Для API 23+ вам необходимо запросить разрешения на чтение и запись, даже если они уже находятся в вашем манифесте.
// Storage Permissions
private static final int REQUEST_EXTERNAL_STORAGE = 1;
private static String[] PERMISSIONS_STORAGE = {
Manifest.permission.READ_EXTERNAL_STORAGE,
Manifest.permission.WRITE_EXTERNAL_STORAGE
};
/**
* Checks if the app has permission to write to device storage
*
* If the app does not has permission then the user will be prompted to grant permissions
*
* @param activity
*/
public static void verifyStoragePermissions(Activity activity) {
// Check if we have write permission
int permission = ActivityCompat.checkSelfPermission(activity, Manifest.permission.WRITE_EXTERNAL_STORAGE);
if (permission != PackageManager.PERMISSION_GRANTED) {
// We don't have permission so prompt the user
ActivityCompat.requestPermissions(
activity,
PERMISSIONS_STORAGE,
REQUEST_EXTERNAL_STORAGE
);
}
}
AndroidManifest.xml
Для официальных документацию о запросах разрешений для API 23+, проверьте https://developer.android.com/training/permissions/requesting.html
Рассмотрим этот цикл
ifstream myFile;
myFile.open("lists.txt");
// the loop is supposed to read each line ofrom the file
// I'll assume that 'line' is a std::string
while (getline(myFile, line ))
{
istringstream ss(line);
while (ss)
{
// What type is 'a'?
ss >> a;
list1.addNode(a);
// Even assuming that 'a' is a char, std::getline extract the newline fromn the input,
// but it doesn't append it to the string. So there is no '\n' in 'ss'
if (a == '\n')
break;
// Now, even if the last element in the row has been extracted, 'ss' is still good
// It's only the next attempt of 'ss >> a' which fails
}
// The following will never execute, because either the line has been consumed
// entirely in the previous loop, or some previous read has failed
while (ss)
{
ss >> a;
list2.addNode(a);
if (a == '\n')
break;
}
// The loop isn't really a loop, it breaks unconditionally
break;
}
. Вы должны проверить потоки после попытки извлечения.
while (getline(myFile, line ))
{
istringstream s1(line);
while (s1 >> a)
{
list1.addNode(a);
}
if ( !getline(myFile, line ) )
break;
istringstream s2(line);
while (s2 >> a)
{
list2.addNode(a);
}
}
его частично решенный, но берущий последнее целое число строки дважды. У кого-либо есть решение?
ifstream inputFile;
inputFile.open("lists.txt");
if( getline(inputFile, line);
istringstream list1_stream(line);
while (list1_stream)
{
list1_stream >> a;
list1.addNode(a);
}
getline(inputFile, line);
istringstream list2_stream(line);
while (list2_stream)
{
list2_stream >> a;
list2.addNode(a);
}
файл содержит:
1 2 3 8
2 4 7 9
вывод:
1 2 3 8 8
2 4 7 9 9