自定义Behavior（二）

来源：互联网发布：vidown mac 编辑：程序博客网时间：2024/05/21 13:54

上次讲了自定义Behavior的child监听dependency的状态变化，这次就接着说child监听实现了NestedScrollingChild的接口的dependency的滑动状态。
需要重写两个方法

    @Override    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {        return super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, nestedScrollAxes);    }    @Override    public void onNestedScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);    }

先来看onStartNestedScroll，这个方法表明我们在这次滑动中关心的方向，如果是X轴，则return nestedScrollAxes == ViewCompat.SCROLL_AXIS_HORIZONTAL;若是关心Y轴方向的滑动，return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL即可。

onNestedScroll这个方法才是我们关注的重点，coordinatorLayout这个参数就不说了，child是指设置了这个Behavior的coordinatorLayout的子View，target则是前面提到的实现了NestedScrollingChild的接口的dependency。dxConsumed、dyConsumed是指x、y轴方向上target消费的像素值，简单来说，就是滚动的距离，至于后面两个参数，百度了，也看了源码的注释，还是不太明白，翻译过来字面意思就是：不被目标自身的滚动操作所消耗的垂直、水平像素，而是用户要求的(本来以为是调用scrollto之类方法产生的，试过了发现不是)。

说完这么多屁话，看个例子
先上效果图
这里写图片描述
仔细看还是和之前的有点区别，在上滑和下滑时，隐藏显示FloatingActionButton和BottomBar。

XML

<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:layout_width="match_parent"        android:layout_height="wrap_content"        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"        app:elevation="0dp">        <TextView            android:layout_width="match_parent"            android:layout_height="50dp"            android:gravity="center"            android:text="topBar"            app:layout_scrollFlags="scroll|enterAlways" />    </android.support.design.widget.AppBarLayout>    <android.support.v4.widget.NestedScrollView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:scrollbars="none"        app:behavior_overlapTop="30dp"        app:layout_behavior="@string/appbar_scrolling_view_behavior">        <include layout="@layout/layout_main" />    </android.support.v4.widget.NestedScrollView>    <TextView        android:layout_width="match_parent"        android:layout_height="50dp"        android:layout_gravity="bottom"        android:background="@color/colorPrimary"        android:gravity="center"        android:text="bottomBar"        app:layout_behavior=".BottomScrollBehavior" />    <android.support.design.widget.FloatingActionButton        android:layout_width="50dp"        android:layout_height="50dp"        android:layout_gravity="bottom|right"        android:layout_marginBottom="70dp"        android:layout_marginRight="20dp"        android:src="@mipmap/ic_launcher_round"        app:elevation="5dp"        app:layout_behavior=".ScrollingBehavior" /></android.support.design.widget.CoordinatorLayout>

也和上一篇的相似，唯一的区别就是BottomBar和FloatingActionButton的Behavior换了
再看自定义的Behavior

ScrollingBehavior

public class ScrollingBehavior extends CoordinatorLayout.Behavior<FloatingActionButton> {    //是否正在执行动画的标示符    private boolean isAnimator;    public ScrollingBehavior(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View directTargetChild, View target, int nestedScrollAxes) {        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;    }    @Override    public void onNestedScroll(CoordinatorLayout coordinatorLayout, FloatingActionButton child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {        if ((dyConsumed > 0 || dyUnconsumed > 0) && !isAnimator && child.getVisibility() == View.VISIBLE) {            hideAnimator(child);        } else if ((dyConsumed < 0 || dyUnconsumed < 0) && !isAnimator && child.getVisibility() != View.VISIBLE) {            showAnimator(child);        }    }    private void showAnimator(View view) {        view.setVisibility(View.VISIBLE);        ViewCompat.animate(view)                .scaleX(1.0f)                .scaleY(1.0f)                .alpha(1.0f)                .setDuration(800)                .setListener(new ViewPropertyAnimatorListener() {                    @Override                    public void onAnimationStart(View view) {                        isAnimator = true;                    }                    @Override                    public void onAnimationEnd(View view) {                        isAnimator = false;                    }                    @Override                    public void onAnimationCancel(View view) {                        isAnimator = false;                    }                })                .start();    }    private void hideAnimator(View view) {        ViewCompat.animate(view)                .scaleX(0)                .scaleY(0)                .alpha(0)                .setDuration(800)                .setListener(new ViewPropertyAnimatorListener() {                    @Override                    public void onAnimationStart(View view) {                        isAnimator = true;                    }                    @Override                    public void onAnimationEnd(View view) {                        isAnimator = false;                        view.setVisibility(View.INVISIBLE);                    }                    @Override                    public void onAnimationCancel(View view) {                        isAnimator = false;                    }                })                .start();    }}

BottomScrollBehavior

public class BottomScrollBehavior extends CoordinatorLayout.Behavior<View> {    private boolean isAnimator;    public BottomScrollBehavior(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, View child, View directTargetChild, View target, int nestedScrollAxes) {        return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;    }    @Override    public void onNestedScroll(CoordinatorLayout coordinatorLayout, View child, View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {        if ((dyConsumed > 0 || dyUnconsumed > 0) && !isAnimator && child.getTranslationY() == 0) {            hideAnimator(child);        } else if ((dyConsumed < 0 || dyUnconsumed < 0) && !isAnimator && child.getTranslationY() == child.getHeight()) {            showAnimator(child);        }        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);    }    private void showAnimator(View view) {        ViewCompat.animate(view)                .translationY(0)                .setDuration(800)                .setListener(new ViewPropertyAnimatorListener() {                    @Override                    public void onAnimationStart(View view) {                        isAnimator = true;                    }                    @Override                    public void onAnimationEnd(View view) {                        isAnimator = false;                    }                    @Override                    public void onAnimationCancel(View view) {                        isAnimator = false;                    }                })                .start();    }    private void hideAnimator(View view) {        ViewCompat.animate(view)                .translationY(view.getHeight())                .setDuration(800)                .setListener(new ViewPropertyAnimatorListener() {                    @Override                    public void onAnimationStart(View view) {                        isAnimator = true;                    }                    @Override                    public void onAnimationEnd(View view) {                        isAnimator = false;                    }                    @Override                    public void onAnimationCancel(View view) {                        isAnimator = false;                    }                })                .start();    }}

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