本篇文章为大家展示了如何在Android中使用Fab(FloatingActionButton)方法实现一个滑动渐变效果，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。
Promoted Actions是指一种操作按钮，它不是放在actionbar中，而是直接在可见的UI布局中（当然这里的UI指的是setContentView所管辖的范围）。因此它更容易在代码中被获取到（试想如果你要在actionbar中获取一个菜单按钮是不是很难？），Promoted Actions往往主要用于一个界面的主要操作，比如在email的邮件列表界面，promoted action可以用于接受一个新邮件。promoted action在外观上其实就是一个悬浮按钮，更常见的是漂浮在界面上的圆形按钮，一般我直接将promoted action称作悬浮按钮，英文名称Float Action Button 简称（FAB，不是FBI哈）。
系统自带的 Fab 也会随着页面上下滚动,但是淡出或者进入的效果太不自然。
这里记录一个小知识点,Fab 随着页面的 RecyclerView 上下滚动而渐变的动画效果。
包含 Fab 控件的布局如下:
<?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" tools:context=".view.activity.MainActivity"> <android.support.design.widget.AppBarLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:theme="@style/AppTheme.AppBarOverlay"> <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" app:layout_scrollFlags="scroll|enterAlways" app:popupTheme="@style/AppTheme.PopupOverlay" /> <android.support.design.widget.TabLayout android:id="@+id/tab_layout" app:tabIndicatorColor="#FFFFFF" android:layout_width="match_parent" android:layout_height="wrap_content"> </android.support.design.widget.TabLayout> </android.support.design.widget.AppBarLayout> <include layout="@layout/content_main" /> <android.support.design.widget.FloatingActionButton android:id="@+id/fab" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_margin="@dimen/fab_margin" android:src="@android:drawable/ic_dialog_email" app:layout_behavior="com.wu.allen.zhuanlan.util.ScrollAwareFABBehavior"/> </android.support.design.widget.CoordinatorLayout>
实现的 Java 代码如下:
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);
}
}
}fab_in.xml 文件如下(fab_out.xml 同理),当然要改变淡出或者进入的样式,一般修改这里的 XML 文件就可以了 :
<?xml version="1.0" encoding="utf-8"?> <set xmlns:android="http://schemas.android.com/apk/res/android"> <alpha android:fromAlpha="0.0" android:toAlpha="1.0"/> <scale android:fromXScale="0.0" android:fromYScale="0.0" android:toXScale="1.0" android:toYScale="1.0" android:pivotX="50%" android:pivotY="50%"/> </set>
<?xml version="1.0" encoding="utf-8"?> <set xmlns:android="http://schemas.android.com/apk/res/android"> <alpha android:fromAlpha="1.0" android:toAlpha="0.0"/> <scale android:fromXScale="1.0" android:fromYScale="1.0" android:toXScale="0.0" android:toYScale="0.0" android:pivotX="50%" android:pivotY="50%"/> </set>
上述内容就是如何在Android中使用Fab(FloatingActionButton)方法实现一个滑动渐变效果，你们学到知识或技能了吗？如果还想学到更多技能或者丰富自己的知识储备，欢迎关注亿速云行业资讯频道。
免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
