QJniArray Class

template <typename T> class QJniArray

The QJniArray class is a template class that represents an array in Java. 更多...

头：	`#include <QJniArray>`
CMake:	`find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake:	`QT += core`
Since:	Qt 6.8
继承：	QJniArrayBase

所有成员列表，包括继承成员

公共类型

	const_iterator
	const_reverse_iterator

公共函数

	QJniArray ()
	QJniArray (Container && container )
	QJniArray (QJniArray<Other> && other )
`(从 6.9 起)`	QJniArray (QJniArrayBase::size_type size )
	QJniArray (QJniObject && object )
	QJniArray (const QJniArray<Other> & other )
	QJniArray (const QJniObject & object )
	QJniArray (jarray array )
	QJniArray (std::initializer_list<T> & list )
	~QJniArray ()
auto	arrayObject () const
QJniArray<T>::const_reference	at (QJniArrayBase::size_type i ) const
QJniArray<T>::iterator	begin ()
QJniArray<T>::const_iterator	begin () const
QJniArray<T>::const_iterator	cbegin () const
QJniArray<T>::const_iterator	cend () const
QJniArray<T>::const_iterator	constBegin () const
QJniArray<T>::const_iterator	constEnd () const
QJniArray<T>::const_reverse_iterator	crbegin () const
QJniArray<T>::const_reverse_iterator	crend () const
QJniArray<T>::iterator	end ()
QJniArray<T>::const_iterator	end () const
QJniArray<T>::reverse_iterator	rbegin ()
QJniArray<T>::const_reverse_iterator	rbegin () const
QJniArray<T>::reverse_iterator	rend ()
QJniArray<T>::const_reverse_iterator	rend () const
容器	toContainer (Container && container = {}) const
QJniArray<T> &	operator= (QJniArray<Other> && other )
QJniArray<T> &	operator= (const QJniArray<Other> & other )
`(从 6.9 起)` QJniArray<T>::reference	operator[] (QJniArrayBase::size_type i )
QJniArray<T>::const_reference	operator[] (QJniArrayBase::size_type i ) const

详细描述

The QJniArray template makes it easy to work with Java methods that return or take a Java array.

注意： Java arrays can hold primitive types and objects. The array itself can be treated like a Java Object, and the JNI framework provides explicit APIs to work with such arrays. In addition, the Java class library provides container types such as List or ArrayList . Objects of those types can not be represented by a QJniArray. Instead, use QJniObject to call the class-specific member functions.

To create a QJniArray instance, either construct it from a corresponding C++ container:

QList<int> intList;
const QJniArray intArray = QJniArray(intList);

or from an initializer list:

const QJniArray intArray{1, 2, 3};

QJniArray will create a new Java array and copy the C++-side data into it.

When calling functions that return an array via QJniObject::callMethod ，譬如 char[] toCharArray() in the Java String class, specify the return type as a C array ( jchar[] in the following):

const auto charArray = stringObject.callMethod<jchar[]>("toCharArray");

The charArray variable will be of type QJniArray<jchar> , and hold a new global reference to the jcharArray JNI object.

Note that the arrays in the code snippets above are all const. Accessing elements in a const array is considerably more efficient than operating on a mutable array.

A QJniArray can also be constructed from an existing jarray or QJniObject . However, note that no type checking is performed to verify that the jarray or QJniObject indeed represents an array holding elements of the specified type, and accessing a mismatching QJniArray results in undefined behavior.

The data in a QJniArray can either be accessed element by element using at () 或 operator[] (), or iterated over.

for (const auto &value : array)
    process(value);

To copy the entire array into a C++ side Qt container, use the toContainer () 函数。

const auto bytes = object.callMethod<jbyte[]>("getBytes");
QByteArray data = bytes.toContainer();

which happens implicitly in

const auto data = object.callMethod<QByteArray>("getBytes");

The return type of toContainer () depends on the type that QJniArray has been instantiated with. For QJniArray<T> this will typically be QList<T> , with the following exceptions:

Specialization	C++ 类型
QJniArray<jbyte>	QByteArray
QJniArray<char>	QByteArray
QJniArray<jstring>	QStringList
QJniArray< QString >	QStringList

An array of a fixed size can also be created without any data, and can then be populated element by element using operator[] :

QJniArray<jint> intArray(size);
for (int i = 0; i < size; ++i)
    intArray[i] = i;

or a mutable iterator:

QJniArray<QString> strings(size);
int i = 0;
for (auto string : strings) // note: not 'auto &string'
    string = u"Row %1"_s.arg(i++);

As in Java, the size of an array can not be changed, but the array variable can be assigned to a different array.

注意： Java arrays are limited to 32 bits, and the size_type member type of QJniArray is jsize , which is a 32bit integer type. Trying to construct a QJniArray from a C++ container that holds more than 2^32 elements will cause a runtime assertion.

成员类型文档编制

`[alias]` QJniArray:: const_iterator

A random-access, const iterator for QJniArray .

`[alias]` QJniArray:: const_reverse_iterator

A reverse iterator for the QJniArray , synonym for std::reverse_iterator<const_iterator> .

成员函数文档编制

`[noexcept]` QJniArray < T > ::iterator QJniArray:: begin ()

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: begin () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: cbegin () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: constBegin () const

返回 STL-style const iterator pointing to the first item in the array.

If the array is 无效 , then this will return the same iterator as the corresponding end () 函数。

另请参阅 end () 和 rbegin ().

`[noexcept]` QJniArray < T > ::iterator QJniArray:: end ()

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: cend () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: constEnd () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: end () const

返回 STL 样式迭代器 pointing just after the last item in the list.

另请参阅 begin () 和 rend ().

`[noexcept]` QJniArray < T > ::reverse_iterator QJniArray:: rbegin ()

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: crbegin () const

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: rbegin () const

返回 STL-style reverse iterator pointing to the first item in the array, in reverse order.

If the array is 无效 , then this will return the same iterator as the corresponding rend () 函数。

另请参阅 rend () 和 begin ().

`[noexcept]` QJniArray < T > ::reverse_iterator QJniArray:: rend ()

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: crend () const

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: rend () const

返回 STL-style reverse iterator pointing just after the last item in the list, in reverse order.

另请参阅 rbegin () 和 end ().

QJniArray < T > ::const_reference QJniArray:: at ( QJniArrayBase::size_type i ) const

QJniArray < T > ::const_reference QJniArray:: operator[] ( QJniArrayBase::size_type i ) const

Returns the value at position i in the wrapped Java array.

i must be a valid index position in the list (i.e., 0 <= i < size ()).

另请参阅 size ().

QJniArray:: QJniArray ()

Default constructor of QJniArray. This does not create a Java-side array, and the instance will be invalid.

另请参阅 isValid .

`[explicit]` template <typename Container, QJniArrayBase::if_compatible_source_container<Container> = true> QJniArray:: QJniArray ( 容器 && container )

Constructs a QJniArray that wraps a newly-created Java array for elements of type Container::value_type , and populates the Java array with the data from container .

约束

Participates in overload resolution only if Container is a container that stores elements of a JNI type or equivalent C++ type, and provides a forward iterator.

The specialization of the constructed QJniArray depends on the value type of the container . For a Container<T> (such as e.g. QList<T> ) it will typically be QJniArray<T> , with the following exceptions:

容器	Specialization
QByteArray	QJniArray<jbyte>
QStringList	QJniArray<jstring>
Container::value_type	Specialization
QJniObject	QJniArray<jobject>

另请参阅 QJniArrayBase::fromContainer () 和 toContainer ().

`[noexcept]` template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray:: QJniArray ( QJniArray < 其它 > && other )

Constructs a QJniArray by moving from other 。 other array becomes 无效 .

约束

Participates in overload resolution only if the element type Other of other is convertible to the element type T of the QJniArray being constructed. However, no actual conversion takes place.

`[explicit, since 6.9]` QJniArray:: QJniArray ( QJniArrayBase::size_type size )

Constructs an empty QJniArray of size size . The elements in the array do not get initialized.

该函数在 Qt 6.9 引入。

`[explicit noexcept]` QJniArray:: QJniArray ( QJniObject && object )

Constructs a QJniArray by moving from object 。 QJniObject becomes 无效 .

注意： This constructor does not perform any validation of whether the Java-side object is an array of the correct type. Accessing a mismatching QJniArray results in undefined behavior.

template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray:: QJniArray (const QJniArray < 其它 > & other )

Constructs a QJniArray by copying other . Both QJniArray objects will reference the same Java array object.

约束

Participates in overload resolution only if the element type Other of other is convertible to the element type T of the QJniArray being constructed. However, no actual conversion takes place.

`[explicit]` QJniArray:: QJniArray (const QJniObject & object )

Constructs a QJniArray that wraps the same Java array as object , creating a new global reference. To construct a QJniArray from an existing local reference, use a QJniObject constructed via fromLocalRef ().

注意： This constructor does not perform any validation of whether the Java-side object is an array of the correct type. Accessing a mismatching QJniArray results in undefined behavior.

`[explicit]` QJniArray:: QJniArray ( jarray array )

Constructs a QJniArray that wraps the Java-side array array , creating a new global reference to array .

注意： This constructor does not perform any validation of whether the Java-side object is an array of the correct type. Accessing a mismatching QJniArray results in undefined behavior.

`[default]` QJniArray:: QJniArray ( std::initializer_list < T > & list )

Constructs a QJniArray that wraps a newly-created Java array for elements of type T , and populates the Java array with the data from list .

另请参阅 QJniArrayBase::fromContainer () 和 toContainer ().

QJniArray:: ~QJniArray ()

销毁 QJniArray object and releases any references held to the wrapped Java array.

auto QJniArray:: arrayObject () const

Returns the wrapped Java object as the suitable jarray type that matches the element type T of this QJniArray 对象。

T	jarray type
jbyte	jbyteArray
jchar	jcharArray
...	...
jobject	jobjectArray
QJniObject	jobjectArray
Q_DECLARE_JNI_CLASS	jobjectArray

template <typename Container = QJniArrayBase::ToContainerType<T>, QJniArrayBase::if_compatible_target_container<T, Container> = true> 容器 QJniArray:: toContainer ( 容器 && container = {}) const

Returns a container populated with the data in the wrapped Java array.

若无 container is provided, then the type of the container returned depends on the element type of this QJniArray 。对于 QJniArray<T> this will typically be QList<T> , with the following exceptions:

Specialization	C++ 类型
QJniArray <jbyte>	QByteArray
QJniArray <char>	QByteArray
QJniArray <jstring>	QStringList
QJniArray < QString >	QStringList

If you pass in a named container (an lvalue) for container , then that container is filled, and a reference to it is returned. If you pass in a temporary container (an rvalue, incl. the default argument), then that container is filled, and returned by value.

This function returns immediately if the array is 无效 .

另请参阅 QJniArrayBase::fromContainer ().

`[noexcept]` template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray < T > &QJniArray:: operator= ( QJniArray < 其它 > && other )

移动 other 到此 QJniArray , and returns a reference to this. The other array becomes 无效 .

约束

Participates in overload resolution only if the element type Other of other is convertible to the element type T of this QJniArray . However, no actual conversion takes place.

template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray < T > &QJniArray:: operator= (const QJniArray < 其它 > & other )

赋值 other 到此 QJniArray , and returns a reference to this. Both QJniArray objects will reference the same Java array object.

约束

Participates in overload resolution only if the element type Other of other is convertible to the element type T of this QJniArray . However, no actual conversion takes place.

`[since 6.9]` QJniArray < T > ::reference QJniArray:: operator[] ( QJniArrayBase::size_type i )

Returns a reference object for value at position i in the wrapped Java array.

i must be a valid index position in the list (i.e., 0 <= i < size ()).

The returned reference object holds the value at position i , and in most cases will convert implicitly to the value. Assigning to the returned reference will overwrite the entry in the Java array. However, calling mutating member functions on the object will not modify the entry in the array. To call member function on the result of this operator, dereference the reference object:

QJniArray<QString> strings = object.callMethod<QString[]>("getStrings");
if (!strings.isEmpty()) {
    if (!(*array[0]).isEmpty()) {
        // ...
    }
}

However, if modifying the value in the array itself is not intended, make the array const, or use at () 代替。

该函数在 Qt 6.9 引入。

另请参阅 at () 和 size ().

QJniArray Class

公共类型

公共函数

详细描述

成员类型文档编制

[alias] QJniArray:: const_iterator

[alias] QJniArray:: const_reverse_iterator

成员函数文档编制

[noexcept] QJniArray < T > ::iterator QJniArray:: begin ()

[noexcept] QJniArray < T > ::const_iterator QJniArray:: begin () const

[noexcept] QJniArray < T > ::const_iterator QJniArray:: cbegin () const

[noexcept] QJniArray < T > ::const_iterator QJniArray:: constBegin () const

[noexcept] QJniArray < T > ::iterator QJniArray:: end ()

[noexcept] QJniArray < T > ::const_iterator QJniArray:: cend () const

[noexcept] QJniArray < T > ::const_iterator QJniArray:: constEnd () const

[noexcept] QJniArray < T > ::const_iterator QJniArray:: end () const

[noexcept] QJniArray < T > ::reverse_iterator QJniArray:: rbegin ()

[noexcept] QJniArray < T > ::const_reverse_iterator QJniArray:: crbegin () const

[noexcept] QJniArray < T > ::const_reverse_iterator QJniArray:: rbegin () const

[noexcept] QJniArray < T > ::reverse_iterator QJniArray:: rend ()

[noexcept] QJniArray < T > ::const_reverse_iterator QJniArray:: crend () const

[noexcept] QJniArray < T > ::const_reverse_iterator QJniArray:: rend () const

QJniArray < T > ::const_reference QJniArray:: at ( QJniArrayBase::size_type i ) const

QJniArray < T > ::const_reference QJniArray:: operator[] ( QJniArrayBase::size_type i ) const

QJniArray:: QJniArray ()

[explicit] template <typename Container, QJniArrayBase::if_compatible_source_container<Container> = true> QJniArray:: QJniArray ( 容器 && container )

约束

[noexcept] template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray:: QJniArray ( QJniArray < 其它 > && other )

约束

[explicit, since 6.9] QJniArray:: QJniArray ( QJniArrayBase::size_type size )

[explicit noexcept] QJniArray:: QJniArray ( QJniObject && object )

template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray:: QJniArray (const QJniArray < 其它 > & other )

约束

[explicit] QJniArray:: QJniArray (const QJniObject & object )

[explicit] QJniArray:: QJniArray ( jarray array )

[default] QJniArray:: QJniArray ( std::initializer_list < T > & list )

QJniArray:: ~QJniArray ()

auto QJniArray:: arrayObject () const

template <typename Container = QJniArrayBase::ToContainerType<T>, QJniArrayBase::if_compatible_target_container<T, Container> = true> 容器 QJniArray:: toContainer ( 容器 && container = {}) const

[noexcept] template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray < T > &QJniArray:: operator= ( QJniArray < 其它 > && other )

约束

template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray < T > &QJniArray:: operator= (const QJniArray < 其它 > & other )

约束

[since 6.9] QJniArray < T > ::reference QJniArray:: operator[] ( QJniArrayBase::size_type i )

内容

`[alias]` QJniArray:: const_iterator

`[alias]` QJniArray:: const_reverse_iterator

`[noexcept]` QJniArray < T > ::iterator QJniArray:: begin ()

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: begin () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: cbegin () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: constBegin () const

`[noexcept]` QJniArray < T > ::iterator QJniArray:: end ()

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: cend () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: constEnd () const

`[noexcept]` QJniArray < T > ::const_iterator QJniArray:: end () const

`[noexcept]` QJniArray < T > ::reverse_iterator QJniArray:: rbegin ()

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: crbegin () const

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: rbegin () const

`[noexcept]` QJniArray < T > ::reverse_iterator QJniArray:: rend ()

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: crend () const

`[noexcept]` QJniArray < T > ::const_reverse_iterator QJniArray:: rend () const

`[explicit]` template <typename Container, QJniArrayBase::if_compatible_source_container<Container> = true> QJniArray:: QJniArray ( 容器 && container )

`[noexcept]` template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray:: QJniArray ( QJniArray < 其它 > && other )

`[explicit, since 6.9]` QJniArray:: QJniArray ( QJniArrayBase::size_type size )

`[explicit noexcept]` QJniArray:: QJniArray ( QJniObject && object )

`[explicit]` QJniArray:: QJniArray (const QJniObject & object )

`[explicit]` QJniArray:: QJniArray ( jarray array )

`[default]` QJniArray:: QJniArray ( std::initializer_list < T > & list )

`[noexcept]` template <typename Other, QJniArrayBase::if_convertible<Other, T> = true> QJniArray < T > &QJniArray:: operator= ( QJniArray < 其它 > && other )

`[since 6.9]` QJniArray < T > ::reference QJniArray:: operator[] ( QJniArrayBase::size_type i )