onBackPressed with extend Fragment

onBackPressed with extend Fragment - android

I have an Activity with android studio which extends to AppCompatActivity:
public class Act_1 extends AppCompatActivity {
And the onBackPressed event works great.
#Override
public void onBackPressed() {
}
This same event I wish to use in an activity that extends to Fragment:
public class Act_2 extends Fragment{
But when I write the code, there is an error message about #Override that says:
"Method does not override method from its superclass"
Is there a solution to this problem?
Thanks

The Act_2 is not an Activity, is a Fragment and the onBackPressed() method is an Activity's method, so you cannot override it in your Fragment. To fix this issue change your Act_2 to extend AppCompatActivity or Activity.

onBackPressed is under Activity not Fragment. What you can do is override the method in Activity.
Like this::
android.support.v4.app.FragmentManager fragmentManager =
getSupportFragmentManager();
int count = fragmentManager.getBackStackEntryCount();
if (count > 0) {
getSupportFragmentManager().popBackStack();
} else {
if (this instanceof HomeActivity) {
//additional code
} else {
finish();
}
}

Related

Get the instance of Activity from the Child Fragment

My activity extends AppCompatActivity, and I started a Fragment there with support library fragment manager:
public MyActivity extends AppCompatActivity {
...
#Override
public void onResume() {
super.onResume();
// show my fragment
getSupportFragmentManager().beginTransaction().add(android.R.id.content, myFragment, TAG).commit();
}
}
My question is, in MyFragment, how can I get the instance of MyActivity who started it?
//NOTE: it extends android.support.v4.app.Fragment
public class MyFragment extends Fragment {
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// How to get the instance of MyActivity here?
// I tried: getActivity() but it returns FragmentActivity
//& MyActivity is AppCompatActivity
}
}
I know there is getActivity() function in Fragment, but it returns FragmentActivity:

Try this
((MyActivity) getActivity()).
then access anything from activity class

How to implement an interface in Fragment from a non parent Activity?

I have not found a clear solution anywhere on stack for this.
Here's my basic set up
public class Activity1 extends AppCompatActivity
{
private OnAttributesUpdatedListener onAttributesUpdatedListener;
public interface OnAttributesUpdatedListener
{
public void onAttributesUpdated();
}
public void setTargetFragment(Fragment fragment)
{
this.onAttributesUpdatedListener = (OnAttributesUpdatedListener) fragment;
}
private void whenFinishedSomethingCallback()
{
onAttributesUpdatedListener.onAttributesUpdated();
}
}
public class Fragment1 extends Fragment implements Activity1.OnAttributesUpdatedListener
{
button.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View view) {
if(rivalButtonClick == 0)
{
Activity1 activity1 = new Activity1();
activity1.setTargetFragment(Fragment1.this);
startActivity(new Intent(getActivity(), activity1.getClass()));
}
}
});
}
I get a null pointer exception and crashes on : onAttributesUpdatedListener.onAttributesUpdated(); because for some reason my listener never gets set properly. What's the proper way to do this?

You need to set the listener at start of the fragment onCreatView() or in onActivityCreated() only if the Desired Activity is a parent Activity of that particular fragment. Below is an example .
public class Activity1 extends AppCompatActivity {
private OnAttributesUpdatedListener onAttributesUpdatedListener;
public interface OnAttributesUpdatedListener {
public void onAttributesUpdated();
}
public void setListener(OnAttributesUpdatedListener onAttributesUpdatedListener) {
this.onAttributesUpdatedListener = onAttributesUpdatedListener;
}
private void whenFinishedSomethingCallback() {
if(onAttributesUpdatedListener!=null)
onAttributesUpdatedListener.onAttributesUpdated();
}
}
public class Fragment1 extends Fragment implements Activity1.OnAttributesUpdatedListener
{
#Override
public void onAttributesUpdated() {
// Do your stuff here
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
((Activity1)getActivity()).setListener(this);
}
}
Read about fragment Life cycle to make use of getActivity(). also remove the listener when fragment is destroyed .
Use LocalBroadcastManager for communicating between in case the Fragment exists in other Activity.

At first create an Interface like this:
public interface Listener{
void doSomething() }
Then implement this interface in your activity.
And also add
Listener listener
In your fragment
And in onAttach method in fragment use this
listener=(Listener)activity
Then call listener whenever you need .

Nested fragments: Detect click on outer fragment from within inner fragment

My application has two nested fragments like in the picture below:
How is it possible to detect clicks on Fragment1 from within the instance of Fragment2?

Off the cuff, I would say to create a listener interface in Fragment1, then implement that interface in Fragment2 and call the appropriate method in the interface in Fragment1's onClick method.
Edit
This is a pretty barebones example, and I haven't tested it, but here's the general theory. Of course, you'll need to add in your logic and fill in necessary methods like onCreate.
public class SampleActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Initialize your activity here
Fragment1 fragment1 = new Fragment1();
Fragment2 fragment2 = new Fragment2();
// Give fragment1 a reference to fragment2
fragment1.registerListener(fragment2);
// Do your fragment transactions here
}
}
public class Fragment1 extends Fragment implements OnClickListener{
// This is the interface. You can put as many abstract methods here as you want
// with whatever parameters you want, but they all have to be overriden
// in fragment2
public interface FragmentClickListener {
void onFragmentClick();
}
FragmentClickListener mListener;
// This fragment needs to have a reference to the other fragment
// This method can take any class that implements FragmentClickListener
public void registerListener(FragmentClickListener mListener) {
this.mListener = mListener;
}
#Override
public void onClick(View view) {
// You must check to make sure something is listening before you use the interface
if (mListener != null) {
//Let the interface know this fragment was clicked
mListener.onFragmentClick();
}
}
}
public class Fragment2 extends Fragment implements FragmentClickListener {
#Override
public void onFragmentClick() {
// Do whatever you want to do when fragment1 is clicked
}
}

How to detect when a fragment appears on the screen?

How could some part of my code be aware of Fragment instance become visible on a screen?
The following snippet will explain my question.
public class MyApp extends Application {
public static final String TAG = MyApp.class.getSimpleName();
#Override
public void onCreate() {
super.onCreate();
registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
...
#Override
public void onActivityResumed(Activity activity) {
Log.d(TAG, activity.getClass().getSimpleName() + " is on screen");
}
#Override
public void onActivityStopped(Activity activity) {
Log.d(TAG, activity.getClass().getSimpleName() + " is NOT on screen");
}
...
});
}
Here i can track when any activity within my app appears on the screen. Is there any way to extend this approach on Fragments?
Something like
Activity.getFragmentManager().registerFragmentLifecycleCallbacks();
UPD. I know nothing about activities implementations, do they use fragments at all and how do they use them (injection via xml, ViewPager etc.) The only thing I have within my class is an application context. Let's assume Activity and Fragment implementations are black boxes and i am not able to make any changes.

In your fragment, override onHiddenChanged(...) method:
#Override
public void onHiddenChanged(boolean hidden) {
super.onHiddenChanged(hidden);
if (hidden) {
Log.d(TAG, ((Object) this).getClass().getSimpleName() + " is NOT on screen");
}
else
{
Log.d(TAG, ((Object) this).getClass().getSimpleName() + " is on screen");
}
}
Hope this work for you!

Without touching the Activity or Fragment code and assuming you don't know the tag or layout it is placed in, there is very little that you can do. The best that I can see is that you could get the FragmentManager in ActivityResumed and ActivityStopped callbacks (because here you have an Activity reference) and apply a BackstackChangedListener. This assumes that you use the backstack when changing between fragments.
The issue with what you are asking is that you want lifecycle callbacks for Fragments on the Application level when you have no control over the middle men, the Activities which are already starved for Fragment callbacks. They do most everything through their FragmentManager, and propagate their own lifecycle callbacks down to the Fragments so that the fragments will behave appropriately. The onResume and onPause callbacks in fragments only occur when they are first created or when the Activity experiences those callbacks. There is only one lifecycle callback for Fragments in Activities, onAttachFragment, which if you could override, would give you references to the Fragments that are attached to the Activity. But you said you can't change the Activity or the Fragment, and you want to know when the Fragments are shown.
So if you don't use the backstack, I don't think there's a way to do what you want.

For putting Fragments inside Activity i use SlidingTabLayout which Google uses. Inside it you have ViewPager and some Adapter to populate many Fragments. First of all you have to put this and this files in your project. Then here there is good tutorial for how you can implement SlidingTabLayout.
1) After you have implemented SlidingTabLayout in your Activity, you can detect when and which Fragment becomes visible from Activity:
mSlidingTabLayout.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//Do nothing
}
#Override
public void onPageSelected(int position) {
if (position == 0) {
//Whenever first fragment is visible, do something
} else if (position == 1) {
//Whenever second fragment is visible, do something
} else if (position == 2) {
//Whenever third fragment is visible, do something
} else if (position == 3) {
//Whenever fourth fragment is visible, do something
}
}
#Override
public void onPageScrollStateChanged(int state) {
//Do nothing
}
});
2) You can detect if Fragment is visible from Fragment itself as i answered here, however this may get called before onCreateView() of Fragment, so check answer in the link:
#Override
public void setUserVisibleHint(boolean visible){
super.setUserVisibleHint(visible);
if (visible){
//when this Fragment is active, do something
}
}
3) You can change also change colors of indicators of each Tab like this from Activity:
mSlidingTabLayout.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
#Override
public int getIndicatorColor(int position) {
if (position == 0) {
return getResources().getColor(R.color.orange);
} else if (position == 1) {
return getResources().getColor(R.color.redDimmed);
} else if (position == 2) {
return getResources().getColor(R.color.yellow);
} else if (position == 3) {
return getResources().getColor(R.color.green);
} else {
return getResources().getColor(R.color.redLight);
}
}
#Override
public int getDividerColor(int position) {
return getResources().getColor(R.color.defaultActionBarBg);
}
});

Use same way as activity
set flag in application class to check visiblity of fragment, use below code in fragment
#Override
public void onStart() {
super.onStart();
Log.e( "Fragment is visible", "Fragment is visible");
Application Class.isFragmentShow = true;
}
#Override
public void onPause() {
super.onPause();
Log.e("Fragment is not visible", "Fragment is not visible");
Application Class.isFragmentShow = false;
}
to communicate with fragment you have to call that activity in which fragment added then use below code
MainFragment fragment = (MainFragment) fragmentManager.findFragmentByTag("MainFragment");
fragment.setFilter();

Don't exist a default way to do, but you can make your own Callbacks, I made this and works fine, first need have a BaseFragment class where we'll handle all fragment events.
public class BaseFragment extends Fragment {
private String fragmentName;
private FragmentLifecycleCallbacks listener;
public void registerCallBacks(String fragmentName){
// handle the listener that implement 'MyApp' class
try{
listener = (FragmentLifecycleCallbacks) getActivity().getApplication();
} catch (ClassCastException e) {
throw new ClassCastException("Application class must implement FragmentLifecycleCallbacks");
}
// set the current fragment Name for the log
this.fragmentName = fragmentName;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
if(listener!=null) {
listener.onAttachFragment(fragmentName);
}
}
#Override
public void onResume() {
super.onResume();
if(listener!=null) {
listener.onResumeFragment(fragmentName);
}
}
#Override
public void onStop() {
super.onStop();
if(listener!=null) {
listener.onStopFragment(fragmentName);
}
}
// 'MyApp' class needs implement this interface to handle all the fragments events
public interface FragmentLifecycleCallbacks{
void onStopFragment(String fragmentName);
void onResumeFragment(String fragmentName);
void onAttachFragment(String fragmentName);
}}
On 'MyApp' class implement the interface of BaseFragment
public class MyApp extends Application implements BaseFragment.FragmentLifecycleCallbacks{
public static final String TAG = MyApp.class.getSimpleName();
#Override
public void onCreate() {
super.onCreate();
}
#Override
public void onStopFragment(String fragmentName) {
Log.d(TAG, fragmentName + " is NOT on screen");
}
#Override
public void onResumeFragment(String fragmentName) {
Log.d(TAG, fragmentName + " is on screen");
}
#Override
public void onAttachFragment(String fragmentName) {
Log.d(TAG, fragmentName + " is attached to screen");
}}
And now each Fragment that you have need extends 'BaseFragment' and register to the global listener
public class FragmentA extends BaseFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_simple, container, false);
// here register to the global listener
registerCallBacks(FragmentA.class.getName());
return rootView;
}}
Hope this helps!

Intercept onWindowFocusChanged() in the activity and propagate that to the interested fragment.

Try this
private Boolean isFragmentVisible()
{
if(getFragmentManager().findFragmentByTag("TAG") != null && getFragmentManager().findFragmentByTag("TAG").isVisible())
{
//The fragment is visible
return true;
}
return false;
}
Alternative way
private Boolean isFragmentVisible()
{
return getFragmentManager().findFragmentByTag("TAG") != null && getFragmentManager().findFragmentByTag("TAG").isVisible();
}

You can know the following with the built in method called "onActivityCreated(Bundle)" this method tells that the fragment has been created thus you get to know that the fragment appears on the screen Click here for reference
Hope it helps

I've looked through what's available without using a base Fragment or Activity class but couldn't find any. I've made an implementation that provides basic (onAdded / onRemoved) functionality for all fragments in your application. It is certainly possible to extend it to report the current state of the fragment (onAttach, onResume, onPause, onDetach, ...).
You can find the code along with a sample here: https://github.com/Nillerr/FragmentLifecycleCallbacks
It works both for non-support library Fragments and support library Fragments through different implementations. The support library class is safer to use and should perform better, because the non-support one uses Reflection to access the fragments, while the support library FragmentManager includes a getFragments() method.

If you are setting a Fragment to your View, you probably have a container where it will be shown. Given that this container is, say, a FrameLayout with id R.id.container, you can do that:
Fragment f = fragmentManager.findFragmentById(R.id.container);
if (f instanceof YourFragment) {
// TODO something when YourFragment is ready
}

Does this interface provide anything helpful to you?
https://github.com/soarcn/AndroidLifecyle/blob/master/lifecycle/src/main/java/com/cocosw/lifecycle/FragmentLifecycleCallbacks.java
It sounds like your best bet if you can't override the Fragment's own onResume() method is to create your own interface that extends ActivityLifecycleCallbacks, then put your logging code in the onFragmentResumed(Fragment yourFragment) method.
You can get a pointer to the Fragment by doing something like this:
int yourFragmentId = 0; //assign your fragment's ID to this variable; Fragment yourFragment.getId();
FragmentManager fm = activity.getFragmentManager();
Fragment f = fm.findFragmentById(yourFragmentId);

whereever u want to check if fragment is visible or not.. just check isMenuVisible() value.
this is fragment's method which i used to check visible fragment when i have to fire some http request from viewpager selected Item.
hope this helps.
in my case i was using this method in onActivityCreated().

In you fragment override method setMenuVisibility If you are using ViewPager and are swiping from left and right, this method is called when the visivility of the fragment gets changed.
Here is a sample from my project
public abstract class DemosCommonFragment extends Fragment {
protected boolean isVisible;
public DemosCommonFragment() {
}
#Override
public void setMenuVisibility(boolean menuVisible) {
super.setMenuVisibility(menuVisible);
isVisible = menuVisible;
// !!! Do Something Here !!!
}
}

Animation listener
I have NOT checked all use cases and there is an unhandled exception. You can play around with it to fit your use case. Please feel free to comment your opinions or use cases it did not solve.
NOTE: You can add fragmentWillDisappear and fragmentDidDisappear by handling for enter in onCreateAnimation.
Parent Fragment:
public class BaseFragment extends Fragment {
private Animation.AnimationListener animationListener;
private void setAnimationListener(Animation.AnimationListener animationListener) {
this.animationListener = animationListener;
}
#Override
public void onAttach(#NonNull Context context) {
super.onAttach(context);
setAnimationListener(new Animation.AnimationListener() {
#Override
public void onAnimationStart(Animation animation) {
fragmentWillAppear(animation);
}
#Override
public void onAnimationEnd(Animation animation) {
fragmentDidAppear(animation);
}
#Override
public void onAnimationRepeat(Animation animation) {
}
});
}
#Override
public Animation onCreateAnimation(int transit, boolean enter, int nextAnim) {
AnimationSet animSet = new AnimationSet(true);
Animation anim = null;
try {
anim = AnimationUtils.loadAnimation(getActivity(), nextAnim);
} catch (Exception error) {
}
if (anim != null) {
anim.setAnimationListener(animationListener);
animSet.addAnimation(anim);
}
return animSet;
}
public void fragmentDidAppear(Animation animation) {
}
public void fragmentWillAppear(Animation animation) {
}
}
Child Fragment:
class ChildFragment extends BaseFragment {
#Override
public void fragmentDidAppear(Animation animation) {
super.fragmentDidAppear(animation);
}
#Override
public void fragmentWillAppear(Animation animation) {
super.fragmentWillAppear(animation);
}
}

How to properly do a global onBackPressed() override?

I want to override onBackPressed() and I have this code in all my activities
int backpress=0;
public void onBackPressed(){
backpress = (backpress + 1);
if (backpress>1) {
this.finish();
}else{
Toast.makeText(getApplicationContext(), R.string.finish, Toast.LENGTH_SHORT).show();
}
}
But I only want to override the function one time if it's possible. Whats the proper way?

Create a Base activity and define this method there. Like
public class BaseActivity extends Activity {
private int backpress = 0;
#Override
public void onBackPressed() {
backpress = (backpress + 1);
if (backpress > 1) {
this.finish();
} else {
Toast.makeText(getApplicationContext(), R.string.finish,
Toast.LENGTH_SHORT).show();
}
}
}
And extend this BaseActivity instead of Activity ino your activity. Like
// Just override BaseActivity instead of Activity class.
public class MyActivity extends BaseActivity {
// Do you task
}

Develop Reference

The Android operating system is a mobile operating system that was developed by Google (GOOGL?) to be primarily used for touchscreen devices, cell phones, and tablets.

onBackPressed with extend Fragment - android

The Act_2 is not an Activity, is a Fragment and the onBackPressed() method is an Activity's method, so you cannot override it in your Fragment. To fix this issue change your Act_2 to extend AppCompatActivity or Activity.

Related

Get the instance of Activity from the Child Fragment

How to implement an interface in Fragment from a non parent Activity?

Nested fragments: Detect click on outer fragment from within inner fragment

How to detect when a fragment appears on the screen?

How to properly do a global onBackPressed() override?

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