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 tried everything to perform click on view in recyclerview item but not succesfull. Read every option on internet and tried it but still not working. Lately I used:
onView(ViewMatchers.withId(R.id.live_rw_liveMatchList))
.perform(RecyclerViewActions.actionOnItemAtPosition(2, MyViewAction.clickChildViewWithId(R.id.pick_pw_pickLeft)));
But all i get is:
android.support.test.espresso.AmbiguousViewMatcherException: 'with id:
hr.psk.android:id/ticket_list_list' matches multiple views in the
hierarchy. Problem views are marked with '****MATCHES****' below.
And it matches only one view (my recyclerview with 13 childs)
I know this should work but it is not working in my project. Tried to perform only click on recyclerviw item in other recyclerview to make it more simple like this:
onView(withId(R.id.ticket_list_list))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
But it gives me the same message back -> Multiple matches problem
somebody help, I really tried everything
onView(withId(R.id.ticket_list_list))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
The error you're getting means that there's another View somewhere that also uses the id ticket_list_list
Is ticket_list_list your actual list view? (the parent of the things that you want to click)
If it is then is it the only one available on the screen? if it is then use the following
onView(allOf(withId(R.id.ticket_list_list), isDisplayed()))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
Adding the isDisplayed() Matcher makes the targeted View more specific by targeting only those that are displayed and ignoring those that are existing but not displayed
If there really is another matcher displayed (or the above doesn't work for you) that has the same id as the one you're trying to match then use the following
onView(allOf(withId(R.id.ticket_list_list), withParentIndex(index_of_matcher_here)))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
Instead of isDisplayed() withParentIndex(some_number) should more specifically target and give you the view that has the id you're looking for along with the index of it
In the very messy instance that the above still doesn't work, maybe because all the returned Views have the same index possibly because they are the children of another View then you can get creative and do something like
onView(allOf(withId(R.id.ticket_list_list), withParent(allOf(withId(if_of_the_parent), withParentIndex(index_of_matcher_here)))))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
to specify the index of the parent instead.
Just mix 'n match your way through it, just make sure to not go crazy on the Matchers and just keep things readable
Use as little as you can (make sure it's readable and maintainable too and not just made up of indexes), you're not trying to get the coordinates for a missile target- you just want the View
I also face the same problem before few days but finally got the solutions from StackOverflow.
If you want to click recycler custom item view click then implement the following code in your project
You need to write this code in java this will help you a lot and saved your time
ClickOnButtonView is control a view action happened in the list item and
UiController class helps you find custom row item
The code is written in Kotlin
#RunWith(AndroidJUnit4::class)
class CampaignFragmentTest {
#get: Rule
val activityTestRule = ActivityTestRule(TestActivity::class.java)
#Test
fun testCustomListClick() {
clickOnButtonAtRow(0)
}
}
private fun clickOnButtonAtRow(position: Int) {
Espresso.onView(ViewMatchers.withId(R.id.list)).perform(RecyclerViewActions.actionOnItemAtPosition<RecyclerView.ViewHolder>
(position, ClickOnButtonView()))
}
inner class ClickOnButtonView : ViewAction {
internal var click = ViewActions.click()
override fun getConstraints(): Matcher<View> {
return click.constraints
}
override fun getDescription(): String {
return " click on custom button view"
}
override fun perform(uiController: UiController, view: View) {
//btnClickMe -> Custom row item view button
click.perform(uiController, view.findViewById(R.id.btnClickMe))
}
}
That error means that it found multiple views with the id R.id.ticket_list_list. There should also be a view hierarchy log that follows the error message you provided, showing the views that Espresso found with that same id marked with ****MATCHES****.
So you can either change the id of the view you want to test or target the view by providing another ViewMatcher as below:
onView(allOf(withId(recyclerViewID), viewMatcher))
.perform(RecyclerViewActions.actionOnItemAtPosition(0, click()));
You Can also create your own custom click action like this :
fun customActionClickOnItemEvent(
#NonNull targetViewId: Int
): ViewAction {
return object : ViewAction {
val click = ViewActions.click()
override fun getDescription(): String = "Item clicked"
override fun getConstraints(): Matcher<View> = click.constraints
override fun perform(uiController: UiController?, view: View?) {
click.perform(uiController,view?.findViewById(targetViewId))
}
}
}
And Calling this function like this :
onView(withId(R.id.rv_products)).perform(
RecyclerViewActions.actionOnItemAtPosition<RecyclerView.ViewHolder>(
1,
customActionClickOnItemEvent(R.id.img_wish_list)
)
)
I would like to create a view with a listener that acts sort of like a container or grocery bag. Any image or text that is dragged into it, gets collected and saved into a local database. Or rather the image name or string gets saved. I've created custom views before that displayed a custom row of data but I'm not sure how to create a "grocery bag" type of view. I've searched Google for creating a custom container view with listener but couldn't find anything related to what I am looking for. I'm not asking anyone to do it for me, just give me some advice or push in the right direction.
Edit
Just to clarify a little more. I already know how to drag and drop a view. The problem with that is that you can drop anywhere. What I want is a view that when something is dropped within its bounds, it gets the views' string or tag. Regardless of what kind of view that may be. Somehow this custom view has to know what kind of view was dropped within its bounds and remove that view on drop.
<view class="at.calista.quatscha.views.SwipebarLayout"
android:id="#+id/sbl"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<!-- Top View -->
<Button android:text="Top" android:id="#+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
<!-- Bottom View -->
<Button android:text="Bottom" android:id="#+id/Button02" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
You would need a method that determines whether two views overlap. For example, something like these methods could work for when the target view and the dragged item view are 2 distinct views in the same container view:
private Rect getScreenBounds(View view)
{
int[] location = new int[2];
view.getLocationOnScreen(location);
return new Rect(location[0], location[1], location[0] + view.getWidth(), location[1] + view.getHeight());
}
private boolean doViewsIntersect(View dropTarget, View item)
{
Rect dropRect = getScreenBounds(dropTarget);
Rect itemRect = getScreenBounds(item);
return Rect.intersects(dropRect, itemRect);
}
However, if the views being dragged are child views on a container, and that container has a special hit area where you want to perform the drop logic, then you can just use that hit area's Rect for the intersect test.
To save information on the View, you have a few options:
You can use view.setTag(key, object) and view.getTag(key) to store whatever information you'd like on each item.
If you are using a custom class for the items, you can just add a method to get the data from the view class.
If you are using multiple different classes for the items, you could make an interface, and implement that interface on each draggable view class.
On an item's release, you could then check whether the areas/views intersect, and if they do, get whatever information you need from the dragged item to process as necessary, either using getTag or the method added to the view.
For example, this could be triggered via an onTouchListener, when you receive a MotionEvent.ACTION_UP event. Here's an example of a listener that you can add on each item:
item.setOnTouchListener(new View.OnTouchListener()
{
#Override
public boolean onTouch(View v, MotionEvent event)
{
if (event.getActionMasked() == MotionEvent.ACTION_UP)
{
if (doViewsIntesect(dropTarget, v))
{
Object data = v.getTag(DATA_KEY);
//process data
((ViewGroup) v.getParent()).removeView(v); // to remove the item afterwards
}
}
return false;
}
});