I came across an app, whose layout puzzles me.
Assume two layout XML files, such that one includes the other:
activity_button.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<include layout="#layout/button"/>
</LinearLayout>%
button.xml
<?xml version="1.0" encoding="utf-8"?>
<Button xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/button"
android:onClick="sendMessage">
</Button>
What is the resource ID of the button?
I thought one always had to specify ID via android:id attribute, so I am confused why this layout works. I also checked the R.java ID entry and it seems to be empty.
android:id
Is not mandatory field for a view in the layout xml file. the only two mandatory fields are the width and height of the view.
Think of situations when you want a layout to simply show some title without any business need to change it through the activity life time. for this need you don't need to obtain this view id, and don't need the overhead of creating id for this view
What is the resource ID of the button?
Doesn't have one
I thought one always had to specify ID via android:id attribute
Why did you think this? You often leave off this attribute for the root views of most layouts. (See LinearLayout of your question)
You do not need an android:id if you never expect to find the view using an ID. Since the onClick is defined in the XML, there's really no purpose in finding the button.
I want to include the below layout in a main layout file, at multiple points, but at each usage, I want to change ONLY the "android:text" attribute of the text view inside the relative layout (as seen below). How can I achieve that?
P.S. I know how to include it in the main layout. This includes the relative layout (as seen below), but the main purpose of creating another layout file is because the code (of the textview) is being repeatedly used in the main layout, and the only attribute that differs is "android:text" between these repeated text views.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/order_id_label"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="test"
android:fontFamily="sans-serif-light"
android:padding="20dp"
android:textSize="20sp"
android:textStyle="bold" />
</RelativeLayout>
in your another Layout file you can use this .
<include layout="#layout/main_layout"/>
And From your activity class you can set text by this.
TextView tv = (TextView) findViewById(R.id.order_id_label)
tv.setText("New Text");
This is the only way you can do this .
If all TextView element arguments are the same you could define this component in a separate file using <merge> </merge> directive and then <include layout="" />
Check here how to reuse
But if any of the TextView argument is changing, i.e. android:text attribute, the best way is to separate all other TextView attributes to custom style and reuse this custom style in different xml layout files
Check here how to use styles
I have one xml file main_layout.xml and in this I have another xml layout popup_layout.xml which is added by :
<include
android:id="#+id/popup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
layout="#layout/popup_layout" />
In the file MainActivity.java I would like to get the popup object so I can change it's textfields etc. What do i write?
I've tested
View v = findViewById(R.id.popup);
TextView tv= (TextView) v.findViewById(R.id.ip_answer);
but it doesn't work
The id attribute for include is not required. Add id attribute to the layout you want to include , then find view by that id an collect it accordingly as the type of layout
eg:
RelativeLayout/LinearLayout= findViewById(id);
then find the text view .
This should work
Let's get straight to code.
Activity Code, onCreate method
setContentView(R.layout.main);
View main_view = findViewById(R.id.main_view);
View view_flipper = main_view.findViewById(R.id.vf);
View first_tab = view_flipper.findViewById(R.id.prev_pane);
The main.xml layout code:
<ViewFlipper android:id="#+id/vf"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<include android:id="#+id/prev_pane" layout="#layout/vf_inner" />
<include android:id="#+id/cur_pane" layout="#layout/vf_inner" />
<include android:id="#+id/next_pane" layout="#layout/vf_inner" />
</ViewFlipper>
The problem!
Main view is correctly found, so is ViewFlipper, yet prev_pane or cur_pane or next_pane are not found, a null pointer is returned. Any ideas why?
This activity is called through a tab by using an Intent. All references are resolved correctly except id's on includes
When I inspect variables, I find the contents of vf_inner layout in mChildren
That's because <include /> tags are not an actual view in your UI hierachy.
They are more of a copy&paste instruction for the android tools.
If you want to find the panes at runtime, add the IDs to the root elements of the included layouts. This way they can be found via findViewById().
One thing you can do is wrap the <include> statements inside a parent layout (which is still a child of your main parent layout). Give those views different ids so you can findViewById each of them separately.
In my layout xml file, I have included other layout xml file (each
with a different android id).
<include layout="#layout/view_contact_name" android:id="+id/test1"/>
<include layout="#layout/view_contact_name" android:id="+id/test2"/>
But when I run it in the emulator, and start Hierarchy Viewer, each of
the layout still shows 'NO_ID', and in my code, I have
findViewById(R.id.test1) and findViewById(R.id.test2) both returns null.
Can anyone please help me with my problem ?
Specify the ID in the <include>
<include layout="#layout/test" android:id="#+id/test1" />
Then use two findViewById to access fields in the layout
View test1View = findViewById(R.id.test1);
TextView test1TextView = (TextView) test1View.findViewById(R.id.text);
Using that approach, you can access any field in any include you have.
I found out, that if you are using <merge> tag in your include layout, then the ID of include transfers to the merge tag which is not real view.
So either remove merge, or replace it with some layout.
Tor Norbye wrote:
The <include> tag is not a real view, so findByView will not find it. The #id attribute (and any other attributes you've set on the include tag) gets applied on the root tag of the included layout instead. So your activity.getView(R.id.included1) should in fact be the <TextView> itself.
Romain Guy indicates that you can override the ID of an included layout by putting an android:id attribute inside the <include> tag.
<include android:id="#+id/cell1" layout="#layout/workspace_screen" />
I think the top answer misses the most important point and might mislead people into thinking the <include/> tag creates a View that holds the include contents.
The key point is that include's id is passed to the root view of the include's layout file.
Meaning that this:
// activity_main.xml
<include layout="#layout/somelayout" android:id="#+id/someid"/>
// somelayout.xml
<?xml version="1.0" encoding="utf-8"?>
<ImageView
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
Becomes this:
// activity_main.xml
<ImageView
android:id="#+id/someid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
yes is like this, but careful when the layout inserted in include field is a custom one and you want to access that root layout. That layout in this case #layout/test test, is actually returned in first line.
test test1View = (test)findViewById(R.id.test1);
you must set id each include tag
included child element set a
new id. if you look how to generate new id, look at this entry:
https://stackoverflow.com/a/15442898/1136117
Problem is we try to use id which is not declared in current layout file.
Instead of declaring again, id can be simply referred using #+id/. If you refactor original id name through Android Studio it does refactor in included layout as well.
<include layout="#layout/toolbar"/>
<TextView
android:id="#+id/txt_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
**android:layout_below="#+id/toolbar"**
android:layout_marginTop="16dp"
android:paddingLeft="8dp"
android:paddingRight="8dp"/>
In a case of using <RecyclerView> find the id of <include> by using an instance of inflated view or else it will return null.
public class ViewHolder extends RecyclerView.ViewHolder {
private mTextView;
public ViewHolder(View view) {
super(view);
View include_1 = view.findViewById(R.id.include_1);
mTextView = (TextView) include_1.findViewById(R.id.text_id);
}
}
If you have set id to either root tag of included layout then you can use that id
or you can set id to included layout.
But you can not set id to both it may throw exception.
<include layout="#layout/view_contact_name" android:id="+id/test1"/>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
....
</LinearLayout>
Or
<include layout="#layout/view_contact_name"/>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="#+id/llBottomMainView"
android:layout_width="match_parent"
android:layout_height="wrap_content">
....
</LinearLayout>
When talking about include you either have an id on the root view inside the included layout file or on the include line itself and not on both. For example:
<include layout="#layout/layout1" android:id="#+id/layout1"/>
Layout 1 file
<RelativeLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/layout2">
</RelativeLayout>
The above example is wrong because technically you have two id's declared for the same layout. So what you have to do is pick which element will have the id.
To specify the id when you are including a xml file is like setting it to any xml element
Example:
*list_layout.xml*
`<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rvNames"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>`
*activity_main.xml*
`<RelativeLayout
tools:context=".MainActivity">
<include
layout="#layout/list_layout"
android:id="#+id/myList" />
</RelativeLayout>`
Now if you want to get that to use in .kt file, just use normally findViewById
Exemplo
*MainActivity.kt*
`val myList: RecycleView = findViewById(R.id.myList)`
Wow, I can't believe this question doesn't have the right answer yet. It's simple tags suck. You can only change things that start with android:layout_ which android:id doesn't match. So the answer is you can't. Sorry. What you can do instead is create a class that will be a ViewGroup which will inflate the included views inside, then add that as a tag in your layout, but that's about it.