Develop Reference

getContext() doesn't return null when fragment not attached?

An async task in a Fragment used to crash my app if the app was suddenly closed. The post execute code ran (e.g. show a Toast), but there was no app anymore.
I thought I fixed this by checking getContext() != null before running post execute code, but I got another crash.
java.lang.IllegalStateException:
at android.support.v4.app.Fragment.requireContext (Fragment.java:614)
at android.support.v4.app.Fragment.getResources (Fragment.java:678)
at android.support.v4.app.Fragment.getString (Fragment.java:700)
at com.grammarbud.android.grammarbud.MainFragment$2.onBillingServiceDisconnected (MainFragment.java:310)
I read that
Fragments now have requireContext(), requireActivity(), requireHost(), and requireFragmentManager() methods, which return a NonNull object of the equivalent get methods or throw an IllegalStateException.
https://developer.android.com/topic/libraries/support-library/revisions.html#27-1-0
Does this mean getContext() doesn't return null anymore? But then what does the below excerpt mean? Will it return null or not when not attached to the Activity? I don't understand the language.
The getActivity and getContext methods return nullable types because when the Fragment is not attached to an Activity, these methods already returned null. There's no change in behaviour, it's just explicitly marked now, so you can safely handle it.
https://stackoverflow.com/a/47253335/3268303
My code, which is run in a Fragment
private void connectToPlayStore() {
mBillingClient.startConnection(new BillingClientStateListener() {
#Override
public void onBillingSetupFinished(#BillingClient.BillingResponse int billingResponseCode) {
if (billingResponseCode == BillingClient.BillingResponse.OK) {
if (getContext() != null) {
queryProductDetails();
}
}
}
#Override
public void onBillingServiceDisconnected() {
// Line below ***CRASHES*** app if closed prematurely
SharedHelper.showToast(getContext(), getString(R.string.no_connection_to_play_store));
}
}
});
}
The SharedHelper function to show the Toast, which would catch if context is null, but execution doesn't get this far it seems to me
public static void showToast(Context context, String message) {
if (context != null) {
Toast newToast = Toast.makeText(context, message, Toast.LENGTH_LONG);
showToast(newToast);
}
}
So how to properly provide for the scenario when an async task is running in a fragment and the app is suddenly closed? Should I try to end connection with BillingClient.endConnection()? Will this guarantee that post execute code is not run? It doesn't explicitly say in the docs.
Also someone mentioned isAdded(). Should I check isAdded() instead of getActivity() != null && getContext() != null?

Load fragment on InfoWindowClick

So I'm trying to do the following in android xamarin.
When you press on a map element an infowindow is shown.When you press that window and an event is linked to the element the app goes to another fragment that is described by the action object. The problem is the moment I press the infowindow the whole app freezes and nothing happens. In the logs I can't see anything and the app stops at the following line:
pager.Adapter = pagerAdapter;
Added a breakpoint there and after saying "step over" the ide doesn't break anymore and the app freezes (no user interaction possible).
So let me start by giving all the relative code and a little explanation.
So first I'll show you what happens on the infowindow click. This happens on a SupportMapFragment that has it's own listener.
void GoogleMap.IOnInfoWindowClickListener.OnInfoWindowClick (Marker p0)
{
InfoPopup ip = CustomJsonConverter.Convert<InfoPopup> (p0.Title);
if (ip == null || ip.Goto == null || !(this.Activity is MainView))
return;
MainView main = (this.Activity as MainView);
p0.HideInfoWindow ();
switch (ip.Goto.type) {
case "InfoFragment":
Info info = InfoController.Items.Find (x => x.Index == ip.Goto.id);
if (info != null) {
main.RunOnUiThread (() => {
main.ShowInfosFragment ();
main.ShowInfoFragment (info);
});
}
break;
case "FaqFragment":
FaQ faq = FaQController.Items.Find (x => x.Index == ip.Goto.id);
if (faq != null) {
main.RunOnUiThread (() => {
main.ShowFaqsFragment ();
main.ShowFaqFragment (faq);
});
}
break;
}
}
I tested it with an action of InfoFragment which gives back an item so that's good. Then it goes to the main.ShowInfosFragment() which is where it freezes. So that method is really simple. This function is in the Activity holding the fragments (thanks Cheesebaron).
public void ShowInfosFragment(){
ShowFragment(1, new InfosFragment (){ InfoSelectedAction = ShowInfoFragment });
}
So the problem giving function is the following. This function is in the Activity holding the fragments (thanks Cheesebaron).
protected void ShowFragment(int index, Android.Support.V4.App.Fragment fragment, bool ignoreType = false){
RemoveSubMenu();
if (pagerAdapter.Count <= index || ignoreType || !(pagerAdapter.GetItem (index).GetType().Equals(fragment.GetType()))) {
pagerAdapter.AddFragment (index, fragment);
SetSubMenu (fragment);
pager.Adapter = pagerAdapter;
}
pager.SetCurrentItem (index, true);
DrawerButtonLayout ();
}
I've used this function a lot and it has always worked to move to the other fragments from the menu or at startup to set the mapfragment.
Anyone sees what's the problem with my code? Tried tons of things but can't seem to figure this one out with my friend google.
Thanks already for reading.
Kind regards,
Karl

Android Action Bar Responding to users

I am having issues with some methods with my app in android. I'm trying to respond to a button pressed by a user. Here is the method:
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.action_search:
openSearch();
return true;
case R.id.action_settings:
openSettings();
return true;
default:
return super.onContextItemSelected(item);
}
}
I was looking at the docs provided from google about this and it says those methods should be called depending on the user's action. Am I missing something?
The error messages area:
Error:(42, 17) error: cannot find symbol method openSearch()
Error:(46, 17) error: cannot find symbol method openSettings()
Any help would be appreciated!
Thanks

You have not defined the methods openSettings() and openSearch() inside the Activity where you define onOptionsItemSelected.
The result of this is that the compiler will tell you that it cannot find symbol method openSearch() and cannot find symbol method openSettings()
You simply have to add the method declaration inside the Activity:
private void openSettings(){
//Execute relevant code
}
private void openSearch(){
//Execute relevant code
}

The above function doesn't get executed on Button pressed event. It is executed when user selected an item from menu.
At the moment, compiler doesn't know if such method signatures exist in the class. You would need to define the functions inside the class, then use them. I guess it will work fine.

MenuItem alpha value lost after orientation change

The Problem
On Android versions < 4.1, the alpha value of the MenuItem is getting reset after an orientation change, BUT it remains disabled.
The code I'm using
DetailsFragment.java
public class DetailsFragment extends SherlockFragment {
private MenuItem miEmail;
...
#Override
public void onPrepareOptionsMenu(Menu menu) {
miEmail= menu.findItem(R.id.menu_email);
super.onPrepareOptionsMenu(menu);
}
private void populateDetails(final Detail oDetail) {
//disable email button if dealer doesn't have option
if(!oDetail.bShowSAM){
miEmail.setEnabled(false);
miEmail.getIcon().setAlpha(50);
}
...
}
}
MyManifest.xml
<activity
android:name=".activities.DetailsActivity"
android:uiOptions="splitActionBarWhenNarrow"
android:configChanges="keyboardHidden|screenSize|orientation">
</activity>
What I expect to happen
When the orientation changes, miEmail is still disabled and the alpha value is still at 50.
What is actually happening
When testing on older devices(2.3,4.0), the MenuItem is remaining disabled but the alpha value is getting reset to the default value. When testing with my devices that are >4.1, it is working as expected.
What I've tried
Googling the problem.......
I've tried to avoid using the android:configChanges="..." and handling the data through savedInstanceState, but I've learned you can't make the MenuItem serializable/parciable, thus not allowing me to pass it through outState bundle object.
I'm fairly new to Android development and I feel as though there is a trivial way of handling this MenuItem, but I cannot figure how else to handle it.
What do you think is the issue?
Any feedback will be greatly appreciated.

Dont set the icon alpha on your custom function, instead, set it on OnPrepareOptionsMenu (with a suitable conditional). You can pass a boolean on savedinstancestate saying whether it should be grayed or not.
In your populateDetails function, you would call invalidateOptionsMenu() to make android remake the action bar icons. Example:
private boolean buttonEnabled;
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
MenuItem miEmail= menu.findItem(R.id.menu_email);
if (buttonEnabled) {
miEmail.setEnabled(true);
miEmail.getIcon().setAlpha(255);
}else{
miEmail.setEnabled(true);
miEmail.getIcon().setAlpha(50);
}
return super.onPrepareOptionsMenu(menu);
}
private void populateDetails(final Detail oDetail) {
//disable email button if dealer doesn't have option
if(!oDetail.bShowSAM){
buttonEnabled = false;
InvalidateOptionsMenu();
}
...
}
}
If you are using the support library for compatibility, use supportInvalidateOptionsMenu instead.
By the way, never use the orientation tag to "fix" the problem, the issue will still appear if you quit the app for a long time and then try to open it. (android pauses the activity initially and will stop it after a while)

Android Development: Undefined Method

Hi I´m new to Android and Eclipse. I have just following the tutorial from developer.android.com. Right now I´m in adding ActionBar
Right now I´m at this part
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case R.id.action_search:
openSearch();
return true;
case R.id.action_settings:
openSettings();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
I have received an error for openSearch() and openSettings(). It said that The method openSettings() is undefined for the type DisplayMessageActivity. What shoud I do now?
Thanks

openSearch() and openSettings() are methods that the author of the tutorial created in order to perform other operations. Search well into the code, there must be somewhere the declaration of those methods, if the author made them visible.
They should look something like this:
public void openSearch() {
//Do something here.
}
public void openSettings() {
//Do something here.
}
Replacing the //Do something here with the code implementation present in the tutorial.

Im up to the same section as you, they haven't provided the methods but you have to implement them as stated above.
However I found code to open up the device settings using this code in the switch;
case R.id.action_settings:
startActivity(new Intent(Settings.ACTION_INPUT_METHOD_SETTINGS));
return true;

define them.
You're basing your code on an incomplete snippet. That snippet makes no expectation of what it means to search or create settings in your app... that's your job to implement. This snippet is only concerned about showing you how to establish the action bar, not the whole application.

The methods openSearch() and openSettings() should be defined. Use the following code. It'd help..
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch(id){
case R.id.action_search :
startActivity(new Intent(Settings.ACTION_SEARCH_SETTINGS));
return true;
case R.id.action_settings :
startActivity(new Intent(Settings.ACTION_INPUT_METHOD_SETTINGS));
return true;
default :
return super.onOptionsItemSelected(item);
}
}

Maybe you should code those methods?
private void openSearch(){
//your code here
}
private void openSettings(){
//your code here
}

Those two methods are just examples how selecting an option can start an action. The implementation was not provided because it was irrelevant to the example. Note that it is not a tutorial, but a single and un-compile-able example of how to add behavior to an options item.