java 在 RecyclerView 中设置 CardView 的背景图片会导致程序在滚动时崩溃
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原文地址: http://stackoverflow.com/questions/29924560/
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StackOverFlow
Setting the background image of a CardView inside RecyclerView causes the program to crash when scrolling
提问by ooxxoo
I have a RecyclerView containing a list of CardViews with information that is pulled from a server, some cards have only a background color but some contains a background image. If the cards all have just background colors, the RecyclerView behaves accordingly (I am able to set the margins and corner radius as well). However, if any one card contains a background image, a crash will happen when I try to scroll up/down the list (although the background image will load without the previously set corner radius).
我有一个 RecyclerView 包含一个 CardViews 列表，其中包含从服务器中提取的信息，有些卡片只有背景颜色，但有些卡片包含背景图像。如果卡片都只有背景颜色，则 RecyclerView 会相应地运行（我也可以设置边距和角半径）。但是，如果任何一张卡片包含背景图像，当我尝试向上/向下滚动列表时会发生崩溃（尽管背景图像将在没有先前设置的角半径的情况下加载）。
Here is the crash log:
这是崩溃日志：
java.lang.ClassCastException: android.graphics.drawable.BitmapDrawable cannot be cast to android.support.v7.widget.RoundRectDrawable
at android.support.v7.widget.CardViewApi21.setBackgroundColor(CardViewApi21.java:107)
at android.support.v7.widget.CardView.setCardBackgroundColor(CardView.java:234)
at co.roverlabs.sdk.ui.CardListAdapter.onBindViewHolder(CardListAdapter.java:88)
at co.roverlabs.sdk.ui.CardListAdapter.onBindViewHolder(CardListAdapter.java:28)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:4402)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:3717)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:3609)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1859)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1311)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1274)
at android.support.v7.widget.LinearLayoutManager.scrollBy(LinearLayoutManager.java:1102)
at android.support.v7.widget.LinearLayoutManager.scrollVerticallyBy(LinearLayoutManager.java:959)
at android.support.v7.widget.RecyclerView$ViewFlinger.run(RecyclerView.java:3062)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:549)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Here is my onBindViewHolder() method (simplified with hard coded values for easier reading):
这是我的 onBindViewHolder() 方法（用硬编码值简化以便于阅读）：
public void onBindViewHolder(final CardViewHolder holder, int position) {
//Set margins
CardView.LayoutParams cardLayoutParams = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, 2000);
cardLayoutParams.setMargins(20, 20, 20, 20);
holder.cardView.setLayoutParams(cardLayoutParams);
//Set background color or image
if(view.hasBackgroundImage()) {
holder.cardView.setBackground(R.drawable.background);
}
else {
holder.cardView.setCardBackgroundColor(Color.CYAN);
}
//Set border radius
holder.cardView.setRadius(20);
//Set elevation
holder.cardView.setCardElevation(0);
Here is my onCreateViewHolder() method and custom Recycler.ViewHolder method:
这是我的 onCreateViewHolder() 方法和自定义 Recycler.ViewHolder 方法：
public CardViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_view, parent, false);
return new CardViewHolder(itemView);
}
public class CardViewHolder extends RecyclerView.ViewHolder {
protected CardView cardView;
public CardViewHolder(View view) {
super(view);
cardView = (CardView)view.findViewById(R.id.single_card_view);
}
}
And finally, here is my XML file for the CardView:
最后，这是我用于 CardView 的 XML 文件：
<android.support.v7.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/single_card_view"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<RelativeLayout
android:id="@+id/single_card_view_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
</RelativeLayout>
</android.support.v7.widget.CardView>
I just wish to know how to set the background of a CardView to a custom image instead of just a color, and if there are any workarounds. It is important for me to be able to set the corner radius of the cards. Thank you!
我只想知道如何将 CardView 的背景设置为自定义图像而不仅仅是颜色，以及是否有任何解决方法。能够设置卡片的角半径对我来说很重要。谢谢！
回答by yigit
Assuming you are using CardView, you cannotchange background drawable because CardView uses background drawable to draw the card. You can change card background color via setCardBackgroundColor.
假设您使用的是 CardView，则无法更改可绘制背景，因为 CardView 使用可绘制背景来绘制卡片。您可以通过setCardBackgroundColor更改卡片背景颜色。
