Develop Reference

How do I launch a specific (explicit) activity of another app

I want to launch a specific activity of another app from my app. For example, on the onCreate of my app, I want to launch the activity named Rolling (not main) activity of com.pas.webcam.pro. I have heard that you must have control of both apps to do this because you must add an intent filter to the manifest of the second app. This is not true though, because activity launcher apps in the Google Play Store can launch the Rolling Activity of IP Webcam Pro.
The Activity Launcher app is open source, so I tried reviewing the source code here. It was too complicated though, so I could not figure out how this app magically launches this activity. There are many other questions like this on Stack Overflow, and I have read every one. I have also tried lots of the code from the answers too, like this:
Intent intent = new Intent(); intent.setComponent(new ComponentName("com.pas.webcam", "com.pas.webcam.RollingActivity")); startActivity(intent);
I have also tried variants of this code from other posts. My app always crashes and I get variants (depending on the code I use) of the following error:
An error occurred
Invalid intent operation. Unable to find explicit activity class {com.pas.webcam.pro/com.pas.webcam.pro.Rolling}; have you declared this activity in your AndroidManifest.xml?
I have put both of the following in my Android Manifest and the same thing happens:
<uses-permission android:name="android.permission.GET_INSTALLED_PACKAGES" />
<activity android:name="com.pas.webcam.pro.RollingActivity"
Thanks in advance for any answers, I really appreciate it, as I have been working on this problem for a while.
Edit: Here is the activity of the app I want to launch: https://i.stack.imgur.com/Fa7Xq.jpg
Edit: David Wasser helped me solve the problem by giving me the code neccessary to solve the problem. It actually works! To anyone who wants to launch a specific activity of another app with code, please use this:
Intent intent = new Intent(); intent.setClassName("com.pas.webcam.pro", "com.pas.webcam.Rolling"); startActivity(intent);
You may replace com.pas.webcam.pro and Rolling with the app and activity of your choice, but this method truly works. Problem Solved!😀

Try this:
Intent intent = new Intent();
intent.setClassName("com.pas.webcam.pro", "com.pas.webcam.Rolling");
startActivity(intent);
Since you refer to the app as "IP webcam pro", I'm assuming the package name is "com.pas.webcam.pro" (found by Internet research).

Open the default photo gallery app

I want the gallery app to be launched in a separate window, not in my app. I also dont want to choose a picture, I just want to open the default gallery app.
Some questions are very similiar to this one, but they all open the gallery not as a standalone app, always inside of the app which has called
startActivity(intent);.
see here. This is my app called SM2. inside, the default gallery app is visible, which is not the desired behaviour.
The following code has no use if there is no package named 'com.android.gallery' on the phone:
Intent launchIntent = getPackageManager().getLaunchIntentForPackage("com.android.gallery");
if (launchIntent != null) {
startActivity(launchIntent);//null pointer check in case package name was not found
}
this opens a gallery in my app, not as wished as a standalone task:
Intent intent1 = new Intent(Intent.ACTION_VIEW, Uri.parse(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_MOVIES)));
startActivity(intent1);
and this does also open the gallery in my app:
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(
"content://media/internal/images/media/"));
startActivity(intent);

It is launched inside of the application
It is being launched in your task. You can use FLAG_ACTIVITY_NEW_TASK on your Intent to have it launch in its own task.
I also dont want to choose a picture, I just want to open the default gallery app
You are welcome to try using CATEGORY_APP_GALLERY, though not all gallery apps might have an activity that supports this.

Apps don't return

I have written custom home screen app from which I am launching apps.
The main problem is the opened apps doesn't return to my home screen app, instead they go to the launcher home screen, even though I have set my home screen app as default home screen. I want these apps to return to my home screen. How can i do that?

If you check documentation for the getLaunchIntentForPackage(..) method you see
"Returns either a fully-qualified Intent that can be used to launch
the main activity in the package, or null if the package does not
contain such an activity. "
That's pretty self explaining.. your "app package name" is not correct, it might be for some apps but not for others.
try something like
PackageManager pManager = getPackageManager();
List<PackageInfo> packs = pManager.getInstalledPackages(PackageManager.GET_INSTALLED_PACKAGES);
for (PackageInfo pi : packs) {
if(pi.packageName.toLowerCase().contains("app package name") )
{
Intent intent = pManager.getLaunchIntentForPackage(pi.packageName);
if (intent != null)
startActivity(intent);
}
}

How does Facebook add badge numbers on app icon in Android?

I know there are several Qs here that ask if its possible to add badges to an android app and they all end up with a NO answer...
But somehow the latest Facebook beta version for Android seems to do something which at least look like a badge even if it is not technically exactly that.
In that post one of the commenters says that it is somehow related to TouchWiz.
And also here they mention it as a feature of the "S3 TouchWiz Jelly Bean Addon".
I still would appreciate information on how does this can be done and if there is some API for this that I can use in my own app (when running in an appropriate environment - i.e. the same device where FB demonstrates this behavior) ?

Hi you can use this lib simply.
Support : Sony,Samsung,LG,HTC,Xiaomi,ASUS,ADW,APEX,NOVA,Huawei,ZUK,OPPO
ShortcutBadger
Add :
int badgeCount = 1;
ShortcutBadger.applyCount(context, badgeCount);
Remove :
ShortcutBadger.applyCount(context, 0);

I have figured out how this is done for Sony devices.
I've blogged about it here. I've also posted a seperate SO question about this here.
Sony devices use a class named BadgeReciever.
Declare the com.sonyericsson.home.permission.BROADCAST_BADGE permission in your manifest file:
Broadcast an Intent to the BadgeReceiver:
Intent intent = new Intent();
intent.setAction("com.sonyericsson.home.action.UPDATE_BADGE");
intent.putExtra("com.sonyericsson.home.intent.extra.badge.ACTIVITY_NAME", "com.yourdomain.yourapp.MainActivity");
intent.putExtra("com.sonyericsson.home.intent.extra.badge.SHOW_MESSAGE", true);
intent.putExtra("com.sonyericsson.home.intent.extra.badge.MESSAGE", "99");
intent.putExtra("com.sonyericsson.home.intent.extra.badge.PACKAGE_NAME", "com.yourdomain.yourapp");
sendBroadcast(intent);
Done. Once this Intent is broadcast the launcher should show a badge on your application icon.
To remove the badge again, simply send a new broadcast, this time with SHOW_MESSAGE set to false:
intent.putExtra("com.sonyericsson.home.intent.extra.badge.SHOW_MESSAGE", false);
I've excluded details on how I found this to keep the answer short, but it's all available in the blog. Might be an interesting read for someone.

There is not a standard way to achieve this; Many makers such as Sony or Samsung have implemented it in their own Android customization.
For example in Samsung, you have to broadcast an intent with BADGE_COUNT_UPDATE action, let MainActivity be your main activity class and count be the number you want to display in your app icon, note that 0 will hide the badge:
Intent intent = new Intent("android.intent.action.BADGE_COUNT_UPDATE");
intent.putExtra("badge_count", count);
intent.putExtra("badge_count_package_name", context.getPackageName());
intent.putExtra("badge_count_class_name", MainActivity.class.getName());
context.sendBroadcast(intent);
Sony devices uses "com.sonyericsson.home.action.UPDATE_BADGE" action with their custom extras as #Marcus Answered, so you have to add "com.sonyericsson.home.permission.BROADCAST_BADGE" permission to your app manifest and:
Intent intent = new Intent("com.sonyericsson.home.action.UPDATE_BADGE");
intent.putExtra("com.sonyericsson.home.intent.extra.badge.ACTIVITY_NAME", MainActivity.class.getName());
intent.putExtra("com.sonyericsson.home.intent.extra.badge.SHOW_MESSAGE", true);
intent.putExtra("com.sonyericsson.home.intent.extra.badge.MESSAGE", String.valueOf(count));
intent.putExtra("com.sonyericsson.home.intent.extra.badge.PACKAGE_NAME", context.getPackageName());
context.sendBroadcast(intent);
Note: it's desirable to query your app's data (context.getPackageName(), MainActivity.class.getName()) rather than hardcode it just in case you do some refactoring in the future.

But somehow the latest Facebook beta version for android does just that...
Not according to the forum thread that contains the screenshot that you linked to. Quoting vakama94:
Well, that's actually TouchWiz and not just the app. I have a Galaxy S II running JellyBean 4.1.2 and it makes the same thing but with some other applications
Whether Samsung has a public API to allow apps to publish numbers to be used as badges, I cannot say. This could be something that they did privately with a few firms.
You are welcome to provide evidence of seeing these badges on a stock Android home screen, such as one of the Nexus series devices.

I answer to this assuming that some flutter dev can search this...
In Flutter, you can achieve this by using
Flutter app badger library.
It is as simple as
FlutterAppBadger.updateBadgeCount(1); // show
FlutterAppBadger.removeBadge(); // hide

How to add a widget to the Android home screen from my app?

I'm writing an application which should be able to add widgets (just text boxes) to the home screen of the user's phone when the user instructs my app to do so. How can I do such a thing?
I know that I can add an app widget but how about adding more?

It is not possible from a app to place a widget in the home screen. Only the home screen can add app widgets to the home screen.
similar links link1, link2, link3
But you can offer user to pick widget from widgetpicker.
Intent pickIntent = new Intent(AppWidgetManager.ACTION_APPWIDGET_PICK);
pickIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, AppWidgetID);
startActivityForResult(pickIntent, KEY_CODE);

This was answered a long time ago, but in case anyone stumbles upon this question I thought I should provide an up-to-date answer.
As of Android O (API 26), you can now pin widgets to the user's launcher from your app!
Simply create the widget in your app's AndroidManifest file and use AppWidgetManager to request that the widget be pinned to the launcher. Note that it is up to the launcher to support this feature, so you must call AppWidgetManager's isRequestPinAppWidgetSupported() method before requesting to pin it.
Here's some documentation from Google that goes into more detail: https://developer.android.com/preview/features/pinning-shortcuts-widgets.html#widgets
Hope this helps!
Edit: It looks like the documentation pages have changed since I posted this answer. Here is a more helpful link that gives a code example of how to pin a widget to a launcher: https://developer.android.com/guide/topics/appwidgets/#Pinning

Looks like Dalvik Droid's links are updated again, the newest link is at requestPinAppWidget
Example:
in MainActivity.java:
private void requestToPinWidget(){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
AppWidgetManager appWidgetManager =
getSystemService(AppWidgetManager.class);
ComponentName myProvider =
new ComponentName(this, AppWidget.class);
assert appWidgetManager != null;
if (appWidgetManager.isRequestPinAppWidgetSupported()) {
Intent pinnedWidgetCallbackIntent = new Intent(this, MainActivity.class);
PendingIntent successCallback = PendingIntent.getBroadcast(this, 0,
pinnedWidgetCallbackIntent, PendingIntent.FLAG_UPDATE_CURRENT);
appWidgetManager.requestPinAppWidget(myProvider, null, successCallback);
}
}
}
Any anywhere in you code you have call requestToPinWidget() to prompt to see if the user wants to add it to the desktop.
Only thing is that this will not add to user's home screen, it will be appended to the page where you see all the apps:

AFAIK default launcher app does not support this. The reason is that user should place everything on the home screen himself. Allowing to place widgets from an application would open doors for apps to "spam" user's home with their "useful" widgets.