| 头： | #include <QList> |
| 继承者： | QItemSelection , QQueue , QSignalSpy , QStringList ，和 QTestEventList |
注意： 此类的所有函数 可重入 .
| class | const_iterator |
| class | iterator |
| typedef | ConstIterator |
| typedef | Iterator |
| typedef | const_pointer |
| typedef | const_reference |
| typedef | difference_type |
| typedef | pointer |
| typedef | reference |
| typedef | size_type |
| typedef | value_type |
| QList () | |
| QList (const QList<T> & other ) | |
| QList (std::initializer_list<T> args ) | |
| ~QList () | |
| void | append (const T & value ) |
| void | append (const QList<T> & value ) |
| const T & | at (int i ) const |
| T & | back () |
| const T & | back () const |
| iterator | begin () |
| const_iterator | begin () const |
| void | clear () |
| const_iterator | constBegin () const |
| const_iterator | constEnd () const |
| bool | contains (const T & value ) const |
| int | count (const T & value ) const |
| int | count () const |
| bool | empty () const |
| iterator | end () |
| const_iterator | end () const |
| bool | endsWith (const T & value ) const |
| iterator | erase (iterator pos ) |
| iterator | erase (iterator begin , iterator end ) |
| T & | first () |
| const T & | first () const |
| T & | front () |
| const T & | front () const |
| int | indexOf (const T & value , int from = 0) const |
| void | insert (int i , const T & value ) |
| iterator | insert (iterator before , const T & value ) |
| bool | isEmpty () const |
| T & | last () |
| const T & | last () const |
| int | lastIndexOf (const T & value , int from = -1) const |
| int | length () const |
| QList<T> | mid (int pos , int length = -1) const |
| void | move (int from , int to ) |
| void | pop_back () |
| void | pop_front () |
| void | prepend (const T & value ) |
| void | push_back (const T & value ) |
| void | push_front (const T & value ) |
| int | removeAll (const T & value ) |
| void | removeAt (int i ) |
| void | removeFirst () |
| void | removeLast () |
| bool | removeOne (const T & value ) |
| void | replace (int i , const T & value ) |
| void | reserve (int alloc ) |
| int | size () const |
| bool | startsWith (const T & value ) const |
| void | swap (QList<T> & other ) |
| void | swap (int i , int j ) |
| T | takeAt (int i ) |
| T | takeFirst () |
| T | takeLast () |
| QSet<T> | toSet () const |
| std::list<T> | toStdList () const |
| QVector<T> | toVector () const |
| T | value (int i ) const |
| T | value (int i , const T & defaultValue ) const |
| bool | operator!= (const QList<T> & other ) const |
| QList<T> | operator+ (const QList<T> & other ) const |
| QList<T> & | operator+= (const QList<T> & other ) |
| QList<T> & | operator+= (const T & value ) |
| QList<T> & | operator<< (const QList<T> & other ) |
| QList<T> & | operator<< (const T & value ) |
| QList<T> & | operator= (const QList<T> & other ) |
| QList & | operator= (QList && other ) |
| bool | operator== (const QList<T> & other ) const |
| T & | operator[] (int i ) |
| const T & | operator[] (int i ) const |
| QList<T> | fromSet (const QSet<T> & set ) |
| QList<T> | fromStdList (const std::list<T> & list ) |
| QList<T> | fromVector (const QVector<T> & vector ) |
| QDataStream & | operator<< (QDataStream & out , const QList<T> & list ) |
| QDataStream & | operator>> (QDataStream & in , QList<T> & list ) |
The QList 类是提供列表的模板类。
QList <T> is one of Qt's generic 容器类 . It stores a list of values and provides fast index-based access as well as fast insertions and removals.
QList <T>, QLinkedList <T>, and QVector <T> provide similar functionality. Here's an overview:
在内部， QList <T> is represented as an array of pointers to items of type T. If T is itself a pointer type or a basic type that is no larger than a pointer, or if T is one of Qt's shared classes ，那么 QList <T> stores the items directly in the pointer array. For lists under a thousand items, this array representation allows for very fast insertions in the middle, and it allows index-based access. Furthermore, operations like prepend () 和 append () are very fast, because QList preallocates memory at both ends of its internal array. (See 算法的复杂性 for details.) Note, however, that for unshared list items that are larger than a pointer, each append or insert of a new item requires allocating the new item on the heap, and this per item allocation might make QVector a better choice in cases that do lots of appending or inserting, since QVector allocates memory for its items in a single heap allocation.
Note that the internal array only ever gets bigger over the life of the list. It never shrinks. The internal array is deallocated by the destructor, by clear (), and by the assignment operator, when one list is assigned to another.
Here's an example of a QList that stores integers and a QList that stores QDate 值：
QList<int> integerList; QList<QDate> dateList;
Qt includes a QStringList 类继承 QList < QString > and adds a convenience function QStringList::join (). ( QString::split () creates QStringLists from strings.)
QList stores a list of items. The default constructor creates an empty list. To insert items into the list, you can use operator<<():
QList<QString> list; list << "one" << "two" << "three"; // list: ["one", "two", "three"]
QList provides these basic functions to add, move, and remove items: insert (), replace (), removeAt (), move ()，和 swap (). In addition, it provides the following convenience functions: append (), prepend (), removeFirst ()，和 removeLast ().
QList uses 0-based indexes, just like C++ arrays. To access the item at a particular index position, you can use operator[](). On non-const lists, operator[]() returns a reference to the item and can be used on the left side of an assignment:
if (list[0] == "Bob") list[0] = "Robert";
因为 QList is implemented as an array of pointers, this operation is very fast ( 常量时间 ). For read-only access, an alternative syntax is to use at ():
for (int i = 0; i < list.size(); ++i) { if (list.at(i) == "Jane") cout << "Found Jane at position " << i << endl; }
at () can be faster than operator[](), because it never causes a 深拷贝 的出现。
A common requirement is to remove an item from a list and do something with it. For this,
QList
提供
takeAt
(),
takeFirst
()，和
takeLast
(). Here's a loop that removes the items from a list one at a time and calls
delete
on them:
QList<QWidget *> list; ... while (!list.isEmpty()) delete list.takeFirst();
Inserting and removing items at either ends of the list is very fast ( 常量时间 in most cases), because QList preallocates extra space on both sides of its internal buffer to allow for fast growth at both ends of the list.
If you want to find all occurrences of a particular value in a list, use indexOf () 或 lastIndexOf (). The former searches forward starting from a given index position, the latter searches backward. Both return the index of a matching item if they find it; otherwise, they return -1. For example:
int i = list.indexOf("Jane"); if (i != -1) cout << "First occurrence of Jane is at position " << i << endl;
If you simply want to check whether a list contains a particular value, use contains (). If you want to find out how many times a particular value occurs in the list, use count (). If you want to replace all occurrences of a particular value with another, use replace ().
QList
's value type must be an
可赋值数据类型
. This covers most data types that are commonly used, but the compiler won't let you, for example, store a
QWidget
作为值；取而代之，存储
QWidget
*. A few functions have additional requirements; for example,
indexOf
() 和
lastIndexOf
() expect the value type to support
operator==()
. These requirements are documented on a per-function basis.
Like the other container classes, QList 提供 Java 风格迭代器 ( QListIterator and QMutableListIterator ) 和 STL 样式迭代器 ( QList::const_iterator and QList::iterator ). In practice, these are rarely used, because you can use indexes into the QList . QList is implemented in such a way that direct index-based access is just as fast as using iterators.
QList does not support inserting, prepending, appending or replacing with references to its own values. Doing so will cause your application to abort with an error message.
To make QList as efficient as possible, its member functions don't validate their input before using it. Except for isEmpty (), member functions always assume the list is not empty. Member functions that take index values as parameters always assume their index value parameters are in the valid range. This means QList member functions can fail. If you define QT_NO_DEBUG when you compile, failures will not be detected. If you don't define QT_NO_DEBUG, failures will be detected using Q_ASSERT () 或 Q_ASSERT_X () with an appropriate message.
To avoid failures when your list can be empty, call isEmpty () before calling other member functions. If you must pass an index value that might not be in the valid range, check that it is less than the value returned by size () but not less than 0.
另请参阅 QListIterator , QMutableListIterator , QLinkedList ，和 QVector .
Qt 样式同义词 QList::const_iterator .
Qt 样式同义词 QList::iterator .
Typedef for const T *. Provided for STL compatibility.
Typedef for const T &. Provided for STL compatibility.
typedef 对于 ptrdiff_t。为兼容 STL 提供。
Typedef for T *. Provided for STL compatibility.
Typedef for T &. Provided for STL compatibility.
typedef 对于 int。为兼容 STL 提供。
typedef 对于 T。为兼容 STL 提供。
构造空列表。
构造副本为 other .
此操作花费 常量时间 ，因为 QList is 隐式共享 . This makes returning a QList from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes 线性时间 .
另请参阅 operator= ().
Construct a list from the std::initializer_list specified by args .
This constructor is only enabled if the compiler supports C++0x
该函数在 Qt 4.8 引入。
Destroys the list. References to the values in the list and all iterators of this list become invalid.
插入 value 在列表末尾。
范例：
QList<QString> list; list.append("one"); list.append("two"); list.append("three"); // list: ["one", "two", "three"]
This is the same as list.insert( size (), value ).
This operation is typically very fast ( 常量时间 )，因为 QList preallocates extra space on both sides of its internal buffer to allow for fast growth at both ends of the list.
另请参阅 operator<< (), prepend ()，和 insert ().
这是重载函数。
Appends the items of the value list to this list.
该函数在 Qt 4.5 引入。
另请参阅 operator<< () 和 operator+= ().
返回项按索引位置 i 在列表中。 i must be a valid index position in the list (i.e., 0 <= i < size ()).
This function is very fast ( 常量时间 ).
另请参阅 value () 和 operator[] ().
此函数为兼容 STL (标准模板库) 提供。它相当于 last (). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
这是重载函数。
Returns an STL-style iterator pointing to the first item in the list.
另请参阅 constBegin () 和 end ().
这是重载函数。
Removes all items from the list.
另请参阅 removeAll ().
Returns a const STL-style iterator pointing to the first item in the list.
Returns a const STL-style iterator pointing to the imaginary item after the last item in the list.
另请参阅 constBegin () 和 end ().
Returns true if the list contains an occurrence of value ；否则返回 false。
This function requires the value type to have an implementation of
operator==()
.
Returns the number of occurrences of value 在列表中。
This function requires the value type to have an implementation of
operator==()
.
另请参阅 contains () 和 indexOf ().
Returns the number of items in the list. This is effectively the same as size ().
此函数为兼容 STL (标准模板库) 提供。它相当于 isEmpty () and returns true if the list is empty.
Returns an STL-style iterator pointing to the imaginary item after the last item in the list.
这是重载函数。
Returns true if this list is not empty and its last item is equal to value ；否则返回 false。
该函数在 Qt 4.5 引入。
另请参阅 isEmpty () 和 contains ().
Removes the item associated with the iterator pos from the list, and returns an iterator to the next item in the list (which may be end ()).
这是重载函数。
Removes all the items from begin up to (but not including) end . Returns an iterator to the same item that end referred to before the call.
Returns a reference to the first item in the list. The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
这是重载函数。
[static]
QList
<
T
> QList::
fromSet
(const
QSet
<
T
> &
set
)
返回 QList object with the data contained in set . The order of the elements in the QList is undefined.
范例：
QSet<int> set; set << 20 << 30 << 40 << ... << 70; QList<int> list = QList<int>::fromSet(set); qSort(list);
另请参阅 fromVector (), toSet (), QSet::toList ()，和 qSort ().
[static]
QList
<
T
> QList::
fromStdList
(const
std::list
<
T
> &
list
)
返回 QList object with the data contained in list . The order of the elements in the QList is the same as in list .
范例：
std::list<double> stdlist; list.push_back(1.2); list.push_back(0.5); list.push_back(3.14); QList<double> list = QList<double>::fromStdList(stdlist);
另请参阅 toStdList () 和 QVector::fromStdVector ().
[static]
QList
<
T
> QList::
fromVector
(const
QVector
<
T
> &
vector
)
返回 QList object with the data contained in vector .
范例：
QVector<double> vect; vect << 20.0 << 30.0 << 40.0 << 50.0; QList<double> list = QVector<T>::fromVector(vect); // list: [20.0, 30.0, 40.0, 50.0]
另请参阅 fromSet (), toVector ()，和 QVector::toList ().
此函数为兼容 STL (标准模板库) 提供。它相当于 first (). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
这是重载函数。
Returns the index position of the first occurrence of value in the list, searching forward from index position from . Returns -1 if no item matched.
范例：
QList<QString> list; list << "A" << "B" << "C" << "B" << "A"; list.indexOf("B"); // returns 1 list.indexOf("B", 1); // returns 1 list.indexOf("B", 2); // returns 3 list.indexOf("X"); // returns -1
This function requires the value type to have an implementation of
operator==()
.
注意， QList uses 0-based indexes, just like C++ arrays. Negative indexes are not supported with the exception of the value mentioned above.
另请参阅 lastIndexOf () 和 contains ().
插入 value at index position i in the list. If i is 0, the value is prepended to the list. If i is size (), the value is appended to the list.
范例：
QList<QString> list; list << "alpha" << "beta" << "delta"; list.insert(2, "gamma"); // list: ["alpha", "beta", "gamma", "delta"]
另请参阅 append (), prepend (), replace ()，和 removeAt ().
这是重载函数。
插入 value in front of the item pointed to by the iterator before . Returns an iterator pointing at the inserted item. Note that the iterator passed to the function will be invalid after the call; the returned iterator should be used instead.
Returns true if the list contains no items; otherwise returns false.
另请参阅 size ().
Returns a reference to the last item in the list. The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
这是重载函数。
Returns the index position of the last occurrence of value in the list, searching backward from index position from 。若 from is -1 (the default), the search starts at the last item. Returns -1 if no item matched.
范例：
QList<QString> list; list << "A" << "B" << "C" << "B" << "A"; list.lastIndexOf("B"); // returns 3 list.lastIndexOf("B", 3); // returns 3 list.lastIndexOf("B", 2); // returns 1 list.lastIndexOf("X"); // returns -1
This function requires the value type to have an implementation of
operator==()
.
注意， QList uses 0-based indexes, just like C++ arrays. Negative indexes are not supported with the exception of the value mentioned above.
另请参阅 indexOf ().
This function is identical to count ().
该函数在 Qt 4.5 引入。
另请参阅 count ().
Returns a list whose elements are copied from this list, starting at position pos 。若 length is -1 (the default), all elements from pos are copied; otherwise length elements (or all remaining elements if there are less than length elements) are copied.
移动项按索引位置 from 到索引位置 to .
范例：
QList<QString> list; list << "A" << "B" << "C" << "D" << "E" << "F"; list.move(1, 4); // list: ["A", "C", "D", "E", "B", "F"]
这如同 insert( to , takeAt ( from )).This function assumes that both from and to are at least 0 but less than size (). To avoid failure, test that both from and to are at least 0 and less than size ().
另请参阅 swap (), insert ()，和 takeAt ().
此函数为兼容 STL (标准模板库) 提供。它相当于 removeLast (). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
此函数为兼容 STL (标准模板库) 提供。它相当于 removeFirst (). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
插入 value 在列表的开头。
范例：
QList<QString> list; list.prepend("one"); list.prepend("two"); list.prepend("three"); // list: ["three", "two", "one"]
This is the same as list.insert(0, value ).
This operation is usually very fast ( 常量时间 )，因为 QList preallocates extra space on both sides of its internal buffer to allow for fast growth at both ends of the list.
此函数为兼容 STL (标准模板库) 提供。它相当于 append ( value ).
此函数为兼容 STL (标准模板库) 提供。它相当于 prepend ( value ).
Removes all occurrences of value in the list and returns the number of entries removed.
范例：
QList<QString> list; list << "sun" << "cloud" << "sun" << "rain"; list.removeAll("sun"); // list: ["cloud", "rain"]
This function requires the value type to have an implementation of
operator==()
.
另请参阅 removeOne (), removeAt (), takeAt ()，和 replace ().
Removes the item at index position i . i must be a valid index position in the list (i.e., 0 <= i < size ()).
另请参阅 takeAt (), removeFirst (), removeLast ()，和 removeOne ().
Removes the first item in the list. Calling this function is equivalent to calling removeAt (0). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
另请参阅 removeAt () 和 takeFirst ().
Removes the last item in the list. Calling this function is equivalent to calling removeAt ( size () - 1). The list must not be empty. If the list can be empty, call isEmpty () before calling this function.
另请参阅 removeAt () 和 takeLast ().
Removes the first occurrence of value in the list and returns true on success; otherwise returns false.
范例：
QList<QString> list; list << "sun" << "cloud" << "sun" << "rain"; list.removeOne("sun"); // list: ["cloud", ,"sun", "rain"]
This function requires the value type to have an implementation of
operator==()
.
该函数在 Qt 4.4 引入。
另请参阅 removeAll (), removeAt (), takeAt ()，和 replace ().
替换项在索引位置 i with value . i must be a valid index position in the list (i.e., 0 <= i < size ()).
另请参阅 operator[] () 和 removeAt ().
Reserve space for alloc 元素。
若 alloc is smaller than the current size of the list, nothing will happen.
Use this function to avoid repetetive reallocation of QList 's internal data if you can predict how many elements will be appended. Note that the reservation applies only to the internal pointer array.
该函数在 Qt 4.7 引入。
Returns the number of items in the list.
Returns true if this list is not empty and its first item is equal to value ；否则返回 false。
该函数在 Qt 4.5 引入。
另请参阅 isEmpty () 和 contains ().
Swaps list other with this list. This operation is very fast and never fails.
该函数在 Qt 4.8 引入。
Exchange the item at index position i with the item at index position j . This function assumes that both i and j are at least 0 but less than size (). To avoid failure, test that both i and j are at least 0 and less than size ().
范例：
QList<QString> list; list << "A" << "B" << "C" << "D" << "E" << "F"; list.swap(1, 4); // list: ["A", "E", "C", "D", "B", "F"]
另请参阅 move ().
Removes the item at index position i and returns it. i must be a valid index position in the list (i.e., 0 <= i < size ()).
若不使用返回值， removeAt () 效率更高。
另请参阅 removeAt (), takeFirst ()，和 takeLast ().
Removes the first item in the list and returns it. This is the same as takeAt (0). This function assumes the list is not empty. To avoid failure, call isEmpty () before calling this function.
此操作花费 常量时间 .
若不使用返回值， removeFirst () 效率更高。
另请参阅 takeLast (), takeAt ()，和 removeFirst ().
Removes the last item in the list and returns it. This is the same as takeAt ( size () - 1). This function assumes the list is not empty. To avoid failure, call isEmpty () before calling this function.
此操作花费 常量时间 .
若不使用返回值， removeLast () 效率更高。
另请参阅 takeFirst (), takeAt ()，和 removeLast ().
返回 QSet object with the data contained in this QList 。由于 QSet doesn't allow duplicates, the resulting QSet might be smaller than the original list was.
范例：
QStringList list; list << "Julia" << "Mike" << "Mike" << "Julia" << "Julia"; QSet<QString> set = list.toSet(); set.contains("Julia"); // returns true set.contains("Mike"); // returns true set.size(); // returns 2
另请参阅 toVector (), fromSet ()，和 QSet::fromList ().
Returns a std::list object with the data contained in this QList 。范例：
QList<double> list; list << 1.2 << 0.5 << 3.14; std::list<double> stdlist = list.toStdList();
另请参阅 fromStdList () 和 QVector::toStdVector ().
返回 QVector object with the data contained in this QList .
范例：
QStringList list; list << "Sven" << "Kim" << "Ola"; QVector<QString> vect = list.toVector(); // vect: ["Sven", "Kim", "Ola"]
另请参阅 toSet (), fromVector ()，和 QVector::fromList ().
Returns the value at index position i 在列表中。
If the index i is out of bounds, the function returns a default-constructed value. If you are certain that the index is going to be within bounds, you can use at () instead, which is slightly faster.
另请参阅 at () 和 operator[] ().
这是重载函数。
If the index i is out of bounds, the function returns defaultValue .
返回 true 若 other is not equal to this list; otherwise returns false.
Two lists are considered equal if they contain the same values in the same order.
This function requires the value type to have an implementation of
operator==()
.
另请参阅 operator== ().
Returns a list that contains all the items in this list followed by all the items in the other 列表。
另请参阅 operator+= ().
Appends the items of the other list to this list and returns a reference to this list.
另请参阅 operator+ () 和 append ().
这是重载函数。
追加 value to the list.
另请参阅 append () 和 operator<< ().
Appends the items of the other list to this list and returns a reference to this list.
另请参阅 operator+= () 和 append ().
这是重载函数。
追加 value to the list.
赋值 other to this list and returns a reference to this list.
返回 true 若 other is equal to this list; otherwise returns false.
Two lists are considered equal if they contain the same values in the same order.
This function requires the value type to have an implementation of
operator==()
.
另请参阅 operator!= ().
返回项按索引位置 i 作为可修改引用。 i must be a valid index position in the list (i.e., 0 <= i < size ()).
This function is very fast ( 常量时间 ).
这是重载函数。
如同 at ().
Writes the list list 到流 out .
This function requires the value type to implement
operator<<()
.
另请参阅 QDataStream 运算符格式 .
Reads a list from stream in into list .
This function requires the value type to implement
operator>>()
.
另请参阅 QDataStream 运算符格式 .