AndroidノートProgeressDialogとスレッド

package tjj.testProgressDialog;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class TestProgressDialogActivity extends Activity
{
	
	private Button bt;
	private TextView tv;
	private ProgressDialog myDialog;
	
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		
		tv = (TextView)findViewById(R.id.tv);
		bt = (Button)findViewById(R.id.button1);
		
		bt.setOnClickListener(showProgressBar);
		
	}
	
	Button.OnClickListener showProgressBar = new Button.OnClickListener()
	{

		@Override
		public void onClick(View v)
		{
			final CharSequence title = getString(R.string.title);
			final CharSequence body = getString(R.string.body);
			
			
			myDialog = ProgressDialog.show(TestProgressDialogActivity.this, title, body, true);
			
			tv.setText(body);
			
			new Thread()
			{
				public void run()
				{
					try
					{
						sleep(3000);
					}
					catch(Exception e)
					{
						e.printStackTrace();
					}
					finally
					{
						//     ，      
						myDialog.dismiss();
					}
				}
			}.start();
		}
		
	};
}