Terminate DocumentsUI opened for the specific root.

If USB is opened in DocumentsUI from storage settings and format it from
context menu, a user expects it goes back to storage settings after
formatting the storage.  However, previous we show Downloads as a result
of redirect from the previous USB storage.

The CL changes the logic for callback so that it finishes the activity
if DocumentsUI is opened for the specific root and the root was removed
while a user stays at the root.

Fixes: 28246076
Change-Id: I5548152fc27fd13bd9b75b3083bcfbdd9f93509e

packages/DocumentsUI/src/com/android/documentsui/BaseActivity.java

@@ -32,6 +32,7 @@ import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.ProviderInfo;
+import android.database.ContentObserver;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Bundle;
@@ -46,7 +47,6 @@ import android.util.Log;
 import android.view.KeyEvent;
 import android.view.Menu;
 import android.view.MenuItem;
-import android.view.WindowManager;
 import android.widget.Spinner;
 
 import com.android.documentsui.SearchViewManager.SearchManagerListener;
@@ -78,6 +78,12 @@ public abstract class BaseActivity extends Activity
     List<EventListener> mEventListeners = new ArrayList<>();
 
     private final String mTag;
+    private final ContentObserver mRootsCacheObserver = new ContentObserver(new Handler()) {
+        @Override
+        public void onChange(boolean selfChange) {
+            new HandleRootsChangedTask(BaseActivity.this).execute(getCurrentRoot());
+        }
+    };
 
     @LayoutRes
     private int mLayoutId;
@@ -118,14 +124,8 @@ public abstract class BaseActivity extends Activity
 
         mRoots = DocumentsApplication.getRootsCache(this);
 
-        mRoots.setOnCacheUpdateListener(
-                new RootsCache.OnCacheUpdateListener() {
-                    @Override
-                    public void onCacheUpdate() {
-                        new HandleRootsChangedTask(BaseActivity.this)
-                                .execute(getCurrentRoot());
-                    }
-                });
+        getContentResolver().registerContentObserver(
+                RootsCache.sNotificationUri, false, mRootsCacheObserver);
 
         mSearchManager = new SearchViewManager(this, icicle);
 
@@ -190,7 +190,7 @@ public abstract class BaseActivity extends Activity
 
     @Override
     protected void onDestroy() {
-        mRoots.setOnCacheUpdateListener(null);
+        getContentResolver().unregisterContentObserver(mRootsCacheObserver);
         super.onDestroy();
     }
 
@@ -793,6 +793,7 @@ public abstract class BaseActivity extends Activity
 
     private static final class HandleRootsChangedTask
             extends PairedTask<BaseActivity, RootInfo, RootInfo> {
+        RootInfo mCurrentRoot;
         DocumentInfo mDefaultRootDocument;
 
         public HandleRootsChangedTask(BaseActivity activity) {
@@ -802,11 +803,10 @@ public abstract class BaseActivity extends Activity
         @Override
         protected RootInfo run(RootInfo... roots) {
             assert(roots.length == 1);
-
-            final RootInfo currentRoot = roots[0];
+            mCurrentRoot = roots[0];
             final Collection<RootInfo> cachedRoots = mOwner.mRoots.getRootsBlocking();
             for (final RootInfo root : cachedRoots) {
-                if (root.getUri().equals(currentRoot.getUri())) {
+                if (root.getUri().equals(mCurrentRoot.getUri())) {
                     // We don't need to change the current root as the current root was not removed.
                     return null;
                 }
@@ -827,6 +827,14 @@ public abstract class BaseActivity extends Activity
                 return;
             }
 
+            // If the activity has been launched for the specific root and it is removed, finish the
+            // activity.
+            final Uri uri = mOwner.getIntent().getData();
+            if (uri != null && uri.equals(mCurrentRoot.getUri())) {
+                mOwner.finish();
+                return;
+            }
+
             // Clear entire backstack and start in new root.
             mOwner.mState.onRootChanged(defaultRoot);
             mOwner.mSearchManager.update(defaultRoot);

packages/DocumentsUI/src/com/android/documentsui/RootsCache.java

@@ -67,7 +67,6 @@ public class RootsCache {
 
     private final Context mContext;
     private final ContentObserver mObserver;
-    private OnCacheUpdateListener mCacheUpdateListener;
 
     private final RootInfo mRecentsRoot;
 
@@ -115,10 +114,6 @@ public class RootsCache {
         }
     }
 
-    static interface OnCacheUpdateListener {
-        void onCacheUpdate();
-    }
-
     /**
      * Gather roots from all known storage providers.
      */
@@ -276,13 +271,6 @@ public class RootsCache {
             return null;
         }
 
-        @Override
-        protected void onPostExecute(Void result) {
-            if (mCacheUpdateListener != null) {
-                mCacheUpdateListener.onCacheUpdate();
-            }
-        }
-
         private void handleDocumentsProvider(ProviderInfo info) {
             // Ignore stopped packages for now; we might query them
             // later during UI interaction.
@@ -441,10 +429,6 @@ public class RootsCache {
         }
     }
 
-    public void setOnCacheUpdateListener(OnCacheUpdateListener cacheUpdateListener) {
-        mCacheUpdateListener = cacheUpdateListener;
-    }
-
     /**
      * Returns the default root for the specified state.
      */