我有3个片段，当我启动app所有片段从服务器同时获取数据时，但我需要一些像youtube view pager fragment
这样的东西当用户滑动标签然后片段开始从服务器下载数据时，
在我的情况下，所有片段都会在同一时间启动asynctask，所以如果你的互联网速度慢，那么应用程序就会停止运行
public class HeadLineFragment extends Fragment {
private static final String TAG = "RecyclerViewFragment";
private static final String KEY_LAYOUT_MANAGER = "layoutManager";
private static final int SPAN_COUNT = 2;
private static final int DATASET_COUNT = 60;
private static final String DW_HOME_PAGE_URL = "https://rss.dw.de/xml/rss-urd-all";
protected LayoutManagerType mCurrentLayoutManagerType;
protected RadioButton mLinearLayoutRadioButton;
protected RadioButton mGridLayoutRadioButton;
protected RecyclerView mRecyclerView;
protected RecyclerAdapter mAdapter;
protected RecyclerView.LayoutManager mLayoutManager;
protected ArrayList<String> titles = new ArrayList();
protected ArrayList<String> ImageURLS = new ArrayList<>();
protected ArrayList<String> description = new ArrayList();
protected ArrayList<RssItem> mDataset = new ArrayList<>();
private TextView textView;
private Context context;
private Elements metalinks;
private String mImageURL;
private Document documentImage;
private ProgressBar mProgressBar;
private int mItemNumber;
private myPagerAdupter _myPagerAdupter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
this._myPagerAdupter= new myPagerAdupter(getChildFragmentManager(),getContext());
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.head_line_fragment, container, false);
new LoadRssFeedsItems().execute(DW_HOME_PAGE_URL);
this.context = rootView.getContext();
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view);
mProgressBar = (ProgressBar) rootView.findViewById(R.id.Progressbar);
mProgressBar.setProgress(0);
LoadRssFeedsItems loadRssFeedsItems = new LoadRssFeedsItems();
loadRssFeedsItems.setCircularProgressView(mProgressBar);
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
if (savedInstanceState != null) {
mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
.getSerializable(KEY_LAYOUT_MANAGER);
}
setRecyclerViewLayoutManager(mCurrentLayoutManagerType);
return rootView;
}
public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
int scrollPosition = 0;
if (mRecyclerView.getLayoutManager() != null) {
scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
.findFirstCompletelyVisibleItemPosition();
}
switch (layoutManagerType) {
case GRID_LAYOUT_MANAGER:
mLayoutManager = new GridLayoutManager(getActivity(), SPAN_COUNT);
mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
break;
case LINEAR_LAYOUT_MANAGER:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
break;
default:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
}
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.scrollToPosition(scrollPosition);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
super.onSaveInstanceState(savedInstanceState);
}
private enum LayoutManagerType {
GRID_LAYOUT_MANAGER,
LINEAR_LAYOUT_MANAGER
}
private class LoadRssFeedsItems extends AsyncTask<String, Integer, String> {
private String mTitle, mDescription, mLink, mPubDate;
private ProgressBar circularProgressView;
public void setCircularProgressView(ProgressBar circularProgressView) {
this.circularProgressView = circularProgressView;
}
protected String doInBackground(String... urls) {
try {
Document rssDocument = Jsoup.connect(DW_HOME_PAGE_URL).timeout(Constants.TIME_OUT).ignoreContentType(true).parser(Parser.xmlParser()).get();
Elements mItems = rssDocument.select(Constants.ITEM);
RssItem rssItem;
mItemNumber = 0;
for (Element element : mItems) {
mItemNumber++;
mTitle = element.select("title").first().text();
mDescription = element.select("description").first().text();
mLink = element.select("link").first().text();
mPubDate = element.select("pubDate").first().text();
Log.i(TAG, "Item title: " + (mTitle == null ? "N/A" : mTitle));
Log.i(TAG, "Item Description: " + (mDescription == null ? "N/A" : mDescription));
Log.i(TAG, "Item link: " + (mLink == null ? "N/A" : mLink));
Log.i(TAG, "Item data: " + (mPubDate == null ? "N/A" : mPubDate));
Log.i(TAG, "Item image link: " + (mImageURL == null ? "N/A" : mImageURL));
Log.i(TAG, "item: : " + mItemNumber);
rssItem = new RssItem(mTitle, mDescription, mPubDate, mLink, mItemNumber, getContext());
mDataset.add(rssItem);
}
} catch (Exception e) {
e.printStackTrace();
}
return "d";
}
@Override
protected void onProgressUpdate(Integer... value) {
super.onProgressUpdate(value);
if (circularProgressView != null) {
circularProgressView.setProgress(value[0]);
}
}
protected void onPostExecute(String result) {
if (mDataset.isEmpty()) {
Snackbar mSnackbar = Snackbar.make(getView(), "Unable to connect Home page", Snackbar.LENGTH_LONG)
.setAction("RETRY", new View.OnClickListener() {
@Override
public void onClick(View view) {
new LoadRssFeedsItems().execute(Constants.HALAT_HAZRA);
}
});
mSnackbar.show();
} else {
mAdapter = new RecyclerAdapter(mDataset);
Log.i(TAG, "m data set size in current affairs: " + mDataset.size());
mRecyclerView.setAdapter(mAdapter);
getImageUrls get_ImageUrls = new getImageUrls();
get_ImageUrls.execute();
}
}
}
private class getImageUrls extends AsyncTask<Void, Void, Void> {
String mLink;
String mLastHalfUrl;
String url;
int dash_A_index;
@Override
protected void onPreExecute() {
Snackbar.make(getView(), "Loding Photos...", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
@Override
protected Void doInBackground(Void... params) {
Log.i(TAG, "Item image link in seacond thread: " + (mImageURL == null ? "N/A" : mImageURL));
try {
for (int i = 0; i < mDataset.size(); i++) {
Thread.sleep(50);
mLink = mDataset.get(i).getLink();
dash_A_index = mLink.indexOf(Constants.BACK_SLASH_A);
mLastHalfUrl = mLink.substring(dash_A_index);
url = mLink.replace(Constants.BASE_URL, "");
url = url.replace(mLastHalfUrl, "");
url = StringUtils.replaceEach(URLEncoder.encode(url, "UTF-8"), new String[]{"+", "*", "%7E"}, new String[]{"%20", "%2A", "~"});
StringBuilder sb = new StringBuilder(url);
url = sb.append(mLastHalfUrl).toString();
url = Constants.BASE_URL + url;
documentImage = Jsoup.connect(url).timeout(Constants.TIME_OUT).get();
metalinks = documentImage.select(Constants.MATA_PROPTY_IMAGE);
mImageURL = metalinks.attr(Constants.CONTENT);
Log.i(TAG, "Item image link in seacond thread home page: " + (mImageURL == null ? "N/A" : mImageURL));
mDataset.get(i).setImageUrl(mImageURL);
}
} catch (Exception e) {
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
Constants.IS_GET_IMAGE_URL=true;
mAdapter.notifyDataSetChanged();
}
}
}
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener, MaterialTabListener {
private Bitmap bitmap;
RecyclerView recyclerView;
private static final String TAG = "viewPge";
RecyclerView.LayoutManager layoutManager;
RecyclerView.Adapter RecyclerViewadapter;
MaterialTabHost tabHost;
private String[] tabs;
ViewPager mViewPager;
private FragmentManager fragmentManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setElevation(0);
tabs = getResources().getStringArray(R.array.tabs);
tabHost = (MaterialTabHost) this.findViewById(R.id.materialTabHost);
mViewPager = (ViewPager) this.findViewById(R.id.myViewPager);
this.mViewPager.setAdapter(new myPagerAdupter(getSupportFragmentManager(),getApplicationContext()));
this.mViewPager.setOffscreenPageLimit(2);
this.mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
tabHost.setSelectedNavigationItem(position);
}
});
for (int i = 0; i < 3; i++) {
tabHost.addTab(
tabHost.newTab().setText(tabs[i])
.setTabListener(this)
);
}
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
} else if (id == R.id.nav_gallery) {
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
@Override
public void onTabSelected(MaterialTab tab) {
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabReselected(MaterialTab tab) {
}
@Override
public void onTabUnselected(MaterialTab tab) {
}
public void addFragment() {
fragmentManager = getSupportFragmentManager();
android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
healthNewFragment recylerViewFragment = new healthNewFragment();
fragmentTransaction.replace(R.id.frag_contaner, recylerViewFragment, "TAG_FRAGEMENT");
// fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
}
片段2
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.context = getContext();
Log.i(TAG_LIFE, "Inside onCreat");
new LoadRssFeedsItems().execute(DW_HOME_PAGE_URL);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Log.i(TAG_LIFE, "Inside onViewCreated");
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.head_line_fragment, container, false);
this.context = rootView.getContext();
Log.i(TAG_LIFE, "Inside onCreateView");
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view);
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
if (savedInstanceState != null) {
mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
.getSerializable(KEY_LAYOUT_MANAGER);
}
setRecyclerViewLayoutManager(mCurrentLayoutManagerType);
return rootView;
}
public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
int scrollPosition = 0;
if (mRecyclerView.getLayoutManager() != null) {
scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
.findFirstCompletelyVisibleItemPosition();
}
switch (layoutManagerType) {
case GRID_LAYOUT_MANAGER:
mLayoutManager = new GridLayoutManager(getActivity(), SPAN_COUNT);
mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
break;
case LINEAR_LAYOUT_MANAGER:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
break;
default:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
}
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.scrollToPosition(scrollPosition);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
super.onSaveInstanceState(savedInstanceState);
}
private enum LayoutManagerType {
GRID_LAYOUT_MANAGER,
LINEAR_LAYOUT_MANAGER
}
private class LoadRssFeedsItems extends AsyncTask<String, Void, String> {
private String mTitle, mDescription, mLink, mPubDate;
protected String doInBackground(String... urls) {
try {
Document rssDocument = Jsoup.connect(Constants.HEALTH).timeout(Constants.TIME_OUT).ignoreContentType(true).parser(Parser.xmlParser()).get();
Document imageURLDocument;
Elements mItems = rssDocument.select(Constants.ITEM);
RssItem rssItem;
String mLastHalfUrl;
String url;
int dash_A_index;
int i = 0;
for (Element element : mItems) {
i++;
mTitle = element.select("title").first().text();
mDescription = element.select("description").first().text();
mLink = element.select("link").first().text();
mPubDate = element.select("pubDate").first().text();
Log.i(TAG, "Item title: " + (mTitle == null ? "N/A" : mTitle));
Log.i(TAG, "Item Description: " + (mDescription == null ? "N/A" : mDescription));
Log.i(TAG, "Item link: " + (mLink == null ? "N/A" : mLink));
Log.i(TAG, "Item data: " + (mPubDate == null ? "N/A" : mPubDate));
Log.i(TAG, "Item image link: " + (mImageURL == null ? "N/A" : mImageURL));
Log.i(TAG, "int i : " + i);
rssItem = new RssItem(mTitle, mDescription, mPubDate, mLink, i, getContext());
mDataset.add(rssItem);
}
} catch (Exception e) {
e.printStackTrace();
}
return "d";
}
protected void onPostExecute(String result) {
if (mDataset == null) {
Log.i(TAG, "Connecction time out");
Toast.makeText(getActivity(), "Connecction time ou)",
Toast.LENGTH_SHORT).show();
}
if (mDataset.isEmpty()) {
Snackbar mSnackbar = Snackbar.make(getView(), "Unable to connect Health", Snackbar.LENGTH_LONG)
.setAction("RETRY", new View.OnClickListener() {
@Override
public void onClick(View view) {
new LoadRssFeedsItems().execute(Constants.HALAT_HAZRA);
}
});
mSnackbar.show();
} else {
mAdapter = new RecyclerAdapter(mDataset);
Log.i(TAG, "m data set size: " + mDataset.size());
mRecyclerView.setAdapter(mAdapter);
getImageUrls get_ImageUrls = new getImageUrls();
get_ImageUrls.execute();
}
}
}
private class getImageUrls extends AsyncTask<Void, Void, Void> {
String mLink;
String mLastHalfUrl;
String url;
int dash_A_index;
@Override
protected Void doInBackground(Void... params) {
Log.i(TAG, "Item image link in seacond thread: " + (mImageURL == null ? "N/A" : mImageURL));
try {
for (int i = 0; i < mDataset.size(); i++) {
mLink = mDataset.get(i).getLink();
dash_A_index = mLink.indexOf(Constants.BACK_SLASH_A);
mLastHalfUrl = mLink.substring(dash_A_index);
url = mLink.replace(Constants.BASE_URL, "");
url = url.replace(mLastHalfUrl, "");
url = StringUtils.replaceEach(URLEncoder.encode(url, "UTF-8"), new String[]{"+", "*", "%7E"}, new String[]{"%20", "%2A", "~"});
StringBuilder sb = new StringBuilder(url);
url = sb.append(mLastHalfUrl).toString();
url = Constants.BASE_URL + url;
documentImage = Jsoup.connect(url).get();
metalinks = documentImage.select(Constants.MATA_PROPTY_IMAGE);
mImageURL = metalinks.attr(Constants.CONTENT);
Log.i(TAG, "Item image link in seacond thread: " + (mImageURL == null ? "N/A" : mImageURL));
mDataset.get(i).setImageUrl(mImageURL);
}
} catch (Exception e) {
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
mAdapter.notifyDataSetChanged();
}
}
答案 0 :(得分：0)
当片段可见时，通过添加以下方法并从CreateView中删除来调用异步任务。通过使用以下方法，只有在选中标签并且您的特定片段可见时，才会加载您的数据。
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
new LoadRssFeedsItems().execute(DW_HOME_PAGE_URL);
}
}