RecyclerView 不能在 onBindViewHolder() 中使用 setText()答案

【问题标题】：RecyclerView can't use setText() in onBindViewHolder()RecyclerView 不能在 onBindViewHolder() 中使用 setText()
【发布时间】：2018-12-04 22:01:56
【问题描述】：

在我的应用程序中，我尝试在 recyclerView 中使用两个布局，一切正常，直到我尝试应用程序并崩溃说：
尝试在空对象引用上调用虚拟方法“void android.widget.TextView.setText(int)”。
错误就在这一行，每次我尝试在第一个布局中设置文本时：

groupsViewHolder.fTeamName.setText(R.string.russia);

第二个布局工作正常，但第一个却不行。
我想要的是解决错误以及是否有比多次使用 switch 更好的方法。感谢您的帮助。
这是我的代码：

MatchesAdapter.java：

public class MatchesAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

final private ListItemClickListener mOnClickListener;
private Context context;


private int mNumberItems;

public MatchesAdapter(Context context, int numberOfItems, ListItemClickListener listener) {
    mNumberItems = numberOfItems;
    mOnClickListener = listener;
    this.context = context;
}

@Override
public int getItemViewType(int position) {
    return position;
}

@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
    Context context = viewGroup.getContext();
    LayoutInflater inflater = LayoutInflater.from(context);
    if (viewType >= 0 && viewType <= 47) {
        int layoutIdForListItem = R.layout.matches_groups_item;
        View view = inflater.inflate(layoutIdForListItem, viewGroup, false);
        Log.e("QQ","Groups");
        return new GroupsViewHolder(view);
    } else {
        int layoutIdForListItem = R.layout.matches_rounds_item;
        View view = inflater.inflate(layoutIdForListItem, viewGroup, false);
        Log.e("QQ","Rounds");
        return new RoundsViewHolder(view);
    }

}

@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder mainHolder, int position) {
 mainHolder;
        String[] array = context.getResources().getStringArray(R.array.times);
        final int itemType = getItemViewType(position);
        if (itemType >= 0 && itemType <= 47) {
            GroupsViewHolder groupsViewHolder = (GroupsViewHolder) mainHolder;
            groupsViewHolder.bind(position);
            switch (position) {
                case 0:
                    groupsViewHolder.listItemDate.setText(array[position]);
                    groupsViewHolder.fTeamName.setText(R.string.russia);
                    groupsViewHolder.sTeamName.setText(R.string.saudi_arabia);
                    break;
                case 1:
                   groupsViewHolder.listItemDate.setText(array[position]);
                    groupsViewHolder.fTeamName.setText(R.string.egypt);                    
                    groupsViewHolder.sTeamName.setText(R.string.uruguay);
                    break;
//.... many cases until case 47 then
} else {
            RoundsViewHolder roundsViewHolder = (RoundsViewHolder) mainHolder;
            roundsViewHolder.bind(position);
            switch (position) {
                 case 48:
                roundsViewHolder.listItemTitle.setText(R.string.round16);
                roundsViewHolder.listItemDate.setText(array[position]);
                roundsViewHolder.fTeamName.setText(R.string.group_a_winner);
                roundsViewHolder.sTeamName.setText(R.string.group_b_runner_up);
                break;
            case 49:
                roundsViewHolder.listItemTitle.setText(R.string.round16);
                roundsViewHolder.listItemDate.setText(array[position]);
                roundsViewHolder.fTeamName.setText(R.string.group_c_winner);
                roundsViewHolder.sTeamName.setText(R.string.group_d_runner_up);
                break;

// until the end of cases then
    @Override
public int getItemCount() {
    return mNumberItems;
}

public interface ListItemClickListener {
    void onListItemClick(int clickedItemIndex);
}

class GroupsViewHolder extends RecyclerView.ViewHolder
        implements OnClickListener {

TextView listItemDate, listItemMatchNumber, fTeamName, sTeamName;
View fTeamView;
View sTeamView;

public GroupsViewHolder(View itemView) {
    super(itemView);

listItemDate = itemView.findViewById(R.id.match_date);
listItemMatchNumber = itemView.findViewById(R.id.match_number);
fTeamView = itemView.findViewById(R.id.groups_match_t1);
fTeamName = fTeamView.findViewById(R.id.match_team_name_for_groups);
sTeamView = itemView.findViewById(R.id.groups_match_t2);
sTeamName = sTeamView.findViewById(R.id.match_team_name_for_groups);
itemView.setOnClickListener(this);

}

void bind(int listIndex) {
    listItemMatchNumber.setText(String.valueOf(listIndex + 1));
}

@Override
public void onClick(View v) {
    int clickedPosition = getAdapterPosition();
    mOnClickListener.onListItemClick(clickedPosition);
}

}

class RoundsViewHolder extends RecyclerView.ViewHolder
        implements OnClickListener {
    TextView listItemTitle, listItemDate, listItemMatchNumber, fTeamName, sTeamName;
    View fTeamView;
    View sTeamView;

public RoundsViewHolder(View itemView) {
    super(itemView);

listItemTitle = itemView.findViewById(R.id.round_card_title);
listItemDate = itemView.findViewById(R.id.round_match_date);
listItemMatchNumber = itemView.findViewById(R.id.round_match_number);
fTeamView = itemView.findViewById(R.id.round_match_t1);
fTeamName = fTeamView.findViewById(R.id.match_team_name);
sTeamView = itemView.findViewById(R.id.round_match_t2);
sTeamName = sTeamView.findViewById(R.id.match_team_name);
itemView.setOnClickListener(this);

}

void bind(int listIndex) {
    listItemMatchNumber.setText(String.valueOf(listIndex + 1));
}


@Override
public void onClick(View v) {
    int clickedPosition = getAdapterPosition();
    mOnClickListener.onListItemClick(clickedPosition);
}}}

matches_groups_item.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content">

<android.support.v7.widget.CardView
    android:id="@+id/mathes_card"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="3dp"
    card_view:cardCornerRadius="4dp">

    <TextView
        android:id="@+id/match_number"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="5dp"
        android:textColor="@color/red"
        android:textSize="18sp" />

    <TextView
        android:id="@+id/match_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="30dp"
        android:text="@string/select_winner" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/tv_informer"
        android:layout_marginTop="45dp"
        android:baselineAligned="false"
        android:orientation="horizontal">

        <include
            android:id="@+id/groups_match_t1"
            layout="@layout/team_no_buttons"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="20dp"
            android:layout_marginStart="20dp" />

        <include
            android:id="@+id/groups_match_t2"
            layout="@layout/team_no_buttons"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </LinearLayout>
</android.support.v7.widget.CardView>
</RelativeLayout>

team_no_button.xml：

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/match_team_name_for_groups"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal" />

matches_rounds_items.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content">

<android.support.v7.widget.CardView
    android:id="@+id/mathes_card"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="3dp"
    card_view:cardCornerRadius="4dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <TextView
                android:id="@+id/round_card_title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:layout_marginTop="5dp"
                android:textColor="@color/red"
                android:textSize="18sp" />

            <TextView
                android:id="@+id/round_match_number"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:layout_marginTop="5dp"
                android:textColor="@color/red"
                android:textSize="18sp" />

            <TextView
                android:id="@+id/round_match_date"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center_horizontal"
                android:layout_marginTop="5dp"
                android:text="@string/select_winner" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginTop="4dp"
            android:baselineAligned="false"
            android:orientation="horizontal">

            <include
                android:id="@+id/round_match_t1"
                layout="@layout/team_no_buttons_shirts"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="20dp"
                android:layout_marginStart="20dp" />

            <TextView
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_gravity="center_vertical"
                android:layout_weight="2"
                android:gravity="center_horizontal"
                android:text="@string/vs" />

            <include
                android:id="@+id/round_match_t2"
                layout="@layout/team_no_buttons_shirts"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="20dp"
                android:layout_marginRight="20dp" />
        </LinearLayout>
    </LinearLayout>
</android.support.v7.widget.CardView>

team_no_buttons_shirts.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">


<TextView
    android:id="@+id/match_team_name"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:textSize="20sp" />

Logcat：

06-26 11:58:13.111 4407-4407/sy.aya.ayaworldcup2018 E/QQ: Groups
06-26 11:58:13.114 4407-4407/sy.aya.ayaworldcup2018 D/AndroidRuntime: Shutting down VM
06-26 11:58:13.128 4407-4407/sy.aya.ayaworldcup2018 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: sy.aya.ayaworldcup2018, PID: 4407
    java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
        at sy.aya.ayaworldcup2018.MatchesAdapter.onBindViewHolder(MatchesAdapter.java:72)
        at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6673)
        at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6714)
        at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5647)
        at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5913)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5752)
        at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5748)
        at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2232)
        at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1559)
        at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1519)
        at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:614)
        at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3812)
        at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3529)
        at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:4082)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:443)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
        at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:761)
        at android.view.View.layout(View.java:19679)
        at android.view.ViewGroup.layout(ViewGroup.java:6075)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2511)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2227)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1407)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6783)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
        at android.view.Choreographer.doCallbacks(Choreographer.java:723)
        at android.view.Choreographer.doFrame(Choreographer.java:658)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6499)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:440)
06-26 11:58:13.129 4407-4407/sy.aya.ayaworldcup2018 E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
        at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:108)

【问题讨论】：

请分享完整的堆栈跟踪
感谢您的回复我试过这个 :stackoverflow.com/a/7841448/7592874 但我得到了同样的错误我应该做些什么吗？
如果您使用 android studio 堆栈跟踪，任何错误都应该默认在 logcat 中
@EmptyBrain 将 logcat 添加到代码中，谢谢。
为了更好的性能，请创建一个全局变量private String[] array;并在构造函数array = context.getResources().getStringArray(R.array.times);中初始化它

标签： android android-recyclerview

【解决方案1】：

您正在使用包含语句 groups_match_t1 或 groups_match_t2 中的 id 覆盖布局 id match_team_name_for_groups（不确定是哪一个），因此当您执行 findViewById() 时，您看不到的 id 是在包含的文件中，但来自包含语句本身的文件。

来自documentation：

您还可以通过在标签中指定它们来覆盖包含布局的根视图的所有布局参数（任何 android:layout_* 属性）。

【讨论】：

抱歉，问题出在两个文本视图上，并且在第二个布局中工作
你的应用程序在位置 0 崩溃了，你怎么知道它在第二个布局中工作？
好的，分享你的matches_rounds_item.xml代码，让我们看看区别
@HongDuan 完成。
还有team_no_buttons_shirts.xml?

【解决方案2】：

正如@Cheticamp所说，你在<include />标签中指定的id（groups_match_t1）会覆盖team_no_buttons.xml中的id（match_team_name_for_groups），所以你只能找到id为groups_match_t1的视图，所以这一行：

fTeamView = itemView.findViewById(R.id.groups_match_t1);

会找到一个视图，其实就是TextView本身，那么：

fTeamName = fTeamView.findViewById(R.id.match_team_name_for_groups);

将返回null，因为fTeamView 内没有TextView。所以你可以使用：

fTeamName = itemView.findViewById(R.id.groups_match_t1);

获取TextView，然后删除fTeamView。

而且因为team_no_buttons_shirts.xml 有一个额外的LinearLayout，id match_team_name 不会被覆盖，所以：

fTeamView = itemView.findViewById(R.id.round_match_t1);

将返回LinearLayout，并且

fTeamName = fTeamView.findViewById(R.id.match_team_name);

将找到正确的TextView，它是LinearLayout 的子代。

另外，Tor Norbye wrote:

<include> 标签不是真正的视图，所以 findByView 不会找到它。 @id 属性（以及您在包含标签上设置的任何其他属性）改为应用于包含布局的根标签。所以你的 activity.getView(R.id.included1) 实际上应该是 <TextView> 本身。

【讨论】：

感谢您的回答，但您让我感到困惑。我应该怎么做才能解决这个错误？
在你的第一个布局中，fTeamView 没用，使用fTeamName = itemView.findViewById(R.id.groups_match_t1); 就足够了。