回收站视图未显示

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【中文标题】回收站视图未显示【英文标题】:Recycler View Not Showing 【发布时间】:2015-02-26 15:30:41 【问题描述】:

我一直在制作一个在导航抽屉中使用回收器视图的应用程序。为什么没有显示回收站视图的内容。视图肯定在那里,因为我可以看到滚动阴影。我不确定我做错了什么,因为应用程序在运行时不会崩溃。

导航抽屉片段:

public class NavigationDrawerFragment extends android.support.v4.app.Fragment 

    public static final String PREF_FILE_NAME = "testPref";
    public static final String KEY_USER_LEARNED_DRAWER = "user_learned_drawer";
    private RecyclerView mRecyclerView;
    private ActionBarDrawerToggle mDrawerToggle;
    private DrawerLayout mDrawerLayout;
    private View containerView;
    private Boolean mUserLearnedDrawer;
    private Boolean mFromSavedInstanceState;
    private DrawerAdapter adapter;

    public NavigationDrawerFragment() 
        mFromSavedInstanceState = false;
    


    @Override
    public void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        mUserLearnedDrawer = Boolean.valueOf(readFromPreferences(getActivity(), KEY_USER_LEARNED_DRAWER, "false"));
        if (savedInstanceState != null)
            mFromSavedInstanceState = true;
        
    

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) 
        // Inflate the layout for this fragment
        View layout = inflater.inflate(R.layout.fragment_navigation_drawer, container, false);
        mRecyclerView = (RecyclerView) layout.findViewById(R.id.drawerList);
        adapter = new DrawerAdapter(getActivity(), getData());
        mRecyclerView.setAdapter(adapter);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        return layout;
    

    public static List<DrawerRow> getData()
        List<DrawerRow> data = new ArrayList<>();
        int icons[] = R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher,R.drawable.ic_launcher;
        String titles[] = "Link 1","Link 2","Link 3","Link 4";
        for (int i = 0 ; i < titles.length && i < icons.length; i++)
            DrawerRow current = new DrawerRow();
            current.iconId = icons[i];
            current.title = titles[i];
            data.add(current);
        

        return data;
    

    public void setUp(int fragmentId, DrawerLayout drawerLayout, Toolbar toolbar) 
        containerView = getActivity().findViewById(fragmentId);
        mDrawerLayout = drawerLayout;
        mDrawerToggle = new ActionBarDrawerToggle(getActivity(), drawerLayout, toolbar, R.string.drawerOpen, R.string.drawerClosed)

            @Override
            public void onDrawerOpened(View drawerView) 
                super.onDrawerOpened(drawerView);
                if(!mUserLearnedDrawer)
                    mUserLearnedDrawer = true;
                    saveToPreferences(getActivity(),KEY_USER_LEARNED_DRAWER, mUserLearnedDrawer+"");
                
                getActivity().invalidateOptionsMenu();
            

            @Override
            public void onDrawerClosed(View drawerView) 
                super.onDrawerClosed(drawerView);
                getActivity().invalidateOptionsMenu();
            
        ;

        if(!mUserLearnedDrawer && !mFromSavedInstanceState)
            mDrawerLayout.openDrawer(containerView);
        

        mDrawerLayout.setDrawerListener(mDrawerToggle);
        mDrawerLayout.post(new Runnable() 
            @Override
            public void run() 
                mDrawerToggle.syncState();
            
        );
    

    public void saveToPreferences(Context context, String prefName, String prefValue)
        SharedPreferences sharedPreferences = context.getSharedPreferences(PREF_FILE_NAME, Context.MODE_PRIVATE);
        SharedPreferences.Editor mEditor = sharedPreferences.edit();
        mEditor.putString(prefName, prefValue);
        mEditor.apply();
    

    public static String readFromPreferences(Context context, String prefName, String defaultValue)
        SharedPreferences sharedPreferences = context.getSharedPreferences(PREF_FILE_NAME, Context.MODE_PRIVATE);
        return sharedPreferences.getString(prefName,defaultValue);
    

适配器:

public class DrawerAdapter extends RecyclerView.Adapter<DrawerAdapter.MyViewHolder>

    private LayoutInflater inflator;
    List<DrawerRow> data = Collections.EMPTY_LIST;

    public DrawerAdapter(FragmentActivity activity, List<DrawerRow> data) 
        inflator = LayoutInflater.from(activity);
        this.data = data;
    


    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) 
        View view = inflator.inflate(R.layout.nav_drawer_row , viewGroup,false);
        MyViewHolder holder = new MyViewHolder(view);
        return holder;
    

    @Override
    public void onBindViewHolder(MyViewHolder viewHolder, int i) 
        DrawerRow current = data.get(i);
        viewHolder.title.setText(current.title);
        viewHolder.icon.setImageResource(current.iconId);
    

    @Override
    public int getItemCount() 
        return 0;
    

    class MyViewHolder extends RecyclerView.ViewHolder
        ImageView icon;
        TextView title;

        public MyViewHolder(View itemView) 
            super(itemView);
            icon = (ImageView) itemView.findViewById(R.id.list_icon);
            title = (TextView) itemView.findViewById(R.id.list_text);
        
    

抽屉行:

public class DrawerRow 
    int iconId;
    String title;

布局:

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_
    android:layout_
    android:id="@+id/drawerLayout">

    <!--Main Content -->
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_
        android:layout_
        android:orientation="vertical">

        <include
            android:id="@+id/app_bar"
            layout="@layout/app_bar" />

        <TextView
            android:layout_
            android:layout_
            android:text="New Text" />

    </LinearLayout>

    <!--Nav Drawer -->
    <fragment
        android:layout_
        android:layout_
        android:layout_gravity="start"
        android:name="uk.co.clickcomputing.hhscweatherstation.NavigationDrawerFragment"
        android:id="@+id/fragment_navigation_drawer"/>

</android.support.v4.widget.DrawerLayout>

抽屉行:

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

    <ImageView
        android:padding="@dimen/list_padding"
        android:id="@+id/list_icon"
        android:layout_
        android:layout_
        android:layout_gravity="center_vertical"
        android:src="@drawable/ic_launcher"/>

    <TextView
        android:padding="@dimen/list_padding"
        android:layout_
        android:layout_
        android:layout_gravity="center_vertical"
        android:text="New Text"
        android:id="@+id/list_text" />
</LinearLayout>

导航抽屉片段布局:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_
    android:layout_
    android:background="#eee"
    android:orientation="vertical">

        <ImageView
            android:layout_
            android:layout_
            android:layout_marginBottom="8dp"
            android:contentDescription="@string/nav_drawer_img_desciption"
            android:scaleType="centerCrop"
            android:src="@drawable/nav_drawer" />
    
        <android.support.v7.widget.RecyclerView
            android:layout_
            android:layout_
            android:id="@+id/drawerList">
    
        </android.support.v7.widget.RecyclerView>
    </LinearLayout>

【问题讨论】:

能分享一下包含RecyclerView的布局文件吗?我的猜测是您设置了宽度或高度来包装内容,默认布局管理器尚不支持。 @yigit 更新了布局 所以我猜到了,默认布局管理器尚不支持回收器视图上的 android:layout_ 。您可以将其更改为 match_parent 或在布局管理器中覆盖 onMeasure 并自己进行测量。 @yigit 仍然没有显示任何内容 这没有意义。您有可以附加的示例应用程序吗? APK 应该足以调试,但如果您可以附加 w/ 源代码,那就太棒了。 【参考方案1】:

问题是您将项目计数返回为 0,这表明没有要显示的行。您应该返回 List 的大小,如下所示。

    @Override
    public int getItemCount() 
        return data.size();
    

【讨论】:

我在更新我的 dataList dataList=getMyItems() 时遇到了这个问题。相反,我使用dataList.addAll(getMyItems());【参考方案2】:

以下行替换

 mRecyclerView.setAdapter(adapter);
 mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));    
mRecyclerView.setAdapter(adapter);

【讨论】:

【参考方案3】:

我同意您需要返回正确的项目编号,但我认为您在将回收站视图的高度设置为 wrap_content 时也可能存在问题。我发现this 链接很有帮助。希望对您有所帮助。

【讨论】:

【参考方案4】:

确保 RecyclerView 父容器宽度未设置为 WrapContent

【讨论】:

就这么简单,很好的答案。我更改为 match_parent 回收器,现在它出现了【参考方案5】:
@Override
public int getItemCount() 
    return data.size();

你所在行的布局高度是android:layout_height="match_parent",但必须是android:layout_height="wrap_content"

【讨论】:

【参考方案6】:

检查您的 RecyclerView 的宽度和高度属性,如果它们设置为包装内容,请将其更改为匹配父级或限制您在某些特定区域中的视图。 还要检查父视图的宽度属性,如果它设置为包装内容,也将其更改为匹配父视图。

【讨论】:

【参考方案7】:

我已经给出了静态高度和 match_parent。它适用于我的示例,我已将其添加到嵌套回收器视图中。

<androidx.recyclerview.widget.RecyclerView
                     android:id="@+id/new_store_page_phoneNumber_rv"
                        android:layout_
                        android:layout_
                        android:scrollIndicators="bottom"
                        android:fadeScrollbars="false"
                        android:layout_gravity="center_vertical"
                        app:adapter="@adapter"
                        android:focusable="true"
                        android:focusableInTouchMode="true"
                        android:clickable="true"
                        android:scrollbarAlwaysDrawHorizontalTrack="true"
                        android:scrollbars="none"
                        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
                        android:orientation="horizontal" />

【讨论】:

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