创建CircleView
public class CircleView extends View { //点击坐标 float x; float y; float radius = 100; //圆心 float cx = 100; float cy = 100; boolean isCircle; public CircleView(Context context) { super(context); } public CircleView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); } @Override public boolean onTouchEvent(MotionEvent event) { x = event.getX(); y = event.getY(); switch (event.getAction()) { case MotionEvent.ACTION_DOWN://只执行一次 isCircle = isCircle(x, y) && isRect(x, y); if (isCircle) { Toast.makeText(getContext(), "点击圆", Toast.LENGTH_SHORT).show(); } break; case MotionEvent.ACTION_MOVE://连续执行 if (isCircle) { //跳转圆心的位置 cx = x; cy = y; invalidate();//刷新界面，调用onDraw } break; default: break; } return true; } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint paint = new Paint(); paint.setColor(Color.GRAY); //矩形 canvas.drawRect(cx - radius, cy - radius, cx + radius, cy + radius, paint); paint.setColor(Color.BLUE); //圆 canvas.drawCircle(cx, cy, radius, paint); } /** * 判断是否在矩形内 * * @param downX * @param downY * @return */ private boolean isRect(float downX, float downY) { boolean isX = downX <= cx + radius && downX >= cx - radius; boolean isy = downY <= cy + radius && downY >= cy - radius; return isX && isy; } //判断当前按下去的位置是否在圆的里面 private boolean isCircle(float downX, float downY) { //运用勾股定理 判断当前点的位置的坐标 计算出来的距离圆心的距离是否大于圆的半径 如果大于圆的半径的话 那么就是大于 否则就是小鱼 //点击的位置减去原来的位置 算出来的是中间到圆心点之间的距离 进行判断 float sqrt = (float) Math.sqrt((downX - cx) * (downX - cx) + (downY - cy) * (downY - cy)); if (sqrt <= radius) { return true; } return false; } }activity_main布局
<com.example.myxiaoyuaoyidong.CircleView android:layout_width="match_parent" android:layout_height="match_parent" />