Android 按钮 弹出对话框

ackage com.example.helloworld;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.view.Menu;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

Button btn=(Button)this.findViewById(R.id.button1);
btn.setOnClickListener( new View.OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Dialog myDialog= new AlertDialog.Builder(MainActivity.this).setTitle("标题").setMessage("提示").create();
myDialog.show();

}
});
}

@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;
}

}