安卓自定义Behavior

自定义Behavior，最外层布局必须是CoordinatorLayout

实现的效果，上滑隐藏TextView，下滑显示TextView

Demo链接：https://share.weiyun.com/53UcCFY

效果如下：

GIF.gif

public class BottomShowBehavior extends CoordinatorLayout.Behavior<TextView>{

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

    // 这个方法的回调时机 ： 即将发生嵌套滚动时 nestedScrollAxes  用于判断滑动的方向
    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, TextView child, View directTargetChild, View target, int nestedScrollAxes) {
        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
    }

    //发生嵌套滚动的时候 回调
    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, TextView child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        //向下滑动
        if (dyConsumed + dyUnconsumed > 0) {
            //隐藏child
            if (child.getVisibility() == View.VISIBLE) {
                Anim.bottomHide(child);
            }
        //向上滑动
        } else {
            //展示child
            if (child.getVisibility() != View.VISIBLE) {
                Anim.bottomShow(child);
            }
        }
    }
}

public class Anim {

    public static void bottomShow(View show) {
        //展示的动画
        show.clearAnimation();
        Animation animationShow = AnimationUtils.loadAnimation(show.getContext(), R.anim.main_tab_bottom_show);
        show.startAnimation(animationShow);
        show.setVisibility(View.VISIBLE);
    }

    public static void bottomHide(View gone) {
        //消失的动画
        gone.clearAnimation(); //清楚自身动画
        Animation animationGone = AnimationUtils.loadAnimation(gone.getContext(), R.anim.main_tab_bottom_hide);
        gone.startAnimation(animationGone);
        gone.setVisibility(View.INVISIBLE);
    }

}

main_tab_bottom_hide.xml

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="300"
        android:fromYDelta="0"
        android:toYDelta="100%" />
</set>

main_tab_bottom_show.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:duration="300"
        android:fromYDelta="100%"
        android:toYDelta="0" />
</set>

别忘了在string里面设置behavior属性

<resources>
    <string name="app_name">BehaviorLibrary</string>
    <string name="bottom_show_behavior">com.sloop.behaviorlibrary.design.BottomShowBehavior</string>
</resources>

使用app:layout_behavior="@string/bottom_show_behavior" 设置即可

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.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=".MainActivity">


    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <TextView
        android:id="@+id/tv_bottom"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_gravity="bottom"
        android:background="#f00"
        android:gravity="center"
        android:text="我是底部"
        android:textColor="#fff"
        app:layout_behavior="@string/bottom_show_behavior" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>