The documentation says you can specify a custom category.
When, why and how would you do it?
What would be the use of it?
The way I understand it, categories are public directives to the android operating system(and other apps) that represent different categories that your app should be a part of.
Example
When the launcher icon is tapped on the home screen, the home application looks through every installed app's manifest for the HOME category -- and if so it displays it in the app drawer.
However, there's more. You can specify categories in your applications manifest that lets the system know that you application can handle the intent category. For example, by putting a ALTERNATIVE category, other apps in the system know that your app can handle that category without specifically knowing the action name! In the following example, custom intent categories are passed through this intent, which is filtered and the corresponding object gets edited(taken from the Notes example app):
<intent-filter android:label="#string/resolve_title">
<action android:name="com.android.notepad.action.EDIT_TITLE" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.ALTERNATIVE" />
<category android:name="android.intent.category.SELECTED_ALTERNATIVE" />
<data android:mimeType="vnd.android.cursor.item/vnd.google.note" />
</intent-filter>
By registering this intent filter in an <activity /> tag, you can edit a "note". The intent data would contain the note, and the intent would get routed to the activity that this filter is registered in.
In Conclusion:
There isn't really a reason you'd use a custom category. They are for Android, and thus don't really make sense in application use. But, if you choose to use them, they can be used in the methods described above. "They provide some specific semantic rules, and if those rules are useful to you then feel free to use them"(Hackbod).
http://developer.android.com/guide/topics/intents/intents-filters.html
Scroll down a bit and you should see a section under "Intent Objects"
They basically describe certain special properties of an activity. for example, adding
<category android:name="android.intent.category.HOME" />
means that the app can be started on the phone's bootup
I'm kinda a noob to Android still, although I have programming experience otherwise.. It says a custom category in your own namespace. I'm guessing that if you are programming multiple apps and you want one app to run another app, you could use a custom category for your intent to force the phone to find your other app to catch the intent with?
When you do not want to use the default category then use the custom category.
Custom categories should use the package name as a prefix, to ensure that they are unique.
Some information is provided on below link:
http://developer.android.com/guide/topics/manifest/category-element.html
Check the below link it has somewhat same question:
Android custom categories
Related
“My First App” has an activity that handles a “share” intent. Its activity in AndroidManifest.xml looks like this:
<activity
android:name="com.example.foo.myfirstapp.MainActivity"
android:label="#string/app_name">
<intent-filter>
<action android:name="android.intent.action.SEND"/>
<category android:name="android.intent.category.DEFAULT"/>
<data android:mimeType="image/jpeg"/>
</intent-filter>
</activity>
In KitKat, sharing an image from the album to “My First App” causes MainActivity to be part of the album’s task. This is the desired behavior.
In Lollipop, sharing an image from the album to “My First App” causes a new instance of “My First App” to be launched. If I look at the overview screen, the album task is there...and then there's a separate entry for "My First App". If I share another image, I wind up with two instances of "My First App"...etc.
Question: How do I make Lollipop process the share intent in the same way as KitKat?
Here's what I've done:
I notice that the intents sent from the Album have different flags set depending on the OS. (I got these using getIntent() and looking at mFlags.)
Kitkat: 0x80001 (524289): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET
Lollipop: 0x18080001 (403177473): FLAG_GRANT_READ_URI_PERMISSION, FLAG_ACTIVITY_MULTIPLE_TASK, FLAG_ACTIVITY_NEW_DOCUMENT, FLAG_ACTIVITY_NEW_TASK
From reading http://developer.android.com/reference/android/content/Intent.html, it seems that these last three flags are causing the problem. Specifically
When paired with FLAG_ACTIVITY_MULTIPLE_TASK both of these behaviors (FLAG_ACTIVITY_NEW_DOCUMENT or FLAG_ACTIVITY_NEW_TASK) are modified to skip the search for a matching task and unconditionally start a new task.
I’ve been attempting to “override” these flags by specifying android:launchMode and android:documentLaunchMode in the activity in AndroidManifest.xml without success.
From http://developer.android.com/reference/android/R.attr.html#documentLaunchMode, using documentLaunchMode “never” seems promising, since
This activity will not be launched into a new document even if the Intent contains Intent.FLAG_ACTIVITY_NEW_DOCUMENT. This gives the activity writer ultimate control over how their activity is used.
but this didn't work.
I also considered android:taskAffinity, but there doesn’t seem to be a way to say “please prefer whatever task launched you”.
Afraid you can't do anything about this. It isn't under your control. This is a change in the way the "Album" app is launching its "share" Intent. If it doesn't want your Activity in its task, you can't force it in there.
If you have issues with having multiple instances of your "share" activity, you could declare your "share" activity as launchMode="singleTask" or launchMode="singleInstance" (depending on your needs. This may, however, break other things.
i have an application which associates pdf files in my Manifest(via intent-filters), so when someone click on pdf link in the default browser i can execute that action with my app and download it with a progressbar. my question is, is it a way that i can associate other files but not "hard coded" in my manifest, but to let the user choose(or write) that file extention in preferences for example and i can add it dynamically from code. i know that probably this can be done with broadcast receiver but cant find any examples or simple code for that matter. ive seen preference menu like that in bsplayer settings .. but cant post image cuz dont have enough reputation.
I will try to explain more detailed my problem, because i think that there was some misunderstanding with the answer below.
i have an application which have the fallowing code in my manifest.
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.BROWSABLE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="http" />
<data android:host="*" />
<data android:pathPattern=".*\\.pdf" />
</intent-filter>
2.i launch my app which registers .pdf files with it. so next time i click on pdf link in my browser, a window pops up, making me choose with what application should i complete that action. if i choose my application, my main activity is launched, in which i use getIntent() and my app downloads the file using progressbar.
3.the problem is that i want to download and other files like that ie. jpg, png .. etc, but giving the user a choice which ones, or even making him write the extentions for the files he wants to download using my application if clicks on link somewhere that leads to that kind of files.
4.to make this thing happen, file extensions should be added dynamically in code somewow and not in manifest. i was looking some examples for broadcast receiver, since that class can use IntentFilter class, but cant really understand what i should be doing with it.
5.My main goal: starting my app, there is layout with some spinner or edit box. the user choose/writes some extension (.dwf). that extension is now registered with my app. if the next time the user browsing internet clicks on link which leads to .dwf file he could choose to continue the action with my app. and the file should be downloaded just like the .pdf
6.sry for my bad english and some help will be appreciated. also code ;)
boolean enabled=prefs.getBoolean(key, false);
int flag=(enabled ?
PackageManager.COMPONENT_ENABLED_STATE_ENABLED :
PackageManager.COMPONENT_ENABLED_STATE_DISABLED);
ComponentName component=new ComponentName(MyActivity.this, TargetActivity.class);
getPackageManager()
.setComponentEnabledSetting(component, flag,
PackageManager.DONT_KILL_APP);
Depending upon your preference you can Disable the activity that handles the File type in your BOOT_COMPLETED Reciever. I Believe you will have to have different activities to handle different file types and then disable selectively
We are localizing our app to be able to easily switch between languages. Everything works nicely except for some cached values that are actually in navigation. We have two options:
completely restart app on language change - in this case I need a notification and force restart
just load new strings into the table - in this case it will require to replace string values and rbuild custom navigation state.
IN both cases we need a way to find out when language switches. Is there an intent we can listen to? If yes could you please advise on which one? I am thinking to go with a broadcast receiver. I am just not sure which intent action it is. In below example what is the SOME_ACTION value?
Thanks in advance.
<receiver android:name="com.v1.application.notifications.LanguageChangeReceiver">
<intent-filter>
<action android:name="android.intent.action.SOME_ACTION" />
</intent-filter>
</receiver>
android.intent.action.CONFIGURATION_CHANGED
I would like to create an Intent-Filter, so that certain links will trigger the start of my application (see this stackoverflow-thread for example: How to register some URL namespace (myapp://app.start/) for accessing your program by calling a URL in browser in Android OS? )
While trying, I figured out, that I dont quite understand how Intents and Intent-Filters (defined in the Manifest.xml) actually work. What is the difference between the following:
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.MAIN" />
or the following:
<category android:name="android.intent.category.LAUNCHER" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.MAIN" />
And what is actually the difference between category and action Intent-Filters. I read this page http://developer.android.com/reference/android/content/Intent.html but I still missing a basic understanding.
Instead of looking at it from your app's point of view, flip it around and look at it from the Intent side.
When an Intent is created, the creator has no idea what apps are on the system to handle that Intent. But the creator does know what it wants to do (e.g., an app might want to let the user pick out a contact from somewhere on the device), and needs to reach out to other apps on the system to ask for what's desired.
To do this, Intents have several pieces of information attached to them. Among them are actions and categories.
The actions define in a general way the action the Intent wants to do, like VIEW a contact, PICK an image from the Gallery, etc.
The category is an additional piece of information that gives the Intent another way to differentiate itself. For example, when a link in the browser is clicked, the Intent that is created has the BROWSABLE category attached to it.
So, when the OS resolves the Intent, it will look for registered Activities or BroadcastReceivers that have an intent filter that includes all of pieces of information. If the Intent specifies the PICK action, Activities that do not have an intent-filter with the PICK action will be discarded from the list of candidates to handle the Intent.
In this way, the combined set of action, categories, type, and (possibly) scheme associated with an Intent serve to pinpoint the set of Activities that can handle the Intent. When you set up your intent-filter in your manifest, you are telling the OS which class of Intents you can handle.
I had to examine the code of android.content.IntentFilter.matchCategories(Set<String> categories) to understand the matching of categories:
Successful match, if your IntentFilter has categories and the Intent doesn't provide Categories
Successful match, if your IntentFilter has all categories of the Intent. The filter also can have additional categories.
No match, if your IntentFilter has no categories and the Intent has categories
No match, if your IntentFilter has not the categories the Intent has
Especially #1 and #3 aren't obvious.
guys. I am trying to build a voip app for android. I want to make use of the built-in android phone dialer. Can you guys give me some reference to it. I have been googling with no luck. Thanks
What you need to do is setup an Intent filter on the Activity you want to make the call. You do this inside your AndroidManifest.xml file. Modify your activity definition to include this intent filter:
<intent-filter>
<action android:name="android.intent.action.CALL" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="tel" />
</intent-filter>
Note: there are some alternative ways to call people (which can be seeing in the AndroidManifest.xml of the source I linked bellow, however this is the main one
Adding this will give the user the option to use your app when making a call, and this can be set as the default app if the user wishes.
You can then get the phone number by adding something like this code to your onCreate() method of your activity:
final Intent i = getIntent();
final Uri phoneUri = i.getData();
phoneUri now contains tel:00000000000 and you can easily get the number out of the Uri object
If you have problems in to future take a look at the android source. I got these bits of code from the phone app source if you want to take a look.
This should open the dialer with new special permissions:
Intent i = new Intent(Intent.ACTION_DIAL, Uri.parse("tel:0000000000"));
startActivity(i);
That should open the dialer with the required telephone number already inserted.