How to animate FloatingActionButton like in Google

问题:

I set FloatingActionButton to bottom of screen and I want to animate the button.

• Hidden when scrolling down
• Shown when scrolling up

Like google implemented it in their Google+ app.

I think CoordinatorLayout and AppBarLayout is needed but how to implement it to use it with the FloatingActionButton?

回答1:

You can achieve it using the default FloatingActionButton changing its default Behavior using the app:layout_behavior attribute:

You can use a layout like:

 <android.support.design.widget.CoordinatorLayout     
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/main_content"
        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:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
            app:layout_scrollFlags="scroll|enterAlways" />

    </android.support.design.widget.AppBarLayout>

    // Your layout, for example a RecyclerView
    <RecyclerView
         .....
         app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="end|bottom"
            android:layout_margin="@dimen/fab_margin"
            android:src="@drawable/ic_done"      
            app:layout_behavior="com.support.android.designlibdemo.ScrollAwareFABBehavior" />

    </android.support.design.widget.CoordinatorLayout>

With the app:layout_behavior you can define your own Behavior. With the onStartNestedScroll() and onNestedScroll() methods you can interact with scroll events.

You can use a Behavior like this. You can find the original code here:

public class ScrollAwareFABBehavior extends FloatingActionButton.Behavior {
    private static final Interpolator INTERPOLATOR = new FastOutSlowInInterpolator();
    private boolean mIsAnimatingOut = false;

    public ScrollAwareFABBehavior(Context context, AttributeSet attrs) {
        super();
    }

    @Override
    public boolean onStartNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                                       final View directTargetChild, final View target, final int nestedScrollAxes) {
        // Ensure we react to vertical scrolling
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL
                || super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);
    }

    @Override
    public void onNestedScroll(final CoordinatorLayout coordinatorLayout, final FloatingActionButton child,
                               final View target, final int dxConsumed, final int dyConsumed,
                               final int dxUnconsumed, final int dyUnconsumed) {
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        if (dyConsumed > 0 && !this.mIsAnimatingOut && child.getVisibility() == View.VISIBLE) {
            // User scrolled down and the FAB is currently visible -> hide the FAB
            animateOut(child);
        } else if (dyConsumed < 0 && child.getVisibility() != View.VISIBLE) {
            // User scrolled up and the FAB is currently not visible -> show the FAB
            animateIn(child);
        }
    }

    // Same animation that FloatingActionButton.Behavior uses to hide the FAB when the AppBarLayout exits
    private void animateOut(final FloatingActionButton button) {
        if (Build.VERSION.SDK_INT >= 14) {
            ViewCompat.animate(button).scaleX(0.0F).scaleY(0.0F).alpha(0.0F).setInterpolator(INTERPOLATOR).withLayer()
                    .setListener(new ViewPropertyAnimatorListener() {
                        public void onAnimationStart(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = true;
                        }

                        public void onAnimationCancel(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
                        }

                        public void onAnimationEnd(View view) {
                            ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
                            view.setVisibility(View.GONE);
                        }
                    }).start();
        } else {
            Animation anim = AnimationUtils.loadAnimation(button.getContext(), R.anim.fab_out);
            anim.setInterpolator(INTERPOLATOR);
            anim.setDuration(200L);
            anim.setAnimationListener(new Animation.AnimationListener() {
                public void onAnimationStart(Animation animation) {
                    ScrollAwareFABBehavior.this.mIsAnimatingOut = true;
                }

                public void onAnimationEnd(Animation animation) {
                    ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
                    button.setVisibility(View.GONE);
                }

                @Override
                public void onAnimationRepeat(final Animation animation) {
                }
            });
            button.startAnimation(anim);
        }
    }

    // Same animation that FloatingActionButton.Behavior uses to show the FAB when the AppBarLayout enters
    private void animateIn(FloatingActionButton button) {
        button.setVisibility(View.VISIBLE);
        if (Build.VERSION.SDK_INT >= 14) {
            ViewCompat.animate(button).scaleX(1.0F).scaleY(1.0F).alpha(1.0F)
                    .setInterpolator(INTERPOLATOR).withLayer().setListener(null)
                    .start();
        } else {
            Animation anim = AnimationUtils.loadAnimation(button.getContext(), R.anim.fab_in);
            anim.setDuration(200L);
            anim.setInterpolator(INTERPOLATOR);
            button.startAnimation(anim);
        }
    }
}

回答2:

As of this post, there are no methods that will automatically handle hiding and showing the FloatingActionButton in the Design Support Libraries. I know this because this was my first assignment at work.

The methods you are thinking of are used to animate the FloatingActionButton up and down when a Snackbar is created, and yes, that will work if you are using a CoordinatorLayout.

Here's my code. It's based off of this repo. It has listeners for RecyclerView and AbsListView that handle animating the button automatically. You can either do

button.show();

or

button.hide();

to hide the button manually, or you can call:

button.attachToListView(listView);

and

button.attachToRecyclerView(recyclerView);

and it will hide on scroll down and show on scroll up with no further code.

Hope this helps!

AnimatedFloatingActionButton:

public class AnimatedFloatingActionButton extends FloatingActionButton
{
    private static final int TRANSLATE_DURATION_MILLIS = 200;
    private final Interpolator mInterpolator = new AccelerateDecelerateInterpolator();
    private boolean mVisible;

public AnimatedFloatingActionButton(Context context, AttributeSet attrs)
{
    super(context, attrs);
    Log.i("Abscroll", "mVisible" + mVisible);
}

public void show() {
    show(true);
}

public void hide() {
    hide(true);
}

public void show(boolean animate) {
    toggle(true, animate, false);
}

public void hide(boolean animate) {
    toggle(false, animate, false);
}

private void toggle(final boolean visible, final boolean animate, boolean force) {
    if (mVisible != visible || force) {
        mVisible = visible;
        int height = getHeight();
        if (height == 0 && !force) {
            ViewTreeObserver vto = getViewTreeObserver();
            if (vto.isAlive()) {
                vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
                    @Override
                    public boolean onPreDraw() {
                        ViewTreeObserver currentVto = getViewTreeObserver();
                        if (currentVto.isAlive()) {
                            currentVto.removeOnPreDrawListener(this);
                        }
                        toggle(visible, animate, true);
                        return true;
                    }
                });
                return;
            }
        }
        int translationY = visible ? 0 : height + getMarginBottom();
        Log.i("Abscroll", "transY" + translationY);
        if (animate) {
            this.animate().setInterpolator(mInterpolator)
                    .setDuration(TRANSLATE_DURATION_MILLIS)
                    .translationY(translationY);
        } else {
            setTranslationY(translationY);
        }
    }
}

private int getMarginBottom() {
    int marginBottom = 0;
    final ViewGroup.LayoutParams layoutParams = getLayoutParams();
    if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
        marginBottom = ((ViewGroup.MarginLayoutParams) layoutParams).bottomMargin;
    }
    return marginBottom;
}

public void attachToListView(@NonNull AbsListView listView)
{
    listView.setOnScrollListener(new AbsListViewScrollDetector() {
        @Override
        void onScrollUp() {
            hide();
        }

        @Override
        void onScrollDown() {
            show();
        }

        @Override
        void setScrollThreshold() {
            setScrollThreshold(getResources().getDimensionPixelOffset(R.dimen.fab_scroll_threshold));
        }
    });
}

public void attachToRecyclerView(@NonNull RecyclerView recyclerView) {
    recyclerView.addOnScrollListener(new RecyclerViewScrollDetector() {
        @Override
        void onScrollUp() {
            hide();
        }

        @Override
        void onScrollDown() {
            show();
        }

        @Override
        void setScrollThreshold() {
            setScrollThreshold(getResources().getDimensionPixelOffset(R.dimen.fab_scroll_threshold));
        }
    });
}
}

AbsListViewScrollDetector:

abstract class AbsListViewScrollDetector implements AbsListView.OnScrollListener {
private int mLastScrollY;
private int mPreviousFirstVisibleItem;
private AbsListView mListView;
private int mScrollThreshold;

abstract void onScrollUp();

abstract void onScrollDown();

abstract void setScrollThreshold();

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    if(totalItemCount == 0) return;
    if (isSameRow(firstVisibleItem)) {
        int newScrollY = getTopItemScrollY();
        boolean isSignificantDelta = Math.abs(mLastScrollY - newScrollY) > mScrollThreshold;
        Log.i("Abscroll", "mLastScrollY " + mLastScrollY);
        Log.i("Abscroll", "newScrollY " + newScrollY);
        if (isSignificantDelta) {
            Log.i("Abscroll", "sig delta");
            if (mLastScrollY > newScrollY) {
                onScrollUp();
                Log.i("Abscroll", "sig delta up");
            } else {
                onScrollDown();
                Log.i("Abscroll", "sig delta down");
            }
        }
        mLastScrollY = newScrollY;
    } else {
        if (firstVisibleItem > mPreviousFirstVisibleItem) {
            onScrollUp();
            Log.i("Abscroll", "prev up");
        } else {
            onScrollDown();
            Log.i("Abscroll", "prev down");
        }

        mLastScrollY = getTopItemScrollY();
        mPreviousFirstVisibleItem = firstVisibleItem;
    }
}

public void setScrollThreshold(int scrollThreshold) {
    mScrollThreshold = scrollThreshold;
    Log.i("Abscroll", "LView thresh " + scrollThreshold);
}

public void setListView(@NonNull AbsListView listView) {
    mListView = listView;
}

private boolean isSameRow(int firstVisibleItem) {
    return firstVisibleItem == mPreviousFirstVisibleItem;
}

private int getTopItemScrollY() {
    if (mListView == null || mListView.getChildAt(0) == null) return 0;
    View topChild = mListView.getChildAt(0);
    return topChild.getTop();
}
}

RecyclerViewScrollDetector:

abstract class RecyclerViewScrollDetector extends RecyclerView.OnScrollListener {
private int mScrollThreshold;

abstract void onScrollUp();

abstract void onScrollDown();

abstract void setScrollThreshold();

@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    boolean isSignificantDelta = Math.abs(dy) > mScrollThreshold;
    if (isSignificantDelta) {
        if (dy > 0) {
            onScrollUp();
            Log.i("Abscroll", "Rview up");
        } else {
            onScrollDown();
            Log.i("Abscroll", "RView down");
        }
    }
}

public void setScrollThreshold(int scrollThreshold) {
    mScrollThreshold = scrollThreshold;
    Log.i("Abscroll", "RView thresh " + scrollThreshold);
}
}

回答3:

Googles Design Support Library will do that.

Try to implement this code to your layout file:

<android.support.design.widget.FloatingActionButton
      android:id="@+id/fab"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:src="@drawable/ic_add_black"
      android:layout_gravity="bottom|end"
      app:elevation="6dp"
      app:pressedTranslationZ="12dp"/>

It's important that you add compile 'com.android.support:design:22.2.0' to your build.gradle. If you're using eclipse there is another way to add this library to your project.

Important resources:
Design Support Library (II): Floating Action Button
Android Design Support Library
Google Releasing A FABulous New Design Support Library [Updated]