我目前有这样的布局设置：
<?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:fitsSystemWindows="true">
<com.google.android.material.appbar.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:elevation="4dp">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:id="@+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="250dp"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<ImageView
android:id="@+id/backdrop"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:scaleType="centerCrop"
android:src="@drawable/android_icon"
app:layout_collapseMode="parallax" />
<androidx.appcompat.widget.Toolbar
android:id="@+id/generic_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:fitsSystemWindows="true"
android:background="@null"
app:layout_collapseMode="pin"/>
</com.google.android.material.appbar.CollapsingToolbarLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.core.widget.NestedScrollView
android:id="@+id/primary_nestedScrollView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<WebView
android:id="@+id/primary_webview"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</androidx.core.widget.NestedScrollView>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
虽然这在大多数情况下都可以正常工作，但是当我要确保其内容填充视口时，webview的滚动存在问题。
如果我将android:fillViewport="true"属性添加到NestedScrollView，则视口将正确填满，并且折叠的工具栏仍会折叠，但是Webview本身无法再滚动。
我已经在一个小演示项目视频中对此进行了演示： https://i.imgur.com/EJevXuz.mp4
（编辑：似乎录音中有一些闪烁的伪像。这是录音问题，与问题无关）
如您所见，当fillViewPort设置为false时，滚动效果很好。尽管符合预期，但内容（内容为深灰色）如果不是简短内容，则不会填充可用空间。
在NestedScrollView上将fillViewPort值设置为true时，内容（背景）确实会填充可用空间，但是在较大内容上的任何滚动似乎都被禁用（WebView在其顶部滚动位置“卡住”了）即使网络视图中的滚动条指示有更多可用内容。
我已经尝试了很多方法来使它再次起作用（包括在网络上找到的几个NestedWebView实现），但到目前为止没有任何效果。
在该布局设置中，如何使用fillViewPort选项再次正确滚动来获取WebView？
答案 0 :(得分：1)
我终于找到了适合我情况的NestedWebView实现。
此实现完全消除了NestedScrollView的必要性，允许Webview根据wrap_content / match_parent布局值（而不是滚动视图的视口处理）自动调整其视口。
这是snachmsm最近添加的一种实现，它是对a similar question的回答：
import android.annotation.SuppressLint;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewParent;
import android.webkit.WebView;
import android.widget.OverScroller;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.view.NestedScrollingChild3;
import androidx.core.view.NestedScrollingChildHelper;
import androidx.core.view.ViewCompat;
/**
* WebView compatible with CoordinatorLayout by snachmsm
* The implementation based on NestedScrollView of design library androidx v1.0.1
*/
public class NestedWebView extends WebView implements NestedScrollingChild3 {
private static final String TAG = "NestedWebView";
private static final int INVALID_POINTER = -1;
private final int[] mScrollOffset = new int[2];
private final int[] mScrollConsumed = new int[2];
private int mLastMotionY;
private NestedScrollingChildHelper mChildHelper;
private boolean mIsBeingDragged = false;
private VelocityTracker mVelocityTracker;
private int mTouchSlop;
private int mActivePointerId = INVALID_POINTER;
private int mNestedYOffset;
private OverScroller mScroller;
private int mMinimumVelocity;
private int mMaximumVelocity;
private int mLastScrollerY;
public NestedWebView(Context context) {
this(context, null);
}
public NestedWebView(Context context, AttributeSet attrs) {
this(context, attrs, android.R.attr.webViewStyle);
}
public NestedWebView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
setOverScrollMode(WebView.OVER_SCROLL_NEVER);
initScrollView();
mChildHelper = new NestedScrollingChildHelper(this);
setNestedScrollingEnabled(true);
}
private void initScrollView() {
mScroller = new OverScroller(getContext());
final ViewConfiguration configuration = ViewConfiguration.get(getContext());
mTouchSlop = configuration.getScaledTouchSlop();
mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { // most common
return true;
}
switch (action & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_MOVE:
final int activePointerId = mActivePointerId;
if (activePointerId == INVALID_POINTER) {
break;
}
final int pointerIndex = ev.findPointerIndex(activePointerId);
if (pointerIndex == -1) {
Log.e(TAG, "Invalid pointerId=" + activePointerId
+ " in onInterceptTouchEvent");
break;
}
final int y = (int) ev.getY(pointerIndex);
final int yDiff = Math.abs(y - mLastMotionY);
if (yDiff > mTouchSlop
&& (getNestedScrollAxes() & ViewCompat.SCROLL_AXIS_VERTICAL) == 0) {
mIsBeingDragged = true;
mLastMotionY = y;
initVelocityTrackerIfNotExists();
mVelocityTracker.addMovement(ev);
mNestedYOffset = 0;
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
break;
case MotionEvent.ACTION_DOWN:
mLastMotionY = (int) ev.getY();
mActivePointerId = ev.getPointerId(0);
initOrResetVelocityTracker();
mVelocityTracker.addMovement(ev);
mScroller.computeScrollOffset();
mIsBeingDragged = !mScroller.isFinished();
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
mIsBeingDragged = false;
mActivePointerId = INVALID_POINTER;
recycleVelocityTracker();
if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
stopNestedScroll();
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
break;
}
return mIsBeingDragged;
}
@SuppressLint("ClickableViewAccessibility")
@Override
public boolean onTouchEvent(MotionEvent ev) {
initVelocityTrackerIfNotExists();
MotionEvent vtev = MotionEvent.obtain(ev);
final int actionMasked = ev.getActionMasked();
if (actionMasked == MotionEvent.ACTION_DOWN) {
mNestedYOffset = 0;
}
vtev.offsetLocation(0, mNestedYOffset);
switch (actionMasked) {
case MotionEvent.ACTION_DOWN:
if ((mIsBeingDragged = !mScroller.isFinished())) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
}
if (!mScroller.isFinished()) {
abortAnimatedScroll();
}
mLastMotionY = (int) ev.getY();
mActivePointerId = ev.getPointerId(0);
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH);
break;
case MotionEvent.ACTION_MOVE:
final int activePointerIndex = ev.findPointerIndex(mActivePointerId);
if (activePointerIndex == -1) {
Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent");
break;
}
final int y = (int) ev.getY(activePointerIndex);
int deltaY = mLastMotionY - y;
if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset,
ViewCompat.TYPE_TOUCH)) {
deltaY -= mScrollConsumed[1];
mNestedYOffset += mScrollOffset[1];
}
if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
final ViewParent parent = getParent();
if (parent != null) {
parent.requestDisallowInterceptTouchEvent(true);
}
mIsBeingDragged = true;
if (deltaY > 0) {
deltaY -= mTouchSlop;
} else {
deltaY += mTouchSlop;
}
}
if (mIsBeingDragged) {
mLastMotionY = y - mScrollOffset[1];
final int oldY = getScrollY();
final int range = getScrollRange();
// Calling overScrollByCompat will call onOverScrolled, which
// calls onScrollChanged if applicable.
if (overScrollByCompat(0, deltaY, 0, oldY, 0, range, 0,
0, true) && !hasNestedScrollingParent(ViewCompat.TYPE_TOUCH)) {
mVelocityTracker.clear();
}
final int scrolledDeltaY = getScrollY() - oldY;
final int unconsumedY = deltaY - scrolledDeltaY;
mScrollConsumed[1] = 0;
dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset,
ViewCompat.TYPE_TOUCH, mScrollConsumed);
mLastMotionY -= mScrollOffset[1];
mNestedYOffset += mScrollOffset[1];
}
break;
case MotionEvent.ACTION_UP:
final VelocityTracker velocityTracker = mVelocityTracker;
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId);
if ((Math.abs(initialVelocity) > mMinimumVelocity)) {
if (!dispatchNestedPreFling(0, -initialVelocity)) {
dispatchNestedFling(0, -initialVelocity, true);
fling(-initialVelocity);
}
} else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEvent.ACTION_CANCEL:
if (mIsBeingDragged) {
if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0,
getScrollRange())) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
mActivePointerId = INVALID_POINTER;
endDrag();
break;
case MotionEvent.ACTION_POINTER_DOWN:
final int index = ev.getActionIndex();
mLastMotionY = (int) ev.getY(index);
mActivePointerId = ev.getPointerId(index);
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);
mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId));
break;
}
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(vtev);
}
vtev.recycle();
return super.onTouchEvent(ev);
}
private void abortAnimatedScroll() {
mScroller.abortAnimation();
stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
}
private void endDrag() {
mIsBeingDragged = false;
recycleVelocityTracker();
stopNestedScroll();
}
private void onSecondaryPointerUp(MotionEvent ev) {
final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
>> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
final int pointerId = ev.getPointerId(pointerIndex);
if (pointerId == mActivePointerId) {
final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
mLastMotionY = (int) ev.getY(newPointerIndex);
mActivePointerId = ev.getPointerId(newPointerIndex);
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
}
}
private void fling(int velocityY) {
int height = getHeight();
mScroller.fling(getScrollX(), getScrollY(), // start
0, velocityY, // velocities
0, 0, // x
Integer.MIN_VALUE, Integer.MAX_VALUE, // y
0, height / 2);
runAnimatedScroll(true);
}
private void runAnimatedScroll(boolean participateInNestedScrolling) {
if (participateInNestedScrolling) {
startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_NON_TOUCH);
} else {
stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
}
mLastScrollerY = getScrollY();
ViewCompat.postInvalidateOnAnimation(this);
}
@Override
public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) {
if (disallowIntercept) {
recycleVelocityTracker();
}
super.requestDisallowInterceptTouchEvent(disallowIntercept);
}
private void initOrResetVelocityTracker() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
}
private void initVelocityTrackerIfNotExists() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
}
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
@Override
protected boolean overScrollBy(int deltaX, int deltaY,
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY,
boolean isTouchEvent) {
// this is causing double scroll call (doubled speed), but this WebView isn't overscrollable
// all overscrolls are passed to appbar, so commenting this out during drag
if (!mIsBeingDragged)
overScrollByCompat(deltaX, deltaY, scrollX, scrollY, scrollRangeX, scrollRangeY,
maxOverScrollX, maxOverScrollY, isTouchEvent);
// without this call webview won't scroll to top when url change or when user pick input
// (webview should move a bit making input still in viewport when "adjustResize")
return true;
}
int getScrollRange() {
//Using scroll range of webview instead of childs as NestedScrollView does.
return computeVerticalScrollRange();
}
@Override
public boolean isNestedScrollingEnabled() {
return mChildHelper.isNestedScrollingEnabled();
}
@Override
public void setNestedScrollingEnabled(boolean enabled) {
mChildHelper.setNestedScrollingEnabled(enabled);
}
@Override
public boolean startNestedScroll(int axes, int type) {
return mChildHelper.startNestedScroll(axes, type);
}
@Override
public boolean startNestedScroll(int axes) {
return startNestedScroll(axes, ViewCompat.TYPE_TOUCH);
}
@Override
public void stopNestedScroll(int type) {
mChildHelper.stopNestedScroll(type);
}
@Override
public void stopNestedScroll() {
stopNestedScroll(ViewCompat.TYPE_TOUCH);
}
@Override
public boolean hasNestedScrollingParent(int type) {
return mChildHelper.hasNestedScrollingParent(type);
}
@Override
public boolean hasNestedScrollingParent() {
return hasNestedScrollingParent(ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
int[] offsetInWindow) {
return dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
int[] offsetInWindow, int type) {
return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type);
}
@Override
public void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed,
@Nullable int[] offsetInWindow, int type, @NonNull int[] consumed) {
mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed,
offsetInWindow, type, consumed);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH);
}
@Override
public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow, int type) {
return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
}
@Override
public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
return mChildHelper.dispatchNestedFling(velocityX, velocityY, false);
}
@Override
public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
}
@Override
public int getNestedScrollAxes() {
return ViewCompat.SCROLL_AXIS_VERTICAL;
}
@Override
public void computeScroll() {
if (mScroller.isFinished()) {
return;
}
mScroller.computeScrollOffset();
final int y = mScroller.getCurrY();
int unconsumed = y - mLastScrollerY;
mLastScrollerY = y;
// Nested Scrolling Pre Pass
mScrollConsumed[1] = 0;
dispatchNestedPreScroll(0, unconsumed, mScrollConsumed, null,
ViewCompat.TYPE_NON_TOUCH);
unconsumed -= mScrollConsumed[1];
if (unconsumed != 0) {
// Internal Scroll
final int oldScrollY = getScrollY();
overScrollByCompat(0, unconsumed, getScrollX(), oldScrollY, 0, getScrollRange(),
0, 0, false);
final int scrolledByMe = getScrollY() - oldScrollY;
unconsumed -= scrolledByMe;
// Nested Scrolling Post Pass
mScrollConsumed[1] = 0;
dispatchNestedScroll(0, 0, 0, unconsumed, mScrollOffset,
ViewCompat.TYPE_NON_TOUCH, mScrollConsumed);
unconsumed -= mScrollConsumed[1];
}
if (unconsumed != 0) {
abortAnimatedScroll();
}
if (!mScroller.isFinished()) {
ViewCompat.postInvalidateOnAnimation(this);
}
}
// copied from NestedScrollView exacly as it looks, leaving overscroll related code, maybe future use
private boolean overScrollByCompat(int deltaX, int deltaY,
int scrollX, int scrollY,
int scrollRangeX, int scrollRangeY,
int maxOverScrollX, int maxOverScrollY,
boolean isTouchEvent) {
final int overScrollMode = getOverScrollMode();
final boolean canScrollHorizontal =
computeHorizontalScrollRange() > computeHorizontalScrollExtent();
final boolean canScrollVertical =
computeVerticalScrollRange() > computeVerticalScrollExtent();
final boolean overScrollHorizontal = overScrollMode == View.OVER_SCROLL_ALWAYS
|| (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollHorizontal);
final boolean overScrollVertical = overScrollMode == View.OVER_SCROLL_ALWAYS
|| (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollVertical);
int newScrollX = scrollX + deltaX;
if (!overScrollHorizontal) {
maxOverScrollX = 0;
}
int newScrollY = scrollY + deltaY;
if (!overScrollVertical) {
maxOverScrollY = 0;
}
// Clamp values if at the limits and record
final int left = -maxOverScrollX;
final int right = maxOverScrollX + scrollRangeX;
final int top = -maxOverScrollY;
final int bottom = maxOverScrollY + scrollRangeY;
boolean clampedX = false;
if (newScrollX > right) {
newScrollX = right;
clampedX = true;
} else if (newScrollX < left) {
newScrollX = left;
clampedX = true;
}
boolean clampedY = false;
if (newScrollY > bottom) {
newScrollY = bottom;
clampedY = true;
} else if (newScrollY < top) {
newScrollY = top;
clampedY = true;
}
if (clampedY && !hasNestedScrollingParent(ViewCompat.TYPE_NON_TOUCH)) {
mScroller.springBack(newScrollX, newScrollY, 0, 0, 0, getScrollRange());
}
onOverScrolled(newScrollX, newScrollY, clampedX, clampedY);
return clampedX || clampedY;
}
}