Android Data Binding using include tag

Question

Update note:

The above example works properly, because release 1.0-rc4 fixed the issue of needing the unnecessary variable.

Original question:

I do exactly as it is described in the documentation and it does not work:

main.xml:

<layout xmlns:andr...
    <data>
    </data>
       <include layout="@layout/buttons"></include>
....

buttons.xml:

<layout xmlns:andr...>
    <data>
    </data>
    <Button
        android:id="@+id/button"
        ...." />

MyActivity.java:

 ... binding = DataBindingUtil.inflate...
binding.button; ->cannot resolve symbol 'button'

how to get button?

Solution 1

The problem is that the included layout isn't being thought of as a data-bound layout. To make it act as one, you need to pass a variable:

buttons.xml:

<layout xmlns:andr...>
  <data>
    <variable name="foo" type="int"/>
  </data>
  <Button
    android:id="@+id/button"
    ...." />

main.xml:

<layout xmlns:andr...
...
   <include layout="@layout/buttons"
            android:id="@+id/buttons"
            app:foo="@{1}"/>
....

Then you can access buttons indirectly through the buttons field:

MainBinding binding = MainBinding.inflate(getLayoutInflater());
binding.buttons.button

As of 1.0-rc4 (just released), you no longer need the variable. You can simplify it to:

buttons.xml:

<layout xmlns:andr...>
  <Button
    android:id="@+id/button"
    ...." />

main.xml:

<layout xmlns:andr...
...
   <include layout="@layout/buttons"
            android:id="@+id/buttons"/>
....

Solution 2

Easy Complete Example

Just set id to included layout, and use binding.includedLayout.anyView.

This example helps passing a value to <include & accessing included views in code.

Step 1

You have layout_common.xml, want to pass String to included layout.

You will create String variable in layout and refer this String to TextView.

<data>
    // declare fields
    <variable
        name="passedText"
        type="String"/>
</data>

<TextView
    android:id="@+id/textView"
    ...
    android:text="@{passedText}"/> //set field to your view.

Step 2

Include this layout to parent layout. Give an id to included layout, so that we can use that in binding class. Now you can pass String passedText to your <include tag.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <LinearLayout
        ..
        >

        <include
            android:id="@+id/includedLayout"
            layout="@layout/layout_common"
            app:passedText="@{@string/app_name}" // here we pass any String 
            />

    </LinearLayout>
</layout>

• You can use now binding.includedLayout.textView in your class.

• You can pass any variables to included layout like above.

  ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
  binding.includedLayout.textView.setText("text");
  

Note Both layouts (parent & included) should be binding layout, wrapped with <layout

Solution 3

just set an id for your include layout

    <include
        android:id="@+id/layout"
        layout="@layout/buttons" />

then

BUTTONSBINDING binding = yourMainBinding.layout;

BUTTONSBINDING is res/layout/buttons.xml

now :

binding.button.setText("simple_Way");

Solution 4

You can make your bind work on your include just adding a ID to it like so:

<include
            android:id="@+id/loading"
            layout="@layout/loading_layout"
            bind:booleanVisibility="@{viewModel.showLoading}" />

Solution 5

An other interesting thing on this is that you can pas variables to the imported layout from the binder like this:

MainBinding binding = MainBinding.inflate(getLayoutInflater());
binding.buttons.setVariable(BR.varID, variable)

View more solutions

Comments

[Andrew Hossam]

like updated developer.android.com/topic/libraries/data-binding/expressio‌​ns

[George Mount]

1.0-rc4 now fixes the problem of needing the unnecessary variable. You can now use simply: <include layout="@layout/buttons" android:id="@+id/buttons"/>. You still need the id so that it will produce a public field for you so that you can access the Button View.

[Nilzor]

Are anyone else having problems binding click events on the layout though?

[George Mount]

Are you using data binding syntax? android:onClick="@{myObj.clickHandler}"

[Sowmia Sundararajan]

Databinding with include support. developer.android.com/topic/libraries/data-binding/…

[Rishabh876]

Main point to remember here is to get the button reference, you need to do binding.{id of include tag}.button instead of binding.button. Took me a while to figure it out.

[Khemraj Sharma]

@GeorgeMount How to call static method from layout element like android:text="{MyClass.getUser().name}" ?

[George Mount]

You can do that either by importing the class name using the <import type="com.example.MyClass"/> in the data section or by using the fully qualified class name in the expression: android:text="@{com.example.MyClass.user.name}"

[CodingTT]

what if you want to pass in two parameters/

[George Mount]

If you want to pass two parameters, you can just do that. <include layout="..." app:param1="@{1}" app:param2="@{2}"/> where param1 and param2 are variables in your included layout.

[Neon Warge]

Apologies, would you care to type the entire layout? This '...' all over the place is pretty much unreadable. Like I don't understand if I still include <merge> tag?

[Ewan]

@NeonWarge There is a complete example at developer.android.com/topic/libraries/data-binding/…. It adds "Data binding doesn't support include as a direct child of a merge element"

[Daniel Carpio Contreras]

I've got an error message that says: "Only one layout element and one data element are allowed"

[iCantC]

In your answer you handled the setText event programmatically ,Instead of TextView if it would have been a Button , then how would you have handled its click event .I know that programmatically binding.includedLayout.button.setOnClickListener would be the alternative,but what if i want to use onClick attribute in XML itself ?

[Khemraj Sharma]

You can pass OnClickListener to included layout. even you can pass anything in binding. Check this answer, if you need more help, let me know. stackoverflow.com/a/51722829/6891563

[Elliptica]

When I do this, I just get a blank field for passedText. The only difference is I don't include the MainActivity code because I just want to pass the string resource in <include> and leave it like that. Why is it always blank though?

[Martin Rajniak]

@GeorgeMount it doesn't work for me with "app" namespace. It has to be "bind" namespace for it to generate correct code. Like this: bind:foo={something}

[M. Wojcik]

@Elliptica As its databinding, I guess the value for passedText should be an ObservableField or a LiveData, otherwise it will never be actually loaded, right @Khemraj?

[IgorGanapolsky]

This doesn't compile. Error: cannot find symbol

[the_prole]

I had to clean/rebuild because I switched over from findViewById.

[Patrick]

I have this error: attribute foo not found.