I am new to Android development, trying to create my own app. It should display a particular YouTube Channel by using the YouTube Data API. I have started with the standard bottom navigation template in Android Studio and used the following project on Github for some start-up help. https://github.com/stressGC/Remake-YouTube-Android
I had to change a few things like the deprecated http call inside the code to keep it running with the new Android APKs. Everything seems fine from my point of view: I can see that the API content looks good and that each title / description / publishdate is placed in the according variables. There is also no error message in the log. When I start the emulator, the app is running fine. But as soon as I switch to the "Dashboard" fragment (where the code is placed), it is empty.
DashboardFragment.java
public class DashboardFragment extends Fragment {
private static String API_KEY = "hidden"; //normaler API key ohne limits, kein oauth
private static String CHANNEL_ID = "hidden";
private static String CHANNEL_GET_URL = "https://www.googleapis.com/youtube/v3/search?part=snippet&order=date&channelId="+CHANNEL_ID+"&maxResults=20&key="+API_KEY+"";
private RecyclerView mList_videos = null;
private VideoPostAdapter adapter = null;
private ArrayList<YouTubeDataModel> mListData = new ArrayList<>();
public DashboardFragment () {
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_dashboard, container, false);
mList_videos = (RecyclerView) view.findViewById(R.id.mList_videos);
initList(mListData);
new RequestYouTubeAPI().execute();
return view;
}
private void initList(ArrayList<YouTubeDataModel> mListData) {
mList_videos.setLayoutManager(new LinearLayoutManager(getActivity()));
adapter = new VideoPostAdapter(getActivity(), mListData);
mList_videos.setAdapter(adapter);
}
// create asynctask to get data from youtube
private class RequestYouTubeAPI extends AsyncTask<Void, String, String>{
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(Void... params) {
URL url = null;
String json = null;
StringBuffer sb = new StringBuffer();
try {
url = new URL(CHANNEL_GET_URL);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
//HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
HttpURLConnection urlConnection = NetCipher.getHttpsURLConnection(url);
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String inputLine = "";
while ((inputLine = br.readLine()) != null) {
sb.append(inputLine);
}
json = sb.toString();
return json;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
@Override
protected void onPostExecute(String response) {
super.onPostExecute(response);
if(response != null){
try {
JSONObject jsonObject = new JSONObject(response);
Log.e("response", jsonObject.toString());
mListData = parseVideoListFromResponse(jsonObject);
initList(mListData);
//adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
public ArrayList<YouTubeDataModel> parseVideoListFromResponse(JSONObject jsonObject) {
ArrayList<YouTubeDataModel> mList = new ArrayList<>();
if (jsonObject.has("items")) {
try {
JSONArray jsonArray = jsonObject.getJSONArray("items");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject json = jsonArray.getJSONObject(i);
if (json.has("id")) {
JSONObject jsonID = json.getJSONObject("id");
String video_id = "";
if (jsonID.has("videoId")) {
video_id = jsonID.getString("videoId");
}
if (jsonID.has("kind")) {
if (jsonID.getString("kind").equals("youtube#video")) {
YouTubeDataModel youtubeObject = new YouTubeDataModel();
JSONObject jsonSnippet = json.getJSONObject("snippet");
String title = jsonSnippet.getString("title");
String description = jsonSnippet.getString("description");
String publishedAt = jsonSnippet.getString("publishedAt");
String thumbnail = jsonSnippet.getJSONObject("thumbnails").getJSONObject("high").getString("url");
youtubeObject.setTitle(title);
youtubeObject.setDescription(description);
youtubeObject.setPublishedAt(publishedAt);
youtubeObject.setThumbnail(thumbnail);
youtubeObject.setVideo_id(video_id);
mList.add(youtubeObject);
}
}
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
return mList;
}
}
VideoPostAdapter.java
public class VideoPostAdapter extends RecyclerView.Adapter<VideoPostAdapter.YouTubePostHolder> {
private ArrayList<YouTubeDataModel> dataSet;
private Context mContext = null;
public VideoPostAdapter(Context mContext, ArrayList<YouTubeDataModel> dataSet) {
this.dataSet = dataSet;
this.mContext = mContext;
}
@NonNull
@Override
public YouTubePostHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.youtube_post_layout,parent,false);
YouTubePostHolder postHolder = new YouTubePostHolder(view);
return postHolder;
}
@Override
public void onBindViewHolder(@NonNull YouTubePostHolder holder, int position) {
// set the views here
TextView textViewTitle = holder.textViewTitle;
TextView textViewDes = holder.textViewDes;
TextView textViewDate = holder.textViewDate;
ImageView ImageThumb = holder.ImageThumb;
YouTubeDataModel object = dataSet.get(position);
textViewTitle.setText(object.getTitle());
textViewDes.setText(object.getDescription());
textViewDate.setText(object.getPublishedAt());
// image will be downloaded from url
}
@Override
public int getItemCount() {
return dataSet.size();
}
public static class YouTubePostHolder extends RecyclerView.ViewHolder{
TextView textViewTitle;
TextView textViewDes;
TextView textViewDate;
ImageView ImageThumb;
public YouTubePostHolder(@NonNull View itemView) {
super(itemView);
this.textViewTitle = (TextView) itemView.findViewById(R.id.textViewTitle);
this.textViewDes = (TextView) itemView.findViewById(R.id.textViewDes);
this.textViewDate = (TextView) itemView.findViewById(R.id.textViewDate);
this.ImageThumb = (ImageView) itemView.findViewById(R.id.ImageThumb);
}
}
}
YouTubeDataModel.java
public class YouTubeDataModel {
private String title = "";
private String description = "";
private String publishedAt = "";
private String thumbnail = "";
public String getVideo_id() {
return video_id;
}
public void setVideo_id(String video_id) {
this.video_id = video_id;
}
private String video_id = "";
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getPublishedAt() {
return publishedAt;
}
public void setPublishedAt(String publishedAt) {
this.publishedAt = publishedAt;
}
public String getThumbnail() {
return thumbnail;
}
public void setThumbnail(String thumbnail) {
this.thumbnail = thumbnail;
}
}
youtube_post_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="wrap_content">
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="200dp">
<ImageView
android:id="@+id/ImageThumb"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorPrimary"/>
<TextView
android:id="@+id/textViewDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="published at"
android:singleLine="true"
android:layout_alignParentRight="true"
android:layout_margin="5dp"
android:textColor="@android:color/white"
android:textSize="12dp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_margin="10dp"
android:orientation="vertical">
<TextView
android:id="@+id/textViewTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="video Title"
android:singleLine="true"
android:textColor="@android:color/white"
android:textSize="22dp"/>
<TextView
android:id="@+id/textViewDes"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="video description"
android:singleLine="true"
android:textColor="@android:color/white"
android:textSize="12dp"/>
</LinearLayout>
</RelativeLayout>
</LinearLayout>
fragment_dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/mList_videos"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
Unfortunately I have no idea why the fragment is still empty. And without any error in Android Studio log I really hope you can help me :/
Inside your RequestYouTubeAPI ASyncTask you have this error code:
} catch (IOException e) {
e.printStackTrace();
return null;
}
Then in onPostExecute you have the following:
@Override
protected void onPostExecute(String response) {
super.onPostExecute(response);
if(response != null){
try {
JSONObject jsonObject = new JSONObject(response);
Log.e("response", jsonObject.toString());
mListData = parseVideoListFromResponse(jsonObject);
initList(mListData);
//adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
Therefore if you get an error, you return null and if onPostExecute is given a null response it does nothing.
So this one place you could have an error and therefore a blank fragment.
Before you fix this, you can prove this is happening like so:
@Override
protected void onPostExecute(String response) {
super.onPostExecute(response);
if(response == null){
Log.e("TUT", "We did not get a response, not updating the UI.");
} else {
try {
JSONObject jsonObject = new JSONObject(response);
Log.e("response", jsonObject.toString());
mListData = parseVideoListFromResponse(jsonObject);
initList(mListData);
//adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}
You can fix this two ways:
in doInBackground change the catch to this:
} catch (IOException e) {
Log.e("TUT", "error", e);
// Change this JSON to match what the parse expects, so you can show an error on the UI
return "{\"yourJson\":\"error!\"}";
}
or onPostExecute:
if(response == null){
List errorList = new ArrayList();
// Change this data model to show an error case to the UI
errorList.add(new YouTubeDataModel("Error");
mListData = errorList;
initList(mListData);
} else {
try {
JSONObject jsonObject = new JSONObject(response);
Log.e("response", jsonObject.toString());
mListData = parseVideoListFromResponse(jsonObject);
initList(mListData);
//adapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
Hope that helps, there may be other errors in the code but this is one case that can happen if there is a problem with the API, the Json, the authorization, the internet etc.