How does Android detect that phone has WhatsApp?
I want to know how this feature technically works:
As far as I understand, there is no official API to check it for now. Before v 2.43 API version there was an official way to check via /v1/contacts API of WhatsApp Business. But now it doesn't work.
So how do they do it now ?
Through their AndroidManifest.xml. Apps declare which Intents they're able to handle and there's one for making calls / sending SMS. Just call queryIntentActivities() on an instance of PackageManager, given an ACTION_{WHATEVER_FEATURE_YOU_WANT_TO_CHECK} Intent configured. This will give you a list of all the matches that would appear as if you tried to make a chooser.
You can check by package name of WhatsApp.
boolean isAppInstalled = appInstalledOrNot("com.whatsapp");Using PackageManager,
private boolean appInstalledOrNot(String packageName) { PackageManager packageManagerm = getPackageManager(); try { packageManager.getPackageInfo(packageName, PackageManager.GET_ACTIVITIES); return true; } catch (PackageManager.NameNotFoundException e) {} return false; }