Android 使用 RecyclerView 时出错：指定的子项已经有父项

Error using the RecyclerView: The specified child already has a parent

提问by Zain Zafar

I am trying to create a listView with a new RecyvlerView Adapter. I have followed the exact guide present on android developer resources. But this is giving me a strange error: The specified child already has a parent. You must call removeView() on the child's parent first.I have the latest SDK. I also define dependencies in gradle.

我正在尝试使用新的 RecyvlerView 适配器创建一个 listView。我遵循了 android 开发人员资源上的确切指南。但这给了我一个奇怪的错误：指定的孩子已经有一个父母。您必须首先在孩子的父级上调用 removeView()。我有最新的 SDK。我还在 gradle 中定义了依赖项。

MyActivity(Main Activity):

我的活动（主要活动）：

public class MyActivity extends Activity {

    private RecyclerView mRecyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        mRecyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());

        // specify an adapter (see also next example)
        mAdapter = new MyAdapter(new String[]{"Zain", "Nadeem"});

        mRecyclerView.setAdapter(mAdapter);
    }
}

MyAdapter :

我的适配器：

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    private String[] mDataset;    
    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(String[] myDataset) {
        mDataset = myDataset;
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        // create a new view
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());  

        View v = inflater.inflate(R.layout.my_text_view, parent, true);
        ViewHolder vh = new ViewHolder(v);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element    
        holder.mTextView.setText(mDataset[position]);
    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataset.length;
    }

    public static class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        public TextView mTextView;
        public ViewHolder(View v) {
            super(v);
            mTextView = (TextView) v.findViewById(R.id.item_title);
        }
    }
}

my_text_view.xml (layout for list items):

my_text_view.xml（列表项的布局）：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="80dp"

    >
    <!-- title -->
    <TextView
        android:id="@+id/item_title"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="@android:color/darker_gray"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        android:textSize="22dp" />

</RelativeLayout>

activity_my.xml (main activity):

activity_my.xml（主要活动）：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_height="fill_parent"
    android:layout_width="fill_parent"
    android:background="@android:color/holo_orange_light"
    >
    <!-- A CardView that contains a TextView -->
    <android.support.v7.widget.RecyclerView
        android:id="@+id/my_recycler_view"
        android:scrollbars="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MyActivity"/>
    </LinearLayout>

And here is the logcat output:

这是 logcat 输出：

10-28 01:20:30.287  22729-22729/osman.zaingz.com.lollipop E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: osman.zaingz.com.lollipop, PID: 22729
    java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
            at android.view.ViewGroup.addViewInner(ViewGroup.java:3562)
            at android.view.ViewGroup.addView(ViewGroup.java:3415)
            at android.view.ViewGroup.addView(ViewGroup.java:3360)
            at android.support.v7.widget.RecyclerView.addView(RecyclerView.java:322)
            at android.support.v7.widget.ChildHelper.addView(ChildHelper.java:79)
            at android.support.v7.widget.RecyclerView$LayoutManager.addViewInt(RecyclerView.java:4845)
            at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:4803)
            at android.support.v7.widget.RecyclerView$LayoutManager.addView(RecyclerView.java:4791)
            at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1316)
            at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1265)
            at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:522)
            at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:1918)
            at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:2155)
            at android.view.View.layout(View.java:14817)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
            at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1660)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1436)
            at android.view.View.layout(View.java:14817)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
            at android.view.View.layout(View.java:14817)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:374)
            at android.view.View.layout(View.java:14817)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
            at android.view.View.layout(View.java:14817)
            at android.view.ViewGroup.layout(ViewGroup.java:4631)
            at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1983)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1740)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
            at android.view.Choreographer.doCallbacks(Choreographer.java:574)
            at android.view.Choreographer.doFrame(Choreographer.java:544)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invoke(Native Method)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)

回答by EC84B4

when inflating you shouldn't attach the view to its parent. you wrote:

膨胀时，您不应将视图附加到其父级。你写了：

View v = inflater.inflate(R.layout.my_text_view, parent, true);

which should be :

这应该是：

View v = inflater.inflate(R.layout.my_text_view, parent, false);

回答by Magadan Artem

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="80dp">

<TextView
    android:id="@+id/item_title"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:textColor="@android:color/darker_gray"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:textSize="22dp" />

</RelativeLayout>

RelativeLayout this is parent of your TextView with id item_title. Then when RecyclerView is trying to add TextView that has parent it throw exception.

RelativeLayout 这是您的 TextView 的父级 id item_title。然后当 RecyclerView 尝试添加具有父级的 TextView 时，它会抛出异常。

Try this code:

试试这个代码：

public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
                                                   int viewType) {
        // create a new view
        Log.d(TAG, "onCreateViewHolder");
        RelativeLayout v = (RelativeLayout)LayoutInflater.from(parent.getContext())
                .inflate(R.layout.list_item, parent, false);
        // set the view's size, margins, paddings and layout parameters
        View view = v.findViewById(R.id.text1);
        v.removeView(view);
        ViewHolder vh = new ViewHolder(view);
        return vh;
    }

回答by Victor

It happens too if you scroll really fast your recyclerview. My case was inserting/moving/... items with DiffUtils and calling TransitionManager.beginDelayedTransition(view)on the root layout (and so, the recyclerview) somewhere in my code before the end of recyclerview animations

如果您真的快速滚动您的回收站视图，也会发生这种情况。我的情况是使用 DiffUtils 插入/移动/...项目并TransitionManager.beginDelayedTransition(view)在 recyclerview 动画结束之前调用 我代码中某处的根布局（因此，recyclerview）

回答by Denis

Maybe it's a little bit late, but I had the same problem (recyclerview-v7:26.1.0) and the reason was that I tried to scroll (by scrollToPosition() method) the list in a position that was currently visible. After I added a check of position before scrolling (scroll only in the invisible position) the issue was resolved

也许有点晚了，但我遇到了同样的问题 (recyclerview-v7:26.1.0)，原因是我试图在当前可见的位置滚动（通过 scrollToPosition() 方法）列表。在滚动之前添加位置检查（仅在不可见位置滚动）后，问题已解决

回答by Shivam Yadav

I solved it by removing `TransitionManager.beginDelayedTransition();

我通过删除 `TransitionManager.beginDelayedTransition(); 解决了这个问题。

回答by mochadwi

For those wondering how to implement custom Transitions& excludeChildrenmethod. Here's my approach looks like so far.

对于那些想知道如何实现自定义Transitions和excludeChildren方法的人。到目前为止，这是我的方法。

In Kotlin: TransitionHelpers.kt

在 Kotlin 中：TransitionHelpers.kt

// single child
private fun useAutoTransition(childView: View, 
                               excludeChildView: Boolean = true
) = AutoTransition().apply {
    excludeChildren(childView, excludeChildView)
    // apply any other method you need here
}

private fun useAutoTransition(@IdRes childViewId: Int, 
                               excludeChildView: Boolean = true
) = AutoTransition().apply {
    excludeChildren(childViewId, excludeChildView)
    // apply any other method you need here
}

// multiple child
fun useAutoTransitions(excludeChildView: Boolean, @IdRes vararg childViewIds: Int) {
        val auto = AutoTransition();

        for (id in childViewIds) {
           auto.excludeChildren(id, excludeChildView)
        }

        return auto;
    }

fun useAutoTransitions(excludeChildView: Boolean, vararg childViews: View) {
        val auto = AutoTransition();

        for (view in childViews) {
           auto.excludeChildren(view, excludeChildView)
        }

        return auto;
    }

In Java: TransitionHelpers.java

在 Java 中：TransitionHelpers.java

I'm using android-retrostreamto support Android API below 24, and still using Java 8 lambda & java.util.* -> java9.util.*

我正在使用android-retrostream来支持低于 24 的 Android API，并且仍在使用 Java 8 lambda &java.util.* -> java9.util.*

import java9.util.stream.Stream;

    public static AutoTransition useAutoTransition(View childView, boolean excludeChildView) {
        AutoTransition auto = new AutoTransition();
        auto.excludeChildren(childView, excludeChildView);

        return auto;
    }

    public static AutoTransition useAutoTransition(@IdRes int childViewId, boolean excludeChildView) {
        AutoTransition auto = new AutoTransition();
        auto.excludeChildren(childViewId, excludeChildView);

        return auto;
    }

    public static AutoTransition useAutoTransitions(final boolean excludeChildView, @IdRes Integer... childViewIds) {
        final AutoTransition auto = new AutoTransition();

        Stream<Integer> ids = Stream.of(childViewIds);
        ids.forEach(id -> auto.excludeChildren(id, excludeChildView));

        return auto;
    }

    public static AutoTransition useAutoTransitions(final boolean excludeChildView, View... childViews) {
        final AutoTransition auto = new AutoTransition();

        Stream<View> views = Stream.of(childViews);
        views.forEach(view -> auto.excludeChildren(view, excludeChildView));

        return auto;
    }

ThatFragment.kt

那个片段.kt

// I'm using KTX Syntethic here
import kotlinx.android.synthetic.main.activity_transitions.layoutParent
import kotlinx.android.synthetic.main.activity_transitions.recyclerViewChild

// Let's implemented it on TransitionManager
override protected fun onCreate(savedInstanceState: Bundle) {
  // single RecyclerView child using View class
  TransitionManager.beginDelayedTransition(layoutParent, useAutoTransition(recyclerViewChild, true))

  // single RecyclerView child using @IdRes
  TransitionManager.beginDelayedTransition(layoutParent, useAutoTransition(R.id.rv_1, true))

  // multiple RecyclerView child                         
  TransitionManager.beginDelayedTransition(layoutParent, useAutoTransitions(true, R.id.rv_child_1, R.id.rv_child_2, R.id.rv_child_n))
}

Hopefully, it's easy to understand!

希望它很容易理解！

Thanks for:

感谢：

• @victor Transitionsproblems when scrolling too fast
• @westy92 Providing the workaround & implement customTransitions

• @victor滚动太快Transitions时出现问题
• @westy92 提供解决方法并实现自定义Transitions

References:

参考：

• Animate all the things (Transitions)
• Implementing excludeChildrensee here
• Beautiful animation with ConstraintLayout & TransitionManager

• 动画所有的东西（过渡）
• 实施excludeChildren见这里
• 使用 ConstraintLayout和 TransitionManager制作精美的动画