Android: 圆圈在点击时移动到随机位置

Question

我正在编写一个程序，在 phone 屏幕上的随机位置绘制一个圆圈。它应该做的是当触摸圆圈时，它会删除该圆圈并将其移动到另一个随机位置。

目前，当点击屏幕时，旧圆圈会被移除，并在屏幕上的另一个随机位置重新绘制。它非常接近，但我想知道我如何克服这个障碍。

public class Circle extends View {
    private float x = 300;
    private float y = 300;
    private int r = 150;
    private final Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
    private Random random = new Random();


    // draws circle
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setColor(Color.RED);
        canvas.drawCircle(x, y, r, mPaint);
    }

    // constructors
    public Circle(Context context) {
        super(context);
        init();
    }

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

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

    void init() {
        // might be used later for some data collection
    }


    // gets random number,,
    void generateRandom() {

        int w = getWidth() - r - 50;
        int h = getHeight()- r - 50;

        int border = r + 50;

        this.x = border + random.nextInt(w-border);
        this.y = border + random.nextInt(h-border);
    }



    // when screen is tapped, old circle removed, new circle drawn
    @Override
    public boolean onTouchEvent(MotionEvent event) {
        generateRandom();
        invalidate();
        return super.onTouchEvent(event);
    }
}

Answer 1

像这样更改代码，

@Override
    public boolean onTouchEvent(MotionEvent event) {
        if (isInsideCircle(event.getX(), event.getY())) {
            generateRandom();
            invalidate();
        }
        return super.onTouchEvent(event);
    }


    boolean isInsideCircle(float xPoint, float yPoint) {
        float dx = (x - xPoint);
        float dxPow = (float) Math.pow(dx, 2);
        float dy = (y - yPoint);
        float dyPow = (float) Math.pow(dy, 2);
        float radPow = (float) Math.pow(r, 2);
        return (dxPow + dyPow) < radPow || (dxPow + dyPow == radPow);
    }

Android: 圆圈在点击时移动到随机位置

Android: Circle moves to random location when tapping it

android

view

ondraw

ontouch