IllegalStateException in ViewPager with Views

[trofimchyk]

IllegalStateException (java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.) when navigate from the last page to the first page or from the first page to the last page.

[HeGanjie]

Cache the 2 extra view, this works for me:

private final List<ImageView> looperViews = new ArrayList<ImageView>(8);
SparseArray<ImageView> cache = new SparseArray<ImageView>(2);

@Override
public void destroyItem(ViewGroup container, int pos, Object object) {
    container.removeView((View) object);
}

@Override
public Object instantiateItem(ViewGroup container, int pos) {
    ImageView page = looperViews.get(pos);
    if (page.getParent() != null) {
        ImageView cachedView = (ImageView) cache.get(pos);
        if (cachedView == null) {
            cachedView = createView(page.getDrawable());
            cache.put(pos, cachedView);
        }
        container.addView(cachedView, 0);
        return cachedView;
    } else {
        container.addView(page, 0);
        return page;
    }
}

private ImageView createView(Drawable drawable) {
    ImageView imgView = (ImageView) inflater.inflate(R.layout.looping_item, null);
    imgView.setImageDrawable(drawable);
    return imgView;
}

[ihenk]

I have the same problem, after trying many ways, still could not solve the problem.

[HeGanjie]

@ihenk This is my current solution. I don't save views, it will create when it needed:

public final List<Map<String, Object>> looperItems;

@Override
public void destroyItem(ViewGroup container, int pos, Object object) {
    container.removeView((View) object);
}

@Override
public Object instantiateItem(ViewGroup container, int pos) {
    final ImageView v = new ImageView(ctx);
    v.setScaleType(ScaleType.FIT_XY);

    Map<String, Object> map = looperItems.get(pos);
    if (map == null) {
        v.setImageResource(R.drawable.img_ad_default);
    } else {
        String imgUrl = map.get("titleImg");
        Picasso.with(ctx).load(imgUrl).error(R.drawable.img_ad_default).into(v);
    }
    container.addView(v, 0);
    return v;
}

[ihenk]

👍 谢谢！这个问题折腾我一天了，终于搞定了。我有试过InfiniteViewPager，但是只支持四个Item以上才行，用了很多方法修改还是不行。同时，我也用了很多方法改LoopViewPager，但是还是没有成功。看你地址是佛山，所以就直接用中文了... :)

[ihenk]

@HeGanjie 你的方法好像有一些问题，我多次尝试后发现，会存在图片加载错位...

[HeGanjie]

@ihenk 贴代码看一下，又或者是你的 getCount() 有问题？

@Override
public int getCount() { return looperItems.size(); }

@Override
public boolean isViewFromObject(View arg0, Object arg1) { return arg0 == arg1; }

[ihenk]

public class NetworkViewPagerAdapter extends PagerAdapter {

private List<String> mUrls;
private DisplayImageOptions options;
protected ImageLoader imageLoader;
private ImageLoadingListener animateFirstListener;

public NetworkViewPagerAdapter(List<String> urls) {
    super();
    if (urls != null) {
        this.mUrls = urls;
    } else {
        this.mUrls = new ArrayList<String>();
    }
    options = DefaultDisplayImageOptions
            .getDefaultDisplayImageOptions(EduApplication.getInstance());
    animateFirstListener = new DefaultAnimateFirstDisplayListener();
    imageLoader = ImageLoader.getInstance();
}

@Override
public int getCount() {
    return mUrls.size();
}

@Override
public boolean isViewFromObject(View view, Object object) {
    return view == object;
}

@Override
public int getItemPosition(Object object) {
    return super.getItemPosition(object);
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    container.removeView((View) object);
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    ImageView view = new ImageView(EduApplication.getInstance());
    view.setScaleType(ScaleType.FIT_XY);
    view.setId(position);
    imageLoader.displayImage(mUrls.get(position), view, options,
            animateFirstListener);
    container.addView(view);
    return view;
}

}

[ihenk]

@HeGanjie 我用的是ImageLoader加载图片，options有设置默认图片的，所以这一块不会有问题...

[ihenk]

@HeGanjie public class DefaultDisplayImageOptions {
public static DisplayImageOptions getDefaultDisplayImageOptions(
Context context) {
//返回图片加载前的默认值
return new DisplayImageOptions.Builder()
.showImageOnLoading(R.drawable.ic_default)
.showImageForEmptyUri(R.drawable.ic_default)
.showImageOnFail(R.drawable.ic_default)
.cacheInMemory(true)
.cacheOnDisk(true)
.considerExifParams(true)
.displayer(
new RoundedBitmapDisplayer(context.getResources()
.getDimensionPixelSize(R.dimen.icon_rounded)))
.build();
}

}

[HeGanjie]

@ihenk 你先换回 android.support.v4.view.ViewPager，调通之后再替换回这个库。

[ihenk]

@HeGanjie 我试过了，用Android自带的ViewPager任何问题的...

[ihenk]

@HeGanjie 你有修改LoopPagerAdapterWrapper及LoopViewPager本身吗？

[HeGanjie]

@ihenk 没有哦 😖

[ihenk]

@HeGanjie 你那里有这个单独的DEMO吗？如果有的话，不知道是否方便发送一份至[email protected] (不方便的话，也没有关系的，还是谢谢你 :) )。主要这个已经搞了我一天了，今天其他什么也没有干，实在是不甘心>_< ...

[ihenk]

@HeGanjie 我发现一个规律是，如果未循环滚动的话，图片一直会显示正常，一旦循环滚动，就不正常了....

[HeGanjie]

@ihenk container.addView(view) 改成 container.addView(v, 0) 试试

[ihenk]

@HeGanjie 我找到原因了，

// mVpPictureHeader.setAdapter(new LoopPagerAdapterWrapper(adapter));之前用得是这包话，写错了
mVpPictureHeader.setAdapter(adapter);//正确

[TracyZhangLei]

can not call adapter.notifyDataSetChanged(), using setAdapter(new Adapter()) for instead

[OtzOrz]

@TracyZhangLei Thank you very much !

[goldingking]

The instantiateItem callback need return a new object but a reference to the same project twice, for there is reuse somewhere.
Just the first one and last position need to be reused, so we can return a new object for those.

in the instantiateItem method of your adapter, you can write like this:

if (position == 0) {
    first = new TextView(context);
    first.setText("" + position);
    container.addView(first);
    return first;
} else if (position == NUM_ITEMS - 1) {
    last = new TextView(context);
    last.setText("" + position);
    container.addView(last);
    return last;
} else {
    container.addView(views.get(position));
    return views.get(position);
}