1.問題描述：
界面中使用了CoordinatorLayout，AppBarLayout，CollapsingToolbarLayout，ViewPage,RecyclerView思币，當(dāng)向上滑動(dòng)AppBarLayout并在慣性滑動(dòng)未停止的時(shí)候滑動(dòng)RecyclerView,此時(shí)會(huì)發(fā)生回彈抖動(dòng)現(xiàn)象
XML布局代碼如下：
<?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"
android:background="@color/c_f2f2f2"
android:orientation="vertical"
tools:context=".MainActivity">
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:background="@color/c_f2f2f2"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:elevation="0dp"
android:layout_height="wrap_content">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:layout_width="match_parent"
app:layout_scrollFlags="scroll"
android:fitsSystemWindows="true"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/c_f2f2f2"
android:orientation="vertical"
app:layout_scrollFlags="scroll">
<TextView
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:background="#ff0000"
android:gravity="center_vertical"
android:paddingLeft="30dp"
android:text="AppBarLayout抖動(dòng)問題"
android:textColor="@color/white"
android:textSize="20sp"
android:textStyle="bold" />
<View
android:layout_width="match_parent"
android:layout_height="120dp"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="10dp"
android:background="#de3f7c" />
<View
android:layout_width="match_parent"
android:layout_height="190dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:background="#ea7293" />
<View
android:layout_width="match_parent"
android:layout_height="370dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
android:layout_marginRight="10dp"
android:background="#1a94bc" />
</LinearLayout>
</com.google.android.material.appbar.CollapsingToolbarLayout>
<View
android:layout_width="match_parent"
android:layout_height="10dp"
android:background="@color/c_f2f2f2" />
<com.google.android.material.tabs.TabLayout
android:id="@+id/magicindicator"
android:layout_width="match_parent"
android:layout_height="40dp"
android:layout_marginLeft="10dp"
android:background="@color/c_f2f2f2" />
</com.google.android.material.appbar.AppBarLayout>
<androidx.viewpager.widget.ViewPager
android:id="@+id/vp_home"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="12dp"
app:layout_behavior="@string/appbar_scrolling_view_behavior" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
2.滑動(dòng)抖動(dòng)問題分析
- CoordinatorLayout向上fling滾動(dòng)無法被外部中斷
- CoordinatorLayout和子View的聯(lián)動(dòng)時(shí)通過CoordinatorLayout.Behavior實(shí)現(xiàn)的，AppBarLayout使用的Behavior繼承了HeaderBehavior土辩。
問題就在這里擂涛。HeaderBehavior的onTouchEvent中使用Scroller實(shí)現(xiàn)了fling操作羞延，但是沒有通過NestedScrolling API對(duì)外開放，也就說一旦HeaderBehavior的fling動(dòng)作形成逛裤，無法由外部主動(dòng)中斷指孤。
RecyclerView向下fling滾動(dòng)
與AppBarLayout同層級(jí)的RecyclerView可以通過升級(jí)過的NestedScrolling API對(duì)AppBarLayout產(chǎn)生影響启涯，比如RecyclerView向下fling時(shí)滑動(dòng)到item 0之后贬堵，如果AppBarLayout可以滑動(dòng)時(shí)會(huì)給AppBarLayout施加一個(gè)同樣向下的fling動(dòng)作,以此形成一個(gè)連貫的下滑fling。
那么問題來了结洼。當(dāng)HeaderBehavior產(chǎn)生的向上的fling沒有結(jié)束時(shí)黎做，RecyclerView又送來向下的fling，抖動(dòng)就產(chǎn)生了松忍。
分析一下HeaderBehavior
當(dāng)檢測(cè)到down事件時(shí), 取消了mScroller的運(yùn)行(如果它正在scroll的話)蒸殿。這里因?yàn)橐L問父類(其實(shí)是父類的父類)的 mScroller變量。
然后通過反射拿到mScroller變量鸣峭，在onInterceptTouchEvent攔截事件中宏所，當(dāng)手指離開的時(shí)候，則停止overScroller動(dòng)畫效果摊溶。
然后通過反射拿到flingRunnable變量爬骤，在onInterceptTouchEvent攔截事件中，當(dāng)手指離開的時(shí)候莫换，則需要remove所有的flingRunnable霞玄。
3.解決問題
自定義AppBarLayout.Behavior
/**
* description：AppBarLayoutBehavior
* Author: 許少東
*/
public class AppBarLayoutBehavior extends AppBarLayout.Behavior {
private static final String TAG = "AppbarLayoutBehavior";
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 = isFlinging;
switch (ev.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
//手指觸摸屏幕的時(shí)候停止fling事件
stopAppbarLayoutFling(child);
break;
default:
break;
}
return super.onInterceptTouchEvent(parent, child, ev);
}
/**
* 反射獲取私有的flingRunnable 屬性，考慮support 28以后變量名修改的問題
* @return Field
* @throws NoSuchFieldException
*/
private Field getFlingRunnableField() throws NoSuchFieldException {
Class<?> superclass = this.getClass().getSuperclass();
try {
// support design 27及一下版本
Class<?> headerBehaviorType = null;
if (superclass != null) {
headerBehaviorType = superclass.getSuperclass();
}
if (headerBehaviorType != null) {
return headerBehaviorType.getDeclaredField("mFlingRunnable");
}else {
return null;
}
} catch (NoSuchFieldException e) {
e.printStackTrace();
// 可能是28及以上版本
Class<?> headerBehaviorType = superclass.getSuperclass().getSuperclass();
if (headerBehaviorType != null) {
return headerBehaviorType.getDeclaredField("flingRunnable");
} else {
return null;
}
}
}
/**
* 反射獲取私有的scroller 屬性拉岁，考慮support 28以后變量名修改的問題
* @return Field
* @throws NoSuchFieldException
*/
private Field getScrollerField() throws NoSuchFieldException {
Class<?> superclass = this.getClass().getSuperclass();
try {
// support design 27及一下版本
Class<?> headerBehaviorType = null;
if (superclass != null) {
headerBehaviorType = superclass.getSuperclass();
}
if (headerBehaviorType != null) {
return headerBehaviorType.getDeclaredField("mScroller");
}else {
return null;
}
} catch (NoSuchFieldException e) {
e.printStackTrace();
// 可能是28及以上版本
Class<?> headerBehaviorType = superclass.getSuperclass().getSuperclass();
if (headerBehaviorType != null) {
return headerBehaviorType.getDeclaredField("scroller");
}else {
return null;
}
}
}
/**
* 停止appbarLayout的fling事件
* @param appBarLayout
*/
private void stopAppbarLayoutFling(AppBarLayout appBarLayout) {
//通過反射拿到HeaderBehavior中的flingRunnable變量
try {
Field flingRunnableField = getFlingRunnableField();
Field scrollerField = getScrollerField();
if (flingRunnableField != null) {
flingRunnableField.setAccessible(true);
}
if (scrollerField != null) {
scrollerField.setAccessible(true);
}
Runnable flingRunnable = null;
if (flingRunnableField != null) {
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時(shí)坷剧，表示當(dāng)前target處于非touch的滑動(dòng)，
//該bug的引起是因?yàn)閍ppbar在滑動(dòng)時(shí)喊暖，CoordinatorLayout內(nèi)的實(shí)現(xiàn)NestedScrollingChild2接口的滑動(dòng)
//子類還未結(jié)束其自身的fling
//所以這里監(jiān)聽子類的非touch時(shí)的滑動(dòng)听隐，然后block掉滑動(dòng)事件傳遞給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;
}
private static class LogUtil{
static void d(String tag, String string){
Log.d(tag,string);
}
}
}
應(yīng)用到AppBarLayout
<com.google.android.material.appbar.AppBarLayout
android:layout_width="match_parent"
android:background="@color/c_f2f2f2"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:elevation="0dp"
app:layout_behavior=".wight.AppBarLayoutBehavior"
android:layout_height="wrap_content">
最終解決問題
