如果你只打算學習一下CoordinatorLayout然後寫2個Demo試試,那麼本文並沒有什麼卵用,但是如果你打算在生產環境使用CoordinatorLayout,那麼強烈推薦閱讀一下本文,可以減少很多彎路,這個東西看起來很好,但是實際上坑也很多。
###前言
很多應用主頁常見的構造模式
一個包含ActionBar和Banner的header+ViewPager的組合模式
比如這樣:
然後需要滾動的時候能夠將 ActionBar和Banner滾出界面,但是又需要ViewPager的TabLayout能固定在屏幕頂部
比如滾動後是這樣:
Github上有很多sticky-viewpager xx-header-viewpager之類的項目提供類似的功能,但是大部分都會存在各種事件衝突問題,比如滑動不流暢,卡頓,彈跳之類的。
好在Android新的SupportLibrary提供了CoordinatorLayout能直接實現類似功能,具體如何使用參考 SupportLibrary中CoordinatorLayout的使用文檔即可,例子也可以直接看cheesesquare
我就談下使用過程中裏面的坑:
不支持ListView,不支持ScrollView,低版本不兼容ViewCompat.setNestedScrollingEnabled
PS.更新
support 23.1+新增了
ViewCompat.setNestedScrollingEnabled(listView/gridview,true);
可以給ListView提供NestedScrolling支持,但是隻在LOLIPOP+版本上生效,下面的方案也一樣。
低版本只能使用RecyclerView
一些文檔/博客文章上說 可以使用一個 可滾動的組件
還有些錯誤的文章說 支持ListView
實際上該組件必須實現了 NestedScrollingChild接口
你可以使用RecyclerView,RecyclerView自身就實現了該接口,如果你要使用其他組件,那麼可能需要繼承原來的View並實現NestedScrollingChild接口
一個實現了NestedScrollingChild的Listview demo如下:
public class NestedScrollingListView extends ListView implements NestedScrollingChild {
private final NestedScrollingChildHelper mScrollingChildHelper;
public NestedScrollingListView(Context context) {
super(context);
mScrollingChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
public NestedScrollingListView(Context context, AttributeSet attrs) {
super(context, attrs);
mScrollingChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mScrollingChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean isNestedScrollingEnabled() {
return mScrollingChildHelper.isNestedScrollingEnabled();
}
@Override
public boolean startNestedScroll(int axes) {
return mScrollingChildHelper.startNestedScroll(axes);
}
@Override
public void stopNestedScroll() {
mScrollingChildHelper.stopNestedScroll();
}
@Override
public boolean hasNestedScrollingParent() {
return mScrollingChildHelper.hasNestedScrollingParent();
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, int[] offsetInWindow) {
return mScrollingChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed,
dxUnconsumed, dyUnconsumed, offsetInWindow);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return mScrollingChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mScrollingChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mScrollingChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
}
其他View也可以使用類似的方式實現。
只對 5.0+ 生效,低版本無效。
RecyclerView滑動的時候不流暢
目前已知 r23.1 & r 23.2 都存在此問題,Google code的提交代碼裏倒是有相關修復記錄,但是目前還沒有發佈。
直接原因是Fling Direction錯誤,導致Fling事件被吃掉了,ACTION_UP/ACTION_CANCEL事件一旦發生,scroll動作直接停止
StackOverFlow上一個高票解決方案是重寫一個FlingBehavior,並配置給AppBar.
注意,這個Behavior是給AppBar的,不是給下面的可滾動組件的。
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="your.package.FlingBehavior">
<!--your views here-->
</android.support.design.widget.AppBarLayout>
public class FlingBehavior extends AppBarLayout.Behavior {
private static final int TOP_CHILD_FLING_THRESHOLD = 3;
private boolean isPositive;
public FlingBehavior() {
}
public FlingBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
velocityY = velocityY * -1;
}
if (target instanceof RecyclerView && velocityY < 0) {
final RecyclerView recyclerView = (RecyclerView) target;
final View firstChild = recyclerView.getChildAt(0);
final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
}
consumed=false;
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}
@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
isPositive = dy > 0;
}
注意consumed計算這部分,會影響滾動形式
請參考父類滾動的實現代碼:
@Override
public boolean onNestedFling(final CoordinatorLayout coordinatorLayout,
final AppBarLayout child, View target, float velocityX, float velocityY,
boolean consumed) {
boolean flung = false;
if (!consumed) {
// It has been consumed so let's fling ourselves
flung = fling(coordinatorLayout, child, -child.getTotalScrollRange(),
0, -velocityY);
} else {
// If we're scrolling up and the child also consumed the fling. We'll fake scroll
// upto our 'collapsed' offset
if (velocityY < 0) {
// We're scrolling down
final int targetScroll = -child.getTotalScrollRange()
+ child.getDownNestedPreScrollRange();
if (getTopBottomOffsetForScrollingSibling() < targetScroll) {
// If we're currently not expanded more than the target scroll, we'll
// animate a fling
animateOffsetTo(coordinatorLayout, child, targetScroll);
flung = true;
}
} else {
// We're scrolling up
final int targetScroll = -child.getUpNestedPreScrollRange();
if (getTopBottomOffsetForScrollingSibling() > targetScroll) {
// If we're currently not expanded less than the target scroll, we'll
// animate a fling
animateOffsetTo(coordinatorLayout, child, targetScroll);
flung = true;
}
}
}
mWasNestedFlung = flung;
return flung;
}
確認你需要滾動哪一步分,你可以簡單根據RecyclerView展示的first item的position來判斷Recyclerview是否在top位置,也有另一種代碼如下:
@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
if (target instanceof RecyclerView) {
final RecyclerView recyclerView = (RecyclerView) target;
consumed = velocityY > 0 || recyclerView.computeVerticalScrollOffset() > 0;
}
return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}
另一個解決方案是使用 smooth-app-bar-layout
具體如何使用請參考它自己的文檔
當header是Toolbar時,demo運作良好,當headerview高度較大時,滑動會發生劇烈抖動,彈跳,暫時還沒去看它源代碼,可能是我使用不正確
不支持adjustResize
可以參考這個問題
http://stackoverflow.com/questions/35599125/adjustresize-does-not-work-with-coordinatorlayout
解決方案是可以通過ViewTreeObserver.OnGlobalLayoutListener監聽界面改變,然後人工處理padding bottom
public class KeyboardUtil {
private View decorView;
private View contentView;
public KeyboardUtil(Activity act, View contentView) {
this.decorView = act.getWindow().getDecorView();
this.contentView = contentView;
//only required on newer android versions. it was working on API level 19
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
}
}
public void enable() {
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
}
}
public void disable() {
if (Build.VERSION.SDK_INT >= 19) {
decorView.getViewTreeObserver().removeOnGlobalLayoutListener(onGlobalLayoutListener);
}
}
//a small helper to allow showing the editText focus
ViewTreeObserver.OnGlobalLayoutListener onGlobalLayoutListener = new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
Rect r = new Rect();
//r will be populated with the coordinates of your view that area still visible.
decorView.getWindowVisibleDisplayFrame(r);
//get screen height and calculate the difference with the useable area from the r
int height = decorView.getContext().getResources().getDisplayMetrics().heightPixels;
int diff = height - r.bottom;
//if it could be a keyboard add the padding to the view
if (diff != 0) {
// if the use-able screen height differs from the total screen height we assume that it shows a keyboard now
//check if the padding is 0 (if yes set the padding for the keyboard)
if (contentView.getPaddingBottom() != diff) {
//set the padding of the contentView for the keyboard
contentView.setPadding(0, 0, 0, diff);
}
} else {
//check if the padding is != 0 (if yes reset the padding)
if (contentView.getPaddingBottom() != 0) {
//reset the padding of the contentView
contentView.setPadding(0, 0, 0, 0);
}
}
}
};
/**
* Helper to hide the keyboard
*
* @param act
*/
public static void hideKeyboard(Activity act) {
if (act != null && act.getCurrentFocus() != null) {
InputMethodManager inputMethodManager = (InputMethodManager) act.getSystemService(Activity.INPUT_METHOD_SERVICE);
inputMethodManager.hideSoftInputFromWindow(act.getCurrentFocus().getWindowToken(), 0);
}
}
}
KeyboardUtil keyboardUtil = new KeyboardUtil(this, findViewById(android.R.id.content));
//enable it
keyboardUtil.enable();
ps.
fitSystemWindow 和 adjustResize 和 FLAG_TRANSLUCENT_STATUS 一起使用 一樣也會有衝突,造成界面縮放不正常。 當時也是用的這個解決方案。
CoordinatorLayout的onScrollListener只支持21+
解決方案:
在Behavior裏監聽滾動,並把數據傳出來
代碼和後一個問題貼在一起
注意 我這裏只監聽了 onDependentViewChanged
並在這裏調用onScroll接口,然後外部實際使用的數據是 headerview.getTop , 並不能覆蓋全部情況,但是我本身只用來做狀態欄漸變色,有其它使用場景請自行修改
當頂部容器不使用Toolbar時,Measure會有問題
解決方案:
自定義一個 Behavior,繼承AppBarLayout.ScrollingViewBehavior
並重載onMeasureChild方法
public class PatchedScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {
private OnScrollListener onScrollListener;
public PatchedScrollingViewBehavior() {
super();
}
public PatchedScrollingViewBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onMeasureChild(CoordinatorLayout parent, View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
Log.e("####", "onMeasureChild");
if (child.getLayoutParams().height == -1) {
List dependencies = parent.getDependencies(child);
if (dependencies.isEmpty()) {
return false;
}
AppBarLayout appBar = findFirstAppBarLayout(dependencies);
if (appBar != null && ViewCompat.isLaidOut(appBar)) {
if (ViewCompat.getFitsSystemWindows(appBar)) {
ViewCompat.setFitsSystemWindows(child, true);
}
int scrollRange = appBar.getTotalScrollRange();
// int height = parent.getHeight() - appBar.getMeasuredHeight() + scrollRange;
int parentHeight = View.MeasureSpec.getSize(parentHeightMeasureSpec);
int height = parentHeight - appBar.getMeasuredHeight() + scrollRange;
int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(height, View.MeasureSpec.AT_MOST);
parent.onMeasureChild(child, parentWidthMeasureSpec, widthUsed, heightMeasureSpec, heightUsed);
return true;
}
}
return false;
}
@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);
}
private static AppBarLayout findFirstAppBarLayout(List<View> views) {
int i = 0;
for (int z = views.size(); i < z; ++i) {
View view = (View) views.get(i);
if (view instanceof AppBarLayout) {
return (AppBarLayout) view;
}
}
return null;
}
@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
View dependency) {
if (onScrollListener != null) {
onScrollListener.onScroll(parent, child, dependency);
}
return super.onDependentViewChanged(parent, child, dependency);
}
public interface OnScrollListener {
void onScroll(CoordinatorLayout parent, View child,
View dependency);
}
public OnScrollListener getOnScrollListener() {
return onScrollListener;
}
public void setOnScrollListener(OnScrollListener onScrollListener) {
this.onScrollListener = onScrollListener;
}
}
REF:
http://stackoverflow.com/questions/30923889/flinging-with-recyclerview-appbarlayout
https://github.com/henrytao-me/smooth-app-bar-layout
https://code.google.com/p/android/issues/detail?id=177729