AppBarLayout滑动回弹以及抖动问题的解决方案以及监听AppBarLayout的滑动状态来动态设置标题

AppBarLayout滑动时回弹以及抖动的解决方案

1，继承AppBarLayout.Behavior来实现自定义的AppBarLayoutBehavior，代码如下：

/**
 *  解决appbarLayout若干问题：
 * （1）快速滑动appbarLayout会出现回弹
 * （2）快速滑动appbarLayout到折叠状态下，立马下滑，会出现抖动的问题
 * （3）滑动appbarLayout，无法通过手指按下让其停止滑动
 */
public class AppBarLayoutBehavior extends AppBarLayout.Behavior {

    private static final String TAG = "CustomAppbarLayoutBehavior";

    private static final int TYPE_FLING = 1;

    private boolean isFlinging;
    private boolean shouldBlockNestedScroll;

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

    @Override
    public boolean onInterceptTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        LogUtil.d(TAG, "onInterceptTouchEvent:" + child.getTotalScrollRange());
        shouldBlockNestedScroll = false;
        if (isFlinging) {
            shouldBlockNestedScroll = true;
        }

        switch (ev.getActionMasked()) {
            case MotionEvent.ACTION_DOWN:
                stopAppbarLayoutFling(child);  //手指触摸屏幕的时候停止fling事件
                break;
        }

        return super.onInterceptTouchEvent(parent, child, ev);
    }

    /**
     * 停止appbarLayout的fling事件
     * @param appBarLayout
     */
    private void stopAppbarLayoutFling(AppBarLayout appBarLayout) {
        //通过反射拿到HeaderBehavior中的flingRunnable变量
        try {
            Class<?> headerBehaviorType = this.getClass().getSuperclass().getSuperclass();
            Field flingRunnableField = headerBehaviorType.getDeclaredField("mFlingRunnable");
            Field scrollerField = headerBehaviorType.getDeclaredField("mScroller");
            flingRunnableField.setAccessible(true);
            scrollerField.setAccessible(true);

            Runnable flingRunnable = (Runnable) flingRunnableField.get(this);
            OverScroller overScroller = (OverScroller) scrollerField.get(this);
            if (flingRunnable != null) {
                LogUtil.d(TAG, "存在flingRunnable");
                appBarLayout.removeCallbacks(flingRunnable);
                flingRunnableField.set(this, null);
            }
            if (overScroller != null && !overScroller.isFinished()) {
                overScroller.abortAnimation();
            }
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes, int type) {
        LogUtil.d(TAG, "onStartNestedScroll");
        stopAppbarLayoutFling(child);
        return super.onStartNestedScroll(parent, child, directTargetChild, target, nestedScrollAxes, type);
    }

    @Override
    public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed, int type) {
        LogUtil.d(TAG, "onNestedPreScroll:" + child.getTotalScrollRange() + " ,dx:" + dx + " ,dy:" + dy + " ,type:" + type);

        //type返回1时，表示当前target处于非touch的滑动，
        //该bug的引起是因为appbar在滑动时，CoordinatorLayout内的实现NestedScrollingChild2接口的滑动子类还未结束其自身的fling
        //所以这里监听子类的非touch时的滑动，然后block掉滑动事件传递给AppBarLayout
        if (type == TYPE_FLING) {
            isFlinging = true;
        }
        if (!shouldBlockNestedScroll) {
            super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
        }
    }

    @Override
    public void onNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dxConsumed, int dyConsumed, int
            dxUnconsumed, int dyUnconsumed, int type) {
        LogUtil.d(TAG, "onNestedScroll: target:" + target.getClass() + " ," + child.getTotalScrollRange() + " ,dxConsumed:"
                + dxConsumed + " ,dyConsumed:" + dyConsumed + " " + ",type:" + type);
        if (!shouldBlockNestedScroll) {
            super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type);
        }
    }

    @Override
    public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, AppBarLayout abl, View target, int type) {
        LogUtil.d(TAG, "onStopNestedScroll");
        super.onStopNestedScroll(coordinatorLayout, abl, target, type);
        isFlinging = false;
        shouldBlockNestedScroll = false;
    }

}

2，然后在布局文件中：

<android.support.design.widget.AppBarLayout
        android:id="@+id/appBarLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/white"
        android:fitsSystemWindows="false"
        app:layout_behavior="XXXXX.AppBarLayoutBehavior"
        >

        ......

</android.support.design.widget.AppBarLayout>

即可。
AppBarLayoutBehavior的Github地址：https://github.com/yuruiyin/AppbarLayoutBehavior

AppBarLayout滑动监听

1，定义一个类AppBarStateChangeListener，代码如下：

public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {

    public enum State {
        EXPANDED,
        COLLAPSED,
        IDLE
    }

    private State mCurrentState = State.IDLE;

    @Override
    public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
        if (i == 0) {
            if (mCurrentState != State.EXPANDED) {
                onStateChanged(appBarLayout, State.EXPANDED);
            }
            mCurrentState = State.EXPANDED;
        } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
            if (mCurrentState != State.COLLAPSED) {
                onStateChanged(appBarLayout, State.COLLAPSED);
            }
            mCurrentState = State.COLLAPSED;
        } else {
            if (mCurrentState != State.IDLE) {
                onStateChanged(appBarLayout, State.IDLE);
            }
            mCurrentState = State.IDLE;
        }
    }

    public abstract void onStateChanged(AppBarLayout appBarLayout, State state);

}

2，然后在代码中，为AppBarLayout组件添加监听如下：

appBarLayout.addOnOffsetChangedListener(new AppBarStateChangeListener() {
            @Override
            public void onStateChanged(AppBarLayout appBarLayout, State state) {
                if( state == State.EXPANDED ) {

                    //展开状态
                    tvTitle.setText("顶部已展开");

                }else if(state == State.COLLAPSED){
                    //折叠状态
                    tvTitle.setText("顶部已折叠");
                }else {
                    //中间状态
//                    ToastUtils.toastInfo("中间",true);

                }
            }
        });

即可。