Access resource defined in theme and attrs.xml android

Question

I have a scenario in which I want to set a Drawable depending upon the theme defined.

To explain this further, Here is what I have in code:

\res\values\attrs.xml

<resources>     <declare-styleable name="AppTheme">         <attr name="homeIcon" format="reference" />     </declare-styleable> </resources> 

res\values\styles.xml

<resources>     <style name="AppTheme" parent="android:style/Theme">         <item name="attr/homeIcon">@drawable/ic_home</item>     </style> </resources> 

AndroidManifest.xml

    <application android:label="@string/app_name"         android:theme="@style/AppTheme">         <activity android:name=".MainActivity" android:label="@string/app_name">             <intent-filter>                 <action android:name="android.intent.action.MAIN" />                 <category android:name="android.intent.category.LAUNCHER" />             </intent-filter>         </activity>     </application> 

So as you have noticed I am defining a custom attr homeIcon and setting the attribute value in AppTheme.

When I define this attribute in a layout XML and try to access it it works smoothly

<ImageView android:id="@+id/img"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:layout_gravity="center"         android:src="?attr/homeIcon" /> 

and renders the Drawable ic_home in an ImageView.

But I am not able to figure out how to access the Drawable programmatically.

I tried to do this with a work around, by defining a holder LayerList Drawable, which results in resource not found exception:

<?xml version="1.0" encoding="utf-8"?> <layer-list     xmlns:android="http://schemas.android.com/apk/res/android" >     <item         android:drawable="?attr/homeIcon" /> </layer-list> 

Summary I want to access the Drawable defined in a custom defined Theme programmatically.

Answer 1

I think you can get the Drawable with this code:

TypedArray a = getTheme().obtainStyledAttributes(R.style.AppTheme, new int[] {R.attr.homeIcon});      int attributeResourceId = a.getResourceId(0, 0); Drawable drawable = getResources().getDrawable(attributeResourceId); a.recycle(); 

Answer 2

Another possible way to do it:

public static int getResIdFromAttribute(final Activity activity,final int attr) {     if(attr==0)         return 0;     final TypedValue typedvalueattr=new TypedValue();     activity.getTheme().resolveAttribute(attr,typedvalueattr,true);     return typedvalueattr.resourceId; } 

Or in Kotlin:

@JvmStatic fun getResIdFromAttribute(activity: Activity, attr: Int): Int {     if (attr == 0)         return 0     val typedValue = TypedValue()     activity.theme.resolveAttribute(attr, typedValue, true)     return typedValue.resourceId } 

no need to recycle anything here...

usage:

int drawableResId=getResIdFromAttribute(this,R.attr.homeIcon); Drawable drawable = getResources().getDrawable(drawableResId);