Gracefully handle slowly appearing Home apps.

When starting a Guest user for the first time, it can take quite
awhile before the Home app enables itself.  So if we're unlocked
and no other Home app is around, chill for 500ms and see if someone
showed up.

Bug: 26267450
Change-Id: I3c4e01ae3681c650ea90b20ffc21835ae264b5e9

src/com/android/settings/FallbackHome.java

@@ -21,25 +21,57 @@ import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.content.pm.ResolveInfo;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Message;
+import android.os.UserManager;
 import android.util.Log;
 
+import java.util.Objects;
+
 public class FallbackHome extends Activity {
     private static final String TAG = "FallbackHome";
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
-
         registerReceiver(mReceiver, new IntentFilter(Intent.ACTION_USER_UNLOCKED));
+        maybeFinish();
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        unregisterReceiver(mReceiver);
     }
 
     private BroadcastReceiver mReceiver = new BroadcastReceiver() {
         @Override
         public void onReceive(Context context, Intent intent) {
-            Log.d(TAG, "User unlocked; leaving to find real home");
-            unregisterReceiver(this);
-            finish();
+            maybeFinish();
+        }
+    };
+
+    private void maybeFinish() {
+        if (getSystemService(UserManager.class).isUserUnlocked()) {
+            final Intent homeIntent = new Intent(Intent.ACTION_MAIN)
+                    .addCategory(Intent.CATEGORY_HOME);
+            final ResolveInfo homeInfo = getPackageManager().resolveActivity(homeIntent, 0);
+            if (Objects.equals(getPackageName(), homeInfo.activityInfo.packageName)) {
+                Log.d(TAG, "User unlocked but no home; let's hope someone enables one soon?");
+                mHandler.sendEmptyMessageDelayed(0, 500);
+            } else {
+                Log.d(TAG, "User unlocked and real home found; let's go!");
+                finish();
+            }
+        }
+    }
+
+    private Handler mHandler = new Handler() {
+        @Override
+        public void handleMessage(Message msg) {
+            maybeFinish();
         }
     };
 }