android弹出对话框

以下摘自:http://php.11519.net/adeve/?p=4

public void QuitApp() {
        new AlertDialog.Builder(Hello.this).setTitle("提示").setMessage(
                "确定退出?").setIcon(R.drawable.quit).setPositiveButton("确定",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {    
                         billdb.close();
                         finish();
                     }
                 }).setNegativeButton("取消",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                     }
                 }).show();

     }

///////////////////////////////////////////////////////

Toast.makeText(Hello.this,"提示信息：",Toast.LENGTH_LONG).show();