Android 返回键退出

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK) {
            new AlertDialog.Builder(this)
                    .setIcon(android.R.drawable.ic_menu_info_details)
                    .setTitle("退出程序")
                    .setMessage("是否要退出？")
                    .setPositiveButton("确定",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                    System.exit(0);
                                }
                            })
                    .setNegativeButton("取消",
                            new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                }
                            }).create().show();
        }
        return super.onKeyDown(keyCode, event);
    }