Unnecessary padding in CardView?

问题

I have implemented CardView in my app and everything works fine except there is a little padding around the image if I put radius to the card.

It appears like this:

But in android docs and in this article the image takes the entire cardview, so can u help me achieve that.

My layout file is like:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="match_parent"
          android:orientation="vertical"
          android:padding="8dp">

<android.support.v7.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="200dp"
    card_view:cardBackgroundColor="@android:color/white"
    card_view:cardCornerRadius="4dp">

    <ImageView
        android:id="@+id/media_image_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"/>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            android:alpha="0.8"
            android:background="?attr/colorPrimary"
            android:padding="4dp">

            <TextView
                android:id="@+id/media_download"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentRight="true"
                android:textSize="11sp"/>

            <TextView
                android:id="@+id/category_name"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:textColor="@color/primary_text"
                android:textSize="12sp"/>

        </RelativeLayout>

</android.support.v7.widget.CardView>

</LinearLayout>

NOTE: The screenshot is captured on a pre-lollipop device.

回答1:

I went through the developer docs again and found that:

On API 20 and before, CardView does not clip the bounds of the Card for the rounded corners. Instead, it adds padding to content so that it won't overlap with the rounded corners.

So for pre-lollipop devices I have to call setPreventCornerOverlap (false); on the cardview.

Update: The same can be done through xml code by adding app:cardPreventCornerOverlap="false" in card view.

回答2:

Setting app:cardPreventCornerOverlap="false" will resolve the problem but also remove corner all pre-lollipop devices. If you want round corner on all devices, add it manually:

card_view_round_corner_background.xml

    <?xml version="1.0" encoding="utf-8"?>      
    <layer-list xmlns:android="http://schemas.android.com/apk/res/android">        
    <item>      
    <shape android:shape="rectangle">                
        <solid android:color="@color/transparent"/>                
        <stroke  android:width="2dp" android:color="@color/Black"/>
        </shape>
        </item>
        <item>            
    <shape android:shape="rectangle">
    <solid android:color="@color/transparent"/>             
    <corners android:radius="6dp"/>              
     <stroke  android:width="2dp" android:color="@color/Black"/>           
     </shape>
    </item>
    </layer-list>

In cardview

    <android.support.v7.widget.CardView android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:focusable="true"
    android:clickable="true"
    android:foreground="?android:attr/selectableItemBackground"card_view:cardCornerRadius="@dimen/conner_radius"
    card_view:cardBackgroundColor="@color/Black"
    card_view:cardElevation="@dimen/z_card">

    <!-- Put your card contain here -->  

    <View
    android:background="@drawable/card_view_round_corner_border"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    />

But this solution only works on solid background such as black or white.

回答3:

Just use FrameLayout instead of LinearLayout, it works

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="-4dp">

    <android.support.v7.widget.CardView
        android:id="@+id/card_view"
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:layout_width="fill_parent"
        android:layout_height="100dp"
        android:layout_gravity="center"
        android:layout_margin="5dp"
        card_view:cardCornerRadius="4dp"
        card_view:cardPreventCornerOverlap="false"
        card_view:cardUseCompatPadding="true"

        >

        <FrameLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal"
            >

            <ImageView
                android:id="@+id/imageView"
                android:tag="image_tag"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_margin="5dp"
                android:layout_weight="1"
                android:src="@drawable/ic_launcher"/>

            <LinearLayout
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginTop="5dp"
                android:layout_weight="2"
                android:orientation="vertical"
                >

                <TextView
                    android:id="@+id/textViewName"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:layout_marginTop="5dp"
                    android:text="Android Name"
                    android:textAppearance="?android:attr/textAppearanceLarge"/>

                <TextView
                    android:id="@+id/textViewVersion"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center_horizontal"
                    android:layout_marginTop="5dp"

                    android:text="Android Version"
                    android:textAppearance="?android:attr/textAppearanceMedium"/>

            </LinearLayout>
        </FrameLayout>

    </android.support.v7.widget.CardView>

</FrameLayout>

来源：https://stackoverflow.com/questions/27668635/unnecessary-padding-in-cardview