所以这是我的问题，我只有一个活动来自我启动我的viewpager片段，在我的viewpager中我有4个包含recyclerViews的片段。每个片段包含由网络上的数据填充的项目，当我点击一个我得到一个WebView片段，但是当我点击后退按钮时我失去了我的poisiton，导致它重新创建整个活动。
我不知道如何不重新创建活动并恢复原来的位置，或者重新创建它但不改变项目的位置并重新回到原来的位置。这是我的代码。我应该放在哪里？！一些帮助非常好。 谢谢!!
我的活动类：
public class LauncherActivity extends AppCompatActivity implements ListFragment.OnNewSelectedInterface{
public static final String VIEWPAGER_FRAGMENT = "view_pager";
private ImageView mImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_launcher);
RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.activity_launcher);
mImageView = (ImageView) findViewById(R.id.logoImageView);
mImageView.startAnimation(AnimationUtils.loadAnimation(this, R.anim.rotate_indefinitely));
if(!isNetworkAvailable()){
alertUserAboutError();
} else {
relativeLayout.postDelayed(new Runnable() {
@Override
public void run() {
ViewPagerFragment savedFragment = (ViewPagerFragment)
getSupportFragmentManager().findFragmentByTag(VIEWPAGER_FRAGMENT);
if(savedFragment == null) {
ViewPagerFragment viewPagerFragment = new ViewPagerFragment();
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.activity_launcher, viewPagerFragment, VIEWPAGER_FRAGMENT);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
}
}, 2000);
}
}
@Override
public void onListNewSelected(int index, ArrayList<Articles> articles) {
WebViewFragment webViewFragment = new WebViewFragment();
Bundle bundle = new Bundle();
bundle.putInt(ViewPagerFragment.KEY_NEW_INDEX, index);
bundle.putParcelableArrayList(ListFragment.KEY_LIST, articles);
webViewFragment.setArguments(bundle);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.activity_launcher, webViewFragment, WebViewFragment.WEBVIEWFRAGMENT);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
private boolean isNetworkAvailable() {
ConnectivityManager manager = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
boolean isAvailable = false;
if (networkInfo != null && networkInfo.isConnected()) {
isAvailable = true;
}
return isAvailable;
}
private void alertUserAboutError() {
AlertDialogFragment alertDialogFragment = new AlertDialogFragment();
alertDialogFragment.show(getFragmentManager(), "error_dialog");
}
}
我的ViewPagerClass：
public class ViewPagerFragment extends Fragment {
public static final String KEY_NEW_INDEX = "key_new_index";
private ViewPager mViewPager;
private TabLayout mTabLayout;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.fragment_view_pager, container, false);
final OldFactFragment oldFactFragment = new OldFactFragment();
final SportFragment sportFragment = new SportFragment();
final BuzzFragment buzzFragment = new BuzzFragment();
final NewsFragment newsFragment = new NewsFragment();
mViewPager = (ViewPager) view.findViewById(R.id.viewPager);
mTabLayout = (TabLayout) view.findViewById(R.id.tabLayout);
mViewPager.setOffscreenPageLimit(4);
mViewPager.setAdapter(new FragmentPagerAdapter(getChildFragmentManager()) {
@Override
public Fragment getItem(int position) {
if(position == 0){
return oldFactFragment;
} else if (position == 1) {
return newsFragment;
} else if (position == 2){
return sportFragment;
} else return buzzFragment;
}
@Override
public CharSequence getPageTitle(int position) {
if(position == 0){
return "Pastly";
} else if (position == 1) {
return "politic";
} else if (position == 2){
return "sport";
} else return "buzz";
}
@Override
public int getCount() {
return 4;
}
});
mTabLayout.setupWithViewPager(mViewPager);
return view;
}
}
我的ListFragment（ViewPager中4个片段的父类）：
public abstract class ListFragment extends Fragment {
public static final String KEY_LIST = "key_list";
public interface OnNewSelectedInterface {
void onListNewSelected(int index, ArrayList<Articles> articles);
}
protected static final String TAG = ListFragment.class.getSimpleName();
protected ArrayList<Articles> mArticlesList;
protected ItemAdapter mArticleAdapter;
protected RecyclerView mRecyclerView;
protected OnNewSelectedInterface mListener;
protected RecyclerView.LayoutManager mManager;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
mListener = (OnNewSelectedInterface) getActivity();
View view = inflater.inflate(R.layout.fragment_list, container, false);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerview);
getInfos(getUrl());
return view;
}
protected abstract String[] getUrl();
private void getInfos(String[] url) {
if (isNetworkAvailable()) {
OkHttpClient client = new OkHttpClient();
for (int i = 0; i < getUrl().length; i++) {
Request request = new Request.Builder().url(url[i]).build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onResponse(Call call, Response response) throws IOException {
try {
String jsonData = response.body().string();
if (response.isSuccessful()) {
Log.v(TAG, jsonData);
getMultipleUrls(jsonData);
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
getCurrentArticles(mArticlesList);
}
});
} else {
alertUserAboutError();
}
} catch (IOException | JSONException e) {
e.printStackTrace();
}
}
@Override
public void onFailure(Call call, IOException e) {
getActivity().runOnUiThread(new Runnable() {
@Override
public void run() {
alertUserAboutError();
}
});
}
});
}
} else{
alertUserAboutError();
}
}
private void getMultipleUrls(String jsonData) throws JSONException {
if (mArticlesList == null) {
mArticlesList = getArticleForecast(jsonData);
} else {
mArticlesList.addAll(getArticleForecast(jsonData));
}
}
private void getCurrentArticles(ArrayList<Articles> articles) {
mArticleAdapter = new ItemAdapter(getActivity(), articles, mListener);
mRecyclerView.setAdapter(mArticleAdapter);
mManager = new LinearLayoutManager(getActivity());
mRecyclerView.setLayoutManager(mManager);
}
private boolean isNetworkAvailable() {
ConnectivityManager manager = (ConnectivityManager) getActivity().
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = manager.getActiveNetworkInfo();
boolean isAvailable = false;
if (networkInfo != null && networkInfo.isConnected()) {
isAvailable = true;
}
return isAvailable;
}
private void alertUserAboutError() {
AlertDialogFragment alertDialogFragment = new AlertDialogFragment();
alertDialogFragment.show(getActivity().getFragmentManager(), "error_dialog");
}
private ArrayList<Articles> getArticleForecast(String jsonData) throws JSONException {
JSONObject forecast = new JSONObject(jsonData);
JSONArray articles = forecast.getJSONArray("articles");
ArrayList<Articles> listArticles = new ArrayList<>(articles.length());
for (int i = 0; i < articles.length(); i++) {
JSONObject jsonArticle = articles.getJSONObject(i);
Articles article = new Articles();
String urlImage = jsonArticle.getString("urlToImage");
article.setTitle(jsonArticle.getString("title"));
article.setDescription(jsonArticle.getString("description"));
article.setImageView(urlImage);
article.setArticleUrl(jsonArticle.getString("url"));
listArticles.add(i, article);
}
return listArticles;
}
}
我的ItemAdapter（适配器类）：
public class ItemAdapter extends RecyclerView.Adapter<ItemAdapter.ArticleViewHolder> {
private final ListFragment.OnNewSelectedInterface mListener;
protected ArrayList<Articles> mArticlesList;
protected Context mContext;
private int mPosition;
private int lastPosition = -1;
public ItemAdapter(Context contexts, ArrayList<Articles> mArticleLi, ListFragment.OnNewSelectedInterface listener){
mContext = contexts;
mArticlesList = mArticleLi;
mListener = listener;
}
@Override
public ArticleViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item_linear, parent, false);
view.findViewById(R.id.textView).setSelected(true);
ArticleViewHolder articleViewHolder = new ArticleViewHolder(view);
articleViewHolder.setIsRecyclable(false);
return articleViewHolder;
}
@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
@Override
public void onBindViewHolder(ArticleViewHolder holder, int position) {
mPosition = position;
holder.bindArticle(mArticlesList.get(position));
setAnimation(holder.itemView, position);
holder.mImageView.setClipToOutline(true);
}
private void setAnimation(View viewToAnimate, int position) {
if (position > lastPosition) {
Animation animation = AnimationUtils.loadAnimation(viewToAnimate.getContext(), android.R.anim.slide_in_left);
viewToAnimate.startAnimation(animation);
lastPosition = position;
}
}
@Override
public int getItemCount() {
return mArticlesList.size();
}
public class ArticleViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener{
private TextView mTitle, mArticle;
private ImageView mImageView;
private ArticleViewHolder(View itemView) {
super(itemView);
mTitle = (TextView) itemView.findViewById(R.id.textView);
mArticle = (TextView) itemView.findViewById(R.id.showTextView);
mImageView = (ImageView) itemView.findViewById(R.id.imageView2);
itemView.setOnClickListener(this);
itemView.setOnLongClickListener(this);
}
private void bindArticle(Articles article) {
mTitle.setText(article.getTitle());
mArticle.setText(article.getDescription());
mArticle.setVisibility(View.INVISIBLE);
Glide.with(mContext).load(article.getImageView()).into(mImageView);
}
@Override
public void onClick(View view) {
mListener.onListNewSelected(getLayoutPosition(), mArticlesList);
}
@Override
public boolean onLongClick(View view) {
String desc = mArticlesList.get(getAdapterPosition()).getDescription();
mArticle.setVisibility(View.VISIBLE);
mArticle.setText(desc);
mArticle.postDelayed(new Runnable() {
public void run() {
mArticle.setVisibility(View.INVISIBLE);
}
}, 3000);
return true;
}
}
}
答案 0 :(得分：0)
在您的方法中onListNewSelected您正在使用旧行片段替换片段
fragmentTransaction.replace(R.id.activity_launcher, webViewFragment, WebViewFragment.WEBVIEWFRAGMENT);
替换添加到容器的现有片段。这与使用相同的containerViewId添加的所有当前添加的片段调用remove（Fragment），然后使用此处给出的相同参数添加（int，Fragment，String）基本相同。
所以你要移除旧的 Fragment 然后添加新的片段当你回来获取旧的片段时，它还没有从那里创建它将从刮擦，所以已经删除了片段的位置。
在使用add方法时，将新的片段添加到上一个片段上面，当您返回已经存在状态为“位置”的前一个片段