PreferenceFragmentCompat自定义布局 [英] PreferenceFragmentCompat custom layout

问题描述

我的PreferenceFragmentCompat需要自定义布局.在

I need a custom layout for my PreferenceFragmentCompat. In the docs for PreferenceFragmentCompat it seems that you can possibly inflate and return a view in onCreateView().

但是NPE结果:-

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setAdapter(android.support.v7.widget.RecyclerView$Adapter)' on a null object reference
                                                                       at android.support.v7.preference.PreferenceFragmentCompat.bindPreferences(PreferenceFragmentCompat.java:511)
                                                                       at android.support.v7.preference.PreferenceFragmentCompat.onActivityCreated(PreferenceFragmentCompat.java:316)
                                                                       at com.cls.example.MyPrefFrag.onActivityCreated(MyPrefFrag.java:42) 

在我检查了PreferenceFragmentCompat:onCreateView的源代码之后，我发现了以下代码:-

After I checked the source of PreferenceFragmentCompat:onCreateView I found the following piece of code :-

 RecyclerView listView = this.onCreateRecyclerView(themedInflater, listContainer, savedInstanceState);
 if(listView == null) {
    throw new RuntimeException("Could not create RecyclerView");
 } else {
    this.mList = listView;   //problem
    ...
    return view;
 }

因此，如果您覆盖onCreateView()并返回自定义布局，则不会调用onCreateRecyclerView()，并且不会设置RecyclerView私有字段mList.因此，setAdapter()上的NPE就会产生.

So if you override onCreateView() and return a custom layout the onCreateRecyclerView() is not called plus the RecyclerView private field mList will not be set. So the NPE on setAdapter() results.

我应该假设对PreferenceFragmentCompat而言，自定义布局是不可行的吗?

Should I assume that having a custom layout is not feasible for PreferenceFragmentCompat ?

推荐答案

您可以在主题中指定自定义布局.

You can specify a custom layout in your theme.

例如:

styles.xml

<style name="YourTheme" parent="Theme.AppCompat">
    <!-- ... -->
    <item name="preferenceTheme">@style/YourTheme.PreferenceThemeOverlay</item>
</style>

<style name="YourTheme.PreferenceThemeOverlay" parent="@style/PreferenceThemeOverlay">
    <item name="android:layout">@layout/fragment_your_preferences</item>
</style>

fragment_your_preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.v7.widget.Toolbar
            android:id="@+id/custom_toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </android.support.design.widget.AppBarLayout>

    <!-- Required ViewGroup for PreferenceFragmentCompat -->
    <FrameLayout
        android:id="@android:id/list_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </FrameLayout>

</LinearLayout>

然后在您的片段类的onViewCreated()中，您可以开始使用视图:

And then in onViewCreated() of your fragment class you can start using the views:

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState)
{
    super.onViewCreated(view, savedInstanceState);

    Toolbar toolbar = (Toolbar)view.findViewById(R.id.custom_toolbar);

    if (toolbar != null)
    {
        getMainActivity().setSupportActionBar(toolbar);
    }
}

这篇关于PreferenceFragmentCompat自定义布局的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！