我有一个包含水平滚动视图（HSV）的View Pager（VP）。如果HSV到达其中一个边缘或者根本无法滚动，则在阻塞方向上的新滑动中，VP应该接管滚动到下一页。我对提出这个问题犹豫不决，因为我找到了类似这样的问题：
Can I use Horizontal Scrollview Inside a Viewpager in Android?
或
horizontalscrollview inside viewpager
但解决方案对我不起作用。 'v instanceof HorizontalScrollView'变为true但viewPager不滚动
任何其他想法如何实现预期的行为？
public class MyViewPager extends ViewPager {
public MyViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
// Update 1
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return true;
//return super.onInterceptTouchEvent(ev);
}
/**
* https://stackoverflow.com/questions/22781496/can-i-use-horizontal-scrollview-inside-a-viewpager-in-android
*/
@Override
protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
if (v instanceof HorizontalScrollView) {
return true;
}
return super.canScroll(v, checkV, dx, x, y);
}
}
子视图：view_pager_page.xml：
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center">
<HorizontalScrollView
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center">
<include layout="@layout/" />
</LinearLayout>
</HorizontalScrollView>
</LinearLayout>
</FrameLayout>
</RelativeLayout>
父视图：view_pager.xml
<android.support.design.widget.CoordinatorLayout>
...
<LinearLayout>
<packagepath.MyViewPager
android:layout_width="match_parent"
android:layout_height="wrap_content">
</packagepath.MyViewPager>
</LinearLayout>
...
<android.support.design.widget.CoordinatorLayout>
更新1 ：当覆盖'onInterceptTouchEvent'并让它始终返回true时，VP滚动，但HSV不会。我认为只有当HSV到达边缘时，这必须返回真的吗？如果是这种情况，我怎么能弄清楚这个方法呢？
更新2 ：我重建了android的触摸事件机制，希望能够深入了解如何拦截运动事件流。例如。在HSV中我可以简单地返回false以让VP消耗这个以及所有后续的运动事件。不幸的是，我需要两个MotionEvent.MOVE类型的运动事件来决定HSV或VP是否应该在到达边缘时滚动（如果HSV已经到达右边缘，右侧滑动向后滚动HSV并且向左滑动滚动到VP的下一页）。但是，如果我跳过MotionEvent.DOWN操作，HSV或VP都不会开始滚动......很难解决。有什么想法吗？
Touchevent Mechanism in Android
（警告：图片不完整且会包含错误，欢迎所有人更正： - ）
更新3 ：最后我明白了。理解Touchevent机制有很大帮助，也是ZeroOne的第一个评论。我有空的时候会发布我的解决方案。
答案 0 :(得分：0)
1.Extend ViewPager Class：
public class ViewPagerContainingHorizontalScrollView extends ViewPager {
private Float x_old;
private boolean bDoIntercept = false;
private boolean bHsvRightEdge = false;
private boolean bHsvLeftEdge = true;
public ViewPagerContainingHorizontalScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
private float calculateDistanceSwipe(MotionEvent ev){
float distance = 0;
if (x_old == null) {
x_old = ev.getX();
} else {
distance = ev.getX() - x_old;
x_old = null;
}
return distance;
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
mDoIntercept = false;
if(ev.getAction() == MotionEvent.ACTION_MOVE) {
float distance = calculateDistanceSwipe(ev);
if (distance < 0) {//scrolling left direction
if (bHsvRightEdge) { //HSV right edge
bDoIntercept = true;
//When scrolling slow VP may not switch page.
//Then HSV snaps back into old position.
//To allow HSV to scroll into non blocked direction set following to false.
bHsvRightEdge = false;
}
bHsvLeftEdge = false;//scrolling left means left edge not reached
} else if (distance > 0) {//scrolling right direction
if (bHsvLeftEdge) { //HSV left edge
bDoIntercept = true;
//When scrolling slow VP may not switch page.
//Then HSV snaps back into old position.
//To allow HSV to scroll into non blocked direction set following to false.
bHsvLeftEdge = false;
}
bHsvRightEdge = false;//scrolling right means right edge not reached
}
}
return super.dispatchTouchEvent(ev);
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
if(bDoIntercept){
return true;
}else{
return super.onInterceptTouchEvent(ev);
}
}
@Override
protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
if (v instanceof HorizontalScrollView) {
HorizontalScrollView hsv = (HorizontalScrollView) v;
int max_scrollX = hsv.getChildAt(0).getWidth() - hsv.getWidth();
int min_scrollX = 0;
int current_scroll_x = hsv.getScrollX();
if (current_scroll_x == max_scrollX) { //HSV right edge
bHsvRightEdge = true;
}
if (current_scroll_x == min_scrollX) { //HSV left edge
bHsvLeftEdge = true;
}
return true;
}
return super.canScroll(v, checkV, dx, x, y);
}
}
答案 1 :(得分：0)
我用一个自定义的HorizontalScrollView解决了这个问题。关键是要覆盖onTouchEvent（）方法，如果您在左侧边缘向右滑动，或者在右侧边缘向左滑动，则返回false。返回false表示此视图不使用touch事件，并且此事件可以使视图层次结构冒泡，由ViewPager处理。
public class HorizontalScrollViewForViewPager extends HorizontalScrollView {
float old_x, old_y;
public HorizontalScrollViewForViewPager(Context context) {
super(context);
}
public HorizontalScrollViewForViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
}
public HorizontalScrollViewForViewPager(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
int action = ev.getActionMasked();
if (action == MotionEvent.ACTION_DOWN) {
//Start of touch. Could be tap, could be drag.
old_x = ev.getX();
old_y = ev.getY();
} else if (action == MotionEvent.ACTION_MOVE) {
//Drag movement underway
float deltaX = ev.getX() - old_x;
float deltaY = ev.getY() - old_y;
if (Math.abs(deltaX) > Math.abs(deltaY)) {
//scrolling more left/right than up/down
if (deltaX > 0 && getScrollX() == 0) {
//dragging left, at left edge of HorizontalScrollView. Don't handle this touch event, let it bubble up to ViewPager
return false;
} else {
//dragging right. Use first child to determine width of content inside HorizontalScrollView
int childWidth = getChildAt(0).getWidth();
if (deltaX < 0 && (this.getScrollX() + this.getWidth()) >= childWidth) {
//swiping left, and at right edge of HorizontalScrollView. Don't handle this touch event, let it bubble up to ViewPager
return false;
}
}
}
}
return super.onTouchEvent(ev);
}
}