android - 为什么不显示位于回收者视图顶部的图像视图？(Why image view located on top of recycler view is not displaying?)

Question

I am trying to add an image view as a banner on top of recycler view.

(我正在尝试将图像视图添加为回收者视图顶部的横幅。)

so in some condition I can hide (View.GONE) or to show that banner image view (View.VISIBLE).

(因此在某些情况下，我可以隐藏（View.GONE）或显示该横幅图像视图（View.VISIBLE）。)

but the problem is, the banner image view will never show when I run the app, even though I have set android:visibility="visible" on the image view xml.

(但是问题是，即使我在图像视图xml上设置了android:visibility="visible" ，横幅图像视图也永远不会在我运行应用程序时显示。)

as you can see, I have image view with red background, but that red background image view will not displaying

(如您所见，我的图像视图带有红色背景，但是红色背景图像视图不会显示)

how to solve this ?

(如何解决呢？)

the layout in my fragment is like this

(我片段中的布局是这样的)

and here is the xml:

(这是xml：)

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
                                                   xmlns:tools="http://schemas.android.com/tools"
                                                   android:layout_width="match_parent"
                                                   android:layout_height="match_parent"
                                                   xmlns:app="http://schemas.android.com/apk/res-auto"
                                                   tools:context=".Fragments.Search.SearchKeywordResultFragment"
                                                   android:id="@+id/constraintLayout_search_keyword_fragment">


    <androidx.recyclerview.widget.RecyclerView
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:scrollbars="vertical"
            tools:listitem="@layout/item_general_event"
            android:id="@+id/recyclerView_keyword_search_result"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintTop_toTopOf="parent" app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"/>

    <ImageView
            android:id="@+id/imageView_banner_search_keyword"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:background="#E91E63"
            android:visibility="visible"
            app:layout_constraintBottom_toBottomOf="@+id/recyclerView_keyword_search_result"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            tools:src="@tools:sample/avatars[3]" />


</androidx.constraintlayout.widget.ConstraintLayout>

  ask by Alexa289 translate from so

Answer 1

Just change your Recycler's TopToTop constrains to the id of the Image view and change it to TopToBottom.

(只需将Recycler的TopToTop约束更改为Image视图的ID，然后将其更改为TopToBottom。)

For doing so you also need to declare the imageview first so you'll be able to address its Id.

(为此，您还需要先声明imageview，以便能够解决其ID。)

Also give the banner width:match_parent

(还给横幅宽度：match_parent)

<ImageView
        android:id="@+id/imageView_banner_search_keyword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:background="#E91E63"
        android:visibility="visible"
   app:layout_constraintBottom_toBottomOf="@+id/recyclerView_keyword_search_result"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        tools:src="@tools:sample/avatars[3]" />

<androidx.recyclerview.widget.RecyclerView
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:scrollbars="vertical"
        tools:listitem="@layout/item_general_event"
        android:id="@+id/recyclerView_keyword_search_result"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="imageView_banner_search_keyword" app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"/>