线程练习中出现的错误

public class MainActivity extends Activity {

    //1.define member variable
    Button bt;
    TextView tv;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //2.init
        init();
        //3.listener
        bt.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                new Thread() {
                    public void run() {
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                        for(int i=0;i<10;i++) {
                            tv.setText("After Update:"+i);
                        }
                    }
                };
            }
        });
        
    }

    private void init() {
        // TODO Auto-generated method stub
        bt=(Button)this.findViewById(R.id.bt);
        tv=(TextView)this.findViewById(R.id.tv);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

new Thread{
        //......
}.start();