I have a text message app which has two main activities:
TextChatActivity - a conversation. Can have multiple instances for multiple conversations.
ConvListActivity - a list of all the activities.
In addition, a TextChatActivity of a certain conversation can be opened via a status bar notification.
What I want to do is to bring a specific TextChatActivity instance to the front.
Let's say I have 2 open conversations (TextChatActivity) A and B, and B is on front.
Now I got a notification that leads to conversation A. I want it to bring conversation A TextChatActivity to front.
How can I do that without opening a new instance of TextChatActivity for conversation A?
Thanks!
Actually, you can't. If you have multiple instances of an activity in the stack, there is no way to address a unique instance of an activity so that you could bring it to the front.
Your architecture is not good. Because of the way Android works, you would be better off if you had a single instance of this activity, and allow the user to switch between conversations, not by creating a new instance of an activity, but just by switching out the underlying data for the existing activity. In this way, you only ever have one instance of the activity and you can simply change the data that you are displaying.
In your "notification" example, the Intent that you start from the notification should have an "extra" that indicates which conversation the user wants to show. You should ensure that there is only one instance of your TextChatActivity by declaring it with launchMode="singleTop" or by setting FLAG_ACTIVITY_SINGLE_TOP when you start it. When onNewIntent() is called in your activity, check the "extras" and adjust the content to show the desired conversation.
If you want to create the "illusion" of an activity per conversation, then you can override `onBackPressed() and manage your own "stack" of conversations in the activity, so that when a user presses the BACK key, you can go back in the "stack" of conversations and show him the previous one, just by modifying the data that is displayed.
Just start an activity and set the flag FLAG_ACTIVITY_CLEAR_TOP
Related
Recently I created a social app. I didn't use fragment and the project is almost finished. I have several Activities like UserProfile, Followers, Followings activity.
Normally it's just working fine. But if user click UserA UserProfile activity -> and then click A's Followers -> select UserB Userprofile activity -> click B's followers activity -> select UserC Userprofile activity....
In this loop, the app would get pretty slower because it opened too many activities at same time and the back stack hold all of them.
I just wonder if there's any optimization I could do for this situation? Because UserProfile activity layout would always same except the user information content. Is that possible to use Fragment for each activity, even though different activities would show up in sequence one by one?
Thanks!
You should architect this in a different way. You should only ever have one UserProfileActivity in the stack. If you already have the UserProfileActivity for User A in the stack, and you want to show the UserProfileActivity for User B, just call startActivity() for UserProfileActivity with Intent.FLAG_ACTIVITY_REORDER_TO_FRONT and pass some extras to indicate that the Activity should show User B. Use the same concept for all of your activities.
To make sure that the BACK button navigation works correctly, you will need to override onBackPressed() and figure out what Activity needs to be shown and with what data. Then call startActivity() and also set Intent.FLAG_ACTIVITY_REORDER_TO_FRONT and provide extras so the Activity will show the correct data.
To assist in keeping track of where you are in the navigation, you might want to create a stack of items that are stored in a static variable somewhere. Each item would indicate what Activity is being shown and with what data. Every time you launch a new Activity, you push a new item on to this stack, and every time the user presses the BACK key, you pop the top item off the stack and then look at the one underneath it to determine what Activity to start and what data to send in the extras.
With this scheme, the user can click around all day long and you will never have more than one instance of each Activity, but the user will still be able to navigate all the way back.
I have three top level activities in my application. Activity A, B & C.
Each one of these activities hosts a navigation drawer. I am trying to figure out the best way to manage the activity stack between these three activities.
For example, When I start the application, Activity A is launched.
Activity A has a navigation drawer like Activities B & C. When I click on Activity B in the drawer, Activity B is launched and clicking on Activity C in the drawer launches Activity C etc...
I don't want to finish these Activies when the drawer launches a new Activity because they load data from a backend service, and when I click the back button I want it to send the application to the background.
Essentially, I am looking for a way to launch the activity if it does not exist, and if it does, just resume it. How can I accomplish this?
I think decoupling retrieving data from the activity is the best option.
The following paragraph is from Tasks and Back Stack:
Because the activities in the back stack are never rearranged, if your application allows users to start a particular activity from more than one activity, a new instance of that activity is created and pushed onto the stack (rather than bringing any previous instance of the activity to the top). As such, one activity in your application might be instantiated multiple times (even from different tasks), as shown in figure 3. As such, if the user navigates backward using the Back button, each instance of the activity is revealed in the order they were opened (each with their own UI state).
So in your case, grabbing the data in the background when the app starts using async tasks and storing them in the database might work out better.
One way to do it would be:
On create of the home activity, quickly grab the home activity's data via async task while showing a progress bar. When done, store it, and display it. Then, launch async tasks for the data for other activities. There are some conditions that could be tricky. For example, you have to make sure you show a progress bar if the user quickly switches to Activity B or C before your data is ready.
Perhaps using a singleton might suite your needs if you do not want to use the DB. Depending on the size of your data, parceling your data and passing it through a bundle might also prove to be a good technique.
What flag must I set for an intent so if the activity is visible with same extra it does not bring up a new one.
My app is somehow like google play. There are different app that are show in AppActivity by sending the app id as an Extra. User can download app and when download is finished, a complete notification is shown which on press brings up the corresponding activity page.
Currently by pressing notification it start a new activity which is correct for when AppActivity is not visible or showing another app. But it also start a new AppActivity even if the AppActivity is visible for same app.
PendingIntent.getActivity(ServiceDownload.this, id,
new Intent(ServiceDownload.this, AppActivity.class)
.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT)
.putExtra(Constants.EXTRA_ID, id), 0);
Use Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP while starting your activity and define it single top at your manifest file.
If activity is somewhere in the stack, it will be brought to top(onNewIntent method will be invoked) and all activities above it, will be destroyed. If it is not in the stack it will be created (onCreate method will be invoked)
Edit: You have to handle onNewIntent to get bundle and update your current activity with new values.
Note: Also remember, system may destroy your activity and your both onCreate and onNewIntent methods can be invoked. Design your activity considering this.
Edit2: If you want to have many app details and user can navigate back with pressing back button. And also one detail for one app. Then you should use fragments. Add fragments by tag of your application id/name (something unique) and while showing an app detail search if any detail page exists with findFragmentByTag method. If it exists remove it and add it to top of the stack.
i have 3 activities A-B-C .Lets say i am on activity B and from a listview there i launch activity C now if a notification comes which has an intent of launching activity C.
So the problem is I am getting multiple instances of activity C
When i use launchMode singleTop or instance or task the problem of multiple activity instance is solved but the newly launced activity does not work properely as it is desired to be.
Please help me out tired of using flags and stuff but not able to overcome this problem.
The scenario is Just like whatsapp , if u r talking to person one and a message of person 2 come as notification ,when u click on that notification the activity relaunches and works properely. This is exactly what i want. Please help me out how to achieve this . :(
Thanxx in advance
What Flags did you try and what exactly is not working, means, how does the Activity behave?
What you describe with WhatsApp could be achieved with two steps:
Use the FLAG_ACTIVITY_SINGLE_TOP for the Activity.
Overwrite the Actvity.onNewIntent(Intent intent) method in the Activity. This method is called instead of creating a new Activity and gives you the new Intent. I assume that the Intent contains all necessary information in the extras.
The user experience should be as follows:
User chooses from the list, which opens the new Activity
He/she can press home or back button from here. This brings the home screen or the list back.
If, for any reason, somebody else calls startActivity for your Activity while it is running, the onNewIntent is called. There you can add code to refresh the content, maybe have an Alert that tells the user that the content has changed, and shows all that to the user.
If the user presses back or home now, he/she will get to the list or home screen
If that is, what you're looking for, then the flag and the method is what you need
In an app I have very reused Activity, that shows a list of stuff happening on a specific day. The day is specified using Intent Extras.
My problem is, that if the user starts at day=1, then chooses day=2 and then day=1, from the menu, then I would like the back button to go to day=2 and then home. That is, I want to do REORDER_TO_FRONT, but not just based on the name of the activity, but also its extras.
There doesn't seam to be any intent flags suitable for this purpose. I've considered implementing my own 'sub activity stack' using onNewIntent, but it probably wouldn't work very well.
Have you tackled similar problems in your apps? Is there perhaps a way to programmatically access the activity stack, and choose which one is suitable to return to?
Manage your own Activity stack! If I'm not mistaken, you use the same Activity to display each day. Make it single top (FLAG_ACTIVITY_SINGLE_TOP). In the launching intent, pass on the current stack, in your example "121".
Respond to the back button event by launching your Activity with a smaller stack: "12" - or if stack is already "", then just let the Activity handle Back event. Then as you mentioned, use the onNewIntent function to update your Activity.