@nonnull错误在填充器（inflater）时出现，有人可以解决这个错误吗？ 我是Android的新手，不知道如何解决这个错误，请问有什么解决办法吗？是主题或其他问题导致的错误吗？我的代码是否存在严重问题？请您帮忙解决此错误。由于这个错误，我的代码无法正常工作。非常感谢您的帮助。
我的代码中的导入如下所示：
import android.content.Context;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.app.DownloadManager;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.support.annotation.Nullable;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.support.v7.widget.DividerItemDecoration;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import java.util.List;
import android.support.annotation.Nullable;
import android.util.Log;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import android.widget.ImageButton;
import android.widget.ProgressBar;
import static android.content.Context.DOWNLOAD_SERVICE;
import java.lang.reflect.Type;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.ref.WeakReference;
import java.lang.reflect.Type;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
public class FilesListingFragment extends android.support.v4.app.Fragment {
private static final String TAG = "FilesListingFragment";
public static final String PATH_FILES = "http://%s:%s/files";
public static final String PATH_STATUS = "http://%s:%s/status";
public static final String PATH_FILE_DOWNLOAD = "http://%s:%s/file/%s";
private String mSenderIp = null, mSenderSSID;
private ContactSenderAPITask mUrlsTask;
private ContactSenderAPITask mStatusCheckTask;
private String mPort, mSenderName;
static final int CHECK_SENDER_STATUS = 100;
static final int SENDER_DATA_FETCH = 101;
RecyclerView file;
ProgressBar progressBar;
TextView mTextView;
private SenderFilesListingAdapter mFilesAdapter;
private UiUpdateHandler uiUpdateHandler;
private static final int SENDER_DATA_FETCH_RETRY_LIMIT = 3;
private int senderDownloadsFetchRetry = SENDER_DATA_FETCH_RETRY_LIMIT, senderStatusCheckRetryLimit = SENDER_DATA_FETCH_RETRY_LIMIT;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_files_listing, null);
file = (RecyclerView) v.findViewById(R.id.files_list);
progressBar = (ProgressBar) v.findViewById(R.id.loading);
mTextView = (TextView) v.findViewById(R.id.empty_listing_text);
mTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
mTextView.setVisibility(View.GONE);
progressBar.setVisibility(View.VISIBLE);
fetchSenderFiles();
}
});
file.setLayoutManager(new LinearLayoutManager(getActivity()));
file.addItemDecoration(new DividerItemDecoration(getResources().getDrawable(R.drawable.lidivider)));/**here is the error */
mFilesAdapter = new SenderFilesListingAdapter(new ArrayList<String>());
file.setAdapter(mFilesAdapter);
uiUpdateHandler = new UiUpdateHandler(this);
return v;
}
public static FilesListingFragment getInstance(String senderIp, String ssid, String senderName, String port) {
FilesListingFragment fragment = new FilesListingFragment();
Bundle data = new Bundle();
data.putString("senderIp", senderIp);
data.putString("ssid", ssid);
data.putString("name", senderName);
data.putString("port", port);
fragment.setArguments(data);
return fragment;
}
@Override
public void onAttach(Context activity) {
super.onAttach(activity);
if (null != getArguments()) {
mSenderIp = getArguments().getString("senderIp");
mSenderSSID = getArguments().getString("ssid");
mPort = getArguments().getString("port");
mSenderName = getArguments().getString("name");
Log.d(TAG, "sender ip: " + mSenderIp);
}
}
@Override
public void onResume() {
super.onResume();
fetchSenderFiles();
checkSenderAPIAvailablity();
}
private void fetchSenderFiles() {
progressBar.setVisibility(View.VISIBLE);
if (null != mUrlsTask)
mUrlsTask.cancel(true);
mUrlsTask = new ContactSenderAPITask(SENDER_DATA_FETCH);
mUrlsTask.execute(String.format(PATH_FILES, mSenderIp, mPort));
}
private void checkSenderAPIAvailablity() {
if (null != mStatusCheckTask)
mStatusCheckTask.cancel(true);
mStatusCheckTask = new ContactSenderAPITask(CHECK_SENDER_STATUS);
mStatusCheckTask.execute(String.format(PATH_STATUS, mSenderIp, mPort));
}
@Override
public void onPause() {
super.onPause();
if (null != mUrlsTask)
mUrlsTask.cancel(true);
}
@Override
public void onDestroy() {
super.onDestroy();
if (null != uiUpdateHandler)
uiUpdateHandler.removeCallbacksAndMessages(null);
if (null != mStatusCheckTask)
mStatusCheckTask.cancel(true);
}
public String getSenderSSID() {
return mSenderSSID;
}
public String getSenderIp() {
return mSenderIp;
}
private void loadListing(String contentAsString) {
Type collectionType = new TypeToken<List<String>>() {
}.getType();
ArrayList<String> files = new Gson().fromJson(contentAsString, collectionType);
progressBar.setVisibility(View.GONE);
if (null == files || files.size() == 0) {
mTextView.setText("No Downloads found.\n Tap to Retry");
mTextView.setVisibility(View.VISIBLE);
} else {
mTextView.setVisibility(View.GONE);
mFilesAdapter.updateData(files);
}
}
private void onDataFetchError() {
progressBar.setVisibility(View.GONE);
mTextView.setVisibility(View.VISIBLE);
mTextView.setText("Error occurred while fetching data.\n Tap to Retry");
}
private long postDownloadRequestToDM(Uri uri, String fileName) {
// Create request for android download manager
DownloadManager downloadManager = (DownloadManager) getActivity().getSystemService(DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setTitle(fileName);
request.setDescription("ShareThem");
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalFilesDir(getActivity(),
Environment.DIRECTORY_DOWNLOADS, fileName);
return downloadManager.enqueue(request);
}
private class SenderFilesListingAdapter extends RecyclerViewArrayAdapter<String, SenderFilesListItemHolder> {
SenderFilesListingAdapter(List<String> objects) {
super(objects);
}
void updateData(List<String> objects) {
clear();
mObjects = objects;
notifyDataSetChanged();
}
@Override
public SenderFilesListItemHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).
inflate(R.layout.listitem_file, parent, false);
return new SenderFilesListItemHolder(itemView);
}
@Override
public void onBindViewHolder(SenderFilesListItemHolder holder, int position) {
final String senderFile = mObjects.get(position);
holder.itemView.setTag(senderFile);
final String fileName = senderFile.substring(senderFile.lastIndexOf('/') + 1, senderFile.length());
holder.title.setText(fileName);
holder.download.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
postDownloadRequestToDM(Uri.parse(String.format(PATH_FILE_DOWNLOAD, mSenderIp, mPort, mObjects.indexOf(senderFile))), fileName);
Toast.makeText(getActivity(), "Downloading " + fileName + "...", Toast.LENGTH_SHORT).show();
}
});
}
}
static class SenderFilesListItemHolder extends RecyclerView.ViewHolder {
TextView title;
ImageButton download;
SenderFilesListItemHolder(View itemView) {
super(itemView);
title = (TextView) itemView.findViewById(R.id.sender_list_item_name);
download = (ImageButton) itemView.findViewById(R.id.sender_list_start_download);
}
}
/**
* Performs network calls to fetch data/status from Sender.
* Retries on error for times bases on values of {@link FilesListingFragment#senderDownloadsFetchRetry}
*/
private class ContactSenderAPITask extends AsyncTask<String, Void, String> {
int mode;
boolean error;
ContactSenderAPITask(int mode) {
this.mode = mode;
}
@Override
protected String doInBackground(String... urls) {
error = false;
try {
return downloadDataFromSender(urls[0]);
} catch (IOException e) {
e.printStackTrace();
error = true;
Log.e(TAG, "Exception: " + e.getMessage());
return null;
}
}
// onPostExecute displays the results of the AsyncTask.
@Override
protected void onPostExecute(String result) {
switch (mode) {
case SENDER_DATA_FETCH:
if (error) {
if (senderDownloadsFetchRetry >= 0) {
--senderDownloadsFetchRetry;
if (getView() == null || getActivity() == null || null == uiUpdateHandler)
return;
uiUpdateHandler.removeMessages(SENDER_DATA_FETCH);
uiUpdateHandler.sendMessageDelayed(uiUpdateHandler.obtainMessage(mode), 800);
return;
} else senderDownloadsFetchRetry = SENDER_DATA_FETCH_RETRY_LIMIT;
if (null != getView())
onDataFetchError();
} else if (null != getView())
loadListing(result);
else Log.e(TAG, "fragment may have been removed, File fetch");
break;
case CHECK_SENDER_STATUS:
if (error) {
if (senderStatusCheckRetryLimit > 1) {
--senderStatusCheckRetryLimit;
uiUpdateHandler.removeMessages(CHECK_SENDER_STATUS);
uiUpdateHandler.sendMessageDelayed(uiUpdateHandler.obtainMessage(CHECK_SENDER_STATUS), 800);
} else if (getActivity() instanceof ReceiverActivity) {
senderStatusCheckRetryLimit = SENDER_DATA_FETCH_RETRY_LIMIT;
((ReceiverActivity) getActivity()).resetSenderSearch();
Toast.makeText(getActivity(), getString(R.string.p2p_receiver_error_sender_disconnected), Toast.LENGTH_SHORT).show();
} else
Log.e(TAG, "Activity is not instance of ReceiverActivity");
} else if (null != getView()) {
senderStatusCheckRetryLimit = SENDER_DATA_FETCH_RETRY_LIMIT;
uiUpdateHandler.removeMessages(CHECK_SENDER_STATUS);
uiUpdateHandler.sendMessageDelayed(uiUpdateHandler.obtainMessage(CHECK_SENDER_STATUS), 1000);
} else
Log.e(TAG, "fragment may have been removed: Sender api check");
break;
}
}
private String downloadDataFromSender(String apiUrl) throws IOException {
InputStream is = null;
try {
URL url = new URL(apiUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000 /* milliseconds */);
conn.setConnectTimeout(15000 /* milliseconds */);
conn.setRequestMethod("GET");
conn.setDoInput(true);
// Starts the query
conn.connect();
int response =
conn.getResponseCode();
Log.d(TAG, "The response is: " + response);
is = conn.getInputStream();
// Convert the InputStream into a string
return readIt(is);
} finally {
if (is != null) {
is.close();
}
}
}
private String readIt(InputStream stream) throws IOException {
Writer writer = new StringWriter();
char[] buffer = new char[1024];
try {
Reader reader = new BufferedReader(
new InputStreamReader(stream, "UTF-8"));
int n;
while ((n = reader.read(buffer)) != -1) {
writer.write(buffer, 0, n);
}
} finally {
stream.close();
}
return writer.toString();
}
}
private static class UiUpdateHandler extends Handler {
WeakReference<FilesListingFragment> mFragment;
UiUpdateHandler(FilesListingFragment fragment) {
mFragment = new WeakReference<>(fragment);
}
@Override
public void handleMessage(Message msg) {
FilesListingFragment fragment = mFragment.get();
if (null == mFragment)
return;
switch (msg.what) {
case CHECK_SENDER_STATUS:
fragment.checkSenderAPIAvailablity();
break;
case SENDER_DATA_FETCH:
fragment.fetchSenderFiles();
break;
}
}
}
fragment_files_listing
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
tools:context=".receiver.FilesListingFragment"
>
<android.support.v7.widget.RecyclerView
android:id="@+id/files_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" />
<ProgressBar xmlns:android="http://schemas.android.com/apk/res/android"
style="@android:style/Widget.Holo.ProgressBar"
android:layout_width="wrap_content"
android:id="@+id/loading"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_gravity="center" />
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/empty_listing_text"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_centerInParent="true"
android:clickable="true"
android:gravity="center"
android:text="No Downloads found.\n Tap to Retry"
android:visibility="gone" />
</RelativeLayout>
R.layout.fragment_files_listingxml 文件。 - Ferran