自定义视图drawArc，检测弧

Question

我创建这是一种弧形滑盖的进步view.I可以借鉴基础上，其中弧的或多或少的自定义视图中绘制路径上用户触摸用户触摸（在x轴）通过计算扫描，我通过首先计算用户沿x轴触摸的百分比来实现这一点。.. 0％将一路向左，100％将一路向右。

我想要更进一步，而不是基于用户按下的x坐标绘制弧线，我只想在用户触及实际弧线绘制路径时使其移动，因此它更逼真。我还是新的自定义视图和我的数学是有限的，但如果我得到一些提示，我将不胜感激，谢谢

class ArcProgress extends View { 

    Context cx; 
    float width; 

    float height; 
    float center_x, center_y; 
    final RectF oval = new RectF(); 
    final RectF touchArea = new RectF(); 

    float sweep = 0; 
    float left, right; 
    int percent = 0; 

    public ArcProgress(Context context) { 
     super(context); 
     cx = context; 

    } 

    public int getPercentage() { 
     return percent; 
    } 

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

     setBackgroundColor(0xfff0ebde); 

     width = (float) getWidth(); 
     height = (float) getHeight(); 

     float radius; 

     if (width > height) { 
      radius = height/3; 
     } else { 
      radius = width/3; 
     } 

     Paint paint = new Paint(); 
     paint.setAntiAlias(true); 
     paint.setColor(0xffd2c8b6); 
     paint.setStrokeWidth(35); 

     paint.setStyle(Paint.Style.STROKE); 

     center_x = width/2; 
     center_y = height/2; 

     left = center_x - radius; 
     float top = center_y - radius; 
     right = center_x + radius; 
     float bottom = center_y + radius; 

     oval.set(left, top, right, bottom); 

      //this is the background arc, it remains constant 
     canvas.drawArc(oval, 180, 180, false, paint); 

     paint.setStrokeWidth(10); 
     paint.setColor(0xffe0524d); 
      //this is the red arc whichhas its sweep argument manipulated by on touch 
     canvas.drawArc(oval, 180, sweep, false, paint); 

    } 

    @Override 
    public boolean onTouchEvent(MotionEvent event) { 

     if (event.getAction() == MotionEvent.ACTION_MOVE) { 

      float xPosition = event.getX(); 
      float yPosition = event.getY(); 
      if (oval.contains(xPosition, yPosition)) { 

       float x = xPosition - left; 
       float s = x * 100; 
       float b = s/oval.width(); 
       percent = Math.round(b); 
       sweep = (180/100.0f) * (float) percent; 

       invalidate(); 

      } else { 
       if (xPosition < left) { 
        percent = 0; 

        sweep = (180/100.0f) * (float) percent; 
        invalidate(); 
       } 
       if (xPosition > right) { 
        percent = 100; 

        sweep = (180/100.0f) * (float) percent; 
        invalidate(); 
       } 
      } 
     } 

     return true; 
    } 
} 

Answer 1

这是否对你的工作？ 你不需要很多数学。您可以计算触摸点距弧线中心的距离（这是一个很容易的圆），并可以与您使用的半径进行比较。这将告诉你，如果点在弧（几乎，见下面的全案）。

Point touchEv = ...; 
Point circleCenter = ...; 

//the radius of the circle you used to draw the arc 
float circleRadius = ...; 
//how far from the arc should a touch point treated as it's on the arc 
float maxDiff = getResources().getDimension(R.dimen.max_diff_dp); 

//calculate the distance of the touch point from the center of your circle 
float dist = Math.pow(touchEv.x-circleCenter.x,2) + Math.pow(touchEv.y- circleCenter.y,2) 
dist = Math.sqrt(dist); 

//We also need the bounding rect of the top half of the circle (the visible arc) 
Rect topBoundingRect = new Rect(circleCenter.x - circleRadius, 
      circleCenter.y - circleRadius, 
      circleCenter.x + circleRadius, 
      circleCenter.y); 


if (Math.abs(dist - circleRadius) <= maxDiff && 
    topBoundingRect.contains(touchEv.x, touchEv.y)) { 
    // the user is touching the arc 

} 

Answer 2

我想让它，只有当用户触摸的实际弧 平局路径

上动弹的onTouchEvent()你需要检查是否xPosition和yPosition正在履行一些条件开始。如果是的话，你做的东西，你现在正在做的。如果不是，return true。

条件：

我们要检查是否x，y是在灰色的弧形背景：

让我们来计算，以该点（X，Y）的距离（ A，b）在中心：

final dist = distance(x, y, a, b) 

distance()是一个简单的欧几里德DISTA点（X，Y）和（A，B）之间NCE：

double distance(int x, int y, int a, int b) 
{ 
    return Math.sqrt((x - a) * (x - a) + (y - b) * (y - b)); 
} 

x，y是在灰色弧背景下，如果y > Y && dist >= r && dist <= R。