Android xml merge layout error on inflate

Question

I have a CustomView class and I want to use xml layout for it. So, my class extends RelativeLayout, inflates xml layout and tries to attach it to self.

public class CustomView extends RelativeLayout
{
  public CustomView (Context context)
  {
     super(context);
     LayoutInflater.from(context).inflate(R.layout.layers_list_item, this, true);
  }
}

If my xml layout has some layout (Linear, for example) as root element it works fine. But when I try to use <merge> tag according to this response I got this error:

<merge /> can be used only with a valid ViewGroup root and attachToRoot=true

My xml layout is like:

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

     <CheckBox
        ... />

     <TextView
        ... />

</merge>

I also tried to remove all attributes from <merge... > tag, got the same result. What's wrong?

UPDATE: The code above is correct. As secretlm mentioned, problem was that <merge> was used as a root element and inflated in another piece od code:

ArrayAdapter<String> adapter = 
    new ArrayAdapter<String>(this, 
                             R.layout.layers_list_item, 
                             R.id.layers_list_item_text);

And with every element added adapter tried to inflate R.layout.layers_list_item which have <merge> as root.

Could you update your children views in tag? – secretlm Dec 26 '12 at 13:17 — secretlm, Dec 26 '12 at 13:17

secretlm · Accepted Answer · 2012-12-26T14:48:13.367

you can't use <merge> as a root element in your final layout without container element. "Using this as the root element is useful when you know that this layout will be placed into a layout that already contains the appropriate parent View to contain the children of the element. This is particularly useful when you plan to include this layout in another layout file using and this layout doesn't require a different ViewGroup container" -- from "developer.android.com"

This example show that how to work with <merge>: http://www.coderzheaven.com/2011/06/26/merge-two-layout-xml-in-android/

Updated:

You should try with Constructor(Context, AttributeSet) from this example. I think it will solve your problem.

file test.xml:

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

     <CheckBox
        android:id="@+id/layers_list_item_switch"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@id/layers_list_item_root"    
        android:layout_alignParentRight="true"
        android:layout_marginLeft="15dp"        
        android:button="@drawable/ic_launcher" />

     <TextView
        android:id="@+id/layers_list_item_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="left|center_vertical"
        android:layout_toLeftOf="@id/layers_list_item_switch"
        android:selectAllOnFocus="true"
        android:text="tret"
        android:ellipsize="marquee"
        android:focusable="true"
        android:focusableInTouchMode="true"
        android:marqueeRepeatLimit="marquee_forever"
        android:singleLine="true"
        android:scrollHorizontally="true"
        android:textColor="@android:color/black"
        android:textSize="16sp"
        android:textStyle="bold"
        android:typeface="serif"
        android:clickable="true" />

</merge>

Test class which extend from RelativeLayout:

public class Test extends RelativeLayout
{       
    public Test(Context context, AttributeSet attrs) {
        super(context, attrs);      
        LayoutInflater.from(context).inflate(R.layout.test, this, true);    
    }
}

Main activity:

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }    
}

Main layout:

<com.example.testlayout.Test
    xmlns:android="http://schemas.android.com/apk/res/android"           
    android:id="@+id/layers_list_item_root"
    android:layout_height = "fill_parent"
    android:layout_width = "fill_parent"      
    />

`` isn't `root element` - it is attached to `CustomView`, which is `RelativeLayout`. Anyway, there is also another layout at higher level - that `CustomView` just describes `ListView` item. — Frederic Blase, Dec 26 '12 at 12:15
@Frederic: I updated my answer, hope it will solve your problem. — secretlm, Dec 26 '12 at 14:50
well, you were right about `root element` - xml with `` as a `root` was used in `ArrayAdapter` constructor, and inflated inside it caused the error — Frederic Blase, Dec 27 '12 at 13:16
^ and mine, never understood that boolean flag on the end of inflate, now i do — Joe Maher, Feb 27 '16 at 01:30
why Test class implementation is required ? Just replacing tag by with valid layout_width and layout_height will also work in this case — Napolean, Jan 04 '18 at 08:28

score -1 · Answer 2 · answered Sep 16 '20 at 08:05

Make sure to specify the complete path from source root in the main layout like this

`<com.example.testlayout.Test      xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layers_list_item_root"
    android:layout_height = "fill_parent"
    android:layout_width = "fill_parent"      
    />`

and not like this 
`<Test      xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layers_list_item_root"
    android:layout_height = "fill_parent"
    android:layout_width = "fill_parent"      
    />`

Android xml merge layout error on inflate

2 Answers2

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