In the onCreateView() method of a fragment, I am trying to initialize a CustomView with behavior similar to a fab button.
Upon clicking on this custom view an animation is supposed to run which utilizes an empty RelativeLayout which is present in the parent ViewGroup in the Fragment.
I am passing this ViewGroup to the CustomView in a constructor.
When I try to create a reference to the empty RelativeLayout by calling ViewGroup.findViewById(R.id.target), the reference create holds null ultimately causing a NullPointerException upon animation
However, if I use ViewGroup.getChildAt(1) to create the reference, the animation works just fine.
By using watchers, I found that the id of the ViewGroup.getChildAt(1) is different from the R.id.target which has been assigned to it via xml.
What sorcery is this?
I have browsed already for a few days to be able to find a question which describes this situation.
Extra Information:
We recently switched from support libraries to androidX.
fragment.xml
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/top_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout>
<!-- Other views -->
</LinearLayout>
<!-- This is the layout i am trying to instantiate -->
<RelativeLayout
android:id="#+id/target"/>
</RelativeLayout>
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 have to create a list whose list items have 2 lines of text. I started building a custom list item, but then I discovered the TwoLineListItem component. I wrote this code:
pageFilterResultView=new TwoLineListItem(containerActivity);
pageFilterResultView.getText1().setText("Test");
However, getText1 returns null, and the second line throws a NullPointerException. So I thought I need to use an inflated layout instead of a constructor. The TwoLineListItem documentation specifies I can use the android.R.layout.two_line_list_item resource for the layout, so I changed the code to:
LayoutInflater inflater=(LayoutInflater)containerActivity.
getSystemService(Context.LAYOUT_INFLATER_SERVICE);
pageFilterResultView=(TwoLineListItem)inflater.inflate(android.R.
layout.two_line_list_item,null);
pageFilterResultView.getText1().setText("Test");
However, this throws a ClassCastException because the layout is actually a LinearLayout. TwoLineListItem inherits from RelativeLayout, so I can't even cast the layout to a higher class in the hierarchy.
So the question is: How do I use TwoLineListItem correctly? Do I have to create my own custom layout for it? If so, what's the point of this component if I still have to do all the work of creating a list item by myself?
How do I use TwoLineListItem correctly?
The TwoLineListItem widget is a facade over two TextViews that have to be provided by you. To use the TwoLineListItem in a ListView's row you'll need a row layout where you have the TwoLineListItem widget with two(at least) TextView children with specific ids(android.R.id.text1 and android.R.id.text2). Something like this:
<?xml version="1.0" encoding="utf-8"?>
<TwoLineListItem xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="#android:id/text1"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<TextView
android:id="#android:id/text2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#android:id/text1"/>
</TwoLineListItem>
Then you can use it in the getView() method like you did:
pageFilterResultView=(TwoLineListItem)inflater.inflate(R.layout.the_layout_file_above,null);
pageFilterResultView.getText1().setText("Test");
Of course you have the possibility of using an included layout file as the child of the TwoLineListItem(as long as you have the two TextViews with the required ids):
<?xml version="1.0" encoding="utf-8"?>
<TwoLineListItem xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<!-- the android version of the two line layout -->
<include layout="#android:layout/two_line_list_item" />
</TwoLineListItem>
but this just increases the layout depth and should be avoided.
If so, what's the point of this component if I still have to do all
the work of creating a list item by myself?
Judging by the fact that you can't use this widget programmatically, I don't see the need for this component either.
put your layout code inside try catch block with ClassCastException it will works fine my Friend . .....
I am trying make application from this project: http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/graphics/FingerPaint.html
But here, there is a Layout that generating dynamicly. I want to create my own layout in xml file. So what should i have to do for it.
Please anyone can help me to make the xml layout from this dynamic layout ??
Thanks.
That example is not creating a "dynamic layout". The layout, which is the part you'd be defining in XML, consists of only one View object, MyView.
What I assume you are referring to by "dynamic layout" is the MyView class, which is a custom View object which accepts touch input and draws on the screen. This cannot be defined in XML... you must write the Java code to handle the logic necessary, since the regular View class (which MyView is extending) does not support such functionality.
What you would need to do is create a Java file defining the MyView class. Say for example, com.example.MyView. Then, in XML, you can include this custom view in your layout by referring to the full name, including the package name. For example...
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:orientation="vertical">
<com.example.MyView>
android:layout_height="fill_parent"
android:layout_width="fill_parent"
</com.example.MyView>
</LinearLayout>
You can use this layout in an activity as usual using setContentView.
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.