Lifecycle guarantees for target fragments
Ported from frameworks/support change id
I824eb312fbdfd6b548fe94aa2cd5b03afbaa97c7
When a target fragment was set using Fragment#setTargetFragment, all
bets were off, especially when restoring from instance state. Order of
lifecyle initialization was undefined meaning that two bugs could
occur, both of which manifested as the target fragment was not
initialized by the time the referring fragment's onCreate ran. One
could happen if the target fragment is on the back stack, the other
could happen if the target fragment was ordered unfortunately in
FragmentManager implementation details. (!)
Fix both by guaranteeing that any target fragment gets pushed forward
to at least the CREATED state before we dispatch any lifecycle events
for the referring fragment.
Add some sanity checks that try to keep developers from setting target
fragments across different FragmentManagers or from creating target
cycles, both of which are bad ideas.
Bug: 33653458
Test: CTS FragmentLifecycleTest
Change-Id: If624d4665d29e205d37b9b384322e64d6d6d3615
diff --git a/core/java/android/app/Fragment.java b/core/java/android/app/Fragment.java
index 73b96f1..612998d 100644
--- a/core/java/android/app/Fragment.java
+++ b/core/java/android/app/Fragment.java
@@ -762,6 +762,24 @@
* are going to call back with {@link #onActivityResult(int, int, Intent)}.
*/
public void setTargetFragment(Fragment fragment, int requestCode) {
+ // Don't allow a caller to set a target fragment in another FragmentManager,
+ // but there's a snag: people do set target fragments before fragments get added.
+ // We'll have the FragmentManager check that for validity when we move
+ // the fragments to a valid state.
+ final FragmentManager mine = getFragmentManager();
+ final FragmentManager theirs = fragment.getFragmentManager();
+ if (mine != null && theirs != null && mine != theirs) {
+ throw new IllegalArgumentException("Fragment " + fragment
+ + " must share the same FragmentManager to be set as a target fragment");
+ }
+
+ // Don't let someone create a cycle.
+ for (Fragment check = fragment; check != null; check = check.getTargetFragment()) {
+ if (check == this) {
+ throw new IllegalArgumentException("Setting " + fragment + " as the target of "
+ + this + " would create a target cycle");
+ }
+ }
mTarget = fragment;
mTargetRequestCode = requestCode;
}
diff --git a/core/java/android/app/FragmentManager.java b/core/java/android/app/FragmentManager.java
index 44f1322..32cf1c3 100644
--- a/core/java/android/app/FragmentManager.java
+++ b/core/java/android/app/FragmentManager.java
@@ -1110,10 +1110,25 @@
}
}
}
+
f.mHost = mHost;
f.mParentFragment = mParent;
f.mFragmentManager = mParent != null
? mParent.mChildFragmentManager : mHost.getFragmentManagerImpl();
+
+ // If we have a target fragment, push it along to at least CREATED
+ // so that this one can rely on it as an initialized dependency.
+ if (f.mTarget != null) {
+ if (!mActive.contains(f.mTarget)) {
+ throw new IllegalStateException("Fragment " + f
+ + " declared target fragment " + f.mTarget
+ + " that does not belong to this FragmentManager!");
+ }
+ if (f.mTarget.mState < Fragment.CREATED) {
+ moveToState(f.mTarget, Fragment.CREATED, 0, 0, true);
+ }
+ }
+
dispatchOnFragmentPreAttached(f, mHost.getContext(), false);
f.mCalled = false;
f.onAttach(mHost.getContext());