为什么程序打开是白屏什么都没有

public class test extends View { 

     private Bitmap mBitmap; 
 public test(Context context) { 
 super(context); 
 // TODO Auto-generated constructor stub 
 character(); 
 } 


 private void character() { 
 // TODO Auto-generated method stub 
 Bitmap bmp = ((BitmapDrawable) getResources().getDrawable(R.drawable.carrot)).getBitmap(); 
 mBitmap = bmp; 
 } 
    protected void drawcharacter(Canvas canvas){ 
     canvas.drawBitmap(mBitmap, 0, 0, null); 
     } 
 }