Android 解析JSON url后,ArrayList似乎为空
我是android开发新手,但我正试图从stackoverflow的经验丰富的用户那里学到很多东西 我有一个小项目,我正在工作,我完全被封锁的原因 我遇到的问题是,当我解析json url并使用android volley库成功创建带有对象的PhotoList数组时,由于某种原因,当我将参数PhotoList传递给myPhotosAdapter()时,我最终得到了一个空数组:( 见下文 mAdapter=新的MyPhotosAdapter(photosList) 我的碎片类Android 解析JSON url后,ArrayList似乎为空,android,json,android-recyclerview,android-volley,Android,Json,Android Recyclerview,Android Volley,我是android开发新手,但我正试图从stackoverflow的经验丰富的用户那里学到很多东西 我有一个小项目,我正在工作,我完全被封锁的原因 我遇到的问题是,当我解析json url并使用android volley库成功创建带有对象的PhotoList数组时,由于某种原因,当我将参数PhotoList传递给myPhotosAdapter()时,我最终得到了一个空数组:( 见下文 mAdapter=新的MyPhotosAdapter(photosList) 我的碎片类 public cla
public class MyDetailFragment extends Fragment {
// Log tag
private static final String TAG = MyDetailFragment.class.getSimpleName();
public static final String ARG_ITEM_ID = "item_id";
protected RecyclerView mRecyclerView;
protected MyPhotosAdapter mAdapter;
protected RecyclerView.LayoutManager mLayoutManager;
protected LayoutManagerType mCurrentLayoutManagerType;
private List<Photo> photosList = new ArrayList<Photo>();
//empty constructor
public MyDetailFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments().containsKey(ARG_ITEM_ID)) {
Activity activity = this.getActivity();
CollapsingToolbarLayout appBarLayout = (CollapsingToolbarLayout) activity.findViewById(R.id.toolbar_layout);
if (appBarLayout != null) {
appBarLayout.setTitle("ID " + getArguments().getString(ARG_ITEM_ID));
}
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
//set the url for the got get the photos
String url = AppConstants.DETAILS_PHOTOS_URL + getArguments().getString(ARG_ITEM_ID);
View rootView = inflater.inflate(R.layout.main_detail, container, false);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view_photos);
mAdapter = new MyPhotosAdapter(photosList);
mRecyclerView.setAdapter(mAdapter);
mLayoutManager = new GridLayoutManager(getActivity(),2);
mRecyclerView.setLayoutManager(mLayoutManager);
// Creating volley request
JsonArrayRequest photosReq = new JsonArrayRequest(url,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
// Parsing json
for (int i = 0; i < response.length(); i++) {
try {
JSONObject obj = response.getJSONObject(i);
Photo p = new Photo();
p.setPhotoUrl(obj.getString("photo_url"));
// adding photo to photos array
photosList.add(p);
} catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getActivity(),
getString(R.string.msg_unknown_error),
Toast.LENGTH_LONG).show();
}
}
// notifying list adapter about data changes
// so that it renders the list view with updated data
//mAdapter.notifyDataSetChanged();
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
Toast.makeText(getActivity(),
getString(R.string.msg_fetch_photos_error),
Toast.LENGTH_LONG).show();
}
});
AppController.getInstance().addToRequestQueue(photosReq);
return rootView;
}
}
还有我的适配器类
public class MyPhotosAdapter extends RecyclerView.Adapter<MyPhotosAdapter.MyViewHolder> {
ImageLoader imageLoader = AppController.getInstance().getImageLoader();
private List<Photo> photosList;
public MyPhotosAdapter(List<Photo> photosList) {
this.photosList = photosList;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.photo_placeholder, parent, false);
return new MyViewHolder(view);
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
Photo p = photosList.get(position);
holder.photo_thumbnail.setImageUrl(p.getPhotoUrl(), imageLoader);
}
@Override
public int getItemCount() {
return photosList.size();
}
public class MyViewHolder extends RecyclerView.ViewHolder {
public NetworkImageView photo_thumbnail;
public MyViewHolder(View itemView) {
super(itemView);
photo_thumbnail = (NetworkImageView) itemView.findViewById(R.id.photo_thumbnail);
}
}
}
有人能告诉我上面的代码有什么问题吗?我已经尝试了我能想到的一切,但仍然没有成功:(:(
提前感谢您的帮助。您的评论被删除了
mAdapter.notifyDataSetChanged();
或者你可以初始化
mAdapter = new MyPhotosAdapter(photosList);
之后
for(int i=0;i
应该可以了。谢谢你收到错误了吗?JSON看起来像什么,你验证过了吗?非常感谢到目前为止的答案。不幸的是,我没有收到任何错误…我将URL记录到控制台,例如,从请求获取的响应对象和try{}的for循环中的photosList数组问题是,由于某种原因,当我试图将PhotoList数组作为参数传递给适配器时,url返回以下json[{“photo_url”:“”},{“photo_url”:“”}]
mAdapter.notifyDataSetChanged();
mAdapter = new MyPhotosAdapter(photosList);
for (int i = 0; i < response.length(); i++) {
try {
......
} catch (JSONException e) {
.....
}
}
mAdapter = new MyPhotosAdapter(photosList);
mRecyclerView.setAdapter(mAdapter);