Android-新的BottomNavigationBar中的PageView-防止重新加载片段 [英] Android - PageView in new BottomNavigationBar - prevent reload fragments

问题描述

在我的StartActivity中，BottomNavigationBar侦听器具有以下设置:

In my StartActivity the BottomNavigationBar Listener has the following setup:

private GuideFragment guideFragment = new GuideFragment();
private MapFragment mapFragment = new MapFragment();
private MoreFragment moreFragment = new MoreFragment();

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        Fragment selectedFragment = null;
        switch (item.getItemId()) {
            case R.id.navigation_guide:
                selectedFragment = guideFragment;
                break;
            case R.id.navigation_map:
                selectedFragment = mapFragment;
                break;
            case R.id.navigation_more:
                selectedFragment = moreFragment;
                break;
        }
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        transaction.replace(R.id.content, selectedFragment);
        transaction.commit();
        return true;
    }

};

如上所述，我想防止所选片段始终重新加载源/视图.我在片段中尝试了一些类似的东西:

As I mentioned above I want to prevent that the selected fragments always reloads the sources/view. I tried out some stuff like - in the fragments:

if (rootView == null)
     inflater.inflate...

但是这些片段仍然会重新创建视图并加载(以我为例)新的webresources.

But the fragments still recreate the view and load (in my case) webresources new.

我阅读了PageView可以提供帮助的内容，尤其是

I read something that a PageView could help, especially

offScreenPageLimit

应该做魔术.

我的主要问题是我应该在哪里实现PageViewer-我的StartActivity是否可以实现?还是可以通过其他方式解决问题?

My main question is where should I implement a PageViewer - Is it possible in my StartActivity? Or can I solve the problem in an other way?

推荐答案

我做到了！不需要 ViewPager .

这是我的解决方案(所有代码均编码在 StartActivity 中，而不是 Fragments 中):

Here is my solution (all coded in StartActivity not in Fragments):

private final GuideFragment guideFragment = new GuideFragment();
private final MapFragment mapFragment = new MapFragment();
private final MoreFragment moreFragment = new MoreFragment();
private final android.app.FragmentManager fm = getFragmentManager();
Fragment active = guideFragment;

private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_guide:
                if(active != guideFragment) {
                    fm.beginTransaction().show(guideFragment).commit();
                }
                else {
                    fm.beginTransaction().hide(active).show(guideFragment).commit();
                }
                active = guideFragment;
                break;
            case R.id.navigation_map:
                fm.beginTransaction().hide(active).show(mapFragment).commit();
                active = mapFragment;
                break;
            case R.id.navigation_more:
                fm.beginTransaction().hide(active).show(moreFragment).commit();
                active = moreFragment;
                break;
        }

        return true;
    }

};

在onCreate列表中，事务将提交.

and in onCreate list the transaction commits.

fm.beginTransaction().add(R.id.content,moreFragment).commit();
fm.beginTransaction().add(R.id.content, mapFragment).commit();
fm.beginTransaction().add(R.id.content, guideFragment).commit();

如果您有3个标签页，那么最后提交第一个标签页片段(fragm3，fragm2，fragm1)非常重要.

It is very important to commit the first tabs fragment last(fragm3,fragm2,fragm1) if you have 3 tabs.

通过不加载每个新片段/刷新，现在可以在智能手机上实现高速性能.

Highly speed performance on the smartphone now by not loading every fragment new/refresh.

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