Develop Reference

How to prevent activity from reloading itself when coming back after visiting other activities?

I have 5 different activities in my app, i enable the user to navigate between those activities by clicking buttons. The main activity has a RecyclerView in it (used to make a feed). the other activities are used for search, profile, notifications, etc. The user opens the app, the main activity is displayed. The user can scroll through the feed (which is the RecyclerView) in the main activity, now the user decides to go to other activities, search, profile, etc. Now, when the user clicks on the button that navigates to the main activity, I want to open back the main activity and display the recycler view at the same scrolling position and with the same items as was when the user just left it off.
Note: I'm not talking here about pressing the back button or using any goBack functions. I want to enable the user to use the main activity and visit all other activities and after all of that he will be able to come back to the main activity and find the feed exactly as he left it off.
In every activity I have five navigation buttons that allowing the user to go from every activity to every activity: click on profileBtn will open the profile activity, etc.
There is a way in which i can back up the state of the recycler view in the main activity before the user wants to go to other activities and restore it when the user clicks on the homeBtn?
Code:
HomeActivity.java:
public void profileBtn_OnClick(android.view.View view)
{
Intent intent = new Intent(getBaseContext(), ProfileActivity.class);
startActivity(intent);
}
ProfileActivity.java, SerachActivity.java, NotificationsActivity.java:
public void homeBtn_OnClick(android.view.View view)
{
/* HERE I WANT TO OPEN BACK THE HOME ACTIVITY AND DISPLAY THE FEED
EXACTLY AS IT WAS WHEN THE USER LEFT IT, HOW DO I DO THAT? */
Intent intent = new Intent(getBaseContext(), HomeActivity.class);
startActivity(intent);
}

You can use the launchMode="singleTask".
The system creates the activity at the root of a new task and routes
the intent to it. However, if an instance of the activity already
exists, the system routes the intent to the existing instance through
a call to its onNewIntent() method, rather than creating a new one.
You can get more information about launchMode here: https://developer.android.com/guide/topics/manifest/activity-element
android:launchMode=["standard" | "singleTop" | "singleTask" | "singleInstance"]
<activity
android:name=".ui.HomeActivity"
android:launchMode="singleTask" />

Please do NOT use the special launch mode singleTask for this purpose. It causes more problems than it solves. These launch modes have complex side-effects that are not obvious and will cause you more problems later.
Your problem is simple to solve using standard Android behaviour. Change your method to look like this:
public void homeBtn_OnClick(android.view.View view)
{
Intent intent = new Intent(getBaseContext(), HomeActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP |
Intent.FLAG_ACTIVITY_SINGLE_TOP);
startActivity(intent);
}
The flag CLEAR_TOP tells Android to remove all activities from the task that are on top of the target Activity (in this case the target Activity is HomeActivity.
The flag SINGLE_TOP tells Android not to recreate HomeActivity, but to reuse the existing instance of it.

How to call overridePendingTransition() when Activity is destroyed?

I've been tweaking a lot with android design and capability of Android to use the maximum potential of an Android framework, I have come across transition, and my question is how to define Activity's Destroyed's animation ?. Say I am starting an activity using intent like so :
Intent intent_info = new Intent(ComponentsPage.this, SecondActivity.class);
startActivity(intent_info);
overridePendingTransition(R.anim.slide_up, R.anim.no_change);
That snippet basically opens up SecondActivity with Slide Up transition. Now i am in second activity and second activity say doesn't have any button but i want whenever Second Activity is closing (Destroyed) it close with slide down animation.
I've tried adding
overridePendingTransition(R.anim.no_change,R.anim.slide_down);
Inside onDestroy() and onStop(), but still no luck, i guess the activity is already closed when those methods are called.

When you try to finish the second activity try to override the finish method inside your SecondActivity as follows:
#Override
public void finish() {
super.finish();
overridePendingTransition(R.anim.no_change, R.anim.slide_down);
}

Force quit of Android App using System.exit(0) doesn't work

when I try to quit my Android application by overwriting the function for the back-button of Android devices and "System.exit(0)", this doesn't work.
I have an activity named "LoginActivity" and an activity named "OverviewActivity".
When I start an intent in OverviewActivity to switch to LoginActivity, this works.
Intent changeViewIntent = new Intent(OverviewActivity.this,
LoginActivity.class);
startActivity(changeViewIntent);
Now I am in LoginActivity and there is the overwritten method:
#Override
public void onBackPressed() {
System.exit(0);
}
But when I press the back-key (e.g. in the device simulator) the screen is blank for a millisecond and then it goes back to the OverviewActivity.
Why is this happening? I just want to force the close when the back-key is pressed.
History disabling for the OverviewActivity in the manifest is no option, because there are several ways to access the OverviewActivity from other activities.
Maybe there is an idea? Android 4 is minimium requirement, so it doesn't have to work on lower versions..
Thanks!

The Exit is possible by deleting the whole activity-call-history and starting the Home-Activity of the Home-Scrren.
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
startActivity(intent);

What you can do is
In your OverviewActivity:
Intent changeViewIntent = new Intent(OverviewActivity.this,
LoginActivity.class);
startActivity(changeViewIntent);
OverviewActivity.this.finish();
after starting the intent you terminate the overview activity
and in LoginActivity
#Override
public void onBackPressed() {
LoginActivity.this.finish();
}
This way your app will exit.
The difference between finish() and System.exit(0)
The VM stops further execution and program will be exit.
Now, in your case the first activity comes back due to activity stack.
So when you move from one activity to another using Intent, do the finish() of current activity like this.
If you want to force quit you can use
android.os.Process.killProcess(android.os.Process.myPid());
System.exit(0);
getParent().finish();
But you should not use System.exit especially if your activity uses other recourses in the background e.g. Internet, Video, etc.

When bringing Android activities from the stack to the front, how do I refresh (reinitialize) them? So to run onCreate again etc

If I'm bringing Android activities from the stack to the front, how do I refresh them? So to run onCreate again etc.
My code below, in conjunction with setting activities in the Android manifest to android:launchMode="singleTask" allows me to initiate an activity if that activity is not already active within the stack, if it is active within the stack it is then brought to the front.
How do I then, if the activity is brought to the front refresh it so that onCreate is ran again etc.
Intent intent = new Intent(myActivity.this,
myActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(intent);

I think FLAG_ACTIVITY_CLEAR_TOP will resolved your problem:
Intent intent = new Intent(myActivity.this, myActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);

I don't think there is an explicit way to refresh onCreate, perhaps you may want to add the code you want reloaded into onResume.
This workaround may work if you want to keep your code in onCreate.
finish();
startActivity(getIntent());

If all you want to do is refresh the content, you should override the onResume method, and add in the code to perform the refresh in this method. To do this, use the following code within the activity that you want to perform the refresh, (ie, not the same activity that you are calling startActivity() from):
#Override
protected void onResume(){
super.onResume();
//add your code to refresh the content
}
Tip: If you are using Android Studio, press Alt+Insert (while you have the Java file open), then click Override Methods, find onResume, and it should provide you with a basic template for the method.
The diagram I added shows the order that the methods are run (this is known as the Activity Lifecycle). onCreate() is run whenever an Activity is first created, followed by onStart(), followed by onResume(). As you can see, when a user returns to an Activity, onCreate() is not run again. Instead, onResume() is the first method that is called. Therefore, by putting your code into the onResume() method, it will be run when the user returns to the activity. (Unlike onCreate(), which will not be run again).
Extra info: Since you will be initially setting the data in onCreate() and then refreshing it within onResume(), you might want to consider moving all of your code used to initially set the data to onResume() as well. This will prevent redundancy.
Edit: Based on your following comment, I can give the following solution:
I'm wanting to properly refresh the page, e.g. if there is a variable count initialised at 0. And though running the activity it's has became equal to 300. When the activity is called (intent) then refreshed, count will once again be equal to it's initial value. Do you know how to do this?
Without your current activity's code, there is not much to work with, but here is some pseudo-code as to how I would accomplish your problem:
public class MyActivity extends Activity {
TextView numberTextView;
int numberToDisplay;
#Override
protected void onCreate(Bundle bundle){
super.onCreate(bundle);
setContentView(myContent);
numberTextView = (TextView) findViewById(R.id.numberTextView);
numberTextView.setText(numberToDisplay+"")//converts the integer to a string
}
#Override
protected void onResume(){
super.onResume();
numberToDisplay = 0;
numberTextView.setText(numberToDisplay+"");
}
}

how to make the Fragment/Activity not go to the backgoround

Normally In an Fragment, implicit intent can be used to start a brower component,if there are several brower component, the Android system will show an selection dialog ,the dialog just overlay the Fragment which send the intent.
but in my situation when selection dialog is shown ,the Fragment go to the background(disappeared) ,and the home screen can be seen.
does anyone encounter this problem ,how to make the Fragment not go to the backgoround.
in onPause method it just look like below in my fragment source
#Override
public void onPause() {
mLog.printMethodLifeCycle("onPause");
super.onPause();
}
and in activity I did not overide the onPause method
AndroidManifest.xml is too long ,can you tell me which part should I post or notice