当使用PagerAdapter的getPageWidth时,Android ViewPager滚动问题只有一个项目

Question

我有一个带有自定义PagerAdapter的ViewPager,它覆盖方法getPageWidth返回0.3f,所以我可以在屏幕上显示多个页面,如下面的博客所示:

http://commonsware.com/blog/2012/08/20/multiple-view-viewpager-options.html

在这种情况下,ViewPager开始为空,用户开始按要求填充页面(图像).图像从左到右填充.一切正常,页面是动态创建的,当有多个图像时,很容易在它们之间滑动.

但是,实例化的页面少于三页时会出现问题.从右侧(无内容)到左侧的滑动手势会产生闪烁,页面从左向右交替移动,就像ViewPager试图将第一页向右移动但稍后转向其原始位置一样.这在整个手势期间发生,并在离开手势时停止.正如我所说,当有足够的页面覆盖整个屏幕宽度并且需要真正的滚动时,这不会发生.

有任何想法吗？

Answer 1

I know this is an old question, but I was just looking for a solution and came across this link (which oddly references this question). Anyway, I was able to figure out a solution based on their comments. The basic idea is to allow touch events based on the state of a boolean flag which you set.

1. 在覆盖onInterceptTouchEvent和onTouchEvent时扩展ViewPager,只有在设置了标志时才调用super.我的班级看起来像这样:

   public class MyViewPager extends ViewPager {
   
       private boolean isPagingEnabled = false;
   
       public MyViewPager(Context context, AttributeSet attrs) {
           super(context, attrs);
       }
   
       public MyViewPager(Context context) {
           super(context);
       }
   
       @Override
       public boolean onInterceptTouchEvent(MotionEvent event) {
           if (isPagingEnabled) {
               return super.onInterceptTouchEvent(event);
           }
           return false;
       }
   
       @Override
       public boolean onTouchEvent(MotionEvent event) {
           if (isPagingEnabled) {
               return super.onTouchEvent(event);
           }
           return false;
       }
   
       public void setPagingEnabled(boolean pagingEnabled) {
           isPagingEnabled = pagingEnabled;
       }
   }
   

2. 在你的布局xml中,用com.yourpackage.MyViewPager元素替换你的com.android.support.v4.ViewPager元素.

3. 由于您在寻呼机适配器中从getPageWidth()返回0.3f,因此您希望在添加第四个项目时启用滚动.当你定义你的寻呼机适配器,并在适配器支持列表中添加或删除任何对象时,棘手的部分是在任何地方都有这行代码.

   mPager.setPagingEnabled(items.size() > 3);
   

Answer 2

Rahuls解决方案有效,但如果您想根据内容自动启用分页,您可以像这样修改ViewPager:

public class MyViewPager extends ViewPager {

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

public MyViewPager(Context context) {
    super(context);
}

@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
    if (canScrollHorizontally(1)||canScrollHorizontally(-1)) {
        return super.onInterceptTouchEvent(event);
    }

    return false;
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    if (canScrollHorizontally(1)||canScrollHorizontally(-1)) {
        return super.onTouchEvent(event);
    }

    return false;
}

}

现在,如果ViewPager是可滚动的,它将允许触摸,否则禁用.