ScrollView 中的 HorizontalScrollView 触摸处理
-
27-09-2019 - |
题
我有一个 ScrollView 包围我的整个布局,以便整个屏幕都可以滚动。此 ScrollView 中的第一个元素是 HorizontalScrollView 块,它具有可以水平滚动的功能。我在horizontalscrollview中添加了一个ontouchlistener来处理触摸事件并强制视图“捕捉”到ACTION_UP事件上最接近的图像。
所以我想要的效果就像普通的 Android 主屏幕一样,你可以从一个屏幕滚动到另一个屏幕,当你抬起手指时它会捕捉到一个屏幕。
除了一个问题之外,这一切都很好用:我需要几乎完全水平地从左向右滑动才能注册 ACTION_UP。如果我至少垂直滑动(我认为很多人在手机上左右滑动时往往会这样做),我将收到 ACTION_CANCEL 而不是 ACTION_UP。我的理论是,这是因为水平滚动视图位于滚动视图内,并且滚动视图劫持垂直触摸以允许垂直滚动。
如何从水平滚动视图中禁用滚动视图的触摸事件,但仍允许滚动视图中其他位置的正常垂直滚动?
这是我的代码示例:
public class HomeFeatureLayout extends HorizontalScrollView {
private ArrayList<ListItem> items = null;
private GestureDetector gestureDetector;
View.OnTouchListener gestureListener;
private static final int SWIPE_MIN_DISTANCE = 5;
private static final int SWIPE_THRESHOLD_VELOCITY = 300;
private int activeFeature = 0;
public HomeFeatureLayout(Context context, ArrayList<ListItem> items){
super(context);
setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
setFadingEdgeLength(0);
this.setHorizontalScrollBarEnabled(false);
this.setVerticalScrollBarEnabled(false);
LinearLayout internalWrapper = new LinearLayout(context);
internalWrapper.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
internalWrapper.setOrientation(LinearLayout.HORIZONTAL);
addView(internalWrapper);
this.items = items;
for(int i = 0; i< items.size();i++){
LinearLayout featureLayout = (LinearLayout) View.inflate(this.getContext(),R.layout.homefeature,null);
TextView header = (TextView) featureLayout.findViewById(R.id.featureheader);
ImageView image = (ImageView) featureLayout.findViewById(R.id.featureimage);
TextView title = (TextView) featureLayout.findViewById(R.id.featuretitle);
title.setTag(items.get(i).GetLinkURL());
TextView date = (TextView) featureLayout.findViewById(R.id.featuredate);
header.setText("FEATURED");
Image cachedImage = new Image(this.getContext(), items.get(i).GetImageURL());
image.setImageDrawable(cachedImage.getImage());
title.setText(items.get(i).GetTitle());
date.setText(items.get(i).GetDate());
internalWrapper.addView(featureLayout);
}
gestureDetector = new GestureDetector(new MyGestureDetector());
setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
if (gestureDetector.onTouchEvent(event)) {
return true;
}
else if(event.getAction() == MotionEvent.ACTION_UP || event.getAction() == MotionEvent.ACTION_CANCEL ){
int scrollX = getScrollX();
int featureWidth = getMeasuredWidth();
activeFeature = ((scrollX + (featureWidth/2))/featureWidth);
int scrollTo = activeFeature*featureWidth;
smoothScrollTo(scrollTo, 0);
return true;
}
else{
return false;
}
}
});
}
class MyGestureDetector extends SimpleOnGestureListener {
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
try {
//right to left
if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
activeFeature = (activeFeature < (items.size() - 1))? activeFeature + 1:items.size() -1;
smoothScrollTo(activeFeature*getMeasuredWidth(), 0);
return true;
}
//left to right
else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
activeFeature = (activeFeature > 0)? activeFeature - 1:0;
smoothScrollTo(activeFeature*getMeasuredWidth(), 0);
return true;
}
} catch (Exception e) {
// nothing
}
return false;
}
}
}
解决方案
更新:我明白了这一点。在我的 ScrollView 上,我需要重写 onInterceptTouchEvent 方法,以便仅在 Y 运动 > X 运动时拦截触摸事件。看起来 ScrollView 的默认行为是每当有任何 Y 运动时都会拦截触摸事件。因此,通过修复,ScrollView 将仅在用户故意沿 Y 方向滚动时拦截该事件,并且在这种情况下将 ACTION_CANCEL 传递给子级。
以下是包含 HorizontalScrollView 的滚动视图类的代码:
public class CustomScrollView extends ScrollView {
private GestureDetector mGestureDetector;
public CustomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
mGestureDetector = new GestureDetector(context, new YScrollDetector());
setFadingEdgeLength(0);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return super.onInterceptTouchEvent(ev) && mGestureDetector.onTouchEvent(ev);
}
// Return false if we're scrolling in the x direction
class YScrollDetector extends SimpleOnGestureListener {
@Override
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
return Math.abs(distanceY) > Math.abs(distanceX);
}
}
}
其他提示
谢谢乔尔给我提供了如何解决这个问题的线索。
我已经简化了代码(不需要 手势检测器)达到同样的效果:
public class VerticalScrollView extends ScrollView {
private float xDistance, yDistance, lastX, lastY;
public VerticalScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
xDistance = yDistance = 0f;
lastX = ev.getX();
lastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
xDistance += Math.abs(curX - lastX);
yDistance += Math.abs(curY - lastY);
lastX = curX;
lastY = curY;
if(xDistance > yDistance)
return false;
}
return super.onInterceptTouchEvent(ev);
}
}
我想我找到了一个更简单的解决方案,只是它使用 ViewPager 的子类而不是(其父级)ScrollView。
更新2013-07-16: :我添加了一个覆盖 onTouchEvent
以及。尽管 YMMV,它可能有助于解决评论中提到的问题。
public class UninterceptableViewPager extends ViewPager {
public UninterceptableViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
boolean ret = super.onInterceptTouchEvent(ev);
if (ret)
getParent().requestDisallowInterceptTouchEvent(true);
return ret;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
boolean ret = super.onTouchEvent(ev);
if (ret)
getParent().requestDisallowInterceptTouchEvent(true);
return ret;
}
}
这类似于 android.widget.Gallery 的 onScroll() 中使用的技术。Google I/O 2013 演示进一步解释了这一点 为 Android 编写自定义视图.
更新2013-12-10: :类似的方法也描述于 Kirill Grouchnikov 发布的有关(当时的)Android Market 应用程序的帖子.
我发现有时一个 ScrollView 重新获得焦点,而另一个 ScrollView 失去焦点。您可以通过仅授予滚动视图焦点之一来防止这种情况:
scrollView1= (ScrollView) findViewById(R.id.scrollscroll);
scrollView1.setAdapter(adapter);
scrollView1.setOnTouchListener(new View.OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
scrollView1.getParent().requestDisallowInterceptTouchEvent(true);
return false;
}
});
这对我来说效果不佳。我改变了它,现在可以顺利运行了。如果有人有兴趣的话。
public class ScrollViewForNesting extends ScrollView {
private final int DIRECTION_VERTICAL = 0;
private final int DIRECTION_HORIZONTAL = 1;
private final int DIRECTION_NO_VALUE = -1;
private final int mTouchSlop;
private int mGestureDirection;
private float mDistanceX;
private float mDistanceY;
private float mLastX;
private float mLastY;
public ScrollViewForNesting(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
final ViewConfiguration configuration = ViewConfiguration.get(context);
mTouchSlop = configuration.getScaledTouchSlop();
}
public ScrollViewForNesting(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public ScrollViewForNesting(Context context) {
this(context,null);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
mDistanceY = mDistanceX = 0f;
mLastX = ev.getX();
mLastY = ev.getY();
mGestureDirection = DIRECTION_NO_VALUE;
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
mDistanceX += Math.abs(curX - mLastX);
mDistanceY += Math.abs(curY - mLastY);
mLastX = curX;
mLastY = curY;
break;
}
return super.onInterceptTouchEvent(ev) && shouldIntercept();
}
private boolean shouldIntercept(){
if((mDistanceY > mTouchSlop || mDistanceX > mTouchSlop) && mGestureDirection == DIRECTION_NO_VALUE){
if(Math.abs(mDistanceY) > Math.abs(mDistanceX)){
mGestureDirection = DIRECTION_VERTICAL;
}
else{
mGestureDirection = DIRECTION_HORIZONTAL;
}
}
if(mGestureDirection == DIRECTION_VERTICAL){
return true;
}
else{
return false;
}
}
}
感谢 Neevek,他的答案对我有用,但当用户开始在水平方向上滚动水平视图(ViewPager)时,它不会锁定垂直滚动,然后在不垂直抬起手指滚动的情况下,它开始滚动底层容器视图(ScrollView) 。我通过对 Neevak 的代码进行轻微更改来修复它:
private float xDistance, yDistance, lastX, lastY;
int lastEvent=-1;
boolean isLastEventIntercepted=false;
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
xDistance = yDistance = 0f;
lastX = ev.getX();
lastY = ev.getY();
break;
case MotionEvent.ACTION_MOVE:
final float curX = ev.getX();
final float curY = ev.getY();
xDistance += Math.abs(curX - lastX);
yDistance += Math.abs(curY - lastY);
lastX = curX;
lastY = curY;
if(isLastEventIntercepted && lastEvent== MotionEvent.ACTION_MOVE){
return false;
}
if(xDistance > yDistance )
{
isLastEventIntercepted=true;
lastEvent = MotionEvent.ACTION_MOVE;
return false;
}
}
lastEvent=ev.getAction();
isLastEventIntercepted=false;
return super.onInterceptTouchEvent(ev);
}
这最终成为了支持v4库的一部分, 嵌套滚动视图. 。因此,我猜大多数情况下不再需要本地黑客。
在运行 3.2 及更高版本的设备上,Neevek 的解决方案比 Joel 的解决方案效果更好。Android中有一个bug会导致java.lang.IllegalArgumentException:如果在 scollview 内使用手势检测器,pointerIndex 超出范围。要重复该问题,请按照 Joel 的建议实现自定义 scollview 并在其中放置一个视图寻呼机。如果您将(不要抬起您的人物)拖动到一个方向(左/右),然后拖动到相反的方向,您将看到崩溃。同样在 Joel 的解决方案中,如果通过对角移动手指来拖动视图寻呼机,一旦手指离开视图寻呼机的内容视图区域,寻呼机将弹回其之前的位置。所有这些问题更多地与 Android 的内部设计或缺乏它有关,而不是 Joel 的实现,Joel 的实现本身就是一段聪明而简洁的代码。