如何创建对话框

AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
				//2.设置标题和内容
				builder.setTitle("退出程序");
				builder.setMessage("你确定要退出吗？");
				//2.1 添加按钮
				builder.setPositiveButton("确定", new OnClickListener() {
					
					@Override
					public void onClick(DialogInterface dialog, int which) {
						// TODO Auto-generated method stub
						Toast.makeText(getApplicationContext(), "正在退出……", 200).show();
					}
				} );
				builder.setNegativeButton("取消", new OnClickListener() {
					
					@Override
					public void onClick(DialogInterface dialog, int which) {
						// TODO Auto-generated method stub
						Toast.makeText(getApplicationContext(), "正在退出……", 200).show();
					}
				});
				
				//3.设置好对话框编译者之后，创建对话框
				AlertDialog dialog = builder.create();
				//4.显示对话框
				dialog.show();[

code="java