如何绘制大于屏幕尺寸的画布，并且能够在android中水平和垂直滚动/平移？ [英] How to draw on canvas greater than screen size and be able to scroll / pan horizontally and vertically in android?

问题描述

我正在寻找一个关于如何在画布上绘制大于屏幕尺寸的示例代码的真实示例（截至目前我正在绘制正常并且无法查看外部屏幕大小）。更重要的是能够滚动/平移屏幕以查看整个画布。
如果需要更多信息，请发表评论。

更新：在这里找到我的答案

解决方案

我的版本是从Monodroid转换而来的，但实现应该看起来差不多。 （我试着把它放回到java中，如果它不是确切的道歉）

1. 为了在屏幕外绘制，画出你想要的任何地方，它将被绘制在屏幕之外。诀窍是通过缩放和平移来查看它。要缩放视图，需要实现ScaleGestureDetector.IOnScaleGestureListener并按如下方式实现onScale方法。

为了平移，您只需实现onTouchEvent，这是无论如何放大。

 私人浮动_scaleFactor; 
私人浮动_xoffset; 
私人浮动_yoffset; 
 
 @override 
 public bool onScale（ScaleGestureDetector检测器）{
 _scaleFactor * = detector.ScaleFactor; 
 _scaleFactor = Math.Max（0.1f，Math.Min（_scaleFactor，5.0f））; 
 invalidate（）; 
返回true; 
 
 
 @override 
 protected void onDraw（Canvas canvas）{
 super.onDraw（canvas）; 
 canvas.save（）; 
 canvas.scale（_scaleFactor，_scaleFactor）; //用于缩放
 canvas.translate（_xoffset，_yoffset）; //用于平铺
 //正常绘图
画布。恢复（）; 
} 
 
 @override 
 public bool onTouchEvent（MotionEvent e）{
 switch（e.action）{
 case MotionEvent.ACTION_DOWN：{
 _prevx = e.getX（）; 
 _prevy = e.getY（）; 
} 
 break; 
 case MotionEvent.ACTION_UP：{
 _xoffset + = e.getX（） -  _prevx; 
 _yoffset + = e.getY（） -  _prevy; 
 invalidate（）; 
 
 _prevx = e.getX（）; 
 _prevy = e.getY（）; 
} 
 break; 
} 
 return _scaleGestureDetector.onTouchEvent（e）; 
} 
  

是一个自定义VIEW对象 - 所以从View继承并实现IOnScaleGestureListener

I am looking for a real example with sample code on how to draw on canvas greater than screen size ( As of now I am drawing normally and not able to view outside screen size). More stress is on being able to scroll / pan the screen to view the whole canvas. If anymore info is required please comment.

Update: Found my answer here Image in Canvas with touch events

解决方案

My version is converted from Monodroid, but the implementation should look about the same. (I tried putting it back into java, apologies if it is not exact)

1. In order to draw outside the screen, just draw where ever you want, it will be drawn outside the screen. The trick is to see it by zooming and panning. For zooming your view needs to implement ScaleGestureDetector.IOnScaleGestureListener and implement the onScale method as below.

2. For panning you just need to implement the onTouchEvent, which is required for zooming anyway.

   private float _scaleFactor;
   private float _xoffset;
   private float _yoffset;
   
   @override
   public bool onScale(ScaleGestureDetector detector){
       _scaleFactor *= detector.ScaleFactor;
       _scaleFactor = Math.Max(0.1f, Math.Min(_scaleFactor, 5.0f));
       invalidate();
       return true;
   } 
   
   @override 
   protected void onDraw(Canvas canvas){
       super.onDraw(canvas);
       canvas.save();
       canvas.scale(_scaleFactor, _scaleFactor);//for zoom
       canvas.translate(_xoffset, _yoffset);//for pan
       //DO NORMAL DRAWING HERE
       canvas.restore();
   }
   
   @override 
   public bool onTouchEvent(MotionEvent e){
       switch (e.action){
           case MotionEvent.ACTION_DOWN:{                        
               _prevx = e.getX();
               _prevy = e.getY();
           }
           break;
           case MotionEvent.ACTION_UP:{
               _xoffset += e.getX() - _prevx;
               _yoffset += e.getY() - _prevy;
               invalidate();
   
               _prevx = e.getX();
               _prevy = e.getY();
           }
           break;
       }
       return _scaleGestureDetector.onTouchEvent(e);
   }
   

NOTE: This code is for a custom VIEW object - so inherit from View and implement IOnScaleGestureListener

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