How to pass custom attributes to nested xml

Question

I have structure like that:

preferences.xml:

... <com.example.MyCustomPreference ... myCustomMessage="@string/abc" android:inputType="..." ... /> ...

preference_my_custom.xml:

<LinearLayout ...> <com.example.MyCustomView ... app:myCustomMessage="?????" ... /> </LinearLayout>

view_my_custom.xml:

<GridView ...> ...EditTexts, TextViews, etc. </GridView>

I would like to pass myCustomMessage's value (I omitted other attributes for simplification) from MyCustomPreference to MyCustomView using XML. MyCustomView reads custom attributes, so I would like to avoid reading attributes in MyCustomPreference programmatically, getting TextViews from MyCustomView and setting them values. However, I really don't know what to type in place of "?????".

How can i do this using XML? Is this possible?

I've seen it. I think my question is slightly different. I don't use <include>, and I don't want to use a reference to a resource, but a value which has already passed as an attribute. — Anad
– Anad, Commented May 29, 2018 at 12:27
Your question is slightly different but as far as I can tell the solution is the same (Data Binding) — Sir Codesalot
– Sir Codesalot, Commented May 29, 2018 at 12:37

Marc Estrada · Accepted Answer · 2018-05-29 12:16:19Z

You have to do it programmatically (unless you use data binding). For example, in your MyCustomPreference you catch de attribute myCustomMessage:

String myCustomMessage = null; TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.MyCustomPreference, 0, 0); try { myCustomMessage = a.getString(R.styleable.MyCustomPreference_myCustomMessage); } finally { a.recycle(); }

Here you got the String value of your attribute. Then, I supose you have inflated your MyCustomView inside your MyCustomPreference. As an example:

View.inflate(getContext(), R.layout.preference_my_custom, this); MyCustomView myCustomView = (MyCustomView) findViewById(R.id.you_custom_view_id);

So, here you can set programmatically your myCustomMessage in your MyCustomView.

myCustomView.setMyCustomMessage(myCustomMessage);

You should create this method to set correctly your text, and if necessary propagate this text to other child views of your MyCustomView.

Now, changing your String resId in your preferences.xml the interface should update as expected.

P.S: Since I don't know all your resource ids, please adapt them to your project.

Thank you for your answer and accurate explanation. Maybe there is no way to do it as simply as I expected, but this solution works perfectly and you have also mentioned data binding, so I can accept your answer.

Harsh Mittal · Accepted Answer · 2018-05-29 13:01:57Z

Create an attribute file for your customeView:

Add in attrs.xml

<declare-styleable name="CustomView"> <attr name="width" format="dimension" /> </declare-styleable>

Used in your customView init:

 public CustomView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomView, defStyle, 0); mWidth = a.getDimensionPixelSize(R.styleable.CustomView_width,0); a.recycle(); }

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