如果触摸到内部，则使它成为可拖动的图形

Question

  

我正在学习自定义视图，所以我决定在中心创建一个圆圈。它工作正常。

现在，我希望此圆圈像 chatHead（如facebook）一样拖动。我已经使用onTouchEvent实现了拖动功能。但是我在屏幕上触摸过的地方都开始拖动。正如我将侦听器添加到整个视图中一样。我想使其在接触到圆圈内后拖动。据我认为，我必须检测Action_Down中的x，y位置是否该点在圆内，然后允许它拖动。但无法实现。

public class CircleDraggingView extends View {

    ///float dX, dY;
    private static final String TAG = "CustomDrawing";
    private float circleRadius = 180;
    boolean isDrawCalledFirstTime = true;
    boolean isAllowedToDrag = true;

    private float center_circle_X = 180;
    private float center_circle_Y = 180;

    private Paint circlePaint;
    private Paint linePaint;
    private Paint textPaint;

    public CircleDraggingView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setFocusable(true);
        setFocusableInTouchMode(true);
        setupPaint();
    }

    private void setupPaint() {
        circlePaint = new Paint();
        circlePaint.setColor(Color.BLACK);
        circlePaint.setAntiAlias(true);
        circlePaint.setStrokeWidth(10);
        circlePaint.setStyle(Paint.Style.STROKE);
        circlePaint.setStrokeJoin(Paint.Join.ROUND);
        circlePaint.setStrokeCap(Paint.Cap.ROUND);

        linePaint = new Paint();
        linePaint.setColor(Color.WHITE);
        linePaint.setAntiAlias(true);
        linePaint.setStrokeWidth((float) 1.5);

        textPaint = new Paint();
        textPaint.setColor(Color.BLACK);
        textPaint.setTextSize(60);
        textPaint.setTextAlign(Paint.Align.CENTER);
        textPaint.setFakeBoldText(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        ///super.onDraw(canvas);
        if (isDrawCalledFirstTime) {
            center_circle_X = canvas.getWidth() / 2;
            center_circle_Y = canvas.getHeight() / 2;

            isDrawCalledFirstTime = false;
        }

        //Center Circle
        circlePaint.setColor(Color.BLACK);
        canvas.drawCircle(center_circle_X, center_circle_Y, circleRadius, circlePaint);
        canvas.drawText("CC", center_circle_X, getyPositionOfText(center_circle_Y, textPaint), textPaint);

        Log.d(TAG, "onDraw:centerX= " + center_circle_X + " centerY= " + center_circle_Y + " Width= "
                + canvas.getWidth() + " Height= " + canvas.getHeight());
    }

    private int getyPositionOfText(float yPositionOfText, Paint mPaint) {
        return (int) ((yPositionOfText) - ((mPaint.descent() + mPaint.ascent()) / 2));
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        int initialX = 0;
        int initialY = 0;
        float initialTouchX = 0;
        float initialTouchY = 0;

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:

                initialTouchX = event.getRawX();
                initialTouchY = event.getRawY();
                Log.d(TAG, "ACTION_DOWN:getRawX= " + event.getRawX() + " getRawY= " + event.getRawY() + " getX= "
                        + event.getX() + " getY= " + event.getY());

                ///path.moveTo(pointX, pointY);
                return true;
            case MotionEvent.ACTION_MOVE:
                Log.d(TAG, "ACTION_MOVE:getRawX= " + event.getRawX() + " getRawY= " + event.getRawY() + " getX= "
                        + event.getX() + " getY= " + event.getY());
                center_circle_X = initialX + (int) (event.getRawX()- initialTouchX);
                center_circle_Y = initialY + (int) (event.getRawY() - initialTouchY);
                break;
            default:
                return false;
        }
        // Force a view to draw again
        ///postInvalidate();
        invalidate();
        return true;
    }

    private boolean isPointInside(float pointX, float pointY) {
        float circleX = getX(), circleY = getY();

        //Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
        Double distance = Math.sqrt(Math.pow((pointX - circleX), 2) + Math.pow((pointY - circleY), 2));
        ////Double distance2 = Math.hypot(pointX-circleX, pointY-circleY);

        boolean isPointInside = false;
        if ((distance * distance) < (circleRadius * circleRadius))
            isPointInside = true;
        return isPointInside;
    }
}

我也尝试了其他一些技巧，但无法实现。