I'm trying to include different layouts in my View depending on the parent Theme
.
Following the idea:
attrs.xml
<attr name="themeLayout" format="reference" />
styles.xml
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="themeLayout">@layout/layout_a</item>
</style>
<style name="AppThemeSecond" parent="Theme.AppCompat.Light.DarkActionBar">
<item name="themeLayout">@layout/layout_b</item>
</style>
activity.xml
<RelativeLayout 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"
tools:context=".MainActivity">
<include layout="?attr/themeLayout" />
</RelativeLayout>
When I run the Code above I'll get the following Exception:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.my.package/com.my.package.MainActivity}: android.view.InflateException: You must specifiy a valid layout reference. The layout ID ?attr/themeLayout is not valid.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
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)
Caused by: android.view.InflateException: You must specifiy a valid layout reference. The layout ID ?attr/themeLayout is not valid.
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:866)
What am I doing wrong? Is it possible to do this at all?
Note #1: I set the Theme
of my MainActivity
to android:theme="@style/AppTheme"
Note #2: In the Design-View of the Layout Editor everything works as expected. If I switch the Theme, the include gets updated properly.
See the following Screenshots as well:
Unfortunately this is not possible but I really like the idea. I have tracked the flow of LayoutInflater
and it requieres the layout
attribute to be TypedValue.TYPE_REFERENCE
which means ?attr
is not allowed. They even left a comment in the method to explain.
public int getAttributeResourceValue(int idx, int defaultValue) { int t = nativeGetAttributeDataType(mParseState, idx); // Note: don't attempt to convert any other types, because // we want to count on aapt doing the conversion for us. if (t == TypedValue.TYPE_REFERENCE) { return nativeGetAttributeData(mParseState, idx); } return defaultValue; }
android.content.res.XmlBlock.java:385
Basically you have done nothing wrong -- the inflation in Preview works differently which caused the confusion.
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