菜单按钮，回退键，退出对话框

public boolean onCreateOptionsMenu(Menu menu){
    	menu.add(0, 0, 0, "关于");
    	menu.add(0, 1, 1, "退出");
    	return super.onCreateOptionsMenu(menu);
    	
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
    	super.onOptionsItemSelected(item);
    	switch (item.getItemId()) {
		case 0:
			openAboutDialog();
			break;
		case 1:
			openQiutDialog();
			break;
		default:
			break;
		}
    	return true;
    }
    
    /**
     * 关于
     */
    private void openAboutDialog(){
    	new AlertDialog.Builder(this).setTitle("关于").setMessage("这是关于的练习")
    	.setPositiveButton("确定", new DialogInterface.OnClickListener(){

			@Override
			public void onClick(DialogInterface dialog, int which) {
				
			}}).show();
    }
    
    /**
     * 退出
     */
    private void openQiutDialog(){
    	new AlertDialog.Builder(this).setTitle("退出").setMessage("你真的要退出吗？")
    	.setPositiveButton("退出", new DialogInterface.OnClickListener(){

			@Override
			public void onClick(DialogInterface dialog, int which) {
				finish();
			}}).setNegativeButton("取消", new DialogInterface.OnClickListener(){

				@Override
				public void onClick(DialogInterface dialog, int which) {
					
				}}).show();
    }
    /**
     * 回退键提示
     * 
     */
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode==KeyEvent.KEYCODE_BACK){
        	openQiutDialog();
        }
        return false;
    }