Add API for deferring fragment start.

Fragments now have the setDeferStart method to signal that a fragment
has lower priority than others. Deferred start fragments will not
always be started immediately; they will be started once any loaders
have finished servicing any outstanding requests. This is useful if
any attached fragments are not immediately visible and can wait to
start until later.

Disabling deferStart on a fragment that is waiting for a deferred
start will start it immediately. Start.

Change-Id: Ia1f004877ca5e88d4f10147d21c7e2e97f141c34

1 files changed, 28 insertions, 1 deletions

diff --git a/core/java/android/app/FragmentManager.java b/core/java/android/app/FragmentManager.java
index 3da4f29..58cd27c 100644
--- a/core/java/android/app/FragmentManager.java
+++ b/core/java/android/app/FragmentManager.java
@@ -709,6 +709,13 @@ final class FragmentManagerImpl extends FragmentManager {
         return AnimatorInflater.loadAnimator(mActivity, anim);
     }
     
+    public void performPendingDeferredStart(Fragment f) {
+        if (f.mDeferStart) {
+            f.mDeferStart = false;
+            moveToState(f, mCurState, 0, 0);
+        }
+    }
+
     void moveToState(Fragment f, int newState, int transit, int transitionStyle) {
         // Fragments that are not currently added will sit in the onCreate() state.
         if (!f.mAdded && newState > Fragment.CREATED) {
@@ -718,7 +725,10 @@ final class FragmentManagerImpl extends FragmentManager {
             // While removing a fragment, we can't change it to a higher state.
             newState = f.mState;
         }
-        
+        // Defer start if requested; don't allow it to move to STARTED or higher.
+        if (f.mDeferStart && newState > Fragment.STOPPED) {
+            newState = Fragment.STOPPED;
+        }
         if (f.mState < newState) {
             // For fragments that are created from a layout, when restoring from
             // state we don't want to allow them to be created until they are
@@ -992,13 +1002,21 @@ final class FragmentManagerImpl extends FragmentManager {
         
         mCurState = newState;
         if (mActive != null) {
+            boolean loadersRunning = false;
             for (int i=0; i<mActive.size(); i++) {
                 Fragment f = mActive.get(i);
                 if (f != null) {
                     moveToState(f, newState, transit, transitStyle);
+                    if (f.mLoaderManager != null) {
+                        loadersRunning |= f.mLoaderManager.hasRunningLoaders();
+                    }
                 }
             }
 
+            if (!loadersRunning) {
+                startPendingDeferredFragments();
+            }
+
             if (mNeedMenuInvalidate && mActivity != null && mCurState == Fragment.RESUMED) {
                 mActivity.invalidateOptionsMenu();
                 mNeedMenuInvalidate = false;
@@ -1006,6 +1024,15 @@ final class FragmentManagerImpl extends FragmentManager {
         }
     }
     
+    void startPendingDeferredFragments() {
+        for (int i=0; i<mActive.size(); i++) {
+            Fragment f = mActive.get(i);
+            if (f != null) {
+                performPendingDeferredStart(f);
+            }
+        }
+    }
+
     void makeActive(Fragment f) {
         if (f.mIndex >= 0) {
             return;