newSubmitButton = (Button) findViewById(R.id.newPlayerSubmit);
Log.v("heeelp",""+newSubmitButton);
Seems simple enough. I have a global Button variable called newSubmitButton. I fetch the Button from an xml file in the project (I promise, the button exists, i didn't mispell the name, etc.) I output the button in the next line, it is null. I try to give it an onClickListener and it throws a null pointer exception. How is this button null? I just instantiated it the line before!
I just instantiated it the line
before!
No you didn't,
newSubmitButton = (Button) findViewById(R.id.newPlayerSubmit)
does not instantiate anything. It simply retrieves the button from the active view. If the button isn't part of the active view (perhaps the layout hasn't been inflated yet?) then your button reference will be null. Are you calling this code in your Activity's onCreate() method? Have you called setContentView() before executing the code in question?
Besides misspelling the name, you might have left out a call to setContentView().
(If that's not the issue, please post more code.)
Did you remember to setContentView() higher up? Just because R.java contains it doesn't mean it's attached to your view.
Related
this is my issues, so my button handler on activity stated my method was never used but i'm already create the button on XML
activity：
XML：
In your XML file change the tools:context in the root LinearLayout to the path of your Activity because this data is being used to bind the onClick action
As I can tell from the screenshots it should be changed to
tools:context=".LanderActivity"
I currently have the following situation:
1) The "main view" which contains the EditText I'm trying to update. (Let's call it mainView)
2) A fragment that is opened whenever I click in a button that is contained in the "main view", the
fragment receives mainView as parameter.
3) An OnClickListener which is set to a button that is contained by the fragment. This listener receives the fragment as parameter.
Basically what I need to do is, each time I click on the button that triggers the listener, I need to update the editText, however it doesn't seem to be working. I believe it has something to do with "notifying" the view, but I haven't been able to get it working no matter what I try. After I update the text I close the fragment and
Basically the code is the following:
public void onClick(View v){
String newMessageContent = "hello world";
fragment1.mainView.editText1.setText(newMessageContent);
FragmentManager manager = this.fragment1.getActivity().getFragmentManager();
manager.beginTransaction().replace(R.id.container,this.fragment1.mainView.getPlaceHolderFragment()).commit();
}
Please note that I have simplified the problem a little bit and changed the name of the fragment/views in order for you guys to understand better. The text "hello world" is actually dynamic, and depends no another parameter that is received by the OnClickListener.
After I click the fragment does get replaced, so I know the onClickListener is working correctly, however I believe there's something wrong with the way the data change is being notified.
I've already looked at many SO questions, however none of them have helped me to achieve what I need.
Any help is appreciated, thanks.
I suggest implementing an interface, say, IUpdateFromFragment with method, say, onUpdate(String message), then let activity implement that interface and inside the fragment just call something like ((IUpdateFromFragment)this.getActivity()).onUpdate(newMessageContent);
I realized the problem was that each time I replaced the fargment via the fragmentManager, the method setActivityView was being called again, which replaced the EditText content.
In order to avoid this, I manually removed the fragment (instead of replacing it), doing the following:
FragmentManager manager = this.selectTemplateFragment.getActivity().getFragmentManager();
manager.beginTransaction().remove(this.selectTemplateFragment).commit();
Update the fragment via transaction, then within the fragment1 class OnViewCreated, you can do mainView.editText1.setText("whatever");
The way you're doing this now, I'm surprised isn't throwing an exception since the view isn't inflated yet.
I have a checkbox in the Android layout file. When the checkbox is clicked i call an empty function in the activity class. This causes the app to stop working. Why is this?
I am assuming that you are using the "onclick" attribute in your XML.
If you are receiving a MethodNotFound exception, it could be one of two things:
You have a typo in either your Activity's method name or your XML's method name, or...
The visibility of your method in your Activity is not public.
When specifying onclick values in XML, the method should look like this in your activity:
public void myOnClickMethod(View v) { ... }
How can I trigger a button click event using code in Android? I want to trigger the button click programmatically when some other event occurs.
Same Problem I am Facing
public void onDateSelectedButtonClick(View v){
/*Something Alarm Management
http://www.java2s.com/Code/Android/Core-Class/Alarmdemo.htm
copied code from this site*/
}
Button code:
<Button
android:onClick="onDateSelectedButtonClick"
android:text="Set notification for this date" />
But I want to call that function OnLoadLayout without OnClickEvent
there is a better way.
View.performClick();
http://developer.android.com/reference/android/view/View.html#performClick()
this should answer all your problems. every View inherits this function, including Button, Spinner, etc.
Just to clarify, View does not have a static performClick() method. You must call performClick() on an instance of View.
For example, you can't just call
View.performClick();
Instead, do something like:
View myView = findViewById(R.id.myview);
myView.performClick();
Just to clarify what moonlightcheese stated:
To trigger a button click event through code in Android
provide the following:
buttonName.performClick();
you can do it this way
private Button btn;
btn = (Button)findViewById(R.id.button2);
btn.performClick();
Just write this simple line of code :-
button.performClick();
where button is the reference variable of Button class and defined as follows:-
private Button buttonToday ;
buttonToday = (Button) findViewById(R.id.buttonToday);
That's it.
Android's callOnClick() (added in API 15) can sometimes be a better choice in my experience than performClick(). If a user has selection sounds enabled, then performClick() could cause the user to hear two continuous selection sounds that are somewhat layered on top of each other which can be jarring. (One selection sound for the user's first button click, and then another for the other button's OnClickListener that you're calling via code.)
Starting with API15, you can use also callOnClick() that directly call attached view OnClickListener. Unlike performClick(), this only calls the listener, and does not do any associated clicking actions like reporting an accessibility event.
If you do not use the sender argument, why not refactor the button handler implementation to separate function, and call it from wherever you want (from the button handler and from the other place).
Anyway, it is a better and cleaner design - a code that needs to be called on button handler AND from some other places deserves to be refactored to own function. Plus it will help you separate UI handling from application logic code. You will also have a nice name to the function, not just onDateSelectedButtonClick().
I'm getting null pointer exceptions when I try to initialize Button and EditText objects in global scope, can't figure it out. I've commented out everything but the bare minimum for the app to display my layout, but this still causes a crash:
private EditText addmoney = (EditText)findViewById(R.id.addmoney);
R.id.addmoney definitely, definitely exists. So what the heck? Is it impossible to declare EditText in global scope? I need to be able to call it from both onCreate and onPause in a class extending Activity, is there maybe another way I should be doing this?
EDIT:
I tried using shade's method of inflating the layout first but it causes errors, apparently your not allowed to use system services before onCreate() has been called and inflating a view requires one.
You have to execute findViewById only after you have set the content for your current activity.
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
addmoney = (EditText)findViewById(R.id.addmoney);//it knows in which file to search for the id
}
Alternatively, you could do something like this:
private View dummy = (View) View.inflate(this, R.layout.dummy, null);
private EditText addmoney = (EditText) dummy.findViewById(R.id.addmoney);
... and in the onCreate (or wherever else):
setContentView (dummy);
Since you already have the parent of the EditText view instantiated, you can reference it without having a NPE.
NOTE: The first parameter of inflate is a Context. Therefore, you need a Context that is alive for this to work.
Ooops, wrong class :D