Android的消息提示AlertDialog

package com.example.test8;

import android.support.v7.app.ActionBarActivity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
	}
	public void btn4Onclick(View view){
		AlertDialog dlg=new AlertDialog.Builder(this)
		.setIcon(R.drawable.ic_launcher)
		.setTitle("Test")
		.setMessage("这是一个测试对话框")
		.setPositiveButton("确定", null)
		.create();
		dlg.show();
	}
	public void btn5Onclick(View view){
		AlertDialog dlg=new AlertDialog.Builder(this)
		.setIcon(R.drawable.ic_launcher)
		.setTitle("有多个按钮")
		.setMessage("这是一个测试对话框")
		.setPositiveButton("确定", new DialogInterface.OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(MainActivity.this, "确定按钮被点击", Toast.LENGTH_LONG).show();
				
			}
		})
		.setNegativeButton("取消", new DialogInterface.OnClickListener() {
			
			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(MainActivity.this, "取消按钮被点击", Toast.LENGTH_LONG).show();
				
			}
		})
		.setNeutralButton("忽略", null)
		.create();
		dlg.show();
	}
}