在画布上绘制交互圆圈

我必须在屏幕上绘制圆圈并通过OnTouch方法获得交互。请帮助我。这是我尝试过的代码。这里的问题是，它不与用户交互intract但是这个代码成功绘制圆形在画布上绘制交互圆圈

public class DrawingView extends View implements OnTouchListener { 

    static int x, y, r = 255, g = 255, b = 255; 
    final static int radius = 30; 
    Paint paint; // using this ,we can draw on canvas 

    public DrawingView(Context context) { 
     super(context); 
     paint = new Paint(); 
     paint.setAntiAlias(true); // for smooth rendering 
     paint.setARGB(255, r, g, b); // setting the paint color 

     // to make it focusable so that it will receive touch events properly 
     setFocusable(true); 

     // adding touch listener to this view 
     this.setOnTouchListener(this); 
    } 

    // overriding the View's onDraw(..) method 
    public void onDraw(Canvas canvas) { 
     paint.setARGB(255, r, g, b); 

     super.onDraw(canvas); 
     // drawing the circle 

     canvas.drawCircle(x, y, radius, paint); 
     randColor(); // calls this method to generate a color before drawing 
     invalidate(); // calls onDraw method 

    } 

    // this is the interface method of "OnTouchListener" 
    public boolean onTouch(View view, MotionEvent event) { 
     x = (int) event.getX() - (radius/2); // some math logic to plot the 
               // circle in exact touch place 
     y = (int) event.getY() - (radius/2); 
     // System.out.println("X,Y:"+"x"+","+y); //see this output in "LogCat" 
     randColor(); // calls this method to generate a color before drawing 
     invalidate(); // calls onDraw method 
     return true; 
    } 

    // this method sets a random color using Math.random() 
    // Note: RGB color values ranges from 0 to 255.. 
    public void randColor() { 
     r = (int) (Math.random() * 255); 
     g = (int) (Math.random() * 255); 
     b = (int) (Math.random() * 255); 
     // Toast.makeText(c, "r,g,b="+r+","+g+","+b,Toast.LENGTH_SHORT).show(); 
    } 
}

但问题是，它并没有得到用户的交互

来源

2014-12-19 shani

它，它制定出来的？ – 2014-12-19 07:56:35

动作只需使用此画圈子

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

public Circle(Context context, float x, float y, int r) { 
    super(context); 
    mPaint.setColor(0xFFFF0000);     
    this.x = x; 
    this.y = y; 
    this.r = r; 
} 
@Override 
protected void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 
    canvas.drawCircle(x, y, r, mPaint); 
}

互动MainActivity类别是这里

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.circle); 
    FrameLayout main = (FrameLayout) findViewById(R.id.main_view); 
    main.addView(new Circle(this, 50, 50, 25)); 

    main.setOnTouchListener(new View.OnTouchListener() { 
     @Override 
     public boolean onTouch(View v, MotionEvent e) { 
      float x = e.getX(); 
      float y = e.getY(); 
      FrameLayout flView = (FrameLayout) v; 
      flView.addView(new Circle(flView.getContext(), x, y, 5)); 
      return true; 
     } 
    }); 
}

来源

2014-12-19 08:05:36

至少几个问题：

您实际上没有测试过触摸x/y落在圆的半径内。您需要一个if子句。现在每次触摸都会调用invalidate()。

事件顺序错误，某些操作被调用的次数太多。就在这里面ondDraw应该工作：

super.onDraw(canvas); 
paint.setARGB(255, r, g, b); // (and you don't need this in the method above) 
canvas.drawCircle(x, y, radius, paint);

来源

2014-12-19 07:44:16

删除invalidate()在onDraw()方法，并在onTouch()获得随机颜色。

您需要在每次触摸动作，触摸位置（或触摸位置）中使用不同的颜色，或者想要更改颜色，然后检查event.getAction()==MotionEvent.ACTION_DOWN中的动作。

来源

2014-12-19 07:48:51

删除onDraw()方法invalidate（），因为当你在invalidating在onDraw()它会调用onDraw Recursivly，并在onTouch（）获得随机颜色。

你想不同的颜色在每一个触摸动作，将在onTouch()随机颜色的方法，或基于触摸下要更改的颜色，然后检查从event.getAction()==MotionEvent.ACTION_DOWN.

来源

2014-12-19 07:55:22

在画布上绘制交互圆圈

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