I have the next situation - I develop the music app, it contains media service.
Also the app contains MainActivity with 4 Fragments in it. In the bottom of each Fragment there is a bar with play, skip next, skip previouse, shuffle and repeat, it looks like that:
The bar in the bottom refers to MainActivity.
Also in Albums tab and Playlist tab there are lists of albums and playlists which you can tap and it will take you to another activity with songs from taped album/playlist. I have only one service, so I bind it to all of it(one Fragment, two activities, actually I have leak but it is another problem)
The question is how can I control media playback(skipnext/previouse, play/pause, shuffle, repeat) from that bar in the bottom.
I already set OnClickListener on buttons and tried to call service method, but in that case I have an error like:
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.media.MediaPlayer.isPlaying()' on a null object reference
I tried both:
private MediaPlayerService mediaPlayerService = MediaPlayerService.getInstance()
and just in case
private MediaPlayerService mediaPlayerService = new MediaPlayerService()(of course last one doesn't work)
I tried to make mediaPlayer singleton and yes it works, but there is another problem with skipNext/Previouse - int songPosition and (ArrayList) of ids should be singleton as well (or static in the class), good, I made it, but then another problem prepareAsync called in state 1 error... W#T#F#... sorry, that is my first project and maybe I made simple things very complicated developing bycicle. Any help will be great.
Thank you.
Ok, finally I found an answer and be honest it wasn't very hard. Actually what I forgot to do is to bind service to MainActivity, after I did it, everything goes well.
Related
I am developing an Android Kotlin application which uses two different activities. In each one I have a button that allow me to move to the other one, to say, in Activity 1 I have a button that calls the follwing:
val intentActivity2 = Intent(this, Activity2::class.java)
startActivity(intentActivity2)
This launches correctly Activity2, which similarly inside it I have another button that calls the first activity to return to it:
val intentActivity1 = Intent(this, Activity1::class.java)
startActivity(intentActivity1)
The problem I have is that I want to have both activities running simultaneously (not needed to be shown at screen at the same time), and the issue right now is that every time I call the "startActivity(intent)" a new activity is created, loosing what I had in the previous one, so when I return to Activity1 everything is reset and the same when I go once again to Activity2. Both activities work fine and do their work, the problem is that I can't freely conmute between them.
Is there a way to have both activities at the same time or to not start a new activity everytime I want to change to the other one?
Thank you,
As someone just said you need ViewModel to retrieve your data after deleting/creating new activities. Maybe you can use fragments to do your things. Fragments are attached to activities and it is easier to use them instead of ViewModel.
I'm building my first Android app in Android Studio (with Java) and I need some help understanding how to pass data through multiple activities.
The setup of affected classes/activities is this:
MainActivity: Opens a dialog called AddDialog (by creating a new Instance of it).
AddDialog (extends AppCompatDialogFragment): A dialog that has some buttons. One of them launches a class called BarcodeScanActivity (using intent).
BarcodeScanActivity: Simple activity that scan QR codes.
I want to pass the list of QR codes scanned by BarcodeScanActivity (I store them in a String Array) to MainActivity in order to use them, although BarcodeScanActivity is launched from the dialog that gets destroyed once buttons are clicked. Because of that I'm unable to set some startActivityForResult on the dialog and chain the result (onActivityResult) back to the MainActivity.
Also since MainActivity launches the AddDialog by creating an instance, I can't set a startActivityForResult there too.
I have tried adding Intent.FLAG_ACTIVITY_FORWARD_RESULT while launching BarcodeScanActivity from AddDialog, hoping that the result from BarcodeScanActivity will be forwarded back to MainActivity where I have created an onActivityResult method since AddDialog gets destroyed, but I don't know if that is even supposed to work as AddDialog is "launched" by a new instance of it, and not by using an intent.
I have thought about using broadcasts as a last resort, although I read that they are insecure, unreliable and not supposed to be used for passing that kind of data.
Any help is highly appreciated! Thanks
I am following the Google tutorial for building your first android application. I got to the point where I needed to implement the actionbar actions with the functions openSearch() and openSettings().
I implemented all of this in the MainActivity.java file.
My question is this:
In the example app you can type a message and then send it and it displays it in a second activity. In the second activity, the top action bar changes and does not display my Search icon or perform the action when the settings button is clicked. In order to have these icons displayed in the action bar for this activity as well, do I need to add those methods and update onOptionsItemSelected method in DisplayMessageActivity.java as well as in MainActivity.java? Is this the only way to carry the action bar icons/actions over? To retype the same methods in each activity that you want them in? Or is there a better way to do it?
My other somewhat related curiosity is this. The method openSettings() is called when I click the 3 vertical dots and then settings. These 3 vertical dots show up on every activity, and settings is always in the list. However clicking settings obviously doesn't perform the call to openSettings() when in the DisplayMessageActivity and not MainActivity. How is it that settings and the vertical dots are carried over?
Second to last, how can I add other selections to the drop down list from the options/vertical dots in the action bar? Settings is always there although it responds differently in each activity which was my first question. But I would like to add certain things to the options menu that are on all activities, and some things that are unique to some activities. I assume there must be a better way than repeating switch statements and methods in every Activity.java file.
And finally, what is the best practice to implement an action bar over multiple activities?
Obviously different activities will often have different icons/actions in the action bar, however some things like the 3 vertical dots(options) and settings within that would obviously be acceptable to have in every Activity, while it would be nice to add other things to the options list I don't see why settings should ever change across activities. Yet as I stated before the method is not called in DisplayMessageActivity unless I repeat the code in DisplayMessageActivity.java that I had added to MainActivity.java. I'm confused as to where I can add these so that they are displayed on all activities without repeating code. And I'm confused as to how the actionbar's options/vertical dots are carried over to all activities while others require the repeating of code in each activities' java file that I want them to show up in.
I know this was a bit of a long winded quesiton, I will clarify if necessary. I'm just a bit confused. I was able to make it through the tutorial fine as I have a decent understanding of java. However google's guide isn't written that well and the Android environment is very confusing to a beginner.
I do understand how things work to a degree, I just want to ensure that I'm actually doing it in a way that when my app grows in complexity it won't be a mess of unnecessarily repeated statements and methods.
Thanks in advance for any assistance and tips.
In order to have these icons displayed in the action bar for this activity as well, do I need to add those methods and update onOptionsItemSelected method in DisplayMessageActivity.java as well as in MainActivity.java? Is this the only way to carry the action bar icons/actions over? To retype the same methods in each activity that you want them in? Or is there a better way to do it?
That is certainly one solution, but as you obviously know, it's not a very good one. There are at least two alternative solutions:
Create a MenuActivity class which implements all the logic for common menu items and then extend this class from all of your activities, rather than extending the standard Activity class.
Use fragments to implement your UI. Fragments are similar to activities in that they create UI elements from an XML layout. One difference is that they live inside a "host activity". In this particular case, the host activity will provide the common menu functionality and each fragment can customize it further depending on your needs.
How is it that settings and the vertical dots are carried over?
Most likely your DisplayMessageActivity overrides onCreateOptionsMenu() and inflates a menu XML layout which was created by Android Studio (or Eclipse?) when you created the activity class.
When my program start I would like to do some settings before is really starting. Forexample choose the user, check the updates and so on. After these settings I would like to start the main program with the appropriate.
Which is the best way to do this?
You can run an AyncTask, or multiple if you need one for each check, in your onCreate() and show a ProgressDialog while the data is being fetched then cancel it in onPostExecute() and move on to the rest of the MainActivity depending on the data that is downloaded. If you need help getting started with AsyncTask you can see this SO answer on the basic structure.
If you use a ProgressDialog then the app will still start but the users will see something and know that data is loading so they won't feel like it is freezing or taking too long to load (or at least they will know why it isn't loaded right away).
AsyncTask Docs
Edit after comment
For what you said you want in your comment you can do this easily with an Activity that has a Dialog Theme. This will give you the functionality you need (a couple Buttons and store the values) but it will look like a little popup. You can't use an actual Dialog as they need an Activity, the same with any menus, AFAIK. Just create your Activity and make it the launcher and main using the Intent-filters then also add the following line to that Activity's tag in the manifest
android:theme="#android:style/Theme.Dialog"
This approach should give you what you need
There are numerous ways to do that.
First - your app is doing some heavy stuff and this may be freezing user interface. In that version do:
1. Create and activity on what you will override onCreate method and set some content with a spinner - so something will be alive and user will see that something is being done.
2. after you will compute all the things that your app need and may I suggest write it to some global variables override onStart method in what change layout to what suit you and give a user a great UI!
Second - you app is not heavy lifting here just throw everything into override of onStart method.
Handy material here for educating:
Hi and thanks in advance for your time and attention.
I actually have 2 questions i'm not too sure about building an android app. Pretty basic stuff I believe:
1) My app is fully on Horizontal mode, like AngryBirds for example. When it starts the user figures out he should hold the phone like that, if he isn't already. And that is setup in the manifest for all the activities and works fine. but is there a way to prevent the physical device tilting to call onCreate again? can i override it's method or whatever? the reason i'm asking, is because i have a few ButtonViews that after you click on them, change their picture. i am using onRetainNonConfigurationInstance() to save the array of those ImageButtons, and i even mark the ones changed with the ImageButton setTag() and getTag() methods, so when onCreate is called because of the device tilt it gets the saved array from getLastNonConfigurationInstance() , but i've been trying to make it work for quite some time now and I just can't get it right. After the device tilt (I'm actually using the emulator so it's Ctrl+F11 but i believe it will happen with a device as well) all of the ImageButtons loose their pictures.. Long story short - are there better ways of doing this that you can recommend or is preventing the tilt from doing anything is possible or better?
2) What is the best way to know how many seconds the user has been on a screen? I tried to use two longs that i get via SystemClock.currentThreadTimeMillis() as follows: get the starting time onCreate, and the ending time on the method i call to move to the second intent just before i startActivity. but I think because they are called from different threads, the endingpoint - startingpoint is not correct. What is the way to insure both of the methods of SystemClock.currentThreadTimeMillis() are called from the same thread, the main thread of the activity that i'm stopwatching? Is there a better way to go around this?
Thanks again.
You are doing the right to handle orientation change. Please refer to this link http://developer.android.com/guide/topics/resources/runtime-changes.html . This will help you to get it working.
Good way would be to count the time between onResume and onPause. OnCreate is not called all the time if you are resuming activity.
1) You can try adding the property android:configChanges="orientation" to your activity in the manifest file. It worked for me when my dynamic Action Bar tabs got messed up upon rotation of the screen.
You need specify orientation in android manifest for each of your activities, it will not call onCreate then. android:screenOrientation look at http://developer.android.com/guide/topics/manifest/activity-element.html
User see and interact with your activity starting since onResume and ends on onPause. Other time it does not guarantee that user actually see and can click on something in the activity. System.getCurrentMillis() is good enough.