CoordinatorLayout简介

• CoordinatorLayoutThe Chinese translation is coordinated layout,It coordinates interactions between sub-layouts,When touched changes the childViewSometimes it will affect the layout and produce a linkage effect,The root cause lies inBehavior类
• CoordinatorLayoutI don't control myselfView,All control is thereBehavior这个类
• 系统里Behavior有FloatingActionButton.Behavior和AppBarLayout.Behavior等等;Our usual user linkages are defined by the systemBehavior来实现
• 系统里面BehavoirSome implement complex control functions.But it is limited after all,We can implement our own in a custom wayBehavior

自定义Behavior有两种方式

1、一个View监听另一个View的状态变化

See the running effect as shown in the figure below：

实现方式如下：

1.继承CoordinatorLayout.Behavior类

/** * 第一种自定义Behavior方式 */
public class DependencyBehavior extends CoordinatorLayout.Behavior<Button> 

2.重写Behavior两个参数的构造方法

    /** * This constructor must be overloaded,因为在CoordinatorLayoutHere use reflection to obtain * Behavior的时候就是拿的这个构造 */
    public DependencyBehavior(Context context, AttributeSet attrs) {
    
        super(context, attrs);
        width = context.getResources().getDisplayMetrics().widthPixels;
    }

3.重写layoutDependsOn和onDependentViewChanged方法

    /** * 确定依赖关系 * * @param parent * @param child to perform an actionView * @param dependency child要依赖的View,,,也就是Child要监听的View * @return Determine dependencies logically */
    @Override
    public boolean layoutDependsOn(CoordinatorLayout parent, Button child, View dependency) {
    
        Log.e("Behavior", "----child: " + child.toString());
        Log.e("Behavior", "----dependency: " + dependency.toString());
        return dependency instanceof DragTextView;
    }

    /** * 状态(大小、位置、Show or not etc)This method is executed when a change occurs * 在这里我们定义child要执行的具体动作 * * @param parent * @param child * @param dependency * @return */
    @Override
    public boolean onDependentViewChanged(CoordinatorLayout parent, Button child, View dependency) {
    
        int top = dependency.getTop();
        int left = dependency.getLeft();

        int x = width - left - child.getWidth();
        int y = top;
        setPosition(child, x, y);
        return true;
    }

4.在xml文件中引用app:layout_behavior

<?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"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:layout_width="88dp"
        android:layout_height="88dp"
        android:background="@color/colorPrimary"
        android:gravity="center"
        android:text="child"
        android:textAllCaps="false"
        android:textColor="@android:color/white"
        app:layout_behavior="com.coordinator.behavior.first.DependencyBehavior" />

    <com.coordinator.behavior.first.DragTextView
        android:layout_width="88dp"
        android:layout_height="88dp"
        android:background="@color/colorAccent"
        android:gravity="center"
        android:text="dependency"
        android:textAllCaps="false"
        android:textColor="@android:color/white" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

2、View监听CoordinatorLayout里的滑动状态

这个要求CoordinatorLayoutThere must be sliding controls inside,At least it has to be doneNestedScrollingChild接口,比如RecyclerView,NestScrollView等滑动控件;
看运行效果：

1.继承CoordinatorLayout.Behaviorclass or systemBehavior类

/** * The second type of customizationBehavior方式 */
public class ScrollBehavior extends CoordinatorLayout.Behavior<FloatingActionButton> {
    

2.重写Behavior两个参数的构造方法

    /** * This constructor must be overloaded,因为在CoordinatorLayoutHere use reflection to obtain * Behavior的时候就是拿的这个构造 */
    public ScrollBehavior(Context context, AttributeSet attrs) {
    
        super(context, attrs);
    }

3.rewrite at leastonStartNestedScroll和onNestedScroll方法,Of course there are others that can be rewritten as well

    /** * 当子View调用NestedScrollingChild的方法startNestedScroll时,会调用该方法. * Be sure to return according to your needstrue,This method determines whether the current control can receive its interiorView(Not a direct childView)滑动时的参数 * * @param coordinatorLayout * @param child This is dependent on other scrollingView的另一个View,这里是FloatingActionButton * @param directTargetChild directly trigger nested scrollingview的对象 * @param target 触发嵌套滚动的view (在这里如果不涉及多层嵌套的话,target和directTargetChild是相同的) * @param nestedScrollAxes Direction flag for nested swipe * @return Determine which direction we care about sliding based on the return value(x轴 / y轴),这里我们关心的是y轴方向 */
    @Override
    public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout,
                                       FloatingActionButton child,
                                       View directTargetChild,
                                       View target,
                                       int nestedScrollAxes) {
    
        Log.e("123", "directTargetChild: " + directTargetChild);
        Log.e("123", "target: " + target);//在这里directTargetChild和target都是NestedScrollView
        return (nestedScrollAxes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0;
    }

    /** * 当子View调用dispatchNestedPreScroll时会调用该方法 * This method is passed in internallyView移动的dx,dy,If you need to consume certaindx,dy,will pass the last parameterconsumed * 进行指定.For example I want to consume half of itdy,就可以写consumed[1]=dy/2 * dxIndicates this scrollingxThe total distance resulting from the direction * * @param coordinatorLayout * @param child 此处是FloatingActionButton * @param target 同上 * @param dxConsumed target已经消费的x方向的距离 * @param dyConsumed target已经消费的x方向的距离 * @param dxUnconsumed x方向剩下的滑动距离 * @param dyUnconsumed y方向剩下的滑动距离 */
    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout,
                               FloatingActionButton child,
                               View target,
                               int dxConsumed,
                               int dyConsumed,
                               int dxUnconsumed,
                               int dyUnconsumed) {
    
        //Log.e("234", "===============dxConsumed: " + dxConsumed);
        Log.e("234", "===============dyConsumed: " + dyConsumed);
        //Log.e("234","===============dxUnconsumed: "+dxUnconsumed);
        Log.e("234", "===============dyUnconsumed: " + dyUnconsumed);
        if (((dyConsumed > 0 && dyUnconsumed == 0)
                || (dyConsumed == 0 && dyUnconsumed > 0))
        ) {
    //上滑隐藏
            child.animate()
                    .scaleY(0).scaleX(0)
                    .setDuration(200)
                    .start();
        } else if (((dyConsumed < 0 && dyUnconsumed == 0)
                || (dyConsumed == 0 && dyUnconsumed < 0))
        ) {
    //下滑显示
            child.animate()
                    .scaleY(1).scaleX(1)
                    .setDuration(200)
                    .start();
        }
    }

4.在xml文件中引用app:layout_behavior

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/text" />

    </androidx.core.widget.NestedScrollView>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="end|bottom"
        android:layout_margin="16dp"
        android:src="@android:drawable/ic_dialog_email"
        app:backgroundTint="@color/colorAccent"
        app:elevation="8dp"
        app:fabSize="mini"
        app:layout_behavior="com.coordinator.behavior.second.ScrollBehavior"
        app:pressedTranslationZ="16dp"
        app:rippleColor="@color/colorPrimary" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

CoordinatorLayout交互原理

1.子View如何拿到Behavior？

比如下面的xmlHow to get it in the fileBehavior的呢？

CoordinatorLayoutThere is a process to add childrenView,Let's start with where to start,

这里的LayoutParam肯定是CoordinatorLayout.LayoutParam生成的吧;

这里明显Behavior就是在LayoutParamsIt can be analyzed in it,就是解析的app:layout_behavior属性;

2.BehaviorHow did you get the incident？

The above is just a special case of code,In fact, in the event delivery,你会发现,所有出现Behavior的地方Behaviorwill take over！I don't want to analyze a little bit in the clouds here,It's so easy to miss the forest for the trees.你就从

dispatchTouchEvent,
onInterception,
onTouchEvent,

These events are analyzed in the code,You can see the code snippet;

Behavior b = lp.getBehavior（）

你懂得,Just transfer all event handling to it;

Implement a coordinated layout yourself

运行效果如下图：

1.Implement your own coordinate layoutBehaviorCoordinatorLayout

public class BehaviorCoordinatorLayout extends RelativeLayout implements NestedScrollingParent,
        ViewTreeObserver.OnGlobalLayoutListener {
    

    public BehaviorCoordinatorLayout(Context context, AttributeSet attrs) {
    
        super(context, attrs);
        getViewTreeObserver().addOnGlobalLayoutListener(this);
    }

    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
    
        return true;
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
    
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
    
            View v = getChildAt(i);
            LP lp = (LP) v.getLayoutParams();
            BeHavior mBehavior = lp.mBehavior;
            if (mBehavior != null) {
    
                mBehavior.onNestedScroll(this, v, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
            }
        }
    }

    @Override
    public void onGlobalLayout() {
    
        int count = getChildCount();
        for (int i = 0; i < count; i++) {
    
            View v = getChildAt(i);
            LP lp = (LP) v.getLayoutParams();
            BeHavior mBehavior = lp.mBehavior;
            if (mBehavior != null) {
    
                mBehavior.onLayoutChild(this, v, 0);
            }
        }
    }

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
    
        return new LP(getContext(), attrs);
    }

2.实现自己的LayoutParams

    @Override
    public LayoutParams generateLayoutParams(AttributeSet attrs) {
    
        return new LP(getContext(), attrs);
    }

    
    public static class LP extends RelativeLayout.LayoutParams {
    

        BeHavior mBehavior;

        public LP(Context c, AttributeSet attrs) {
    
            super(c, attrs);

            TypedArray ta = c.obtainStyledAttributes(attrs, R.styleable.BehaviorCoordinatorLayout_Layout);

            if (ta.hasValue(R.styleable.BehaviorCoordinatorLayout_Layout_custom_layout_behavior)) {
    
                String clStr = ta.getString(R.styleable.BehaviorCoordinatorLayout_Layout_custom_layout_behavior);
                Log.e("tag", clStr);
                mBehavior = parseBehavior(c, attrs, clStr);
                Log.e("tag", (mBehavior == null) + " ");
            }
            ta.recycle();
        }


        public BeHavior parseBehavior(Context context, AttributeSet attrs, String name) {
    
            try {
    
                Class<?> clazz = Class.forName(name, false, context.getClassLoader());
                Constructor c = clazz.getConstructor(Context.class, AttributeSet.class);
                c.setAccessible(true);
                return (BeHavior) c.newInstance(context, attrs);
            } catch (Exception e) {
    
                e.printStackTrace();
                return null;
            }
        }


    }

3.实现自己的Behavior类

public class BeHavior<V extends View> {
    


    public BeHavior(Context context, AttributeSet attrs) {
    
    }

    public boolean onLayoutChild(BehaviorCoordinatorLayout parent, V child,
                                 int layoutDirection) {
    
        return false;
    }


    public void onNestedScroll(BehaviorCoordinatorLayout coordinatorLayout, V child,
                               View target, int dxConsumed, int dyConsumed, int dxUnconsumed,
                               int dyUnconsumed) {
    
    }
    
}

4.实现自己的Behavior子类

ublic class ImageViewBehavior extends BeHavior<ImageView> {
    

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

    int maxHeight = 400;
    int originHeight = 0;

    @Override
    public boolean onLayoutChild(BehaviorCoordinatorLayout parent, ImageView child, int layoutDirection) {
    
        if (originHeight == 0) {
    
            originHeight = child.getHeight();
        }
        return super.onLayoutChild(parent, child, layoutDirection);
    }

    @Override
    public void onNestedScroll(BehaviorCoordinatorLayout coordinatorLayout, ImageView child,
                               View scrollview, int dxConsumed, int dyConsumed,
                               int dxUnconsumed, int dyUnconsumed) {
    

        if (scrollview.getScrollY() > 0) {
    
            BehaviorCoordinatorLayout.LP lp = (BehaviorCoordinatorLayout.LP) child.getLayoutParams();
            lp.height = lp.height - Math.abs(dyConsumed);
            if (lp.height <= originHeight) {
    
                lp.height = originHeight;
            }
            child.setLayoutParams(lp);
        } else if (scrollview.getScrollY() == 0) {
    
            BehaviorCoordinatorLayout.LP lp = (BehaviorCoordinatorLayout.LP) child.getLayoutParams();
            lp.height = lp.height + Math.abs(dyUnconsumed);
            if (lp.height >= maxHeight) {
    
                lp.height = maxHeight;
            }
            child.setLayoutParams(lp);
        }

    }
}

public class ToolbarBehavior extends BeHavior<Toolbar> {
    

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

    int maxHeight = 400;

    @Override
    public void onNestedScroll(BehaviorCoordinatorLayout coordinatorLayout, Toolbar child, View scrollView,
                               int dxConsumed, int dyConsumed,
                               int dxUnconsumed, int dyUnconsumed) {
    
        if (scrollView.getScrollY() <= maxHeight) {
    
            child.setAlpha(scrollView.getScrollY() * 1.0f / maxHeight);
        } else if (scrollView.getScrollY() == 0) {
    
            child.setAlpha(0);
        }
    }

}

5.xml布局中引用

<?xml version="1.0" encoding="utf-8"?>
<com.coordinator.behavior.custom.BehaviorCoordinatorLayout 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">

    <ImageView
        android:id="@+id/img"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:adjustViewBounds="true"
        android:scaleType="fitXY"
        android:contentDescription="@string/app_name"
        android:src="@mipmap/london"
        app:custom_layout_behavior="com.coordinator.behavior.custom.ImageViewBehavior" />


    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/img">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/text" />

    </androidx.core.widget.NestedScrollView>


    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="@color/colorPrimary"
        app:custom_layout_behavior="com.coordinator.behavior.custom.ToolbarBehavior" />
</com.coordinator.behavior.custom.BehaviorCoordinatorLayout>