在应用程序中有导航抽屉，每个抽屉代表一个片段，每个片段都有一个AsyncTask来下载单独的数据。我正在通过这些代码更改碎片
private void setupNavigationDrawerContent(NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
switch (menuItem.getItemId()) {
case R.id.home_main:
menuItem.setChecked(true);
actionBar.setTitle("Home");
drawerLayout.closeDrawer(GravityCompat.START);
if(getSupportFragmentManager().findFragmentByTag("ranking")==null)
{
getSupportFragmentManager().beginTransaction().add(R.id.list_view_container,
new Home(), "ranking").
addToBackStack("ranking").
setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.commit();
}
else
{
getSupportFragmentManager().popBackStack("ranking", 0);
}
return true;
case R.id.national_events:
menuItem.setChecked(true);
actionBar.setTitle("National events");
drawerLayout.closeDrawer(GravityCompat.START);
if(getSupportFragmentManager().findFragmentByTag("ranking3")==null)
{
getSupportFragmentManager().beginTransaction().add(R.id.list_view_container,
new NationalEvents(), "ranking3").
addToBackStack("ranking3").
setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.commit();
}
else
{
getSupportFragmentManager().popBackStack("ranking3", 3);
}
return true;
case R.id.workshops:
menuItem.setChecked(true);
actionBar.setTitle("Workshops");
drawerLayout.closeDrawer(GravityCompat.START);
if(getSupportFragmentManager().findFragmentByTag("ranking4")==null)
{
getSupportFragmentManager().beginTransaction().add(R.id.list_view_container,
new Workshops(), "ranking4").
addToBackStack("ranking4").
setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
.commit();
}
else
{
getSupportFragmentManager().popBackStack("ranking4", 4);
}
return true;
用于下载数据的代码是
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View home_view = inflater.inflate(R.layout.list_view, container, false);
tf = Typeface.createFromAsset(getActivity().getAssets(), "fonts/cool_jazz.ttf");
swipeLayout = (SwipeRefreshLayout) home_view.findViewById(R.id.swipe_container);
swipeLayout.setColorSchemeColors(R.color.md_purple_500,
R.color.md_deep_purple_A400,
R.color.md_pink_500,
R.color.md_red_500);
mRecyclerView = (RecyclerView) home_view.findViewById(R.id.recycler_view);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mProgressBar = (ProgressBar) home_view.findViewById(R.id.progress_bar);
mProgressBar.setVisibility(View.VISIBLE);
mDescription=(TextView)home_view.findViewById(R.id.desription);
mDescription.setText(getString(R.string.national_events));
mDescription.setTypeface(tf);
iu1=(TextView)home_view.findViewById(R.id.iu1);
iu1.setTypeface(tf);
iu2=(TextView)home_view.findViewById(R.id.iu2);
iu2.setTypeface(tf);
iu3=(TextView)home_view.findViewById(R.id.iu3);
iu3.setTypeface(tf);
iu4=(TextView)home_view.findViewById(R.id.iu4);
iu4.setTypeface(tf);
iu5=(TextView)home_view.findViewById(R.id.iu5);
iu5.setTypeface(tf);
iu6=(TextView)home_view.findViewById(R.id.iu6);
iu6.setTypeface(tf);
internet=(RelativeLayout)home_view.findViewById(R.id.internet_unavailable);
internet.setVisibility(View.GONE);
Senturl = "http://javatechig.com/?json=get_recent_posts&count=45";
new MainActivityData().execute(Senturl);
swipeLayout.setOnRefreshListener(this);
return home_view;
}
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);setRetainInstance(true);
}
@Override
public void onRefresh() {
mProgressBar.setVisibility(View.GONE);
internet.setVisibility(View.GONE);
new MainActivityData().execute(Senturl);
}
public class MainActivityData extends AsyncTask<String,Void,Integer>
{
@Override
protected void onPreExecute() {
getActivity().setProgressBarIndeterminateVisibility(true);
}
@Override
protected Integer doInBackground(String... params) {
Integer result = 0;
HttpURLConnection urlConnection;
try {
URL url = new URL(params[0]);
urlConnection = (HttpURLConnection) url.openConnection();
int statusCode = urlConnection.getResponseCode();
// 200 represents HTTP OK
if (statusCode ==200 ) {
BufferedReader r = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder response = new StringBuilder();
String line;
while ((line = r.readLine()) != null) {
response.append(line);
}
parseResult(response.toString());
result = 1; // Successful
} else {
result = 0; //"Failed to fetch data!";
}
} catch (Exception e){
if(e.getLocalizedMessage()!=null){
Log.d(TAG, e.getLocalizedMessage());
}
}
return result; //"Failed to fetch data!";
}
@Override
protected void onPostExecute(Integer result) {
// Download complete. Let us update UI
mProgressBar.setVisibility(View.GONE);
swipeLayout.setRefreshing(false);
mDescription.setVisibility(View.GONE);
if (result == 1) {
new Thread(new Runnable() {
@Override
public void run() {
mAdapter = new MembersAdapter(getActivity(),membersList);
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
if (mAdapter != null)
{
mRecyclerView.setAdapter(mAdapter);
}}
});
}
}).start();
} else {
internet.setVisibility(View.VISIBLE);
}
}
}
private void parseResult(String result) {
try {
JSONObject response = new JSONObject(result);
JSONArray posts = response.optJSONArray("posts");
membersList = new ArrayList<>();
for (int i = 0; i < posts.length(); i++) {
JSONObject post = posts.optJSONObject(i);
Members item = new Members();
item.setTitle(post.optString("title"));
item.setThumbnail(post.optString("thumbnail"));
item.setDescription(post.optString("content"));
item.setDate(post.optString("date"));
//item.setSub_title(post.optString("sub_title"));
membersList.add(item);
}
} catch (JSONException e) {
e.printStackTrace();
}
}
事情工作正常但是当我在非常短的时间间隔内更改多个片段时，应用程序正在崩溃。我认为这一切都是由于给系统提供了很多AysncTasks。可能是想暂停AsyncTask。
答案 0 :(得分：0)
我建议将每个AsyncTask放在一个单独的非ui保留片段中（一个不包含任何视图的片段，并在setRetainInstance(true)中使用onCreate()方法进行初始化。{ {1}}会将数据加载到此片段中，并且在重新配置期间，由于AsyncTasks，它不会被销毁。然后，在重新配置之后，您可以从此片段中检索数据并按照您的意愿执行操作 - 填充适配器等等。