How to launch another app in Android app

One app in Android launches another application generally there are 2 different cases,

The package name of the application being launched is known and unknown in two cases:

1 The package name of the app being launched is known:

   /** launches another applied code, where the app's package named PackageName, the        application's entry is packagename.mainactivity,      None of the 2 application Androidmanifest.xml files for this method need to be modified     **/       Intent Intent = new Intent ();       Intent.setcomponent (New ComponentName ("PackageName", "packagename.mainactivity"));       Intent.setaction (Intent.action_view);       StartActivity (Intent);    

2 The package name of the application being launched is unknown:

This situation is not known about the package name of the app, but the final launch of the app is through the package name. So a way to get the package name of the app in the phone.
The pre-installed and non-system applications can be judged by the method below, returning a list of package names:

Public list<packageinfo> Getallapps () {             list<packageinfo> apps = new arraylist<packageinfo> ();             Packagemanager Packagemanager = This.getpackagemanager ();             Get all apps in your phone             list<packageinfo> paklist = packagemanager.getinstalledpackages (0);                 for (int i = 0; i < paklist.size (); i++) {                 PackageInfo Pak = (packageinfo) paklist.get (i);                 Determine if a non-system preinstalled application  (greater than 0 is pre-installed for the system, less than or equal to 0 for non-system applications)               if ((Pak.applicationInfo.flags & Pak.applicationInfo.FLAG_ SYSTEM) <= 0) {                     apps.add (Pak);                 }             }             return apps;     }   

Since this is a list collection of package names: We're still not sure which app we're going to launch, okay, we can get the app name further.

Public string[] Launchapp () {           Packagemanager Packagemanager = This.getpackagemanager ();           list<packageinfo> packages = Getallapps ();         Str3=new string[packages.size ()];        PackageInfo pa = null;           for (int i=0;i<packages.size (); i++) {               pa = packages.get (i);               Get the app name. The STR3 here is an array of my definition that hosts the application name.            Str3[i] = Packagemanager.getapplicationlabel (pa.applicationinfo). toString ();             }     return STR3;    }   

Finally, you can judge each item based on the number of app names and string[] groups that we want to start. If true, the application is launched and, if Fause, the next judgment is made.

How to launch another app in Android app