如果 ViewPager 滚动到最后一页之外，如何显示警报

Question

我有一个带有 3 个片段的 viewpager。如果我在视图寻呼机中滚动到最后一页之外，我需要显示祝酒词或提醒“没有更多可用页面”。

我尝试了很多，但没有任何帮助。

任何帮助都应该非常感谢。

我已经添加了代码sn-p，请通过它

ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {
      boolean callHappened;
      int selectedIndex;
      boolean mPageEnd;
    @Override
    public void onPageSelected(int position) {
        selectedIndex = position;
    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        // TODO Auto-generated method stub

        if( mPageEnd && arg0 == myViewPagerAdapter.getCount()-1 && !callHappened){
            Log.d(getClass().getName(), "Okay");
            mPageEnd = false;//To avoid multiple calls.
            callHappened = true;
        }else{
            mPageEnd = false;
        }
    }
    @Override
    public void onPageScrollStateChanged(int arg0) {
        // TODO Auto-generated method stub
        if(selectedIndex == myViewPagerAdapter.getCount() - 1)
        {
            mPageEnd = true;
        }
    }
};

Answer 1

您应该尝试为视图寻呼机制作自定义视图寻呼机类

    public class CustomViewPagerEndSwipe extends ViewPager {

    public CustomViewPagerEndSwipe(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    float mStartDragX;
    OnSwipeOutListener mListener;


    public void setOnSwipeOutListener(OnSwipeOutListener listener) {
        mListener = listener;
    }


    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        float x = ev.getX();
        switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mStartDragX = x;
            break;
        case MotionEvent.ACTION_MOVE:
            if (mStartDragX < x && getCurrentItem() == 0) {
                mListener.onSwipeOutAtStart();
            } else if (mStartDragX > x && getCurrentItem() == getAdapter().getCount() - 1) {
                mListener.onSwipeOutAtEnd();
            }
            break;
        }
        return super.onInterceptTouchEvent(ev);
    }

    public interface OnSwipeOutListener {
        public void onSwipeOutAtStart();
        public void onSwipeOutAtEnd();
    }
}

在你的布局xml中使用这个类

<com.utils.customview.CustomViewPagerEndSwipe
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            />

从您的活动和片段中实现侦听器，您将从界面获得最后一页吐司

viewPager.setOnSwipeOutListener(this);

Answer 2

使用了您的原始代码中的一些代码和@Mohit Suthar 中的代码，但是，如果用户尝试在第一页之前滑动，@Mohit Suthar 的答案将提供许多警报（原因是因为它不使用提问者的代码“callHappened”变量以避免多次调用）

如果用户在片段的上部区域向左滑动，则以下代码无法提供完美的工作。等待修改

我建议使用枚举来进行滑动操作，因为如果您有其他自定义逻辑，它会很灵活。

public class CustomViewPagerEndSwipe extends ViewPager {
    public CustomViewPagerEndSwipe(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    float mStartDragX;
    SwipeAction mSwipeAction;
    OnSwipeOutListener mListener;
    boolean callHappened = false;
    public void setOnSwipeOutListener(OnSwipeOutListener listener) {
        mListener = listener;
    }
    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        float x = ev.getX();
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mStartDragX = x;
                callHappened = false;
                break;
            case MotionEvent.ACTION_MOVE:
                if (!callHappened) {
                    if (mStartDragX < x && getCurrentItem() == 0) {
                        mSwipeAction = SwipeAction.BEFORE_START_PAGE;
                        mListener.onSwipe(mSwipeAction);
                        callHappened = true;
                    } else if (mStartDragX > x && getCurrentItem() == getAdapter().getCount() - 1) {
                        mSwipeAction = SwipeAction.AFTER_LAST_PAGE;
                        mListener.onSwipe(mSwipeAction);
                        callHappened = true;
                    }
                }
                break;
        }
        return super.onInterceptTouchEvent(ev);
    }
    public enum SwipeAction {
        BEFORE_START_PAGE, AFTER_LAST_PAGE
    }
    public interface OnSwipeOutListener {
        void onSwipe(SwipeAction pSwipeAction);
    }
}

您在活动/片段中调用的代码

viewPager.setOnSwipeOutListener(new CustomViewPagerEndSwipe.OnSwipeOutListener() {
    @Override
    public void onSwipe(CustomViewPagerEndSwipe.SwipeAction pSwipeAction) {
        switch (pSwipeAction) {
            case BEFORE_START_PAGE:
                new AlertDialog.Builder(getActivity()).setMessage("Swipe out start").create().show();
                break;
            case AFTER_LAST_PAGE:
                new AlertDialog.Builder(getActivity()).setMessage("Swipe out end").create().show();
                break;
        }
    }
});

Answer 3

更新自 @Mohit Suthar 的回答。在我的情况下，我使用吐司，我希望不那么敏感，希望少一些发生。

private final static long TIME_MS = 2000;
private final static long THRESHOLD = 50;

OnSwipeOutListener mListener;
float mStartDragX;

private boolean activated = false;
private Timer mTimer;
private TimerTask mTimerTask;

@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
    float x = ev.getX();
    switch (ev.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mStartDragX = x;
            break;
        case MotionEvent.ACTION_MOVE:
            Log.JSC("TEST", "1 : " + (mStartDragX < x - 20 && getCurrentItem() == 0));
            Log.JSC("TEST", "2 : " + (activated));
            Log.JSC("TEST", "3 : " + mStartDragX);
            Log.JSC("TEST", "4 : " + x);
            Log.JSC("TEST", "5 : " + (x - 20));

            if (mStartDragX < x - THRESHOLD && getCurrentItem() == 0) {
                if (!activated) {
                    activated = true;
                    prepareTimer();
                    mTimer.schedule(mTimerTask, TIME_MS);
                    if (mListener != null) {
                        mListener.onSwipeOutAtStart();
                    }
                }
            } else if (mStartDragX - THRESHOLD > x && getCurrentItem() == getAdapter().getCount() - 1) {
                if (!activated) {
                    activated = true;
                    prepareTimer();
                    mTimer.schedule(mTimerTask, TIME_MS);
                    if (mListener != null) {
                        mListener.onSwipeOutAtEnd();
                    }
                }
            }
            break;
    }
    try {
        return super.onInterceptTouchEvent(ev);
    } catch (IllegalArgumentException e) {
        return false;
    }
}

private void prepareTimer() {
    mTimer = new Timer();
    mTimerTask = new TimerTask() {
        @Override
        public void run() {
            activated = false;
        }
    };
}

Answer 4

您可以使用viewpager.canScrollHorizontally(View.SCROLL_AXIS_HORIZONTAL) 方法进行检查，如果它返回 false，那么您在查看寻呼机的最后一项。