Obtain android attr in custom view

Question

I have a custom view which extends RelativeLayout. I have some custom attrs in attrs.xml. Is there a way to obtain common android attrs like android:clickable like we do with custom attributes?

class MyView(context: Context, attributeSet: AttributeSet?): RelativeLayout(context, attributeSet) {
  init {
      val attrs = context.obtainStyledAttributes(attributeSet, R.styleable.MyView)
    
      if (attrs.getBoolean(android.R.attr.clickable, true)) {
          ...
      }
    
      attrs.recycle()
  }

}

This compiler accepts, but it crashed on runtime. Anyone have come across similar use case? I would like to avoid creating duplicate attrs for custom view which are already defined in SDK.

By extending `RelativeLayout` the custom view inherits its attributes. You usually don't need to "touch" them unless your intention is to change the parent's behaviour which, actually, might be confusing/unpredictable for a user/developer. — Onik, Oct 27 '20 at 09:15

score 0 · Answer 1 · answered Oct 27 '20 at 12:42

More or less, the answer was in front of me the whole time. One thing that I had to understand, that when you create a stylable its basically an IntArray. Now when you obtain attributes and pass yout stylable reference, it maps attributes bassed on its definition. So in order to obtain other attributes, which are not declared in your local attrs, like those android: which are in the SDK, you need to pass those references in as an IntArray:

class MyView(context: Context, attributeSet: AttributeSet?): RelativeLayout(context, attributeSet) {
    init {
        val attrs = context.obtainStyledAttributes(attributeSet, intArrayOf(android.R.attr.clickable))

        if (attrs.getBoolean(0, true)) {
            ...
        }

        attrs.recycle()
    }
}

score -1 · Answer 2 · answered Oct 27 '20 at 09:56

-1

Yeah, probably this one should work

at attrs.xml you should declare smth like that

    <declare-styleable name="MyCustomView">
        <attr name="android:clickable" />
    </declare-styleable>

And at your MyCustomView class you should obtain desired properties from typed array like:

val clickable = typedArray.getBoolean(R.styleable.MyCustomView_android_clickable, false)

answered Oct 27 '20 at 09:56

Alexander Dadukin

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I know this. I want to avoid this if there is already a an attribute of this kind in SDK. – parohy Oct 27 '20 at 12:25
Why do you want to avoid it? – Alexander Dadukin Oct 27 '20 at 13:03
Because I don't want to have duplicate attribute names. This could confuse in future why having `android:clickable` and `app:clickable` if both represent the same exact expected behaviour. – parohy Oct 27 '20 at 13:07
this one method will allow you to intercept `android:clickable` as you declare ``. Please, read it carefully – Alexander Dadukin Oct 27 '20 at 13:08
You should only to declare `android:clickable` at your view – Alexander Dadukin Oct 27 '20 at 13:10
@parohy, do you have a chance to try it? – Alexander Dadukin Oct 27 '20 at 13:21

Obtain android attr in custom view

2 Answers2