Cardview角落背景不透明 [英] Cardview corner background not transparent

问题描述

我有一个CardView支持小部件的自定义实现，但是当我将其包含在布局文件中时，似乎无法使角的背景透明.但是，如果我只是将CardView支持小部件放在布局文件中，则它会突然起作用.如何使自定义组件的角部透明?

I have a custom implementation of a CardView support widget but I can't seem to get the background for the corners transparent when I include it in my layout-file. However, if I simply place the CardView support widget in my layout-file it suddenly works. How can I get the corners transparent for my custom component?

这是CardView的自定义实现的布局文件:

This is the layout file for my custom implementation of the CardView:

view_card.xml

view_card.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/view_card"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    style="@style/Custom.Widget.CardView">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="@dimen/default_padding">

    <TextView
        android:id="@+id/view_mainText"
        style="@style/Custom.Widget.TextView.Header"
        android:textColor="@color/instruction_balloon_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/view_subText"
        android:textSize="@dimen/text_size_medium"
        android:textColor="@color/instruction_balloon_text"
        android:singleLine="false"
        android:text="Please remove white corners :-("
        android:textIsSelectable="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

styles.xml

styles.xml

<style name="Custom.Widget.CardView" parent="CardView">
    <item name="cardBackgroundColor">@color/card_backgroundColor</item>
    <item name="cardCornerRadius">12dp</item>
</style>

这是我的布局文件，其中包括两个CardView.第一个具有白色角，第二个与view_card.xml基本上具有相同的布局，但没有白色角(透明).

And this is my layout file that includes the two CardViews. The first one with the white corners and the second one that's basically the same layout as view_card.xml but without the white corners (transparent).

example.xml

example.xml

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

    <some.private.namespace.CardView
        android:id="@+id/custom_card_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/default_margin" />

    <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/view_card"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/default_margin"
        style="@style/Custom.Widget.CardView">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:padding="@dimen/default_padding">

            <TextView
                android:id="@+id/view_mainText"
                style="@style/Custom.Widget.TextView.Header"
                android:textColor="@color/instruction_balloon_text"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />

            <TextView
                android:id="@+id/view_subText"
                android:textSize="@dimen/text_size_medium"
                android:textColor="@color/instruction_balloon_text"
                android:singleLine="false"
                android:text="I have no white corners :-)"
                android:textIsSelectable="true"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>
    </android.support.v7.widget.CardView>
    ... some other views
</LinearLayout>

更新1

我尝试了Just89的解决方案，但是在较低的Android版本上导致崩溃.

I tried Just89's solution, however it results in a crash on lower Android versions.

 android.graphics.drawable.ColorDrawable cannot be cast to android.support.v7.widget.RoundRectDrawableWithShadow

快速搜索后，我发现了以下信息. android.graphics.drawable.ColorDrawable无法投射到android.support.v7.widget.RoundRectDrawableWithShadow

After a quick search I found the following post. android.graphics.drawable.ColorDrawable cannot be cast to android.support.v7.widget.RoundRectDrawableWithShadow

答案建议使用以下方法设置背景颜色:setCardBackgroundColor. 但是，这将带回白角.

The answer suggests to set the background color using:setCardBackgroundColor. However this will bring back the white corners.

更新2

可接受的答案将解决此问题，但这不是首选的解决方案.创建导致这些白角的自定义CardView组件时，我犯了一个错误.检查此答案，看看我做错了什么.

The accepted answer will solve this problem, however it's not the preferred solution. I made a mistake when creating the custom CardView component that was causing these white corners. Check this answer to see what I did wrong.

推荐答案

在自定义实现中的可用上下文上使用以下代码:

Use the following code, on a place where the context is available, in your custom implementation:

setBackgroundColor(ContextCompat.getColor(context, android.R.color.transparent));

对于低于Lollipop的android版本，请使用以下代码，以避免上述崩溃.

Use the following code for android versions lower than Lollipop to avoid the mentioned crash.

  if (android.os.Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP){
     getBackground().setAlpha(0);
  } else {
     setBackgroundColor(ContextCompat.getColor(context, android.R.color.transparent);
  }

这篇关于Cardview角落背景不透明的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！