问题:
当我旋转设备时，我的应用程序中片段中包含的信息将重新加载。由于此应用程序从互联网中提取信息，这意味着在重新收集数据时一段时间内没有数据。
我的尝试:
我已经阅读了许多文章和 S/O 问题，它们给出了一些通用指针并尝试了它们的解决方案，从清单中的 android:configChanges="orientation|screenSize" 到在我的 MainActivity 和 FragmentActivity 中添加 setRetainInstance(true);。这两个解决方案都无法使我的片段不重新加载。我在应用程序中的另一个活动（详细活动，在用户选择新闻故事时激活）中使用了 android:configChanges 并且它在那里正常工作，可以防止活动重新加载。
我的应用程序结构:
这是一个简单的应用程序，从"Hacker News" API 中提取数据并向用户显示。用户可以使用NavigationDrawer选择不同的新闻类型。导航抽屉中的每个项目都是加载到 MainActivity.class 中的不同片段。这里涉及的片段是 HomeFragment.class，它加载主要新闻故事。
我为什么要在这里提问:
我似乎找不到任何适用于我当前应用程序结构的解决方案，因此我希望获得帮助，尝试找到解决这个看似琐碎（但令人困惑）问题的解决方案。
代码:
MainActivity.java
package com.material.tdapps.hackernews.activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import com.material.tdapps.hackernews.R;
public class MainActivity extends AppCompatActivity implements FragmentDrawer.FragmentDrawerListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar appToolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(appToolbar);
//noinspection ConstantConditions
getSupportActionBar().setDisplayShowHomeEnabled(true);
FragmentDrawer drawerFragment = (FragmentDrawer) getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
drawerFragment.setUp(R.id.fragment_navigation_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), appToolbar);
drawerFragment.setDrawerListener(this);
displayView(0);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
return id == R.id.action_settings || super.onOptionsItemSelected(item);
}
@Override
public void onDrawerItemSelected(View view, int position) {
displayView(position);
}
private void displayView(int position){
Fragment fragment = null;
String title = getString(R.string.app_name);
switch (position) {
case 0:
fragment = new HomeFragment();
title = getString(R.string.title_news);
break;
case 1:
fragment = new ShowFragment();
title = getString(R.string.title_show);
break;
case 2:
fragment = new AskFragment();
title = getString(R.string.title_ask);
break;
case 3:
fragment = new JobsFragment();
title = getString(R.string.title_job);
break;
default:
break;
}
if (fragment != null){
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.container_body, fragment);
fragmentTransaction.commit();
getSupportActionBar().setTitle(title);
}
}
}
HomeFragment.java
package com.material.tdapps.hackernews.activity;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import com.material.tdapps.hackernews.JSON.JSONNewsParser;
import com.material.tdapps.hackernews.R;
import com.material.tdapps.hackernews.model.StoryFeed;
import com.material.tdapps.hackernews.model.StoryItem;
import java.net.MalformedURLException;
public class HomeFragment extends Fragment {
StoryFeed storyFeed;
Context context;
ListView listView;
NewsListAdapter newsListAdapter;
public HomeFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_home, container, false);
setRetainInstance(true);
context = this.getActivity();
storyFeed = new StoryFeed();
newsListAdapter = new NewsListAdapter(this);
listView = (ListView) rootView.findViewById(R.id.newsListView);
if (savedInstanceState != null && (savedInstanceState.getSerializable("previousFeed") != null)) {
Log.e("NOTIFY >> ", "GOING TO BUNDLE");
storyFeed = (StoryFeed)savedInstanceState.getSerializable("previousFeed");
listView.setAdapter(newsListAdapter);
newsListAdapter.notifyDataSetChanged();
} else {
Log.e("NOTIFY >> ", "GOING TO ASYNCTASK");
new AsyncLoadNewsFeed().execute();
listView.setAdapter(newsListAdapter);
}
setRetainInstance(true);
return rootView;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
@Override
public void onDetach() {
super.onDetach();
}
private class AsyncLoadNewsFeed extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
JSONNewsParser newsParser = new JSONNewsParser();
storyFeed = newsParser.parseJSON("https://hacker-news.firebaseio.com/v0/topstories.json",0,30);
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if (storyFeed == null || storyFeed.getStoryCount() == 0){
StoryItem nullStoryItem = new StoryItem();
nullStoryItem.setTitle("ERROR: Null error!");
nullStoryItem.setNumberComments(0);
nullStoryItem.setScore(0);
nullStoryItem.setBodyText("NULL");
nullStoryItem.setTime(0);
nullStoryItem.setAuthor("NULL");
nullStoryItem.setUrl("http://www.google.com");
storyFeed.addStory(nullStoryItem);
}
newsListAdapter.notifyDataSetChanged();
}
}
class NewsListAdapter extends BaseAdapter {
private LayoutInflater layoutInflater;
public NewsListAdapter(HomeFragment homeFragment){
layoutInflater = (LayoutInflater) homeFragment.getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
@Override
public int getCount() {
return storyFeed.getStoryCount();
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
class listViewHolder {
TextView titleTxtV;
TextView timeTxtV;
TextView scoreTxtV;
TextView authorTxtV;
TextView domTxtV;
Button commentB;
RelativeLayout detailsLayout;
listViewHolder(View v) {
titleTxtV = (TextView) v.findViewById(R.id.titleText);
timeTxtV = (TextView) v.findViewById(R.id.timeText);
scoreTxtV = (TextView) v.findViewById(R.id.pointsText);
authorTxtV = (TextView) v.findViewById(R.id.authorText);
domTxtV = (TextView) v.findViewById(R.id.domainText);
commentB = (Button) v.findViewById(R.id.commentButton);
detailsLayout = (RelativeLayout) v.findViewById(R.id.newsDetailRelLayout);
}
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
View listItem = convertView;
listViewHolder holder;
if (listItem == null) {
listItem = layoutInflater.inflate(R.layout.news_item_layout, parent, false );
holder = new listViewHolder(listItem);
listItem.setTag(holder);
} else {
holder = (listViewHolder) listItem.getTag();
}
holder.titleTxtV.setText(storyFeed.getStory(position).getTitle());
holder.timeTxtV.setText("Posted " + storyFeed.getStory(position).getTime());
holder.authorTxtV.setText(" By " + storyFeed.getStory(position).getAuthor());
holder.scoreTxtV.setText(storyFeed.getStory(position).getScore() + " Points ");
holder.commentB.setText(Integer.toString(storyFeed.getStory(position).getNumberComments()));
try {
holder.domTxtV.setText("(" + storyFeed.getStory(position).getURLDomain() + ")");
} catch (MalformedURLException e) {
e.printStackTrace();
}
holder.commentB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent showComments = new Intent(getActivity(), CommentActivity.class);
getActivity().startActivity(showComments);
}
});
holder.detailsLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent showDetails = new Intent(getActivity(), DetailWebActivity.class);
Bundle detailsBundle = new Bundle();
//detailsBundle.putSerializable("newsFeed", storyFeed);
showDetails.putExtra("news",storyFeed);
showDetails.putExtras(detailsBundle);
showDetails.putExtra("position", position);
getActivity().startActivity(showDetails);
}
});
return listItem;
}
}
}
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.material.tdapps.hackernews" >
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/HackerNewsTheme" >
<activity
android:name=".activity.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".activity.CommentActivity"
android:label="@string/title_activity_comment"
android:parentActivityName=".activity.MainActivity"
android:configChanges="orientation|screenSize">
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.material.tdapps.hackernews.activity.MainActivity" />
</activity>
<activity
android:name=".activity.DetailWebActivity"
android:label="@string/title_activity_detail_web"
android:parentActivityName=".activity.MainActivity"
android:configChanges="orientation|screenSize">
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.material.tdapps.hackernews.activity.MainActivity" />
</activity>
</application>
</manifest>
if (savedInstanceState == null) { displayView(0); } else { //不执行任何操作 }- Tanishq dubey