我是第一次使用片段。我正在尝试从片段中获取来自youtube的视频列表。我正在从Firebase检索YouTube网址，并从中提取播放列表ID。该播放列表ID作为参数传递给片段，然后片段将列出播放器中存在的所有视频。我可以成功检索片段中的播放列表ID，但网址中的ID更改为null。任何帮助都是可取的。在此先感谢。
CollegeGallery.java
public CollegeImageGrid imagegrid;
private static final String TAG = "CollegeGallery";
public GridView grid_image, grid_video;
public DatabaseReference ref;
private String collegeid;
private TextView moreimages, morevideos;
private String playlistid;
public void setPlayid(String playlistid) {
this.playlistid = playlistid;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_college_gallery);
ref = FirebaseDatabase.getInstance().getReference("collegedata");
//this will get the data from previous intent
collegeid = getIntent().getStringExtra("gallery");
grid_image = findViewById(R.id.grid_image);
// grid_video = findViewById(R.id.grid_video); //for grid view of videos
moreimages = findViewById(R.id.more_images);
morevideos = findViewById(R.id.more_videos);
//a list of string will be passed to imagegrid object
ref.child(String.valueOf(collegeid)).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
//object of College class to get getImageurls() which has the list of urls
College clg = dataSnapshot.getValue(College.class);
//setting the list to imagegrid, passing url from this activity to imageview.
imagegrid = new CollegeImageGrid(CollegeGallery.this,clg.getImageurls());
//setting adapter to grid with the list of urls
grid_image.setAdapter(imagegrid); //check error, getCount is null, crashes application.
//extracting playlist id
String playid = getYoutubeVideoId(clg.getVideourls());
//fragment code
YoutubeVideoList yt = new YoutubeVideoList();
FragmentTransaction tr = getSupportFragmentManager().beginTransaction();
tr.replace(R.id.youtube_frag, YoutubeVideoList.newInstance(playid)).commit();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(CollegeGallery.this, "No images", Toast.LENGTH_SHORT).show();
}
});
moreimages.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent image_in = new Intent(CollegeGallery.this,AllCollegeImages.class);
image_in.putExtra("image",collegeid);
startActivity(image_in);
}
});
//will take to activity with only playlist video list fragment
morevideos.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(CollegeGallery.this, CompleteVideoList.class));
}
});
}
//function to extract playlist id
public static String getYoutubeVideoId(String youtubeUrl) {
String video_id = "";
if (youtubeUrl != null && youtubeUrl.trim().length() > 0 && youtubeUrl.startsWith("http")) {
String expression = "^.*?(?:list)=(.*?)(?:&|$)";
CharSequence input = youtubeUrl;
Pattern pattern = Pattern.compile(expression, Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(input);
if (matcher.matches()) {
String groupIndex1 = matcher.group(1);
video_id = groupIndex1;
}
}
return video_id;
}
}
YoutubeVideoList.java（片段）
private static String ARG_Param1;
private static String id;
List<YoutubeVideoModel> vids;
Button btn;
YoutubeAdapter adapter;
RecyclerView recyclerView;
RecyclerView.LayoutManager manager;
String mparam1;
public YoutubeVideoList() {
}
//retrieving playlist id from the previous activity
public static YoutubeVideoList newInstance(String id) {
YoutubeVideoList yt = new YoutubeVideoList();
Bundle args = new Bundle();
args.putString(ARG_Param1, id);
yt.setArguments(args);
return yt;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mparam1 = getArguments().getString(ARG_Param1);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_youtube_video_list, container, false);
}
@Override
public void onViewCreated(View container, Bundle savedInstanceState) {
super.onViewCreated(container, savedInstanceState);
recyclerView = container.findViewById(R.id.vidReclycer);
manager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(manager);
recyclerView.setHasFixedSize(false);
id = mparam1;
//right here, id has the playlist id
System.out.println("this is the playlist id------------------->"+id);
String url = "https://www.googleapis.com/youtube/v3/playlistItems?key=AIzaSyBmISPZAjsrku2_yKLcTW4Y6qq6aqlht-0&playlistId="+id+"&part=snippet&maxResults=36";
//even url has the value but the list is not shown and id changes to null
System.out.println(url);
RequestQueue queue = Volley.newRequestQueue(getContext());
StringRequest request = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
vids = new ArrayList<>();
try {
JSONObject mainObject = new JSONObject(response);
JSONArray itemArray = (JSONArray) mainObject.get("items");
for (int i = 0; i < itemArray.length(); i++) {
String title = itemArray.getJSONObject(i).getJSONObject("snippet").getString("title");
String url = itemArray.getJSONObject(i).getJSONObject("snippet").getJSONObject("thumbnails").getJSONObject("maxres").getString("url");
String vidid = itemArray.getJSONObject(i).getJSONObject("snippet").getJSONObject("resourceId").getString("videoId");
YoutubeVideoModel vid = new YoutubeVideoModel(title, url, vidid);
vids.add(vid);
}
adapter = new YoutubeAdapter(getContext(), vids);
recyclerView.setAdapter(adapter);
recyclerView.getAdapter().notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// Log.e("Error in request", error.getMessage());
}
});
queue.add(request);
}
}
```this is the image of my logcat. It prints id and url as required, but then it changes to null
最佳答案
在您的CollegeGallery.java代替：yt.newInstance(playid)
写这个YoutubeVideoList.newInstance(playid)
如果没有用，还请从YoutubeVideoList片段中删除static String id