Android - footer scrolls off screen when used in CoordinatorLayout
Solution 1:
I use a simplified version of Learn OpenGL ES's solution (https://stackoverflow.com/a/33396965/778951) -- which improves on Noa's solution (https://stackoverflow.com/a/31140112/1317564). It works fine for my simple quick-return toolbar above a TabLayout with footer buttons in each tab's ViewPager content.
Just set the FixScrollingFooterBehavior as the layout_behavior on the View/ViewGroup you want to keep aligned at the bottom of the screen.
Layout:
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?android:attr/actionBarSize"
android:minHeight="?android:attr/actionBarSize"
app:title="Foo"
app:layout_scrollFlags="scroll|enterAlways|snap"
/>
<android.support.design.widget.TabLayout
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="com.spreeza.shop.ui.widgets.FixScrollingFooterBehavior"
/>
</android.support.design.widget.CoordinatorLayout>
Behavior:
public class FixScrollingFooterBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout appBarLayout;
public FixScrollingFooterBehavior() {
super();
}
public FixScrollingFooterBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
if (appBarLayout == null) {
appBarLayout = (AppBarLayout) dependency;
}
final boolean result = super.onDependentViewChanged(parent, child, dependency);
final int bottomPadding = calculateBottomPadding(appBarLayout);
final boolean paddingChanged = bottomPadding != child.getPaddingBottom();
if (paddingChanged) {
child.setPadding(
child.getPaddingLeft(),
child.getPaddingTop(),
child.getPaddingRight(),
bottomPadding);
child.requestLayout();
}
return paddingChanged || result;
}
// Calculate the padding needed to keep the bottom of the view pager's content at the same location on the screen.
private int calculateBottomPadding(AppBarLayout dependency) {
final int totalScrollRange = dependency.getTotalScrollRange();
return totalScrollRange + dependency.getTop();
}
}
Solution 2:
Update
The solution below doesn't work for 5.1 as it works in 5 - instead of getTop use getTranslationY in any of the calculations you do.
layout.getTop()-->(int)layout.getTranslationY()
appbar.getTop()+toolbar.getHeight()-->(int)(appbar.getTranslationY()+toolbar.getHeight())
Update 2 with the new support library - 22.2.1 - there is no diff between 5.1 and prev versions, you should only use getTop and ignore the previous update in this answer
Original solution After looking into many directions turns out the solution is actually simple - add paddingBottom to the fragment and adjust it as the page scrolls.
The padding is needed to cover for the changes in the toolbar y position - the coordinator layout is moving the entire page up and down as the toolbar disappears and reappears.
This can be achieved by extending AppBarLayout.ScrollingViewBehavior and setting this as the behavior of the fragment element of the activity.
Here are the basics of the code - it works for an activity with only a toolbar - you can replace it with appbar.getTop() + toolbar.getHeight() and this will work better if your appbar includes tabs.
activity.xml
<android.support.design.widget.CoordinatorLayout
android:id="@+id/main"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:elevation="3dp"
app:elevation="3dp">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_scrollFlags="scroll|enterAlways"
/>
</android.support.design.widget.AppBarLayout>
<fragment
android:id="@+id/fragment"
android:name="com.example.noa.footer2.MainActivityFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="com.example.noa.footer2.MyBehavior"
tools:layout="@layout/fragment"/>
</android.support.design.widget.CoordinatorLayout>
fragment.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="48dp"
android:background="@android:color/holo_green_dark"
tools:context=".MainActivityFragment">
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@null"/>
<View
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_alignParentBottom="true"
android:background="@android:color/holo_red_light"/>
</RelativeLayout>
MainActivityFragment#onActivityCreated
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
CoordinatorLayout.LayoutParams lp = (LayoutParams) getView().getLayoutParams();
MyBehavior behavior = (MyBehavior) lp.getBehavior();
behavior.setLayout(getView());
}
MyBehavior
public class MyBehavior extends AppBarLayout.ScrollingViewBehavior {
private View layout;
public MyBehavior() {
}
public MyBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
boolean result = super.onDependentViewChanged(parent, child, dependency);
if (layout != null) {
layout.setPadding(layout.getPaddingLeft(), layout.getPaddingTop(), layout
.getPaddingRight(), layout.getTop());
}
return result;
}
public void setLayout(View layout) {
this.layout = layout;
}
}
Solution 3:
I started out with Noa's solution (https://stackoverflow.com/a/31140112/1317564) and it worked for finger drags, but I was running into trouble with flings. After spending some time to trace the method calls and trying out different ideas, here is the solution I ended up with:
// Workaround for https://code.google.com/p/android/issues/detail?id=177195
// Based off of solution originally found here: https://stackoverflow.com/a/31140112/1317564
@SuppressWarnings("unused")
public class CustomScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout appBarLayout;
private boolean onAnimationRunnablePosted = false;
@SuppressWarnings("unused")
public CustomScrollingViewBehavior() {
}
@SuppressWarnings("unused")
public CustomScrollingViewBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {
if (appBarLayout != null) {
// We need to check from when a scroll is started, as we may not have had the chance to update the layout at
// the start of a scroll or fling event.
startAnimationRunnable(child, appBarLayout);
}
return super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
}
@Override
public boolean onMeasureChild(CoordinatorLayout parent, final View child, int parentWidthMeasureSpec, int widthUsed,
int parentHeightMeasureSpec, int heightUsed) {
if (appBarLayout != null) {
final int bottomPadding = calculateBottomPadding(appBarLayout);
if (bottomPadding != child.getPaddingBottom()) {
// We need to update the padding in onMeasureChild as otherwise we won't have the correct padding in
// place when the view is flung, and the changes done in onDependentViewChanged will only take effect on
// the next animation frame, which means it will be out of sync with the new scroll offset. This is only
// needed when the view is flung -- when dragged with a finger, things work fine with just
// implementing onDependentViewChanged().
child.setPadding(child.getPaddingLeft(), child.getPaddingTop(), child.getPaddingRight(), bottomPadding);
}
}
return super.onMeasureChild(parent, child, parentWidthMeasureSpec, widthUsed, parentHeightMeasureSpec, heightUsed);
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, final View child, final View dependency) {
if (appBarLayout == null)
appBarLayout = (AppBarLayout) dependency;
final boolean result = super.onDependentViewChanged(parent, child, dependency);
final int bottomPadding = calculateBottomPadding(appBarLayout);
final boolean paddingChanged = bottomPadding != child.getPaddingBottom();
if (paddingChanged) {
// If we've changed the padding, then update the child and make sure a layout is requested.
child.setPadding(child.getPaddingLeft(),
child.getPaddingTop(),
child.getPaddingRight(),
bottomPadding);
child.requestLayout();
}
// Even if we didn't change the padding, if onDependentViewChanged was called then that means that the app bar
// layout was changed or was flung. In that case, we want to check for these changes over the next few animation
// frames so that we can ensure that we capture all the changes and update the view pager padding to match.
startAnimationRunnable(child, dependency);
return paddingChanged || result;
}
// Calculate the padding needed to keep the bottom of the view pager's content at the same location on the screen.
private int calculateBottomPadding(AppBarLayout dependency) {
final int totalScrollRange = dependency.getTotalScrollRange();
return totalScrollRange + dependency.getTop();
}
private void startAnimationRunnable(final View child, final View dependency) {
if (onAnimationRunnablePosted)
return;
final int onPostChildTop = child.getTop();
final int onPostDependencyTop = dependency.getTop();
onAnimationRunnablePosted = true;
// Start looking for changes at the beginning of each animation frame. If there are any changes, we have to
// ensure that layout is run again so that we can update the padding to take the changes into account.
child.postOnAnimation(new Runnable() {
private static final int MAX_COUNT_OF_FRAMES_WITH_NO_CHANGES = 5;
private int previousChildTop = onPostChildTop;
private int previousDependencyTop = onPostDependencyTop;
private int countOfFramesWithNoChanges;
@Override
public void run() {
// Make sure we request a layout at the beginning of each animation frame, until we notice a few
// frames where nothing changed.
final int currentChildTop = child.getTop();
final int currentDependencyTop = dependency.getTop();
boolean hasChanged = false;
if (currentChildTop != previousChildTop) {
previousChildTop = currentChildTop;
hasChanged = true;
countOfFramesWithNoChanges = 0;
}
if (currentDependencyTop != previousDependencyTop) {
previousDependencyTop = currentDependencyTop;
hasChanged = true;
countOfFramesWithNoChanges = 0;
}
if (!hasChanged) {
countOfFramesWithNoChanges++;
}
if (countOfFramesWithNoChanges <= MAX_COUNT_OF_FRAMES_WITH_NO_CHANGES) {
// We can still look for changes on subsequent frames.
child.requestLayout();
child.postOnAnimation(this);
} else {
// We've encountered enough frames with no changes. Do a final layout request, and don't repost.
child.requestLayout();
onAnimationRunnablePosted = false;
}
}
});
}
}
I'm not a fan of rechecking the layout on every animation frame, and this solution isn't perfect as I've seen some issues if programmatically expanding/collapsing the app bar layout, but for now I haven't found a better solution. The performance is fine on a new device and acceptable on an older device. If someone else does, please feel free to take my answer as a source and repost.