Question

如果用户按下某个活动，我希望我的应用程序退出。以下是该活动的代码。

public class MainActivity extends FragmentActivity implements DenkoListFragment.ListSelectListener {

    private SlidingMenu menu;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        displayView(0);

        menu = new SlidingMenu(this);
        menu.setTouchModeAbove(SlidingMenu.TOUCHMODE_FULLSCREEN);
        menu.setShadowWidthRes(R.dimen.shadow_width);
        menu.setShadowDrawable(R.drawable.shadow);
        menu.setBehindOffsetRes(R.dimen.slidingmenu_offset);
        menu.setFadeDegree(0.35f);
        menu.attachToActivity(this, SlidingMenu.SLIDING_CONTENT);
        menu.setMenu(R.layout.menu_frame);

        menu.setSelected(true);

        getSupportFragmentManager()
                .beginTransaction()
                .replace(R.id.menu_frame, new DenkoListFragment())
                .commit();
    }

    private void displayView(int position) {

        Fragment fragment = null;
        switch (position) {
            case 0:
                fragment = new MainViewFragment();
                break;
            case 1:
                fragment = new StationViewFragment();
                break;
            case 2:
                fragment = new MapViewFragment();
                break;

            default:
                break;
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.content_frame, fragment).commit();
        } else {

        }
    }

    @Override
    public void select(int index) {
        displayView(index);
        menu.showContent();
    }

    @Override
    public void onBackPressed() {
        if (menu.isMenuShowing()) {
            menu.showContent();
        } else {
            new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_alert).setTitle("Exit")
                    .setMessage("Are you sure you want to exit?")
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            finish();
                            System.exit(0);
                        }
                    }).setNegativeButton("No", null).show();
        }
    }

}

需要应用程序两次按下（和两次确认）才能退出。是什么解释了这种行为，有什么方法可以解决这个问题吗？

Answer 1

从onBackPress()方法中删除以下代码段。它仅由SlideMenu处理。

if (menu.isMenuShowing()) {
     menu.showContent();
}

来自SlidingFragmentActivity来电onBackPress的代码：

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
    boolean b = mHelper.onKeyUp(keyCode, event);
    if (b) return b;
    return super.onKeyUp(keyCode, event);
}

mHelper.onKeyUp(keyCode, event)会调用SlidingActivityHelper的方法：

public boolean onKeyUp(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && mSlidingMenu.isMenuShowing()) {
        showContent();   //Close the SlidingMenu and show the content view.
        return true;
    }
    return false;
}

Answer 2

super.onBackPressed();会按照您的要求执行操作，只需包含super.onBackPressed();而不是System.exit(0);，因为它会调用onBackpressed的{{1}}方法。所以， Activity方法正确接听电话。

onDestroy

退出按钮后退按钮按下不起作用

2 个答案: