First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)
Most of them come with the advice to use android:id instead of just id in the XML file. I did.
From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.
In my location_layout.xml, I use:
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="#+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
In my Activity I do:
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.
So what the heck am I doing wrong?
I'll appreciate any comments.
which returns null
Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Possibly, you are calling findViewById before calling setContentView?
If that's the case, try calling findViewById AFTER calling setContentView
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.
This would be wrong
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context);
}
This is correct
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context,attrs);
}
Alongside the classic causes, mentioned elsewhere:
Make sure you've called setContentView() before findViewById()
Make sure that the id you want is in the view or layout you've given to setContentView()
Make sure that the id isn't accidentally duplicated in different layouts
There is one I have found for custom views in standard layouts, which goes against the documentation:
In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:
Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.
In onCreate:
setContentView(R.layout.my_layout);
FrameView fv = findViewById(R.id.frame_for_custom_layout);
MyCustomView cv = new MyCustomView(context);
fv.addView(cv);
which puts the custom view in the frame.
In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:
TextView tv = (TextView) findViewById( R.id.textview1 );
and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:
setContentView(R.layout.main);
instead of
setContentView(R.layout.main2);
I noticed this after I arrived here, on the site.
#Override
protected void onStart() {
// use findViewById() here instead of in onCreate()
}
A answer for those using ExpandableListView and run into this question based on it's title.
I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.
FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is,
findViewById()
after
setContentView().
The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:
<include layout="#layout/content_main" />
When I added that to activity_main.xml, no more NullPointer.
I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...
I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.
I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.
So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.
In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!
In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.
TextView footerView = (TextView) placesListView.findViewById(R.id.footer);
Changing this to inflate the footer view instead of finding it by ID solved this issue.
View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);
Just wanted to throw my specific case in here. Might help someone down the line.
I was using the directive in my Android UI XML like this:
Parent view:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:visibility="gone" />
Child view (retry_button):
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/retry"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.
Fixed parent:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:id="#+id/retry"
android:visibility="gone" />
Fixed child:
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.
For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?
Set the activity content from a layout resource.
ie.,setContentView(R.layout.basicXml);
In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages"
in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element.
it is occur when use copy and paste to create new activity
I have the same problem, but I think its worth sharing with you guys.
If you have to findViewById in custom layout, for example:
public class MiniPlayerControllBar extends LinearLayout {
//code
}
you cannot get the view in constructor.
You should call findViewById after view has inflated.
Their is a method you can override onFinishInflate
My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.
INFLATE THE LAYOUT !! (which contains the id)
In my case findViewById() returned null, because the layout in which the element was written, was not inflated...
Eg.
fragment_layout.xml
<ListView
android:id="#+id/listview">
findViewById(R.id.listview) returned null, because I had not done
inflater.inflate(R.layout.fragment_layout, ..., ...);
before it.
Hope this answer helps some of y'all.
In my case I had inflated the layout but the child views were returning null. Originally I had this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
tvText = (TextView) findViewById(R.id.tvListviewFooter);
...
}
However, when I changed it to the following it worked:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
...
}
The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:
footerView.findViewById...
It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.
In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:
password = (EditText)findViewById(R.id.r_password);
In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.
findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment
You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)
In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object.
For example, I did this in parent object:
Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);
Then I passed the hdSpinner as a parameter during creation of the adapter object:
mTransactionAdapter = new TransactionAdapter(getActivity(),
R.layout.transactions_list_item, null, from, to, 0, hdSpinner);
I was facing a similar problem when I was trying to do a custom view for a ListView.
I solved it simply by doing this:
public View getView(int i, View view, ViewGroup viewGroup) {
// Gets the inflater
LayoutInflater inflater = LayoutInflater.from(this.contexto);
// Inflates the layout
ConstraintLayout cl2 = (ConstraintLayout)
inflater.inflate(R.layout.custom_list_view, viewGroup, false);
//Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated.
TextView tv1 = (TextView)cl2.findViewById(cl2);
Ways to debug and find the issue:
Comment out all findViewById in your activity.
Comment out everything except onCreate and setContentView
Run the project and see if any layout is set
In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.
So I changed the activity_main.xml file name to activity_main_lib.xml.
So make sure you do not have any duplicate layout names in your whole project.
The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.
For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.
For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.
I am trying to manipulate the visibility of RelativeLayout on a certain click event, using the visibility attribute.
After adding event handlers to each list item, I can check that the visibility status is changing, but in the Android emulator, the screen doesn't change at all (and I have tested it with visibility="visible" in the XML to make sure that it would show up).
Here's the code for the click handler:
someHolder.itemView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
LayoutInflater layoutSeed = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View baseView = layoutSeed.inflate(R.layout.activity_listings, null, false);
RelativeLayout popup = (RelativeLayout) baseView.findViewById(R.id.popupContainer);
Log.d("Tag1",Integer.toString(popup.getVisibility()));
popup.setVisibility(View.VISIBLE);
Log.d("Tag2",Integer.toString(popup.getVisibility()));
}
});
Logcat shows the status change. I've also tried to invalidate() and postInvalidate() on both baseView and popup, as well as popup.bringToFront() and the combinations of these and so far nothing's working.
Any suggestions or possible routes to investigate?
If the RelativeLayout you are trying to change visibility is already in the screen, you don't need to inflate it again. Please make a reference to already inflated one and change its visibility
holder.relativeLayout.setVisibility(View.GONE);
Gone will remove the view from your layout. Use Invisible instead of gone.
when you click on button your View is replace by button's OnClick(View v) method.
so you just write down
v.popup(View.GONE)
Look at this line of code:
View baseView = layoutSeed.inflate(R.layout.activity_listings, null, false);
RelativeLayout popup = (RelativeLayout) baseView.findViewById(R.id.popupContainer);
Log.d("Tag1",Integer.toString(popup.getVisibility()));
Actually, you're trying to create a new baseView and set it gone. If you want to set the row item gone, you should remove it from your adapter temporary instead such as (if you set itemView to gone, you should be careful with the resuing view of the adapter):
removeItemAt(getAdapterPosition())
notifyDataRemoved(getAdapterPosition())
I've been working on making my own custom ImageView class on Android. I've read the documentation on layouts, fragments, activities and ImageView.
I've looked at Stack posts on how to create an ImageView programatically but I've run into a snag I can't seem find a solution to (reading the top hits for searching the above error did not apply to my issue).
I have an activity, and inside that activity I have a fragment. Inside the fragment I am creating an ImageView (its called iImage but its just an extended ImageView class).
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState)
{
// Inflate the layout for this fragment
iImage image = new iImage(getActivity());
image.setImageResource(R.drawable.name_splash);
LinearLayout.LayoutParams par = new LinearLayout.LayoutParams(1500,1100);
image.setLayoutParams(par);
container.addView(image);
View rootView = inflater.inflate(R.layout.fragment_edit_photo, container, false);
return rootView;
}
However, when I run the app, it loads, and it works just fine, however I get this error:
java.lang.RuntimeException: Unable to start activity ComponentInfo{co.name.app/co.name.app.CameraEditorActivity}: java.lang.NullPointerException: Layout parameters cannot be null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
....
Caused by: java.lang.NullPointerException: Layout parameters cannot be null
at android.view.View.setLayoutParams(View.java:11470)
at co.name.app.EditPhotoFragment.onCreateView(EditPhotoFragment.java:89)
Can you advise what the underlying issue is?
I can not reproduce your error, your code works in my test case.
The Layout parameters error for sure refers to image? Check if all components in R.layout.fragment_edit_photo have layout data.
If so, the underlying issue may be that the fragment's parent container layout might not be a LinearLayout. Also check if your SDK is up to date.
I'm following along with the tutorial here
https://developer.android.com/training/basics/firstapp/building-ui.html
and I'm confused as to why they say to edit fragment_main.xml instead of activity_main.xml. In the MainActivy.java file, the onCreate() method has a line that says
setContentView(R.layout.activity_main);
Why does it complain when I try to change it to
setContentView(R.layout.fragment_main);
Any pointers would be appreciated.
The activity is a container of fragments, a fragment is like an UI layer which can be added, modified or deleted in execution time. also in the activity layout you can have added "static" fragments.
There can be a lot of causes for your error if you swap the layouts, maybe your activity code tries to reference some views that are not in the fragment layout or viceversa, maybe the activity layout has references to fragments, etc... You can name your layouts as you want, but you need to set the layout that matches with your code in your activities/fragments
you have to use
setContentView(R.layout.activity_main);
in your program where as setContentView(R.layout.fragment_main); is used when you use Different Fragments in One Activity
and you getting error because there is no xml file present named fragment_main.xml in res folder.
its just name fragment_main or activity_main if you wish you can give your GF :D name also,
i.e when you add a layout file to res/layout path an entry will be maid in R.java
say you create main.xml in res/layout, and when you clean your project an entry R.layout.main
will be added to R.java its just the name whatever you give to file.
may be you getting error because that file not there or might be that file don't hold layout in it.
Both are optional. But, It's always better using one layout to avoid confusion into your code. Which in this case I will suggest using activity_main.xml and delete the fragment_activity.xml following the below procedure:
1.Creat project normally.
2.Copy fragment_main.xml to activity_main.xml (content). Then delete fragment_main.xml
3.In MainActivity.java delete the following content :
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
and
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
Hope this help