prevent相同片段在popBackStack添加多次 [英] Prevent the same Fragment to be added multiple times in popBackStack

问题描述

我的活动是由3嵌套片段。还有就是我的 MainFragment 的默认显示， ProductFragment 可从它被调用，那么 DetailFragment 可以从 ProductFragment 。

My activity is composed of 3 nested Fragments. There is my MainFragment that is displayed by default, ProductFragment that can be called from it, then DetailFragment can be called from ProductFragment.

我可以回去之间来回我的 ProductFragment 和 DetailFragment 。通过这样做，所述popStackBack方法正在积累相似的片段。然后，如果我点击后退按钮，它会回去通过所有片段尽可能多的时间，我打电话给他们。

I can go back and forth between my ProductFragment and DetailFragment. By doing so, the popStackBack method is accumulating similar fragments. Then, if I click on the back button, It will go back through all the Fragments as many time I called them.

什么是被关在后面的堆栈，以避免同一片段的正确方法？

What is the proper way to avoid the same Fragment to be kept in the back stack ?

编辑：

我首先打电话给我的主要片段：

I firstly call my main fragment :

    if (savedInstanceState == null) {
        getFragmentManager()
            .beginTransaction()
            .add(R.id.container, new SearchFragment(), "SEARCH_TAG")
            .commit();
    }

下面是code，从该活动呼吁片段：

Here is the code that calls the fragments from the activity :

    FragmentManager fm = getFragmentManager();
    FragmentTransaction ft = fm.beginTransaction();
    ft.setCustomAnimations(R.animator.enter_from_bottom, R.animator.exit_to_top, R.animator.enter_from_bottom, R.animator.exit_to_top);
    ft.replace(R.id.container, new FactFragment(), "FACT_TAG");
    ft.addToBackStack("FACT_TAG");
    ft.commit();

然后，在后面点击：

Then, on back click :

@Override
public void onBackPressed() {
    getFragmentManager().popBackStack();
}

我试图让我的当前片段的标签，并执行有关它的一些具体的code，但它不能很好地工作。我也试图 addToBackStack（）仅在当前片段是不是已经加入到backStack但它搞砸了我的片段视图。

I tried to get the tag of my current fragment and execute some specific code related to it but it doesn't work well. I also tried to addToBackStack() only when current Fragment wasn't already added to the backStack but it messed up my fragment view.

推荐答案

下面是我的解决方案。也许很脏，但它的工作原理。我实现它返回一个点击之前所显示的片段的标签的方法上背面按钮：

Here is my solution. Maybe dirty but it works. I implemented a method that returns the tag of the fragment that is displayed before clicking the on back button :

public String getActiveFragment() {

    if (getFragmentManager().getBackStackEntryCount() == 0) {
        return null;
    }

    String tag = getFragmentManager()
        .getBackStackEntryAt(getFragmentManager()
        .getBackStackEntryCount() - 1)
        .getName();

    return tag;
}

然后，在我的 onBack pressed（）方法：

    // Get current Fragment tag
    String currentFrag = getActiveFragment();

    if(currentFrag.equals("PRODUCT_TAG")) {

        // New transaction to first Fragment
        FragmentManager fm = getFragmentManager();
        FragmentTransaction ft = fm.beginTransaction();
        ft.setCustomAnimations(R.animator.enter_from_right, R.animator.exit_to_left, R.animator.enter_from_right, R.animator.exit_to_left);
        ft.replace(R.id.container, new SearchFragment(), "MAIN_TAG");
        ft.commit();

    } else {

        // Go to Fragment-1
        getFragmentManager().popBackStack();
    }

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