Question

我有三个片段：

A是我的主要片段，B是登录片段，成功登录将进入C片段。

当我点击后退按钮时，我需要从片段C移动到片段A。

我的问题是，当我点击后退按钮时，我仍然会从片段A移动片段B.

如何解决我的问题？

这是我的切换片段功能：

public void switchFragment(Fragment fragment) {
    FragmentManager manager = getActivity().getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.mainFrame, fragment, null);
    transaction.addToBackStack(null);
    transaction.commit();
}

片段（NewHomepage）到B（LoginFragment）片段：

switchFragment(LogInFragment.newInstance());

这是我的B片段，当它来自C片段时，它具有值logged来决定是否切换A片段。

我认为问题必须在这里，当回到A片段并单击后退按钮想要退出APP时，我可以看到logcat show 1 =＆gt;和2 =＆gt;

String logged = memberData.getUD_MBTYPENAME(); //get the value when login succeed 
        Log.d(TAG,"1=>"+logged);
        //If UD_MBTYPENAME is not null，change to A fragment
        if (!TextUtils.isEmpty(logged)) {
            Log.d(TAG,"2=>"+logged);
            ((MainActivity) getActivity()).switchFragment(NewHomepage.newInstance());
        }

这是关于onKeyDown和switchFragment的我的MainActivity：

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

        if (getSupportFragmentManager().getBackStackEntryCount() == 1) {
            quickDialog();//It's a alert dialog
            return false;
        }
    }
    return super.onKeyDown(keyCode, event);
}

public void switchFragment(Fragment fragment) {
    FragmentManager manager = getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.mainFrame, fragment, null);
    transaction.addToBackStack(null);
    transaction.commit();
}

参考更改此类代码，如果我不使用transaction.addToBackStack(null);，问题仍然存在，即使删除transaction.addToBackStack(null);

当我回到A时，我必须再次点击两次以显示警告对话框，我不知道当我第一次点击A片段时发生了什么。

if (!TextUtils.isEmpty(logged)){
        Log.d(TAG,"2=>"+logged);

        hideFragment(LogInFragment.newInstance());
        switchFragment(NewHomepage.newInstance());
    }

public void switchFragment(Fragment fragment) {
    FragmentManager manager = getActivity().getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.replace(R.id.mainFrame, fragment, null);
    //remove it will fix my issue , but I have to click back twice to show alert dialog , I don't know what happened click it first time in A fragment.
    //transaction.addToBackStack(null);
    transaction.commit();
}

public void hideFragment(Fragment fragment) {
    FragmentManager manager = getActivity().getSupportFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
    transaction.hide(fragment);
    transaction.commit();
}

删除hideFragment并在switchFragment上使用manager.popBackStack();，问题将得到解决。

Answer 1

尝试

如果已经添加片段，它将显示片段。

使用fragmentTransaction.show方法重新使用现有片段，即保存的实例。

public void switchFragment (Fragment oldFragment, Fragment newFragment, int frameId) {

    boolean addFragment = true;

    FragmentManager fragmentManager = getFragmentManager ();
    String tag = newFragment.getArguments ().getString ("TAG");
    Fragment fragment = fragmentManager.findFragmentByTag (tag);

    // Check if fragment is already added
    if (fragment != null && fragment.isAdded ()) {
        addFragment = false;
    }

    // Hide previous fragment
    String oldFragmentTag = oldFragment.getArguments ().getString (BaseFragment.TAG);

    if (!tag.equals (oldFragmentTag)) {
        FragmentTransaction hideTransaction = fragmentManager.beginTransaction ();
        Fragment fragment1 = fragmentManager.findFragmentByTag (oldFragmentTag);
        hideTransaction.hide (fragment1);
        hideTransaction.commit ();
    }

    // Add new fragment and show it
    FragmentTransaction addTransaction = fragmentManager.beginTransaction ();

    if (addFragment) {
        addTransaction.add (frameId, newFragment, tag);
        addTransaction.addToBackStack (tag);
    }
    else {
        newFragment = fragmentManager.findFragmentByTag (tag);
    }

    addTransaction.show (newFragment);

    addTransaction.commit ();
}

删除片段问题

1 个答案: