我已经解决了项目（here）的最后一个问题，但是出现了一个新问题...
我将所需的类放在这里，以便或多或少的懒惰人都可以从那里读取内容。
第1步。启动应用程序
第2步。从导航栏中选择一个项目
第3步-错误。。数据未加载，没有任何显示。
第4步。从导航栏选择任何其他项目
第5步。一切正常。
基本上是第一次“不起作用”。步骤4之后，一切正常，直到我进行任何更改或重建应用程序为止。
MainActivity
public class MainActivity extends AppCompatActivity {
private DrawerLayout drawer;
private Handler mHandler;
private static final String TAG_00 = "home";
private static final String TAG_01 = "gui_yast";
private static final String TAG_02 = "gui_network";
private static final String TAG_03 = "gui_users";
private static final String TAG_04 = "gui_remote";
private static final String TAG_05 = "gui_disks";
private static final String TAG_06 = "gui_install";
private static final String TAG_07 = "gui_custom";
private static final String TAG_08 = "gui_gvim";
private static final String TAG_09 = "cli_fs";
private static final String TAG_10 = "cli_intro";
private static final String TAG_11 = "cli_vim";
private static final String TAG_12 = "cli_remote";
private static final String TAG_13 = "cli_init";
private static final String TAG_14 = "cli_process";
private static final String TAG_15 = "cli_users";
private static final String TAG_16 = "cli_software";
private static final String TAG_17 = "cli_admin";
private static final String TAG_18 = "cli_rescue";
public static String CURR_TAG = TAG_00;
private NavigationView navigationView;
public int navItemIndex = 0;
private String[] fragmentTitles;
boolean shouldLoadHomeOnBack = true;
Fragment fragment;
Utils u = Utils.getInstance();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
fragmentTitles = getResources().getStringArray(R.array.nav_fragment_titles);
mHandler = new Handler();
navigationView = findViewById(R.id.nav_view);
drawer = findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
setUpNavigationView();
if (savedInstanceState == null) {
navItemIndex = 0;
CURR_TAG = TAG_00;
loadHomeFragment();
}
}
public void loadHomeFragment() {
selectNavMenu();
setToolbarTitle();
if (getSupportFragmentManager().findFragmentByTag(CURR_TAG) != null) {
drawer.closeDrawers();
return;
}
Log.d("FragmentTransaction","Step before transaction");
Runnable pendingRunnable = new Runnable() {
@Override
public void run() {
Fragment fragment = getHomeFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
Log.d("FragmentTransaction","Transaction began");
fragmentTransaction.replace(R.id.frame_container, fragment, CURR_TAG);
fragmentTransaction.commitAllowingStateLoss();
Log.d("FragmentTransaction","Transaction "+CURR_TAG+" is finished");
}
};
mHandler.post(pendingRunnable);
drawer = findViewById(R.id.drawer_layout);
drawer.closeDrawers();
invalidateOptionsMenu();
}
private Fragment getHomeFragment() {
switch (navItemIndex) {
case 0:
u.setItemLoaded(0);
fragment = new HomeFragment();
return fragment;
default:
u.setItemLoaded(navItemIndex);
new AsyncListLoad(u.getURL(navItemIndex),this).execute();
fragment = new ContentFragment();
return fragment;
}
}
private void setToolbarTitle() {
getSupportActionBar().setTitle(fragmentTitles[navItemIndex]);
}
private void selectNavMenu() {
navigationView.getMenu().getItem(navItemIndex).setChecked(false);
}
private void setUpNavigationView() {
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
int id = item.getItemId();
switch (id) {
case R.id.nav_home:
navItemIndex = 0;
CURR_TAG = TAG_00;
break;
case R.id.gui_yast:
navItemIndex = 1;
CURR_TAG = TAG_01;
break;
case R.id.gui_network:
navItemIndex = 2;
CURR_TAG = TAG_02;
break;
case R.id.gui_users:
navItemIndex = 3;
CURR_TAG = TAG_03;
break;
// There's 18, so I'll skip them
}
loadHomeFragment();
return true;
}
});
}
@Override
public void onBackPressed() {
DrawerLayout drawer = findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawers();
return;
}
// This code loads home fragment when back key is pressed
// when user is in other fragment than home
if (shouldLoadHomeOnBack) {
// checking if user is on other navigation menu
// rather than home
if (navItemIndex != 0) {
navItemIndex = 0;
CURR_TAG = TAG_00;
loadHomeFragment();
return;
}
}
super.onBackPressed();
}
@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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
实用程序
public class Utils {
private static final Utils ourInstance = new Utils();
public static Utils getInstance() {
return ourInstance;
}
private Utils() {
}
public ArrayList<String> subURL = new ArrayList<>();
public String getSubURL(int i) {
return subURL.get(i);
}
public void addSubURL(String subURL, int stringIndex) {
this.subURL.add(stringIndex,subURL);
}
public void clearSubList() {
subURL.clear();
}
public int itemLoaded;
public int subItemLoaded;
private ArrayList<DataItem> dataSet = new ArrayList<>();
private ArrayList<Article> articleSet = new ArrayList<>();
public void setItemLoaded(int itemLoaded) {
this.itemLoaded = itemLoaded;
}
public int getItemLoaded() {
return itemLoaded;
}
public void setDataSet(ArrayList<DataItem> dataSet) {
this.dataSet = dataSet;
}
public ArrayList<DataItem> getDataSet() {
return dataSet;
}
public ArrayList<Article> getArticleSet() {
return articleSet;
}
public void setArticleSet(ArrayList<Article> articleSet) {
this.articleSet = articleSet;
}
public int getSubItemLoaded() {
return subItemLoaded;
}
public void setSubItemLoaded(int subItemLoaded) {
this.subItemLoaded = subItemLoaded;
}
public String getURL(int itemLoaded) {
switch (itemLoaded) {
case 1:
return "http://susehowto.dx.am/gui/yast";
case 2:
return "http://susehowto.dx.am/gui/network";
case 3:
return "http://susehowto.dx.am/gui/users";
case 4:
return "http://susehowto.dx.am/gui/remote";
case 5:
return "http://susehowto.dx.am/gui/disks";
case 6:
return "http://susehowto.dx.am/gui/install";
case 7:
return "http://susehowto.dx.am/gui/custom";
case 8:
return "http://susehowto.dx.am/gui/gvim";
case 9:
return "http://susehowto.dx.am/cli/fs";
case 10:
return "http://susehowto.dx.am/cli/intro";
case 11:
return "http://susehowto.dx.am/cli/vim";
case 12:
return "http://susehowto.dx.am/cli/remote";
case 13:
return "http://susehowto.dx.am/cli/init";
case 14:
return "http://susehowto.dx.am/cli/process";
case 15:
return "http://susehowto.dx.am/cli/users";
case 16:
return "http://susehowto.dx.am/cli/software";
case 17:
return "http://susehowto.dx.am/cli/admin";
case 18:
return "http://susehowto.dx.am/cli/rescue";
default:
return "";
}
}
}
AsyncListLoad
public class AsyncListLoad extends AsyncTask<String,Void,ArrayList<DataItem>> {
private Activity activity;
private String target_url;
private ArrayList<DataItem> dataSet;
private Utils u = Utils.getInstance();
private ProgressDialog dialog;
public AsyncListLoad(String url, Activity activity) {
this.activity = activity;
dialog = new ProgressDialog(activity);
this.target_url = url;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog.setIndeterminate(false);
dialog.setMessage("Ładowanie zawartości");
dialog.setCancelable(false);
dialog.show();
}
@Override
protected ArrayList<DataItem> doInBackground(String... strings) {
dataSet = new ArrayList<>();
try {
Document mSectionDocument = Jsoup.connect(target_url).get();
Elements mElementSectionSize = mSectionDocument.select("div[class=section]");
int mElementSize = mElementSectionSize.size();
u.clearSubList();
for (int i=0; i < mElementSize; i++) {
Elements mElementSectionTitle = mSectionDocument.select("span[class=section-name]").select("a").eq(i);
String mSectionTitle = mElementSectionTitle.text();
Elements sectionLinks = mSectionDocument.select("span[class=section-name]").select("a").eq(i);
String sectionLink = sectionLinks.attr("href");
u.addSubURL(sectionLink,i);
Elements mElementSectionDesc = mSectionDocument.select("span[class=section-desc]").eq(i);
String mSectionDesc = mElementSectionDesc.text();
if(i>9)u.addSubURL(target_url+"/section_"+(i+1),i);
else u.addSubURL(target_url+"/section_0"+(i+1),i);
dataSet.add(new DataItem(mSectionTitle,mSectionDesc));
Log.d("DataItemCreation","Item no. "+i+" added");
Log.d("DataItemCreation","Link: "+u.getSubURL(i));
Log.d("DataItemCreation","Item title: "+dataSet.get(i).getTopicTitle());
Log.d("DataItemCreation","Item description: "+dataSet.get(i).getTopicDesc());
}
publishProgress();
} catch (HttpStatusException h) {
Toast.makeText(activity,"Network error",Toast.LENGTH_SHORT).show();
} catch (IOException e) {
e.printStackTrace();
}
return dataSet;
}
@Override
protected void onPostExecute(ArrayList<DataItem> arrayList) {
arrayList = this.dataSet;
u.setDataSet(arrayList);
Log.d("DataSetup","DataSet acquired and loaded.");
dialog.dismiss();
RecyclerView recyclerView = activity.findViewById(R.id.content_rv);
ContentAdapter adapter = (ContentAdapter) recyclerView.getAdapter();
adapter.notifyDataSetChanged();
}
}
ContentFragment
public class ContentFragment extends Fragment {
public ContentAdapter adapter;
Utils u = Utils.getInstance();
private static final String TAG = "ContentFragment";
protected ArrayList<DataItem> dataSet;
protected RecyclerView.LayoutManager lm;
protected RecyclerView recyclerView;
public ContentFragment() {
//empty public constructor
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
initData();
adapter = new ContentAdapter(dataSet, getActivity());
lm = new LinearLayoutManager(getActivity());
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable final ViewGroup container, Bundle savedInstanceState) {
final View v = inflater.inflate(R.layout.content_fragment,container,false);
v.setTag(TAG);
recyclerView = v.findViewById(R.id.content_rv);
setCustomAdapter(recyclerView, lm, adapter);
final SwipeRefreshLayout rLayout = v.findViewById(R.id.content_swipe);
rLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
rLayout.setRefreshing(true);
Toast.makeText(getActivity(),"Refreshed!",Toast.LENGTH_SHORT).show();
rLayout.setRefreshing(false);
}
});
return v;
}
private void initData() {
dataSet = u.getDataSet();
}
public void setCustomAdapter(RecyclerView recyclerView, RecyclerView.LayoutManager layoutManager, ContentAdapter adapter) {
recyclerView.removeAllViews();
Log.d("Fragment","RecyclerView added");
recyclerView.setLayoutManager(layoutManager);
Log.d("Fragment","LayoutManager is set");
recyclerView.setAdapter(adapter);
Log.d("Fragment","Adapter is set");
adapter.notifyDataSetChanged();
}
}
ContentAdapter
public class ContentAdapter extends RecyclerView.Adapter<ContentAdapter.ContentViewHolder> {
private ArrayList<DataItem> dataSet;
Utils u = Utils.getInstance();
private Context context;
public ContentAdapter(ArrayList<DataItem> itemSet, Context context) {
this.context = context;
this.dataSet = itemSet;
}
@Override
public long getItemId(int position) {
return super.getItemId(position);
}
@NonNull
@Override
public ContentAdapter.ContentViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.data_item,parent,false);
final ContentViewHolder vHolder = new ContentViewHolder(v);
vHolder.itemLayout.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.d("SubItemClick","Item "+vHolder.getAdapterPosition()+" is clicked!");
u.setSubItemLoaded(vHolder.getAdapterPosition());
Intent run = new Intent(context,DynamicActivity.class);
Bundle fragData = new Bundle();
fragData.clear();
fragData.putString("link",u.getSubURL(vHolder.getAdapterPosition()));
fragData.putInt("ClickedID",vHolder.getAdapterPosition());
run.putExtras(fragData);
context.startActivity(run);
}
});
return vHolder;
}
@Override
public void onBindViewHolder(@NonNull ContentViewHolder holder, int position) {
holder.topicTitle.setText(dataSet.get(position).getTopicTitle());
holder.topicDesc.setText(dataSet.get(position).getTopicDesc());
Log.d("ViewHolderSetup","ViewHolder is bind");
}
@Override
public int getItemCount() {
return dataSet.size();
}
public static class ContentViewHolder extends RecyclerView.ViewHolder {
public CardView itemLayout;
public TextView topicTitle;
public TextView topicDesc;
public ContentViewHolder(View itemView) {
super(itemView);
itemLayout = itemView.findViewById(R.id.dataitem_container);
topicTitle = itemView.findViewById(R.id.topic_title);
topicDesc = itemView.findViewById(R.id.topic_desc);
}
}
}
答案 0 :(得分：0)
@ADM提供的解决方案（问题下方的评论）：数据加载后，需要提供回调，以便应用程序能够填充已加载的内容。
从本质上讲，我创建了一个名为OnDataLoadListener的接口，并在其中放置了onDataLoadListener空隙（注意大小写，这对于创建此类接口很重要）。然后，在加载数据时，我在ContentAdapter内将此空称为填充数据。
无论如何，我都会尽快上传代码-感谢您的帮助，因为问题已解决！