Android 绘制的三角形路径留下痕迹

阶级三角

public class Triangle extends View {
    private int x, y;
    private int _xDelta, _yDelta;
    private Point triangleA = new Point();
    private Point triangleB = new Point();
    private Point triangleC = new Point();
    public static Path trianglePath = new Path();
    private Paint paintTriangle = new Paint();

    public Triangle(Context context) {
        super(context);
        init(null, 0);
    }

    public Triangle(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs, 0);
    }

    public Triangle(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(attrs, defStyleAttr);
    }

    private void init(AttributeSet attrs, int defStyleAttyr) {
        paintTriangle.setColor(Color.RED);
        paintTriangle.setStyle(Style.FILL);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            _xDelta = X - x;
            _yDelta = Y - y;
            break;
        case MotionEvent.ACTION_UP:
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            break;
        case MotionEvent.ACTION_POINTER_UP:
            break;
        case MotionEvent.ACTION_MOVE:
            x = X - _xDelta;
            y = Y - _yDelta;
            break;
        }
        invalidate();
        return true;

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        triangleA.set(x - 100 - 10, y + 100 + 10);
        triangleB.set(x, y - 100 - 10);
        triangleC.set(x + 100 + 10, y + 100 + 10);
        trianglePath.moveTo(triangleA.x, triangleA.y);
        trianglePath.lineTo(triangleB.x, triangleB.y);
        trianglePath.lineTo(triangleC.x, triangleC.y);
        trianglePath.lineTo(triangleA.x, triangleA.y);
        trianglePath.close();
        canvas.drawPath(trianglePath, paintTriangle);

        invalidate();
    }

}

ActivityMain.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.squaremovement.MainActivity" >

<com.example.squaremovement.Triangle
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

</RelativeLayout>

三角形在移动时会留下一条轨迹，因此如何删除它并只保留新位置。还是有其他解决办法？

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这只是我的主应用程序的一个测试，我必须查看此路径是否包含其他路径。

在绘制三角形之前，请尝试清除画布：

canvas.drawColor(0, Mode.CLEAR);

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我想不出来，但我不能这样使用它，因为我需要在另一个视图中使用路径，通过使用边界或类似的东西来查看它是否包含另一个路径

我刚刚在ondraw中创建了如下路径

    @Override
    protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    triangleA.set(x - 100 - 10, y + 100 + 10);
    triangleB.set(x, y - 100 - 10);
    triangleC.set(x + 100 + 10, y + 100 + 10);
    Path trianglePath = new Path();

    trianglePath.moveTo(triangleA.x, triangleA.y);
    trianglePath.lineTo(triangleB.x, triangleB.y);
    trianglePath.lineTo(triangleC.x, triangleC.y);
    trianglePath.lineTo(triangleA.x, triangleA.y);
    trianglePath.close();

    canvas.drawPath(trianglePath, paintTriangle);

}

---

它不起作用，它做的唯一一件事就是把背景变成黑名单。我刚刚学会了如何画：D

    @Override
    protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    triangleA.set(x - 100 - 10, y + 100 + 10);
    triangleB.set(x, y - 100 - 10);
    triangleC.set(x + 100 + 10, y + 100 + 10);
    Path trianglePath = new Path();

    trianglePath.moveTo(triangleA.x, triangleA.y);
    trianglePath.lineTo(triangleB.x, triangleB.y);
    trianglePath.lineTo(triangleC.x, triangleC.y);
    trianglePath.lineTo(triangleA.x, triangleA.y);
    trianglePath.close();

    canvas.drawPath(trianglePath, paintTriangle);

}