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com.trolltech.qt.core
Class QAbstractFileEngineIterator

java.lang.Object
  extended by com.trolltech.qt.QSignalEmitter
      extended by com.trolltech.qt.QtJambiObject
          extended by com.trolltech.qt.core.QAbstractFileEngineIterator
All Implemented Interfaces:
QtJambiInterface

public abstract class QAbstractFileEngineIterator
extends QtJambiObject

The QAbstractFileEngineIterator class provides an iterator interface for custom file engines.

If all you want is to iterate over entries in a directory, see QDirIterator instead. This class is only for custom file engine authors.

QAbstractFileEngineIterator is a unidirectional single-use virtual iterator that plugs into QDirIterator, providing transparent proxy iteration for custom file engines.

You can subclass QAbstractFileEngineIterator to provide an iterator when writing your own file engine. To plug the iterator into your file system, you simply return an instance of this subclass from a reimplementation of QAbstractFileEngine::beginEntryList().

Example:

    QAbstractFileEngineIterator *
    CustomFileEngine::beginEntryList(QDir::Filters filters, const QStringList &filterNames)
    {
        return new CustomFileEngineIterator(filters, filterNames);
    }

QAbstractFileEngineIterator is associated with a path, name filters, and entry filters. The path is the directory that the iterator lists entries in. The name filters and entry filters are provided for file engines that can optimize directory listing at the iterator level (e.g., network file systems that need to minimize network traffic), but they can also be ignored by the iterator subclass; QAbstractFileEngineIterator already provides the required filtering logics in the matchesFilters() function. You can call dirName() to get the directory name, nameFilters to get a stringlist of name filters, and filters to get the entry filters.

The pure virual function hasNext returns true if the current directory has at least one more entry (i.e., the directory name is valid and accessible, and we have not reached the end of the entry list), and false otherwise. Reimplement next to seek to the next entry.

The pure virtual function currentFileName returns the name of the current entry without advancing the iterator. The currentFilePath function is provided for convenience; it returns the full path of the current entry.

Here is an example of how to implement an interator that returns each of three fixed entries in sequence.

    class CustomIterator : public QAbstractFileEngineIterator
    {
    public:
        CustomIterator(const QStringList &nameFilters, QDir::Filters filters)
            : QAbstractFileEngineIterator(nameFilters, filters), index(0)
        {
            // In a real iterator, these entries are fetched from the
            // file system based on the value of path().
            entries << "entry1" << "entry2" << "entry3";
        }

        bool hasNext() const
        {
            return index < entries.size() - 1;
        }

        QString next()
        {
           if (!hasNext())
               return QString();
           ++index;
           return currentFilePath();
        }

        QString currentFilePath()
        {
            return entries.at(index);
        }

    private:
        QStringList entries;
        int index;
    };

Note: QAbstractFileEngineIterator does not deal with QDir::IteratorFlags; it simply returns entries for a single directory.

See Also:
QDirIterator

Nested Class Summary
 
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter
QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I>
 
Constructor Summary
QAbstractFileEngineIterator(QDir.Filters filters, java.util.List<java.lang.String> nameFilters)
          Constructs a QAbstractFileEngineIterator, using the entry filters filters, and wildcard name filters nameFilters.
 
Method Summary
 QFileInfo currentFileInfo()
          The virtual function returns a QFileInfo for the current directory entry.
abstract  java.lang.String currentFileName()
          This pure virtual function returns the name of the current directory entry, excluding the path.
 java.lang.String currentFilePath()
          Returns the path to the current directory entry.
 QDir.Filters filters()
          Returns the entry filters for this iterator.
static QAbstractFileEngineIterator fromNativePointer(QNativePointer nativePointer)
          This function returns the QAbstractFileEngineIterator instance pointed to by nativePointer
abstract  boolean hasNext()
          This pure virtual function returns true if there is at least one more entry in the current directory (i.e., the iterator path is valid and accessible, and the iterator has not reached the end of the entry list).
 java.util.List<java.lang.String> nameFilters()
          Returns the name filters for this iterator.
abstract  java.lang.String next()
          This pure virtual function advances the iterator to the next directory entry, and returns the file path to the current entry.
 java.lang.String path()
          Returns the path for this iterator.
 
Methods inherited from class com.trolltech.qt.QtJambiObject
dispose, disposed, finalize, reassignNativeResources, tr, tr, tr
 
Methods inherited from class com.trolltech.qt.QSignalEmitter
blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread
 
Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface com.trolltech.qt.QtJambiInterface
disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership
 

Constructor Detail

QAbstractFileEngineIterator

public QAbstractFileEngineIterator(QDir.Filters filters,
                                   java.util.List<java.lang.String> nameFilters)

Constructs a QAbstractFileEngineIterator, using the entry filters filters, and wildcard name filters nameFilters.

Method Detail

currentFilePath

public final java.lang.String currentFilePath()

Returns the path to the current directory entry. It's the same as prepending path to the return value of currentFileName.

See Also:
currentFileName

filters

public final QDir.Filters filters()

Returns the entry filters for this iterator.

See Also:
QDir::filter, nameFilters, path

nameFilters

public final java.util.List<java.lang.String> nameFilters()

Returns the name filters for this iterator.

See Also:
QDir::nameFilters, filters, path

path

public final java.lang.String path()

Returns the path for this iterator. QDirIterator is responsible for assigning this path; it cannot change during the iterator's lifetime.

See Also:
nameFilters, filters

currentFileInfo

public QFileInfo currentFileInfo()

The virtual function returns a QFileInfo for the current directory entry. This function is provided for convenience. It can also be slightly faster that creating a QFileInfo object yourself, as the object returned by this function might contain cached information that QFileInfo otherwise would have to access through the file engine.

See Also:
currentFileName

currentFileName

public abstract java.lang.String currentFileName()

This pure virtual function returns the name of the current directory entry, excluding the path.

See Also:
currentFilePath

hasNext

public abstract boolean hasNext()

This pure virtual function returns true if there is at least one more entry in the current directory (i.e., the iterator path is valid and accessible, and the iterator has not reached the end of the entry list).

See Also:
QDirIterator::hasNext

next

public abstract java.lang.String next()

This pure virtual function advances the iterator to the next directory entry, and returns the file path to the current entry.

This function can optionally make use of nameFilters and filters to optimize its performance.

Reimplement this function in a subclass to advance the iterator.

See Also:
QDirIterator::next

fromNativePointer

public static QAbstractFileEngineIterator fromNativePointer(QNativePointer nativePointer)
This function returns the QAbstractFileEngineIterator instance pointed to by nativePointer

Parameters:
nativePointer - the QNativePointer of which object should be returned.

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