Custom attributes in Android fragments

Question

I'd like to define custom attributes in Android fragment using XML (without using bundle additional parameters) like declare-styleable in custom controls. But there are no constructors with AttrSet parameters, so is it possible? Can i just override public void onInflate(android.app.Activity activity, android.util.AttributeSet attrs, android.os.Bundle savedInstanceState) in order to get attributes support?

Solution 1

The Link for Support4Demos is changed or can be changed so posting the complete solution. Here it goes.

1. Create attrs.xml file in res/values folder. Or add the below content if file already exists.

   <?xml version="1.0" encoding="utf-8"?>
   <resources>
   <declare-styleable name="MyFragment">
       <attr name="my_string" format="string"/>
       <attr name="my_integer" format="integer"/>
   </declare-styleable> 
   

2. Override the onInflate delegate of fragment and read attributes in it

   /**
    * Parse attributes during inflation from a view hierarchy into the
    * arguments we handle.
    */
   @Override
   public void onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState) {
       super.onInflate(activity, attrs, savedInstanceState);
       Log.v(TAG,"onInflate called");
   
       TypedArray a = activity.obtainStyledAttributes(attrs,R.styleable.MyFragment);
   
       CharSequence myString = a.getText(R.styleable.MyFragment_my_string);
       if(myString != null) {
           Log.v(TAG, "My String Received : " + myString.toString());
       }
   
       int myInteger = a.getInt(R.styleable.AdFragment_my_integer, -1);
       if(myInteger != -1) {
           Log.v(TAG,"My Integer Received :" + myInteger);
       }
   
       a.recycle();
   }
   

3. Pass these attributes in your layout file as following. Just an example

   <?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto"
       android:layout_width="match_parent"
       android:layout_height="match_parent" >
   
       <TextView
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:text="This is android activity" />
   
       <fragment
           android:id="@+id/ad_fragment"
           android:name="com.yourapp.packagename.MyFragment"
           android:layout_width="fill_parent"
           android:layout_height="50dp"
           android:layout_alignParentBottom="true"
           app:my_string="Hello This is HardCoded String. Don't use me"
           app:my_integer="30" />
   
   </RelativeLayout>
   

Thats all. Its a working solution.

While doing this if you see any namespace error in xml. try project cleaning again and again. This is pathetic but eclipse and adt misbehaves sometimes.

Hope it helps others :)

Cheers

Solution 2

@Override
public void onInflate(Activity activity, AttributeSet attrs, Bundle savedInstanceState) {
    super.onInflate(activity, attrs, savedInstanceState); 
    // Your code here to process the attributes
}

Comments

[tdevaux]

Works, but make sure to clear Lint markers (Android Tools > Clear Lint Markers). I spent 10mn trying to figure out why it was not building!

[dhaag23]

Thanks tdevaux, I only spent 5 minutes before re-reading this. I have 5 more minutes available in my life!

[Pocha]

My Android Studio kept showing the custom attributes in XML with red underline indicating there is an error, but the whole project built just fine. FYI for someone who might think that they aint doing it right looking at those error in their layout file.

[Helin Wang]

you can use http://schemas.android.com/apk/res-auto instead of xmlns:app="schemas.android.com/apk/res/com.yourapp.packagena‌​me" to auto-substitute package name. stackoverflow.com/questions/10448006/…

[TacB0sS]

OK I've missed that one before. If you, like me, copy pasted this from a couple of places, pay attention and make sure the namespaces match, e.g. xmlns:${NameSpace} and same in the attribute ${NameSpace}:attribute="..."

[Vitalii]

Android Studio shows that onInflate(Activity activity ... is deprecated. You can use new handler like this (Kotlin): override fun onInflate(context: Context?, attrs: AttributeSet?, savedInstanceState: Bundle?) { super.onInflate(context, attrs, savedInstanceState) val styledAttributes = context?.obtainStyledAttributes(attrs, R.styleable.MyFragment_my_string) val text = styledAttributes?.getText(R.styleable.MyFragment_my_string) styledAttributes?.recycle() }