Android使用ScrollView导致鼠标点击事件无效

在这里插入图片描述

平台

测试平台:

RK3288 + Android8.1
RK3588 + Android 12

问题

 首先, 这个问题的前提是, 使用的输入设备是**鼠标**, 普通的触摸屏并不会出现这个问题. 大致的流程是APP的UI布局中采用ScrollView作为根容器, 之后添加各类子控件, 在一起准备就绪后, 使用鼠标进行功能测试, 出现无法点击控件触发事件响应.

<ScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <LinearLayout
            style="@style/settingsItems">
            <TextView style="@style/TV"
                android:text="XXX"
                android:layout_weight="1"
                />
            <Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="BTN"/>
        </LinearLayout>
        <LinearLayout
            style="@style/settingsItems">
            <TextView style="@style/TV"
                android:text="XXX"
                android:layout_weight="1"
                />
            <Button
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="BTN"/>
        </LinearLayout>
				<!--可以写多几个-->
    </LinearLayout>
</ScrollView>

分析

最先从onInterceptTouchEvent函数入手, 各个层级的LOG大致分析, 由下往上发现控件BUTTON中根本没有捕获到MotionEvent, 那原因只可能是父控件自己捕获了而不下发. 兜兜转转最终来到了ScrollView.

通过重写onInterceptHoverEvent 判断是否时间已被捕获

  @Override
	public boolean onInterceptHoverEvent(MotionEvent event) {
		boolean b = super.onInterceptHoverEvent(event);
		Logger.d(TAG, "onInterceptHoverEvent " + b);
		return b;
	}

从输出的LOG可以看出来, 当使用鼠标的时候, TRUE 和 FALSE 均有可能出现(在后面排查是才发现这和控件处的位置有关), 当TRUE是, 说明事件由ScrollView处理了, 子控件自然就接收不到事件下发.

顺着onInterceptHoverEvent往上查:

frameworks/base/core/java/android/view/ViewGroup.java

    public boolean onInterceptHoverEvent(MotionEvent event) {
        if (event.isFromSource(InputDevice.SOURCE_MOUSE)) {
            final int action = event.getAction();
            final float x = event.getX();
            final float y = event.getY();
            if ((action == MotionEvent.ACTION_HOVER_MOVE
                    || action == MotionEvent.ACTION_HOVER_ENTER) && isOnScrollbar(x, y)) {
                return true;
            }
        }
        return false;
    }

从代码中可以看出, 基本的判断条件都是成立的, 鼠标输入 + MOVE/ENTER时间, 最后一个是isOnScrollbar, 顾名思义输入鼠标的位置在ScrollBar 上?

frameworks/base/core/java/android/view/View.java


    boolean isOnScrollbar(float x, float y) {
        if (mScrollCache == null) {
            return false;
        }
        x += getScrollX();
        y += getScrollY();
        if (isVerticalScrollBarEnabled() && !isVerticalScrollBarHidden()) {
            final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
            getVerticalScrollBarBounds(null, touchBounds);
            if (touchBounds.contains((int) x, (int) y)) {
                return true;
            }
        }
        if (isHorizontalScrollBarEnabled()) {
            final Rect touchBounds = mScrollCache.mScrollBarTouchBounds;
            getHorizontalScrollBarBounds(null, touchBounds);
            if (touchBounds.contains((int) x, (int) y)) {
                return true;
            }
        }
        return false;
    }

    private void getVerticalScrollBarBounds(@Nullable Rect bounds, @Nullable Rect touchBounds) {
        if (mRoundScrollbarRenderer == null) {
            getStraightVerticalScrollBarBounds(bounds, touchBounds);
        } else {
            getRoundVerticalScrollBarBounds(bounds != null ? bounds : touchBounds);
        }
    }
    private void getStraightVerticalScrollBarBounds(@Nullable Rect drawBounds,
            @Nullable Rect touchBounds) {
        final Rect bounds = drawBounds != null ? drawBounds : touchBounds;
        if (bounds == null) {
            return;
        }
        final int inside = (mViewFlags & SCROLLBARS_OUTSIDE_MASK) == 0 ? ~0 : 0;
        final int size = getVerticalScrollbarWidth();
        int verticalScrollbarPosition = mVerticalScrollbarPosition;
        if (verticalScrollbarPosition == SCROLLBAR_POSITION_DEFAULT) {
            verticalScrollbarPosition = isLayoutRtl() ?
                    SCROLLBAR_POSITION_LEFT : SCROLLBAR_POSITION_RIGHT;
        }
        final int width = mRight - mLeft;
        final int height = mBottom - mTop;
        switch (verticalScrollbarPosition) {
            default:
            case SCROLLBAR_POSITION_RIGHT:
                bounds.left = mScrollX + width - size - (mUserPaddingRight & inside);
                break;
            case SCROLLBAR_POSITION_LEFT:
                bounds.left = mScrollX + (mUserPaddingLeft & inside);
                break;
        }
        bounds.top = mScrollY + (mPaddingTop & inside);
        bounds.right = bounds.left + size;
        bounds.bottom = mScrollY + height - (mUserPaddingBottom & inside);

        if (touchBounds == null) {
            return;
        }
        if (touchBounds != bounds) {
            touchBounds.set(bounds);
        }
        final int minTouchTarget = mScrollCache.scrollBarMinTouchTarget;
        if (touchBounds.width() < minTouchTarget) {
            final int adjust = (minTouchTarget - touchBounds.width()) / 2;
            if (verticalScrollbarPosition == SCROLLBAR_POSITION_RIGHT) {
                touchBounds.right = Math.min(touchBounds.right + adjust, mScrollX + width);
                touchBounds.left = touchBounds.right - minTouchTarget;
            } else {
                touchBounds.left = Math.max(touchBounds.left + adjust, mScrollX);
                touchBounds.right = touchBounds.left + minTouchTarget;
            }
        }
        if (touchBounds.height() < minTouchTarget) {
            final int adjust = (minTouchTarget - touchBounds.height()) / 2;
            touchBounds.top -= adjust;
            touchBounds.bottom = touchBounds.top + minTouchTarget;
        }
    }

/**
     * <p>ScrollabilityCache holds various fields used by a View when scrolling
     * is supported. This avoids keeping too many unused fields in most
     * instances of View.</p>
     */
    private static class ScrollabilityCache implements Runnable {

        /**
         * Scrollbars are not visible
         */
        public static final int OFF = 0;

        /**
         * Scrollbars are visible
         */
        public static final int ON = 1;

        /**
         * Scrollbars are fading away
         */
        public static final int FADING = 2;

        public boolean fadeScrollBars;

        public int fadingEdgeLength;
        public int scrollBarDefaultDelayBeforeFade;
        public int scrollBarFadeDuration;

        public int scrollBarSize;
        public int scrollBarMinTouchTarget;
        public ScrollBarDrawable scrollBar;
        public float[] interpolatorValues;
        public View host;

        public final Paint paint;
        public final Matrix matrix;
        public Shader shader;

        public final Interpolator scrollBarInterpolator = new Interpolator(1, 2);

        private static final float[] OPAQUE = { 255 };
        private static final float[] TRANSPARENT = { 0.0f };

        /**
         * When fading should start. This time moves into the future every time
         * a new scroll happens. Measured based on SystemClock.uptimeMillis()
         */
        public long fadeStartTime;

        /**
         * The current state of the scrollbars: ON, OFF, or FADING
         */
        public int state = OFF;

        private int mLastColor;

        public final Rect mScrollBarBounds = new Rect();
        public final Rect mScrollBarTouchBounds = new Rect();

        public static final int NOT_DRAGGING = 0;
        public static final int DRAGGING_VERTICAL_SCROLL_BAR = 1;
        public static final int DRAGGING_HORIZONTAL_SCROLL_BAR = 2;
        public int mScrollBarDraggingState = NOT_DRAGGING;

        public float mScrollBarDraggingPos = 0;

        public ScrollabilityCache(ViewConfiguration configuration, View host) {
            fadingEdgeLength = configuration.getScaledFadingEdgeLength();
            scrollBarSize = configuration.getScaledScrollBarSize();
            scrollBarMinTouchTarget = configuration.getScaledMinScrollbarTouchTarget();
            scrollBarDefaultDelayBeforeFade = ViewConfiguration.getScrollDefaultDelay();
            scrollBarFadeDuration = ViewConfiguration.getScrollBarFadeDuration();

            paint = new Paint();
            matrix = new Matrix();
            // use use a height of 1, and then wack the matrix each time we
            // actually use it.
            shader = new LinearGradient(0, 0, 0, 1, 0xFF000000, 0, Shader.TileMode.CLAMP);
            paint.setShader(shader);
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));

            this.host = host;
        }

        public void setFadeColor(int color) {
            if (color != mLastColor) {
                mLastColor = color;

                if (color != 0) {
                    shader = new LinearGradient(0, 0, 0, 1, color | 0xFF000000,
                            color & 0x00FFFFFF, Shader.TileMode.CLAMP);
                    paint.setShader(shader);
                    // Restore the default transfer mode (src_over)
                    paint.setXfermode(null);
                } else {
                    shader = new LinearGradient(0, 0, 0, 1, 0xFF000000, 0, Shader.TileMode.CLAMP);
                    paint.setShader(shader);
                    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
                }
            }
        }

        public void run() {
            long now = AnimationUtils.currentAnimationTimeMillis();
            if (now >= fadeStartTime) {

                // the animation fades the scrollbars out by changing
                // the opacity (alpha) from fully opaque to fully
                // transparent
                int nextFrame = (int) now;
                int framesCount = 0;

                Interpolator interpolator = scrollBarInterpolator;

                // Start opaque
                interpolator.setKeyFrame(framesCount++, nextFrame, OPAQUE);

                // End transparent
                nextFrame += scrollBarFadeDuration;
                interpolator.setKeyFrame(framesCount, nextFrame, TRANSPARENT);

                state = FADING;

                // Kick off the fade animation
                host.invalidate(true);
            }
        }
    }

View中的代码有点多, 简单的来说, 就是isOnScrollbar 这个函数通过获取ScrollBar的位置大小信息判断输入的事件是否处于其捕获的范围.

通过反射调用getVerticalScrollBarBounds并输出读取的信息: touchRect=[1464,0][1512,674], 基本可以判定是滚动条的位置.


Rect touchRect = new Rect();
getVerticalScrollBarBoundsRe(null, touchRect);
Logger.d(TAG, "touchRect=" + touchRect.toShortString());

void getVerticalScrollBarBoundsRe(Rect r, Rect r2){
		try {
			@SuppressLint("SoonBlockedPrivateApi")
			Method getVerticalScrollBarBounds = View.class.getDeclaredMethod("getVerticalScrollBarBounds", Rect.class, Rect.class);
			getVerticalScrollBarBounds.setAccessible(true);
			getVerticalScrollBarBounds.invoke(this, r, r2);
		} catch (NoSuchMethodException e) {
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		}
	}

计算宽度1512 - 1464 = 48, 这个宽度默认在系统中又定义, 如果是自定义的ScrollBar则大小不一定是48, 根据configuration.getScaledMinScrollbarTouchTarget();查到源码的定义如下:

frameworks/base/core/java/android/view/ViewConfiguration.java

private static final int MIN_SCROLLBAR_TOUCH_TARGET = 48;

/**
 * @return the minimum size of the scrollbar thumb's touch target in pixels
 * @hide
 */
public int getScaledMinScrollbarTouchTarget() {
    return mMinScrollbarTouchTarget;
}