WebView 在帶有 CollapsibleToolBarLayout 的 NestedScrollView 中不滾動

Question

我目前有這樣的布局設置：

<?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>

雖然這大部分工作正常，但當我想確保其內容填充視口時，webview 的滾動存在問題。

如果我將android:fillViewport="true"屬性添加到 NestedScrollView ，則視口會正確填充並且折疊工具欄仍然折疊，但 webview 本身無法再滾動。

我已經在一個小演示項目視頻中演示了這一點： https://i.imgur.com/EJevXuz.mp4

（編輯：錄音似乎有一些閃爍的偽影。這是一個錄音問題，與問題無關）

如您所見，當 fillViewPort 設置為 false 時，滾動效果很好。 盡管正如預期的那樣，如果內容（具有深灰色背景）很短/很小，它不會填滿可用空間。

當 NestedScrollView 上的 fillViewPort 值設置為 true 時，內容（的背景）確實填充了可用空間，但似乎禁用了對較大內容的任何滾動（WebView 被“卡在”其頂部滾動位置），即使webview 中的滾動條表示有更多內容可用。

我已經嘗試了很多方法來讓它再次工作（包括在網絡上找到的幾個 NestedWebView 實現），但到目前為止無濟於事。

在此布局設置中，如何在 fillViewPort 選項再次正確滾動的情況下獲得 WebView？

Answer 1

我終於找到了適合我情況的 NestedWebView 實現。

此實現完全消除了 NestedScrollView 的必要性，允許 webview 根據wrap_content / match_parent布局值自動調整其視口，而不是滾動視圖的視口處理。

這是 snachmsm 最近添加的一個實現，作為對類似問題的回答：

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;
    }
}

Answer 2

Leon_Lucardie,

縮放 webview 后，此代碼不適用於水平滾動。