FloatingActionButton上滑隐藏下滑显示
此交互是FAB的经典交互了，具体效果见如下视频：
可以看到RecyclerView占满整个屏幕后，RecyclerView继续上滑会使FloatingActionButton隐藏，RecyclerView向下滑动会使FloatingActionButton显示。
这个交互是通过给
FloatingActionButton配置app:layout_behavior属性实现的。但是，需要注意的是： 1. 页面根布局必须是CoordinatorLayout2.RecyclerView必须配置成app:layout_behavior="@string/appbar_scrolling_view_behavior"
下面奉上实现此效果的代码：
1. xml文件代码
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.yorek.yltodo.ui.activity.TodoFolderActivity">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:background="@android:color/white">
<android.support.design.widget.CollapsingToolbarLayout
android:id="@+id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:titleEnabled="false">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:layout_marginTop="?attr/actionBarSize"
app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="0.5"
android:background="@android:color/white">
<ImageView
android:id="@+id/iv_folder_icon"
android:layout_width="48dp"
android:layout_height="48dp"
android:layout_alignParentStart="true"
android:layout_marginStart="24dp"
android:background="@drawable/bg_task_circle_ededed"
android:scaleType="centerInside"
android:src="@drawable/ic_home_ff53c4ac_24dp"
android:transitionName="@string/transition_task_icon"/>
<TextView
android:id="@+id/tv_folder_count"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@id/iv_folder_icon"
android:layout_marginTop="24dp"
android:layout_marginStart="24dp"
android:textColor="@color/ff999999"
android:textSize="18sp"
android:transitionName="@string/transition_task_count"/>
<TextView
android:id="@+id/tv_folder_progress_value"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:layout_below="@id/tv_folder_count"
android:layout_marginTop="24dp"
android:layout_marginBottom="24dp"
android:layout_marginEnd="24dp"
android:textColor="#ff9d9d9d"
android:transitionName="@string/transition_task_progress_value"/>
<ProgressBar
android:id="@+id/pb_folder_progress"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignBottom="@id/tv_folder_progress_value"
android:layout_alignParentStart="true"
android:layout_marginBottom="6dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="24dp"
android:layout_toStartOf="@id/tv_folder_progress_value"
android:background="@color/ffebebeb"
android:max="100"
android:maxHeight="4dp"
android:minHeight="4dp"
android:progress="50"
android:transitionName="@string/transition_task_progress"/>
</RelativeLayout>
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:navigationIcon="?attr/homeAsUpIndicator"
app:layout_collapseMode="pin"
android:theme="@style/AppTheme.AppBarOverlay"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@android:color/white"
app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
<android.support.design.widget.FloatingActionButton
android:id="@+id/fab"
android:layout_width="56dp"
android:layout_height="56dp"
android:layout_gravity="bottom|end"
android:layout_margin="@dimen/fab_margin"
android:src="@drawable/ic_add_white_24dp"
app:backgroundTint="@color/ff497de2"
app:fabSize="auto"
app:layout_behavior="com.yorek.yltodo.ui.widget.behavior.ScrollAwareFABBehavior"
app:rippleColor="@color/ff2b5ec1"/>
</android.support.design.widget.CoordinatorLayout>
上面强调了，AppBarLayout里面的内容不是必须的，根据自己的需求写。
2. ScrollAwareFABBehavior代码
package com.yorek.yltodo.ui.widget.behavior;
import android.content.Context;
import android.support.design.widget.CoordinatorLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPropertyAnimatorListener;
import android.support.v4.view.animation.FastOutSlowInInterpolator;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Interpolator;
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);
}
}
private void animateOut(final FloatingActionButton button) {
ViewCompat.animate(button).translationY(button.getHeight() + getMarginBottom(button)).setInterpolator(INTERPOLATOR).withLayer()
.setListener(new ViewPropertyAnimatorListener() {
@Override
public void onAnimationStart(View view) {
ScrollAwareFABBehavior.this.mIsAnimatingOut = true;
}
@Override
public void onAnimationCancel(View view) {
ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
}
@Override
public void onAnimationEnd(View view) {
ScrollAwareFABBehavior.this.mIsAnimatingOut = false;
view.setVisibility(View.INVISIBLE);
}
}).start();
}
private void animateIn(FloatingActionButton button) {
button.setVisibility(View.VISIBLE);
ViewCompat.animate(button).translationY(0)
.setInterpolator(INTERPOLATOR).withLayer().setListener(null)
.start();
}
private int getMarginBottom(View v) {
int marginBottom = 0;
final ViewGroup.LayoutParams layoutParams = v.getLayoutParams();
if (layoutParams instanceof ViewGroup.MarginLayoutParams) {
marginBottom = ((ViewGroup.MarginLayoutParams) layoutParams).bottomMargin;
}
return marginBottom;
}
}
注意，第一部中配置的layout_behavior需要加上此文件的包名。