轮播图

最近几天忙着写项目，就没有时间来写文字了，今天抽点点空来记录这两天写的一个轮播图，说实在的真的很受伤，还是技术太差劲了！！！一个简单小小的轮播图写了几天，写出来全是bug，不是点点移动对不上就是不能向右滑动，最后可以向右滑动之后又出现没图片，我把bug一一贴出来，希望能帮助到看客。说明一下，最后还是用别人写好的现成代码修改一下用上了，不过在解决bug的过程中确实学到不少知识。
先贴上现在运行正常可用的代码：

导包省略。。。。。。

public class HomeFragment extends Fragment implements ViewPager.OnPageChangeListener {
public static final String URL = “http://spark.api.xiami.com/sdk?v=sdk&method=mobile.sdk-image&device_id=de717e77-6330-3c13-b601-e3c6228d4f16&api_key=bbf59448b1d2a0254d033bfe3b4d8a30&call_id=1443063251736&api_sig=5c29b6c2ffed24d7f5b481d7deb0511e“;
private ViewPager viewPager;
private LinearLayout linearLayout;
private List imageViewList;

private int currentIndex = 600-1; //初始值private long lastTime;private boolean isCyclical = true;private Handler handler = new Handler();Runnable r = new Runnable() {    @Override    public void run() {        if (isCyclical) {            if (System.currentTimeMillis() - lastTime > 2000) {                currentIndex++;                viewPager.setCurrentItem(currentIndex);                lastTime = System.currentTimeMillis();            }            //递归循环，图片切换速度3秒一张            handler.postDelayed(r, 3000);        }    }};private Gson gson;@Nullable@Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {    View inflate = inflater.inflate(R.layout.home_fragment, null);    viewPager = (ViewPager) inflate.findViewById(R.id.home_viewpager);    linearLayout = (LinearLayout) inflate.findViewById(R.id.ll_home_points);    gson = new Gson();    imageViewList = new ArrayList<>();    OkHttpUtils            .get()            .url(URL)            .build()            .execute(new StringCallback() {                @Override                public void onError(Call call, Exception e) {                }                @Override                public void onResponse(String response) {                    //拿到网络请求的数据                    doSomething(response);                }            });    return inflate;}private List<DataInfo.DataEntity.ImgsEntity> imgs;private void doSomething(String s) {    DataInfo info = gson.fromJson(s, DataInfo.class);    DataInfo.DataEntity entity = info.getData();    imgs = entity.getImgs();    for (int i = 0; i < imgs.size(); i++) {        ImageView imageView = new ImageView(getActivity());        imageView.setScaleType(ImageView.ScaleType.FIT_XY);        Glide.with(this)                .load(imgs.get(i).getPic_url_yasha())                .diskCacheStrategy(DiskCacheStrategy.ALL)                .into(imageView);        imageViewList.add(imageView);        ImageView dot = new ImageView(getActivity());        dot.setImageResource(R.drawable.point_selector1);        dot.setPadding(10, 5, 10, 5);        linearLayout.addView(dot);    }    gatData();}private void gatData() {    MyAdapter adapter = new MyAdapter();    viewPager.setAdapter(adapter);    viewPager.setCurrentItem(currentIndex);    viewPager.setOnPageChangeListener(this);    handler.post(r);}@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}@Overridepublic void onPageSelected(final int position) {    Log.e("位置：", position + "");    currentIndex = position;    int index = position % imageViewList.size();    setCurrentSelector(index);    lastTime = System.currentTimeMillis();}@Overridepublic void onPageScrollStateChanged(int state) {}private void setCurrentSelector(int index) {    for (int i = 0; i < linearLayout.getChildCount(); i++) {        ImageView child = (ImageView) linearLayout.getChildAt(i);        if (i == index) {            child.setImageResource(R.drawable.point_selector);        } else {            child.setImageResource(R.drawable.point_selector1);        }    }}class MyAdapter extends PagerAdapter {    @Override    public int getCount() {        return Integer.MAX_VALUE;  //最大值，可以认为无限大    }    @Override    public boolean isViewFromObject(View view, Object object) {        return view == object;    }    @Override    public Object instantiateItem(ViewGroup container, final int position) {        //在0~imageViewList.size()之间循环        int index = position % imageViewList.size();        if (imageViewList.size() > 0) {            View view = imageViewList.get(index);            if (container.equals(view.getParent())) {

// container.removeView(view);
}
container.addView(view);
return view;
}

        return null;    }    @Override    public void destroyItem(ViewGroup container, int position, Object object) {        int index = position % imageViewList.size();        container.removeView(imageViewList.get(index));    }}@Overridepublic void onDestroy() {    super.onDestroy();    handler.removeCallbacks(r);}

}
下面就把出现的bug贴一下，
项目框架是用fragment搭建的，加上轮播图后切换页面再回来就会出现崩溃，报的异常是：
问题原因：viewpager会有预加载的设置，切换的时候已经加载了一个父组件，不把以前的移除就回崩溃：

把instantiateItem方法里面改成这样bug就解决了：
position %= datas.size();
if (position<0){
position = datas.size()+position;
}
ImageView view = datas.get(position);

         ViewParent vp =view.getParent();           if (vp!=null){               ViewGroup parent = (ViewGroup)vp;               parent.removeView(view);           }           container.addView(view);             return view;  

下面开始贴出第二个神奇bug:

解决方法很简单，就是把destroyItem方法里代码去掉，什么都不写，完美解决！
public void destroyItem(ViewGroup container, int position, Object object) {

    }

由于我们在instantiateItem()方法中已经处理了remove的逻辑，因此这里并不需要处理。如果加上了remove的调用，则会出现ViewPager的内容为空的情况。

好了，纠结几天的轮播图终于写好了，可以开心的过十一了，大家十一快乐！