168

Anybody could explain the meaning of "android.R.id.content" ?

How is it being used ?

http://developer.android.com does not have any explanation.

public static final int content
Since: API Level 1

Constant Value: 16908290 (0x01020002)

Community
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koayst
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    `android.R.id.content` gives you the root element of a view, without having to know its actual name/type/ID. Check out http://stackoverflow.com/questions/4486034/android-how-to-get-root-view-from-current-activity – Philipp Reichart Oct 15 '11 at 08:46
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    This is useful in fragment transactions like: mFragmentTransaction.add(android.R.id.content, myFragment); – IgorGanapolsky Jan 07 '14 at 18:53
  • @IgorGanapolsky An example app performs this kind of transaction in a conditional:`if(fragmentManager.findFragmentById(android.R.id.content)==null) {fragmentManager.beginTransaction(android.R.id.content, list).add().commit();}` Can you tell which `View`'s root element is this? – Solace Dec 26 '14 at 09:45
  • @Zarah Are you sure your syntax is correct here and compilable? – IgorGanapolsky Dec 26 '14 at 12:57
  • What is the class of the layout associated with `android.R.id.content `? – Sushant Mar 23 '16 at 18:55
  • @Sushant Since it (`android.R.id.content`) gives you the root element as Philipp Reichart points out, without having to know its actual name / **type** / ID, you can either do type checks to find out if it's a `RelativeLayout`, `LinearLayout`, etc. Or you can just cast to `ViewGroup` if you just need the reference to the view. – James B Oct 01 '19 at 15:44

5 Answers5

117

As Philipp Reichart commented:

android.R.id.content gives you the root element of a view, without having to know its actual name/type/ID. Check out Get root view from current activity

In case anyone need, you can get this view with View Binding by using binding.root

Leonardo Sibela
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Gili
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    A practical example of it's use can be found in paragraph 2: http://developer.android.com/guide/topics/ui/actionbar.html#Tabs – OrhanC1 Apr 13 '14 at 18:54
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    "gives you the root element _of a view_, without having to know its actual name/type/ID" How does it know which view is it that we want the root element of. – Solace Jul 06 '15 at 21:28
  • In case anyone need, you can get this view with View Binding by using `binding.root` – Leonardo Sibela Nov 06 '22 at 20:55
28

The android.R.id.content ID value indicates the ViewGroup of the entire content area of an Activity.

It can be used with Fragment:

public class MyActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                .add(android.R.id.content, MyFragment.newInstance())
                .commit();
        }
    }

    ...

}

The code above will insert the View created by Fragment into the ViewGroup identified by android.R.id.content.

DYS
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10

Google designers develop Android UX with specific or recommended design guidelines. The layout android.R.id.content defines a linearlayout with a few attributes Android believes are a good standard.

Thus loading a Fragment Manager's root view with android.R.id.content ensures these guidelines are implemented.

NOTE: This layout has set the attribute: android:addStatesFromChildren="true" to allow child fragments to overwrite attributes in this rootview.

As of version 19, android.R.id.content is defined in a file: auto_complete_list.xml 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/content"
    android:orientation="vertical"
    android:layout_width="match_parent" 
    android:layout_height="wrap_content"
    android:background="@android:drawable/edit_text"
    android:divider="@android:drawable/divider_horizontal_textfield"
    android:addStatesFromChildren="true">
TheChrisONeil
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1

From Fragment Example

Snackbar.make(requireContext(), requireActivity().findViewById(android.R.id.content), item.getCategoryName(), Snackbar.LENGTH_SHORT).show();
Kumar Santanu
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0

android.R.id.content is very useful for when you need a view, for example:

Show Snackbar:

Snackbar.make(activity.findViewById(android.R.id.content), MESSAGE, Snackbar.LENGTH_LONG).show();

Fragment transaction

 getSupportFragmentManager().beginTransaction()
                .add(android.R.id.content, FragmnetTest.newInstance())
                .commit();
Rasoul Miri
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