再按一次退出应用实现

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {

if ((System.currentTimeMillis() - mExitTime) > 2000) {
toShowToast("再按一次退出");
mExitTime = System.currentTimeMillis();
} else {
ActivityManager.AppExit();
}
return true;
}
return super.onKeyDown(keyCode, event);
}

/**
* 退出应用程序
*/
public static void AppExit()
{
try
{

System.exit(0);
}
catch (Exception e)
{
}
}