如何繪製形狀像橢圓形，線和手勢

Question

計算面積以Play商店中的飛利浦Lumify應用的參考android.Please幫助我產生這種形狀。

Answer 1

創建custom view和並覆蓋onDraw(Canvas canvas)方法，你必須draw your shape裏面像這樣：

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

    if(touched) 
     canvas.drawCircle(centerX, centerY, radius, mPaint); 
} 

然後處理內部onTouchEvent方法姿態：

@Override 
public boolean onTouchEvent(MotionEvent e) { 
    float x = e.getX(); 
    float y = e.getY(); 

    switch (e.getAction()) { 
     case MotionEvent.ACTION_DOWN: 
      touched = true; 
      centerX = x; 
      centerY = y; 
      break; 
     case MotionEvent.ACTION_MOVE: 
      // calculate radius 
      radius = Math.abs(centerX - x); 
      break; 
     case (MotionEvent.ACTION_UP) : 
      touched = false; 
      break; 
    } 
    // call next frame 
    postInvalidate(); 
    return true; 
} 

也canvas.drawOval方法見。