您经常需要显示一个对话框窗口，以便从用户那里得到确认。这时，可以重写在Activity基类中定义的受保护的onCreateDialog()方法来显示一个对话框窗口。

package com.example.androidtest;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.widget.Toast;

public class DialogActivity extends Activity implements OnClickListener {

	CharSequence[] items = {"Google", "Apple", "Microsoft"};
	boolean[] itemsChecked = new boolean[items.length];
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_dialog);
		
		Button btn = (Button)this.findViewById(R.id.button1);
		btn.setOnClickListener(this);
	}
	
	public void onClick(View v)
	{
		showDialog(0);
	}
	
	@Override
	protected Dialog onCreateDialog(int id)
	{
		switch(id)
		{
		case 0:
			Builder builder = new AlertDialog.Builder(this);
			builder.setIcon(R.drawable.ic_launcher);
			builder.setTitle("title");
			builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
				@Override
				public void onClick(DialogInterface dialog, int which) {
					//这里要用getBaseContext()来获取DialogActivity的上下文对象。
					Toast.makeText(getBaseContext(), "OK clicked!", Toast.LENGTH_SHORT).show();
				}
			});
			
			builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
				@Override
				public void onClick(DialogInterface dialog, int which) {
					Toast.makeText(getBaseContext(), "Cancel clicked!", Toast.LENGTH_SHORT).show();
				}
			});
			
			builder.setMultiChoiceItems(items, itemsChecked, new DialogInterface.OnMultiChoiceClickListener() {
				@Override
				public void onClick(DialogInterface dialog, int which, boolean isChecked) {
					Toast.makeText(getBaseContext(), items[which] + (isChecked ? " checked!" : " unchecked!"), Toast.LENGTH_SHORT).show();
				}
			});
			
			return builder.create();
		}
		
		return null;
	}
}

运行效果