[MaterialContainerTransform] Add support for predictive back

catalog/java/io/material/catalog/musicplayer/MusicPlayerLibraryDemoFragment.java

@@ -21,6 +21,8 @@
 import android.content.Context;
 import android.os.Bundle;
 import android.os.Parcelable;
+
+import androidx.core.view.OneShotPreDrawListener;
 import androidx.fragment.app.Fragment;
 import androidx.recyclerview.widget.DividerItemDecoration;
 import androidx.recyclerview.widget.GridLayoutManager;
@@ -40,8 +42,8 @@
 import androidx.core.view.ViewCompat;
 import androidx.transition.Transition;
 import androidx.transition.TransitionManager;
-import com.google.android.material.transition.Hold;
 import com.google.android.material.transition.MaterialContainerTransform;
+import com.google.android.material.transition.MaterialFade;
 import com.google.android.material.transition.MaterialFadeThrough;
 import com.google.android.material.transition.MaterialSharedAxis;
 import io.material.catalog.musicplayer.AlbumsAdapter.AlbumAdapterListener;
@@ -83,6 +85,10 @@ public void onViewCreated(@NonNull View view, @Nullable Bundle bundle) {
     toolbar.setOnMenuItemClickListener(this);
     MaterialSharedAxis sharedAxis = new MaterialSharedAxis(MaterialSharedAxis.Z, true);
     setList(listTypeGrid, listSorted, sharedAxis);
+
+    // Wait until all views in the entering fragment have been measured and laid out
+    postponeEnterTransition();
+    OneShotPreDrawListener.add((ViewGroup) view.getParent(), this::startPostponedEnterTransition);
   }
 
   @Override
@@ -101,16 +107,7 @@ public void onAlbumClicked(View view, Album album) {
     MaterialContainerTransform transform =
         new MaterialContainerTransform(requireContext(), /* entering= */ true);
     fragment.setSharedElementEnterTransition(transform);
-
-    // Use a Hold transition to keep this fragment visible beneath the MaterialContainerTransform
-    // that transitions to the album details screen. Without a Hold, this fragment would disappear
-    // as soon its container is replaced with a new Fragment.
-    Hold hold = new Hold();
-    // Add root view as target for the Hold so that the entire view hierarchy is held in place as
-    // one instead of each child view individually. Helps keep shadows during the transition.
-    hold.addTarget(R.id.container);
-    hold.setDuration(transform.getDuration());
-    setExitTransition(hold);
+    fragment.setEnterTransition(new MaterialFade());
 
     getParentFragmentManager()
         .beginTransaction()

lib/java/com/google/android/material/transition/MaterialContainerTransform.java

@@ -972,21 +972,11 @@ public void onAnimationUpdate(ValueAnimator animation) {
           }
         });
 
-    addListener(
-        new TransitionListenerAdapter() {
-          @Override
-          public void onTransitionStart(@NonNull Transition transition) {
-            // Add the transition drawable to the root ViewOverlay
-            ViewUtils.getOverlay(drawingView).add(transitionDrawable);
-
-            // Hide the actual views at the beginning of the transition
-            startView.setAlpha(0);
-            endView.setAlpha(0);
-          }
+    animator.addListener(
+        new Animator.AnimatorListener() {
 
-          @Override
-          public void onTransitionEnd(@NonNull Transition transition) {
-            removeListener(this);
+          void showTransitionEnd() {
+            animator.removeListener(this);
             if (holdAtEndEnabled) {
               // Keep drawable showing and views hidden (useful for Activity return transitions)
               return;
@@ -998,6 +988,29 @@ public void onTransitionEnd(@NonNull Transition transition) {
             // Remove the transition drawable from the root ViewOverlay
             ViewUtils.getOverlay(drawingView).remove(transitionDrawable);
           }
+
+          @Override
+          public void onAnimationStart(@NonNull Animator animation) {
+            // Add the transition drawable to the root ViewOverlay
+            ViewUtils.getOverlay(drawingView).add(transitionDrawable);
+
+            // Hide the actual views at the beginning of the transition
+            startView.setAlpha(0);
+            endView.setAlpha(0);
+          }
+
+          @Override
+          public void onAnimationEnd(@NonNull Animator animation) {
+            showTransitionEnd();
+          }
+
+          @Override
+          public void onAnimationCancel(@NonNull Animator animation) {
+            showTransitionEnd();
+          }
+
+          @Override
+          public void onAnimationRepeat(@NonNull Animator animation) {}
         });
 
     return animator;
@@ -1573,4 +1586,9 @@ private ProgressThresholdsGroup(
       this.shapeMask = shapeMask;
     }
   }
+
+  @Override
+  public boolean isSeekingSupported() {
+    return true;
+  }
 }