java - Clearing and setting the default home application

Question

How in the world does Nova manage this? I'm literally trying to do exactly the same thing: provide users with a button to press to clear and pick their new default launcher.

I'm able to get the default app name and display it:

       private String getPrefered(Intent i) {
       PackageManager pm = this.getActivity().getPackageManager();
       final ResolveInfo mInfo = pm.resolveActivity(i, 0);
       return (String) pm.getApplicationLabel(mInfo.activityInfo.applicationInfo);
   }

where Intent i is

Intent home = new Intent("android.intent.action.MAIN");
        home.addCategory("android.intent.category.HOME");

Then I call up the system ResolveActivity,

private void makePrefered() {
       Intent selector = new Intent("android.intent.action.MAIN");
       selector.addCategory("android.intent.category.HOME");                          
       selector.setComponent(new ComponentName("android", "com.android.internal.app.ResolverActivity"));
       startActivity(selector);
   }

The picker comes up and functions correctly, but it doesn't actually set or clear any values. While debugging it, it seems as if I'm missing some extras? When I call the makePrefered method, I get the following log message,

I/ActivityManager(  602): START {act=android.intent.action.MAIN cat=[android.intent.category.HOME] cmp=android/com.android.internal.app.ResolverActivity u=0} from pid 22641

When I use the Nova implementation I see all of this however,

    I/PackageManager(  602): Result set changed, dropping preferred activity for Intent { act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10200000 (has extras) } type null
I/ActivityManager(  602): START {act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10200000 cmp=android/com.android.internal.app.ResolverActivity (has extras) u=0} from pid 22905
I/ActivityManager(  602): START {act=android.intent.action.MAIN cat=[android.intent.category.HOME] flg=0x10200000 cmp=com.mycolorscreen.canvas/.Launcher (has extras) u=0} from pid 22905

1. How can I get in there and see what's being sent along with that bundle?
2. How can I just clear the preferred app? Don't tell me you can't, I've seen enough of those answers. Nova does it and does it exactly the way that I would like to.

Answer 1

The code to do this is actually just a very clever work around.

When a component with

        <category android:name="android.intent.category.HOME" />

is enabled, generally from an install of a new home application, the default home app gets cleared.

To take advantage of this by creating an empty activity with the home component like this.

<activity
            android:name="com.t3hh4xx0r.haxlauncher.FakeHome"
            android:enabled="false">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>     

When you want to set your new default, you enable this component, then call the home intent and then disable your fake home component again.

public static void makePrefered(Context c) {
       PackageManager p = c.getPackageManager();
       ComponentName cN = new ComponentName(c, FakeHome.class);
       p.setComponentEnabledSetting(cN, PackageManager.COMPONENT_ENABLED_STATE_ENABLED, PackageManager.DONT_KILL_APP);

       Intent selector = new Intent(Intent.ACTION_MAIN);
       selector.addCategory(Intent.CATEGORY_HOME);            
       c.startActivity(selector);

       p.setComponentEnabledSetting(cN, PackageManager.COMPONENT_ENABLED_STATE_DISABLED, PackageManager.DONT_KILL_APP);
   }

The end result is that the system thinks a new home app was installed, so the default is cleared allowing you to set yours with no special permissions.

Thank you to Kevin from TeslaCoil and NovaLauncher for the information on how this is done!