个矩形。在我的 MainActivity 中，我调用视图如下：

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 中创建 canvas:

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 AsyncTask class，它也在 BouncingBall 中。 AsyncTask 获取一个框列表，每个框有四个值：x,y,width,height。

盒子class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 添加框，因为我无法直接访问 Canvas，你知道我应该如何进行吗？任何帮助将不胜感激

Answer 1

我认为最简单的方法是通过 Box class 的构造函数注入 canvas。不过，就我个人而言，我不会在 View 之外作画。我建议将您的画移到 BouncingBallView2 内并添加一个从您的 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 Class 借鉴 Canvas

Draw on a Canvas from another Class

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