我使用json webservices为recyclerview提供了一个自定义适配器。我必须逐个解析网址并使用onscrolllistener（）显示cardview。我的问题是，当我按下后退按钮并在我在最近的应用程序中打开（当时调用onResume时），它将仅显示在调用onPause时调用的URL。那么当我调用onResume时，如何刷新listview。
Thanks in Advance,
Here my code synepet..
public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private GridLayoutManager mGridManager;
private ProgressBar mProgressBar;
private static String url = "https://www.googleapis.com/youtube/v3/playlists?part=snippet&channelId=UCGyZswzm4G-wEfRQHgMSAuw&maxResults=50&key=AIzaSyCi0ApXYk08YpzyEO8jYJanaud-Epti6ks&pageToken=CDIQAQ";
JSONArray contacts = null;
private String mNextToken;
JSONObject jsonObj;
private boolean loading = true;
int visibleItemCount, totalItemCount, pastVisiblesItems;
private List<PlayListItem> mContactList = new ArrayList<PlayListItem>();
private PlayListItem mContact;
private Bundle mbundle;
String name2 = "Arasu";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
// Calling async task to get json
new GetContacts().execute();
mAdapter = new CardAdapter(MainActivity.this, mContactList);
mRecyclerView.setAdapter(mAdapter);
getScreenOrientation();
}
@Override
public void onResume() {
super.onResume();
}
@Override
protected void onPause() {
super.onPause();
System.out.println("Size2---->" + mContactList.size());
}
private class GetContacts extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Showing progress dialog
mProgressBar.setVisibility(View.VISIBLE);
mProgressBar.setMax(100);
}
@Override
protected Void doInBackground(Void... arg0) {
// Creating service handler class instance
ServiceHandler sh = new ServiceHandler();
// Making a request to url and getting response
String jsonArray = sh.makeServiceCall(url, ServiceHandler.GET);
//Log.d("Response: ", "> " + jsonArray);
if (jsonArray != null) {
try {
jsonObj = new JSONObject(jsonArray);
if (jsonObj.has("nextPageToken")) {
loading = true;
mNextToken = jsonObj.getString("nextPageToken");
} else {
loading = false;
}
// Getting JSON Array node
contacts = jsonObj.getJSONArray("items");
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
String title = c.getJSONObject("snippet").getString("title");
String time = c.getJSONObject("snippet").getString("publishedAt");
String playlist_id = c.get("id").toString();
// Find Screen size and set the Image for this size
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
double x = Math.pow(dm.widthPixels / dm.xdpi, 2);
double y = Math.pow(dm.heightPixels / dm.ydpi, 2);
double screenInches = Math.sqrt(x + y);
int inch = (int) Math.round(screenInches);
String image = null;
try {
if (inch <= 4) {
image = c.getJSONObject("snippet").getJSONObject("thumbnails").getJSONObject("medium").getString("url");
} else if (inch > 4 && inch <= 6) {
image = c.getJSONObject("snippet").getJSONObject("thumbnails").getJSONObject("medium").getString("url");
} else if (inch > 6 && inch <= 10) {
image = c.getJSONObject("snippet").getJSONObject("thumbnails").getJSONObject("medium").getString("url");
} else {
image = c.getJSONObject("snippet").getJSONObject("thumbnails").getJSONObject("default").getString("url");
}
} catch (IndexOutOfBoundsException e) {
e.printStackTrace();
}
mContact = new PlayListItem();
mContact.setmTitle(title);
mContact.setmID(playlist_id);
mContact.setmTime(time);
mContact.setmThumbnailURL(image);
mContact.setmNextToken(mNextToken);
mContactList.add(mContact);
}
} catch (JSONException e) {
e.printStackTrace();
}
} else {
Log.e("ServiceHandler", "Couldn't get any data from the url");
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
// Dismiss the progress dialog
if (mProgressBar.isShown())
mProgressBar.setVisibility(ProgressBar.GONE);
mAdapter.notifyDataSetChanged();
mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = mGridManager.getChildCount();
totalItemCount = mGridManager.getItemCount();
pastVisiblesItems = mGridManager.findFirstVisibleItemPosition();
if (loading) {
if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
Log.v("...", "Last Item Wow !");
if (jsonObj.has("nextPageToken")) {
url = "https://www.googleapis.com/youtube/v3/playlists?part=snippet&channelId=UCGyZswzm4G-wEfRQHgMSAuw&maxResults=50&key=AIzaSyCi0ApXYk08YpzyEO8jYJanaud-Epti6ks&pageToken=" + mNextToken;
System.out.println("url--->" + url);
new GetContacts().execute();
} else {
url = "https://www.googleapis.com/youtube/v3/playlists?part=snippet&channelId=UCGyZswzm4G-wEfRQHgMSAuw&maxResults=50&key=AIzaSyCi0ApXYk08YpzyEO8jYJanaud-Epti6ks&pageToken=" + mNextToken;
System.out.println("url----else--->" + url);
new GetContacts().execute();
}
loading = false;
}
}
}
});
}
}
}
public class CardAdapter extends RecyclerView.Adapter<CardAdapter.ViewHolder> {
private List<PlayListItem> mItems;
private Activity activity;
public ImageLoader imageLoader;
public CardAdapter(Activity activity, List<PlayListItem> items) {
this.activity = activity;
this.mItems = items;
imageLoader = new ImageLoader(activity.getApplicationContext());
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.recycler_outer_playlist_cardview, viewGroup, false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder viewHolder, final int i) {
System.out.println("Title Value is----------->"+mItems.get(0));
PlayListItem nature = mItems.get(i);
Log.d("Title Value is","----------->"+nature.getmTitle());
viewHolder.tvTitle.setText(nature.getmTitle());
final String playListID = nature.getmID();
final String thumnailsURL = nature.getmThumbnailURL();
final Calendar c = Calendar.getInstance();
int cur_year = c.get(Calendar.YEAR);
int cur_month = c.get(Calendar.MONTH) + 1;
int cur_day = c.get(Calendar.DAY_OF_MONTH);
int cur_hour = c.get(Calendar.HOUR_OF_DAY);
int cur_minute = c.get(Calendar.MINUTE);
// Getting updated date from url
String string = nature.getmTime();
String[] parts = string.split("-");
String part1 = parts[0]; // 004
String part2 = parts[1]; // 034556
String part3 = parts[2];
String[] part4 = part3.split("T");
String part5 = part4[0];
String part6 = part4[1];
// Toast.makeText(activity, "Given Date is : " + part1 + "/" + part2 + "/" + part3, Toast.LENGTH_LONG).show();
// Log.d("Updated Current Day", part5);
int giv_yr = Integer.parseInt(part1);
int giv_mnt = Integer.parseInt(part2);
int giv_day = Integer.parseInt(part5);
// Difference Two dates
int day_yr = 0, day_mnt = 0, day_day = 0;
if (cur_year >= giv_yr) {
if (cur_year >= giv_yr) {
day_yr = cur_year - giv_yr;
} else {
day_yr = giv_yr - cur_year;
}
if (cur_month >= giv_mnt) {
day_mnt = cur_month - giv_mnt;
} else {
day_mnt = giv_mnt - cur_month;
}
if (cur_day >= giv_day) {
day_day = cur_day - giv_day;
} else {
day_day = giv_day - cur_day;
}
}
String yr = Integer.toString(day_yr);
String mnt = Integer.toString(day_mnt);
String days = Integer.toString(day_day);
if (day_day == 0)
viewHolder.tvTime.setText("Updated Today");
else if (day_day < 7)
viewHolder.tvTime.setText("Updated " + days + " Days ago");
else if (day_day < 30) {
int week = day_day / 7;
String Week = Integer.toString(week);
viewHolder.tvTime.setText("Updated " + Week + " Weeks ago");
} else {
viewHolder.tvTime.setText("Updated " + mnt + " Months ago");
}
//imageLoader.DisplayImage(nature.getmThumbnailURL(), viewHolder.imgThumbnail);
Picasso.with(activity)
.load(nature.getmThumbnailURL())
/*.placeholder(R.drawable.my_thumnail)*/
.into(viewHolder.imgThumbnail);
viewHolder.item_view.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(activity, VideoPlayActivity.class);
intent.putExtra("PLAYLIST_ID", playListID);
intent.putExtra("THUMNAIL_URL", thumnailsURL);
v.getContext().startActivity(intent);
}
});
/*System.out.println("URL -------------->"+nature.getmThumbnailURL());
// String img_url = nature.getmThumbnailURL();
try {
URL url = new URL(nature.getmThumbnailURL());
Bitmap bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
System.out.println("Image bmp -------------->"+bmp);
//imageView.setImageBitmap(bmp);
viewHolder.imgThumbnail.setImageBitmap(bmp);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}*/
}
@Override
public int getItemCount() {
return mItems.size();
}
class ViewHolder extends RecyclerView.ViewHolder {
public ImageView imgThumbnail;
public TextView tvTitle;
public TextView tvID;
public TextView tvTime;
public View item_view;
public ViewHolder(View itemView) {
super(itemView);
imgThumbnail = (ImageView) itemView.findViewById(R.id.img_thumbnail);
tvTitle = (TextView) itemView.findViewById(R.id.tv_title);
//tvID = (TextView) itemView.findViewById(R.id.tv_id);
tvTime = (TextView) itemView.findViewById(R.id.tv_time);
item_view = itemView;
}
}
}
答案 0 :(得分：0)
I made a small mistake declaring String URL as static but it should be final also assign to another String variable. Finally set the adapter and notifyDataSetChanged where placed in onStart().
private final static String URL = "https://www.googleapis.com/youtube/v3/playlists?part=snippet&channelId=UCGyZswzm4G-wEfRQHgMSAuw&maxResults=50&key=AIzaSyCi0ApXYk08YpzyEO8jYJanaud-Epti6ks&pageToken=CDIQAQ";
private String url = URL;
JSONArray contacts = null;
private String mNextToken;
JSONObject jsonObj;
private boolean loading = true;
int visibleItemCount, totalItemCount, pastVisiblesItems;
private List<PlayListItem> mContactList;
private PlayListItem mContact;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
mRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
// Calling async task to get json
if (mContactList == null)
mContactList = new ArrayList<PlayListItem>();
System.out.println("onCreate :: Size2---->" + mContactList.size());
}
@Override
protected void onStart() {
super.onStart();
if (mContactList != null)
mContactList.clear();
url = URL;
new GetContacts().execute();
if (mAdapter == null)
mAdapter = new CardAdapter(MainActivity.this, mContactList);
mRecyclerView.setAdapter(mAdapter);
mAdapter.notifyDataSetChanged();
getScreenOrientation();
System.out.println("onStart :: Size2---->" + mContactList.size());
}
@Override
protected void onResume() {
ActivitySwitcher.animationIn(findViewById(R.id.container_first),
getWindowManager());
super.onResume();
System.out.println("onResume :: Size2---->" + mContactList.size());
mAdapter.notifyDataSetChanged();
}