public class CanvasView extends View
{
     Paint paint;    
     public CanvasView(Context context, AttributeSet attrs) 
     {    
         super(context);    
         paint = new Paint();   
        ……
     }    
       
     @Override    
     protected void onDraw(Canvas canvas) 
     {    
    	……
     }    
}

然后我在它所在的activity的布局文件里这么写的：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
    <com.zero.client.CanvasView
        android:id="@+id/CanvasView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</RelativeLayout>

然后在activity里面，为了把它实例化，写的是：

CanvasView canvasView;
canvasView = (CanvasView)findViewById(R.id.CanvasView);

但是这样之后canvasView仍然是null，请问我应该怎么写才是对的？ 谢谢~~