Develop Reference

DialogFragment custom view no background

I'm trying to inflate a custom view in a DialogFragment but the container view's are not showing up. Note I haven't found any post that matches this exactly, so if there is, please share, TIA.
here is my XML (very simple)
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="#drawable/billnotifselectiondialog"
android:layout_marginHorizontal="45dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent">
<Button
android:id="#+id/btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:background="#color/secondary_200"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
My Class:
class BillNotifSelectionDialog: DialogFragment() {
private lateinit var binding: TestDialogLayoutBinding
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View = TestDialogLayoutBinding.inflate(LayoutInflater.from(context),container, false).apply {
binding = this
}.root
}
I'm invoking the class in my fragment with
BillNotifSelectionDialog().show(parentFragmentManager, "tag")
Here is the result, I can only see the button, not the ConstraintLayout:

This is a common issue of using ConstraintLayout as the root layout of DialogFragments.
One fix is to Replace it with RelativeLayout; but it's not recommended as per documentation quote:
For better performance and tooling support, you should instead build your layout with ConstraintLayout.
Instead of that you'd fix it programmatically by designating the dialog layout to match the parent with dialog.window.setLayout:
class BillNotifSelectionDialog : DialogFragment() {
//..... rest of code omitted
override fun onStart() {
super.onStart()
dialog!!.window!!.setLayout(MATCH_PARENT, MATCH_PARENT)
}
}

you need to override onCreateDialog instead of onCreateView in DialogFragment.
class BillNotifSelectionDialog : DialogFragment() {
private lateinit var binding: TestDialogLayoutBinding
override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
binding = TestDialogLayoutBinding.inflate(layoutInflater)
return AlertDialog.Builder(requireContext())
.setView(binding.root)
.create()
}
to test the result, I changed your xml code that the background color is teal_200 and button color is purple_700
the code result

Android View Binding: Custom View shows duplicate SwipeRefreshLayout progress indicators

In my fragment, I am displaying a list of items using a Custom View that contains a SwipeRefreshLayout.
When I swipe to refresh, I can see two refreshing indicators and one of them never disappears.
See it here
I obviously have only one SwipeRefreshLayout in my hierarchy and this appeared when I migrated my code to View Binding.
Here are the details of my code and of the behaviour.
I have a fragment that displays a list of items, I'm using a Custom View com.myapp.ItemsListView I built for this purpose.
<?xml version="1.0" encoding="utf-8"?>
<com.myapp.ItemsListView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/myItems"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
In order to access this custom view, I am using View Binding. In my fragment, that's what it looks like:
// ItemsFragment.kt
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding = FragmentItemsBinding.inflate(inflater, container, false)
return binding?.root
}
and I then access anything in this custom view via binding?.myItems.
And my custom view uses a SwipeRefreshLayout as its root and contains a RecyclerView:
<?xml version="1.0" encoding="utf-8"?>
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/swipeToRefresh"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/items"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />
<TextView
android:id="#+id/missingContent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:text="#string/missing_content_message"
app:drawableTopCompat="#drawable/ic_missing_content_24dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
Following this question I'm using this piece of code to inflate the custom view:
// ItemsListView.kt
class ItemsListView(context: Context, attrs: AttributeSet) : SwipeRefreshLayout(context, attrs) {
private var b: ItemsListBinding? = null
init {
b = ItemsListBinding.inflate(LayoutInflater.from(context), this, true)
}
}
From the code, I customized my SwipeRefreshLayout to look different than the default:
b?.swipeToRefresh?.setSize(LARGE)
b?.swipeToRefresh?.setColorSchemeResources(
R.color.colorPrimary,
R.color.colorPrimaryDark
)
And I access b?.swipeToRefresh to set a listener, display or hide the progress indicator.
fun setListener(listener: OnRefreshListener) {
b?.swipeToRefresh?.setOnRefreshListener(listener)
}
fun showProgress() {
b?.swipeToRefresh?.isRefreshing = true
}
fun hideProgress() {
b?.swipeToRefresh?.isRefreshing = false
}
However, as you can see on the video clip, there is a black progress indicator that sticks and never goes away.
I have tried to access the SwipeRefreshLayout via b?.root and it results in the same behaviour.
In the end, I just do not understand why there are two SwipeRefreshLayout displayed on my screen. I noticed this problem when I introduced View Binding (I previously used Kotlin Synthetics). I'd like to inflate only one SwipeRefreshLayout in the hierarchy.

can't find how to align an element in a fragment to center of the screen without changing the container's height to match parent [xml question]

let's start from the main activity. my main activity has a fragment container with height set to wrap content and is enclosed inside a scroll view. The scroll view fills the screen.
[this is why I can't set it to match parent. because other fragments wont fit then. Also, I can't set the first fragment as a separate activity because this is a part of a training project and most of it was already built with tests in place.]
The first fragment I have has a single button in it and that fragment's height is set to match parent [which is the container with wrap content].
the button inside the fragment is aligned to the centre of the screen for its fragment xml. but, since wrap is enabled for the container, the button is now at the top in the main activity.
now, setting the height for the fragment as some fixed value might solve the problem when the height of the device is fixed. but, in other cases, the button's location might not be shown as wanted.
You will find a screenshot below which will give you a better understanding of my problem.
the top is the fragment layout while the bottom is the main activity layout. all I want is the button to be at the centre of the screen regardless of the screen size.
main acivity -
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- TODO: Add a FragmentContainerView with navigation/mobile_navigation as the navHost -->
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.fragment.app.FragmentContainerView
android:id="#+id/nav_host_fragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:name="androidx.navigation.fragment.NavHostFragment"
app:defaultNavHost="true"
app:navGraph="#navigation/mobile_navigation" />
</ScrollView>
</androidx.constraintlayout.widget.ConstraintLayout>
fragment activity -
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/layout_start_order"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.order.StartOrderFragment">
<Button
android:id="#+id/start_order_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="#dimen/base_margin"
android:layout_marginTop="#dimen/base_margin"
android:layout_marginEnd="#dimen/base_margin"
android:text="#string/start_order"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
I also tried turning the fragment layout into a binding layout and setting the height manually. but, it's giving a val cannot be assigned error. [the same binding variable allows me to change the button text.] the screenshot below is of the same attempt.
the same kotlin code as above -
package com.example.lunchtray.ui.order
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.navigation.fragment.findNavController
import com.example.lunchtray.R
import com.example.lunchtray.databinding.FragmentStartOrderBinding
class StartOrderFragment : Fragment() {
// Binding object instance corresponding to the fragment_start_order.xml layout
// This property is non-null between the onCreateView() and onDestroyView() lifecycle callbacks,
// when the view hierarchy is attached to the fragment.
private var _binding: FragmentStartOrderBinding? = null
// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
_binding = FragmentStartOrderBinding.inflate(inflater, container, false)
val root: View = binding.root
// Navigate to entree menu
binding.startOrderBtn.setOnClickListener {
// TODO: navigate to the EntreeMenuFragment
findNavController().navigate(R.id.action_startOrderFragment_to_entreeMenuFragment)
}
return root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.layoutStartOrder.height = 1 //error
binding.startOrderBtn.text = "wwmfkkf" //so, binding variable isn't the problem
//todo - remove button text assignment
}
/**
* This fragment lifecycle method is called when the view hierarchy associated with the fragment
* is being removed. As a result, clear out the binding object.
*/
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
Any form of help is appreciated. Thank You.

Why does findViewById returning null when searching for the RecyclerView?

Why is val rv: RecyclerView = findViewById(R.id.material_list_rv) returning null?
MainActivity
class MainActivity : AppCompatActivity() {
var adaptor: MaterialListAdaptor = MaterialListAdaptor()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
if (savedInstanceState == null) {
supportFragmentManager.commit {
setReorderingAllowed(true)
add<MaterialListFragment>(R.id.fragment_container_view)
}
}
initRecyclerView()
setRecyclerViewData()
}
private fun initRecyclerView(){
val rv: RecyclerView = findViewById(R.id.material_list_rv)
rv.layoutManager = LinearLayoutManager(this#MainActivity)
rv.adapter = adaptor
}
private fun setRecyclerViewData(){
val l = DataSource.createMaterialList()
adaptor.setDataSet(l)
}
}
activity_main
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<androidx.fragment.app.FragmentContainerView
android:id="#+id/fragment_container_view"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
MaterialListFragment
class MaterialListFragment : Fragment() {
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
return inflater.inflate(R.layout.fragment_material_list, container, false)
}
}
fragment_material_list
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MaterialListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/material_list_rv"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginBottom="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:listitem="#layout/material_list_rv_list_item" />
</androidx.constraintlayout.widget.ConstraintLayout>

The problem
You placed the call to findViewById in MainActivity.onCreate. It's too early for that, the Fragment's view hasn't been created at that point.
You should be looking for the view in your MaterialListFragment. If you call findViewById in onCreateView, it will work. Like this:
val root = inflater.inflate(R.layout.fragment_material_list, container, false)
val rv = root.findViewById(R.id. material_list_rv)
// Do whatever (eg assign rv to a field in the Fragment to use it later)
return root
Some advice
Even if your code worked, try to have Activities, Fragments and custom Views manage their own children.
If the upper containers dive deep into their children, it's very easy to make mistakes (like the one here!) and you lose the ability to update internal details of Fragments and Views without breaking the containing Activity.
Activity/Fragment lifecycle chart
To orient yourself, keep this in mind (though this diagram is EXTREMELY simplified):

You are looking for RecylerView in MainActivity, where it does not exist.
Instead you should try to access it in FragmentActivity.

Fragment with ViewPager having blank pages after returning to it from another fragment

In my application I'm trying to create 2 fragments with ViewPagers. The fragments have 3 tabs/pages each with RecyclerViews and they are supposed to be backed by a database, so I'm keeping them in a List.
class MainActivity : AppCompatActivity() {
val fragments = listOf(SwipeFragment(), SwipeFragment())
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
supportFragmentManager.beginTransaction().replace(R.id.placeholder, fragments[0]).commit()
button1.setOnClickListener {
supportFragmentManager.beginTransaction().replace(R.id.placeholder, fragments[0]).commit()
}
button2.setOnClickListener {
supportFragmentManager.beginTransaction().replace(R.id.placeholder, fragments[1]).commit()
}
}
}
The problem is that after navigating away from the SwipeFragment and going back, the view seems empty. Then, if you navigate to e.g. the leftmost page, the rightmost one "appears" (when you go to it).
This results in the middle page staying empty. (the reason for it being that FragmentStatePagerAdapter keeps only the current page and 2 adjacent ones by default. The middle one doesn't get refreshed in a layout with 3 tabs - I tried it also with 5 tabs and I'm able to bring all of them back by going back and forth).
After some debugging I saw that the fragments that represent pages don't get removed from the FragmentManager, but the main SwipeFragment is. I can't get my head around how FragmentManager really works, even after reading almost all of the source code.
If I were able to somehow safely remove the fragments from the FragmentManager, it may work.
I've tried some techniques for saving state, but the framework does that automatically (which might actually be the cause of this problem).
I'm just a beginner in Android, so there's probably a better way to do this anyway. I'll leave the rest of the files here for reference.
activity_main.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"
android:orientation="vertical"
tools:context="com.example.test.MainActivity">
<FrameLayout
android:id="#+id/placeholder"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="0"
android:orientation="horizontal">
<Button
android:id="#+id/button1"
style="?android:buttonBarButtonStyle"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="button1" />
<Button
android:id="#+id/button2"
style="?android:buttonBarButtonStyle"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="button2" />
</LinearLayout>
</LinearLayout>
SwipeFragment.kt
class SwipeFragment : Fragment() {
// TODO: set up and keep the database here
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater!!.inflate(R.layout.fragment_swipe, container, false)
view.tab_layout.setupWithViewPager(view.pager)
view.pager.adapter = DummyPagerAdapter(activity.supportFragmentManager, index)
return view
}
}
fragment_swipe.xml
<android.support.v4.view.ViewPager
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.test.SwipeFragment">
<android.support.design.widget.TabLayout
android:id="#+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</android.support.v4.view.ViewPager>
ItemListFragment.kt
class ItemListFragment() : Fragment() {
// Or keep the database here?
// Probably not the best idea though
override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {
val view = inflater!!.inflate(R.layout.fragment_item_list, container, false)
if (view is RecyclerView) {
view.layoutManager = LinearLayoutManager(view.context)
view.adapter = MyItemRecyclerViewAdapter(DummyContent.ITEMS)
}
return view
}
}
DummyPagerAdapter.kt
class DummyPagerAdapter(manager: FragmentManager, val parentIndex: Int) :
FragmentStatePagerAdapter(manager) {
override fun getItem(position: Int): Fragment = ItemListFragment()
override fun getPageTitle(position: Int): CharSequence = "${ position + 1 }"
override fun getCount(): Int = 3
}
And a basic implementation of RecyclerView.Adapter generated by Android Studio
MyItemRecyclerViewAdapter.kt
class MyItemRecyclerViewAdapter(val values: List<DummyItem>) :
RecyclerView.Adapter<MyItemRecyclerViewAdapter.ViewHolder>() {
...
}
fragment_item_list.xml
<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/list"
android:name="com.example.test.ItemListFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layoutManager="LinearLayoutManager"
tools:context="com.example.test.ItemListFragment"
tools:listitem="#layout/fragment_item" />

You should use childFragmentManager instead of activity.supportFragmentManager inside SwipeFragment.
view.pager.adapter = DummyPagerAdapter(childFragmentManager, index)
The difference between getSupportFragmentManager() and getChildFragmentManager() is discussed here.
Basically, the difference is that Fragment's now have their own internal FragmentManager that can handle Fragments. The child FragmentManager is the one that handles Fragments contained within only the Fragment that it was added to. The other FragmentManager is contained within the entire Activity.

In my case childFragmentManager didn't help. I think we can use a pattern "Observer" to update existing fragments of ViewPager with new data when return from another fragment.