-
-
Save suclike/b16f21c4730347f55852a7f90282cce6 to your computer and use it in GitHub Desktop.
FAB behavior that lets FAB scroll out towards the bottom in sync with AppBarLayout scrolling out towards the top
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| /** | |
| * Behavior for FABs that does not support anchoring to AppBarLayout, but instead translates the FAB | |
| * out of the bottom in sync with the AppBarLayout collapsing towards the top. | |
| * <p> | |
| * Extends FloatingActionButton.Behavior to keep using the pre-Lollipop shadow padding offset. | |
| */ | |
| public class AppBarBoundFabBehavior extends FloatingActionButton.Behavior { | |
| public AppBarBoundFabBehavior(Context context, AttributeSet attrs) { | |
| super(); | |
| } | |
| @Override | |
| public boolean layoutDependsOn(CoordinatorLayout parent, FloatingActionButton child, View dependency) { | |
| if (dependency instanceof AppBarLayout) { | |
| ((AppBarLayout) dependency).addOnOffsetChangedListener(new FabOffsetter(parent, child)); | |
| } | |
| return dependency instanceof AppBarLayout || super.layoutDependsOn(parent, child, dependency); | |
| } | |
| @Override | |
| public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton fab, View dependency) { | |
| //noinspection SimplifiableIfStatement | |
| if (dependency instanceof AppBarLayout) { | |
| // if the dependency is an AppBarLayout, do not allow super to react on that | |
| // we don't want that behavior | |
| return true; | |
| } | |
| return super.onDependentViewChanged(parent, fab, dependency); | |
| } | |
| } |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| public class FabOffsetter implements AppBarLayout.OnOffsetChangedListener { | |
| private final CoordinatorLayout parent; | |
| private final FloatingActionButton fab; | |
| public FabOffsetter(@NonNull CoordinatorLayout parent, @NonNull FloatingActionButton child) { | |
| this.parent = parent; | |
| this.fab = child; | |
| } | |
| @Override | |
| public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) { | |
| // fab should scroll out down in sync with the appBarLayout scrolling out up. | |
| // let's see how far along the way the appBarLayout is | |
| // (if displacementFraction == 0.0f then no displacement, appBar is fully expanded; | |
| // if displacementFraction == 1.0f then full displacement, appBar is totally collapsed) | |
| float displacementFraction = -verticalOffset / (float) appBarLayout.getHeight(); | |
| // need to separate translationY on the fab that comes from this behavior | |
| // and one that comes from other sources | |
| // translationY from this behavior is stored in a tag on the fab | |
| float translationYFromThis = coalesce((Float) fab.getTag(R.id.fab_translationY_from_AppBarBoundFabBehavior), 0f); | |
| // top position, accounting for translation not coming from this behavior | |
| float topUntranslatedFromThis = fab.getTop() + fab.getTranslationY() - translationYFromThis; | |
| // total length to displace by (from position uninfluenced by this behavior) for a full appBar collapse | |
| float fullDisplacement = parent.getBottom() - topUntranslatedFromThis; | |
| // calculate and store new value for displacement coming from this behavior | |
| float newTranslationYFromThis = fullDisplacement * displacementFraction; | |
| fab.setTag(R.id.fab_translationY_from_AppBarBoundFabBehavior, newTranslationYFromThis); | |
| // update translation value by difference found in this step | |
| fab.setTranslationY(newTranslationYFromThis - translationYFromThis + fab.getTranslationY()); | |
| } | |
| @Override | |
| public boolean equals(Object o) { | |
| if (this == o) return true; | |
| if (o == null || getClass() != o.getClass()) return false; | |
| OnOffsetChangedListener that = (OnOffsetChangedListener) o; | |
| return parent.equals(that.parent) && fab.equals(that.fab); | |
| } | |
| @Override | |
| public int hashCode() { | |
| int result = parent.hashCode(); | |
| result = 31 * result + fab.hashCode(); | |
| return result; | |
| } | |
| } |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| <?xml version="1.0" encoding="utf-8"?> | |
| <resources xmlns:tools="http://schemas.android.com/tools" tools:ignore="MissingTranslation"> | |
| <item type="id" name="fab_translationY_from_AppBarBoundFabBehavior"/> | |
| </resources> |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment