Develop Reference

Android fragment preloading data

Hello I'm trying to make an application that has multiple bottomnaviagtion tabs.
Currently it works because fragment data (for example, images) are static. However, if I want to make them dynamic, I'll have to create a preloader.
So I want to display a loading layout (for example R.layout.loading) UNTIL (async) function has completed and obtained data from server. Then I want to replace the layout in the fragment with a new layout (R.layout.datafragment)
Fragment onCreateView:
return inflater.inflate(R.layout.loading, container, false);
In summary it should work exactly like youtube bottom tabs.

You should create in your activity layout a placeholder for those dynamic fragments and a loader which is by default gone, but when you start loading data from the server you should make it visible (loader). Then, when you load necessary data, just start fragment transition and place whatever fragment you have loaded.

Your parent activity's layout should be like this:
<?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">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--Navigation View and Fragment Container-->
</RelativeLayout>
<RelativeLayout
android:id="#+id/progress_layout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"/>
</RelativeLayout>
</RelativeLayout>
Then you simply show/hide progressLayout based on your requirement. Thanks

Clicking on Fragment goes through in Activity

I have a button in my MainActivity that opens FragmentA. FragmentA covers the whole screen, but I still see the button from MainActivity, and I can still click on it.
I've tried using clickable in my fragment layout but it's not working
MainActivty
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
button.setOnClickListener {
val fragmentManager = this#MainActivity.supportFragmentManager
fragmentManager.beginTransaction()
.add(R.id.fragment_container, AFragment())
.addToBackStack(null)
.commit()
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:id="#+id/fragment_container">
<Button
android:text="Button Main"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/button" app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent" app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"/>
</android.support.constraint.ConstraintLayout>
fragment_a.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clickable="true"
android:focusable="true">
android:background="#color/colorPrimary"
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="A"/>
</LinearLayout>

This is happening because you placed your Button inside of the ConstraintLayout you're using as the container of your Fragment.
When you add a fragment into a container like what you're doing, it's simply adding it in the same manner as if it was a View.
Therefore, if you add a Fragment into a ConstraintLayout that already possesses a Button as a child, the Fragment will be shown alongside the Button due to ConstraintLayout allowing for overlapping Views.
This is also why, if your container was a LinearLayout, then adding a Fragment will place the fragment underneath your Button instead.
So, with that in mind, the solution would be to handle it as if they were Views.
If you added a View into a layout and you have another View overlapping, how would you get rid of it?
The most common solution would be to set the Button's visibility to INVISIBLE or GONE when the Fragment is added.
Another solution might be to raise the elevation of the Fragment, so it's now higher than your Button.
Of course, you may also remove the button from the Container and place it inside a Fragment too.
This way, you can use the replace() method in a FragmentManager to replace the Fragment containing your Button with the Fragment you want to show.

Android Studio - How to programmatically add layout_below param to CardViews inside a PercentRelativeLayout

I am here because I am trying to set programmatically the layout_below parameter of some cardViews without success.
These cardViews are located inside a PercentRelativeLayout (I do not know if it is relevant but these cardviews have been added programmatically too).
I show you the code to make it clear.
...
<android.support.percent.PercentRelativeLayout
android:id="#+id/prl"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.CardView
xmlns:percent="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="#+id/cv0"
android:layout_width="match_parent"
percent:layout_heightPercent="65%"
percent:layout_marginTopPercent="2%"
percent:layout_marginLeftPercent="2%"
percent:layout_marginRightPercent="2%"
card_view:cardCornerRadius="2dp"
card_view:cardElevation="4dp">
</android.support.v7.widget.CardView>
<android.support.v7.widget.CardView
xmlns:percent="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="#+id/cv1"
// here I would like to add android:layout_below="#+id/cv0"
android:layout_width="match_parent"
percent:layout_heightPercent="65%"
percent:layout_marginTopPercent="2%"
percent:layout_marginLeftPercent="2%"
percent:layout_marginRightPercent="2%"
card_view:cardCornerRadius="2dp"
card_view:cardElevation="4dp">
</android.support.v7.widget.CardView>
<android.support.v7.widget.CardView
xmlns:percent="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:id="#+id/cv2"
// here I would like to add android:layout_below="#+id/cv1"
android:layout_width="match_parent"
percent:layout_heightPercent="65%"
percent:layout_marginTopPercent="2%"
percent:layout_marginLeftPercent="2%"
percent:layout_marginRightPercent="2%"
card_view:cardCornerRadius="2dp"
card_view:cardElevation="4dp">
</android.support.v7.widget.CardView>
</android.support.percent.PercentRelativeLayout>
...
I tried to do something like this in my Java code but without success.
PercentRelativeLayout prl = (PercentRelativeLayout) view.findViewById(R.id.prl);
CardView cv = (CardView) LayoutInflater.from(getActivity()).inflate(R.layout.cv_block, prl, false);
cv.setId(currentId++);
prl.addView(cv);
cv = (CardView) LayoutInflater.from(getActivity()).inflate(R.layout.cv_block, prl, false);
cv.setId(currentId++);
RelativeLayout.LayoutParams cv_lp = (RelativeLayout.LayoutParams) cv.getLayoutParams();
cv_lp.addRule(RelativeLayout.BELOW,currentId-2);
/* I have also tried to call cv.requestLayout() but nothing changed */
prl.addView(cv);
As you can see, I am trying to generate cardviews and insert them one below the other.
Thanks in advance for your help.

PercentRelativeLayout is depreciated, so you are encouraged to use other type of layout.
This class was deprecated in API level 26.1.0.
consider using ConstraintLayout and associated layouts instead. The following shows how to replicate the functionality of percentage layouts with a ConstraintLayout. The Guidelines are used to define each percentage break point, and then a Button view is stretched to fill the gap:
ConstraintLayout gives lots of opportunities.
More about PercentRelativeLayout deprecation here.
More about ConstraintLayout and how to use it here or video tutorial.

View added from XML file is not shown in its parent view

In my Player activity I am trying to add a view from a different XML by calling addView:
view = (ViewGroup)findViewById(R.id.player_ConstraintLayout);
notifierView = LayoutInflater.from(view.getRootView().getContext())
.inflate(R.layout.notifier, null);
view.addView(notifierView);
// view.invalidate();
The Player activity comes with this associated XML file:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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/player_ConstraintLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.android.Player">
...
</android.support.constraint.ConstraintLayout>
And the one I want to add is notifier.xml:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ff0000"
android:translationZ="9dp"
android:elevation="9dp">
</android.support.constraint.ConstraintLayout>
I have debugged the app and by inspecting variable view I can confirm that the notifierView has been added and is in the children list of the view. However the notifierView is not shown, even I have expected it to be of full screen size and red. When I inspected notifierView in debugger, it showed its mTop, mBottom, mLeft, and mRight variables being all 0. I assuming it means that the
android:layout_width="match_parent"
android:layout_height="match_parent"
have been ignored? Or is there some other reason why I don't see this notifierView at all?
EDIT/UPDATE:
Let me show you more of the code, as the previous above is a little simplified one.
In Player activity I have:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_player);
notifier = new Notifier((ViewGroup)findViewById(R.id.player_ConstraintLayout));
...
}
and in Notifier.java I have
Notifier(ViewGroup view) {
handler = new android.os.Handler();
LayoutInflater inflater = LayoutInflater.from(view.getRootView().getContext());
notifierView = inflater.inflate(R.layout.notifier, view, false);
}

ConstraintLayout doesn't actually support match_parent for its children. You have to use this for "match parent" width:
android:layout_width="0dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
And this for "match parent" height:
android:layout_height="0dp"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
Additionally, your LayoutInflater.inflate() call should be changed. When you pass null as the second argument, you don't give the system enough information to understand how to parse layout_ attributes on the inflated view; you should pass a real parent (in this case, view). However, if you change null to view, the return value of the inflate() call will change, so you have to add an additional param (attachToRoot) to make sure the rest of the semantics don't change.
LayoutInflater inflater = LayoutInflater.from(view.getRootView().getContext());
notifierView = inflater.inflate(R.layout.notifier, view, false);

(Posted solution on behalf of the question author).
Invalidate Caches / Restart helped. Android Studio sometime gets things wrong.

How to add a title to a fragment in Android

In AndroidStudio, I selected "New->Fragment->Fragment (List)" to create a list of items. It works fine and displays all the items; however, I would like to have a title at the top.
If I add another TextView to the "fragment_item_list.xml" file, then the title appears in all the items in the list. From other questions I figured that if I create another LinearLayout xml layout file (something like "list_header.xml") and put a TextView in it, I can use a layout inflater to inflate this layout in the fragment activity, e.g. in onCreateView,
View header = inflater.inflate(R.layout.list_header,container,false);
but then I don't know what to do with header to make it display somewhere in the fragment. I can add it to the original activity by calling container.addView(header); but how can I add it to the fragment?
I don't want to change the ActionBar title, firstly just for aesthetics, and secondly because the fragment covers it up. Ideally there would be a header like in an alert dialog.

Let me try to understand you. You want to add a title to your fragment list (like an header), not in the ActionBar. Right?
Looking the fragment_item_list.xml we have this: (I follow your steps: "New->Fragment->Fragment (List)")
<?xml version="1.0" encoding="utf-8"?>
<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:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:listitem="#layout/fragment_item" />
The RecyclerView is a container used for populate a list, in other words, the RecyclerView (or ListView) contain all the list only. So, you have to add another container (like LinearLayout, RelativeLayout, etc.) as root of the layout to add more views to the layout. Example using the LinearLayout:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/text_header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello World! I'm a header!"/>
<android.support.v7.widget.RecyclerView
android:id="#+id/list"
android:name="com.veroapps.myapplication.ItemFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:listitem="#layout/fragment_item" />
</LinearLayout>
With this you will have a list with a title at the top. Now, you can manage the title TextView in the ItemFragment(name of the fragment generated by Android Studio). And of course there are more ways to do that, but this is an easy one.
Hope this help you.

In your Fragment java class, there should be a method called onCreateView this is where you set the layout for your Fragment (and where the list is added). It will look something like this:
public static class ExampleFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.example_fragment, container, false);
}
}
In this Fragment the layout is inflated by this code inflater.inflate(R.layout.example_fragment, container, false); and this means there's is an xml file defining the layout called example_fragment.xml.
Your code will be the same, when you find this XML file. You can add other views inside it.
You will want to add another TextView above the RecyclerView or ListView already in that file.
Something like this:
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<TextView
...
android:text="YOUR TITLE" />
<RecyclerView
... />
</LinearLayout>