How to launch an Activity from another Application in Android

If you don't know the main activity, then the package name can be used to launch the application.

Intent launchIntent = getPackageManager().getLaunchIntentForPackage("com.package.address");if (launchIntent != null) {     startActivity(launchIntent);//null pointer check in case package name was not found}

I know this has been answered but here is how I implemented something similar:

Intent intent = getPackageManager().getLaunchIntentForPackage("com.package.name");if (intent != null) {    // We found the activity now start the activity    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);    startActivity(intent);} else {    // Bring user to the market or let them choose an app?    intent = new Intent(Intent.ACTION_VIEW);    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);    intent.setData(Uri.parse("market://details?id=" + "com.package.name"));    startActivity(intent);}

Even better, here is the method:

public void startNewActivity(Context context, String packageName) {    Intent intent = context.getPackageManager().getLaunchIntentForPackage(packageName);    if (intent != null) {        // We found the activity now start the activity        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);        context.startActivity(intent);    } else {        // Bring user to the market or let them choose an app?        intent = new Intent(Intent.ACTION_VIEW);        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);        intent.setData(Uri.parse("market://details?id=" + packageName));        context.startActivity(intent);    }}

Removed duplicate code:

public void startNewActivity(Context context, String packageName) {    Intent intent = context.getPackageManager().getLaunchIntentForPackage(packageName);    if (intent == null) {        // Bring user to the market or let them choose an app?        intent = new Intent(Intent.ACTION_VIEW);        intent.setData(Uri.parse("market://details?id=" + packageName));    }    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);    context.startActivity(intent);}

I found the solution. In the manifest file of the application I found the package name: com.package.address and the name of the main activity which I want to launch: MainActivityThe following code starts this application:

Intent intent = new Intent(Intent.ACTION_MAIN);intent.setComponent(new ComponentName("com.package.address","com.package.address.MainActivity"));startActivity(intent);