addView()出错，咋回事啊

package my.test;


import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.LinearLayout;

public class TestActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        final DrawView dv = new DrawView(this);
        LinearLayout  lin =(LinearLayout)this.findViewById(R.layout.main);
        //dv.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,ViewGroup.LayoutParams.MATCH_PARENT));
        dv.setMinimumWidth(300);
        dv.setMinimumHeight(500);

        dv.setOnTouchListener(new OnTouchListener(){
            public boolean onTouch(View v, MotionEvent event) {
                dv.currentX = (event.getX());
                dv.currentY = (event.getY());
                dv.invalidate();
                return true;
            }
        });
        lin.addView(dv);//这里总出错！
    }    
}