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);

    }