我正在这个项目中，我从联系人列表中生成了CSV文件，现在应该使用RxJava将所有文件打包为一个zip存档，因此我试图获取方法来创建使用onComplete方法调用的档案。但是应用程序因此错误而崩溃：
Attempt to invoke direct method 'boolean appjoe.wordpress.com.testdemo.Tab2$FileHelper.zip(java.lang.String, java.lang.String)' on a null object reference
这是我的代码：
路径：/storage/emulated/0/Android/data/com.wordpress.appjoe/csv
File location = new File(Environment.getExternalStorageDirectory(), "Android/data/com.wordpress.appjoe/csv/");
File fileLocation;
FileOutputStream dest;
String path;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_tab2, container, false);
mbutton = v.findViewById(R.id.extractContact);
mbutton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
// Permission has already been granted
Observer observer = new Observer() {
@Override
public void onSubscribe(Disposable d) {
mCursor = getCursor();
fCursor = getCursor();
location.mkdirs();
path = location.getAbsolutePath();
try {
dest = new FileOutputStream(path);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
@Override
public void onNext(Object o) {
contactData = o.toString();
fCursor.moveToPosition(count);
fileLocation = new File(path, getName(fCursor)+".csv");
try {
FileOutputStream fileOut = new FileOutputStream(fileLocation);
fileOut.write(contactData.getBytes());
fileOut.flush();
fileOut.close();
} catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void onError(Throwable e) {
}
@Override
public void onComplete() {
mCursor.close();
fCursor.close();
// Creating archive once the CSV files are generated
if (fileHelper.zip(path, location.getParent())) {
Toast.makeText(getContext(), "Zip successful", Toast.LENGTH_SHORT).show();
}
Log.d("fileLocation", "location: " + location.getParent());
Log.d("fileLocation", "path: " + path);
Log.d("Observer_contact", "Completed");
}
};
io.reactivex.Observable.create(new ObservableOnSubscribe<String>() {
@Override
public void subscribe(ObservableEmitter<String> emitter) throws Exception {
try {
for (count = 0; count < mCursor.getCount(); count++) {
emitter.onNext(loadContacts(count));
}
emitter.onComplete();
} catch (Exception e) {
emitter.onError(e);
}
}
}).subscribeOn(Schedulers.io())
.distinct()
.subscribeWith(observer);
}
}
});
// Inflate the layout for this fragment
return v;
}
RxJava实现以获取联系人：
public String loadContacts(int i) {
StringBuilder mBuilder = new StringBuilder();
ContentResolver mContentResolver = getActivity().getContentResolver();
mCursor.moveToPosition(i);
if (mCursor.getCount() > 0 ) {
String id = getID(mCursor);
String name = getName(mCursor);
int hasPhoneNumber = hasNumber(mCursor);
if (hasPhoneNumber > 0) {
mBuilder.append("\"").append(name).append("\"");
Cursor cursor = mContentResolver.query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
null,
ContactsContract.CommonDataKinds.Phone.CONTACT_ID + "= ?",
new String[]{id}, null);
assert cursor != null;
while (cursor.moveToNext()) {
String phoneNumber = cursor.getString(cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER))
.replaceAll("\\s", "");
// if number is not existing in the list, then add number to the string
if (!(mBuilder.toString().contains(phoneNumber))) {
mBuilder.append(", ").append(phoneNumber);
}
}
cursor.close();
}
}
return mBuilder.toString();
}
获取必要信息的方法：
private Cursor getCursor() {
ContentResolver mContentResolver = getActivity().getContentResolver();
return mContentResolver.query(ContactsContract.Contacts.CONTENT_URI,
null, null, null, ContactsContract.Contacts.DISPLAY_NAME + " ASC");
}
private String getID(Cursor cursor) {
String id = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts._ID));
return id;
}
private String getName(Cursor cursor) {
String name = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME));
return name;
}
private int hasNumber(Cursor cursor) {
return Integer.parseInt(cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.HAS_PHONE_NUMBER)));
}
生成存档的类
// Custom class to help with zipping of generated CSVs
private class FileHelper {
private static final int BUFFER_SIZE = 2048;
private String TAG = FileHelper.class.getName();
private String parentPath = "";
private String destinationFileName = "Contacts_CSV.zip";
private boolean zip (String sourcePath, String destinationPath) {
new File(destinationPath).mkdirs();
FileOutputStream fileOutputStream;
ZipOutputStream zipOutputStream = null;
try {
if (!destinationPath.endsWith("/")) {
destinationPath = destinationPath + "/";
}
String destination = destinationPath + destinationFileName;
File file = new File(destination);
if (!file.exists()) {
file.createNewFile();
}
fileOutputStream = new FileOutputStream(file);
zipOutputStream = new ZipOutputStream(new BufferedOutputStream(fileOutputStream));
parentPath = new File(sourcePath).getParent() + "/";
zipFile(zipOutputStream, sourcePath);
} catch (IOException e) {
e.printStackTrace();
Log.d(TAG,e.getMessage());
return false;
} finally {
if (zipOutputStream!=null)
try {
zipOutputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return true;
}
private void zipFile (ZipOutputStream zipOutputStream, String sourcePath) throws IOException {
java.io.File files = new java.io.File(sourcePath);
java.io.File[] fileList = files.listFiles();
String entryPath="";
BufferedInputStream input;
for (java.io.File file : fileList) {
if (file.isDirectory()) {
} else {
byte data[] = new byte[BUFFER_SIZE];
FileInputStream fileInputStream = new FileInputStream(file.getPath());
input = new BufferedInputStream(fileInputStream, BUFFER_SIZE);
entryPath = file.getAbsolutePath().replace(parentPath, "");
ZipEntry entry = new ZipEntry(entryPath);
zipOutputStream.putNextEntry(entry);
int count;
while ((count = input.read(data, 0, BUFFER_SIZE)) != -1) {
zipOutputStream.write(data, 0, count);
}
input.close();
}
}
}
}
答案 0 :(得分：0)
我通过删除类FileHelper并将FileHelper内部的两个方法都设置为主类的私有方法来解决了这个问题。这样，从onComplete()调用方法不会导致程序崩溃，并且可以成功生成zip文件。