PySide.QtCore.QXmlStreamReader class provides a fast parser for reading well-formed XML via a simple streaming API.
PySide.QtCore.QXmlStreamReader is a faster and more convenient replacement for Qt's own SAX parser (see PySide.QtXml.QXmlSimpleReader ). In some cases it might also be a faster and more convenient alternative for use in applications that would otherwise use a DOM tree (see PySide.QtXml.QDomDocument ). PySide.QtCore.QXmlStreamReader reads data either from a PySide.QtCore.QIODevice (见 PySide.QtCore.QXmlStreamReader.setDevice() ), or from a raw PySide.QtCore.QByteArray (见 PySide.QtCore.QXmlStreamReader.addData() ).
Qt 提供 PySide.QtCore.QXmlStreamWriter 为写入 XML。
The basic concept of a stream reader is to report an XML document as a stream of tokens, similar to SAX. The main difference between PySide.QtCore.QXmlStreamReader and SAX is how these XML tokens are reported. With SAX, the application must provide handlers (callback functions) that receive so-called XML events from the parser at the parser's convenience. With PySide.QtCore.QXmlStreamReader , the application code itself drives the loop and pulls tokens from the reader, one after another, as it needs them. This is done by calling PySide.QtCore.QXmlStreamReader.readNext() , where the reader reads from the input stream until it completes the next token, at which point it returns the PySide.QtCore.QXmlStreamReader.tokenType() . A set of convenient functions including PySide.QtCore.QXmlStreamReader.isStartElement() and PySide.QtCore.QXmlStreamReader.text() can then be used to examine the token to obtain information about what has been read. The big advantage of this pulling approach is the possibility to build recursive descent parsers with it, meaning you can split your XML parsing code easily into different methods or classes. This makes it easy to keep track of the application's own state when parsing XML.
A typical loop with PySide.QtCore.QXmlStreamReader 看起来像这样:
xml = QXmlStreamReader()
...
while not xml.atEnd():
xml.readNext();
... # do processing
if xml.hasError():
... # do error handling
PySide.QtCore.QXmlStreamReader is a well-formed XML 1.0 parser that does not include external parsed entities. As long as no error occurs, the application code can thus be assured that the data provided by the stream reader satisfies the W3C's criteria for well-formed XML. For example, you can be certain that all tags are indeed nested and closed properly, that references to internal entities have been replaced with the correct replacement text, and that attributes have been normalized or added according to the internal subset of the DTD.
若发生错误当剖析时， PySide.QtCore.QXmlStreamReader.atEnd() and PySide.QtCore.QXmlStreamReader.hasError() return true, and PySide.QtCore.QXmlStreamReader.error() returns the error that occurred. The functions PySide.QtCore.QXmlStreamReader.errorString() , PySide.QtCore.QXmlStreamReader.lineNumber() , PySide.QtCore.QXmlStreamReader.columnNumber() ，和 PySide.QtCore.QXmlStreamReader.characterOffset() are for constructing an appropriate error or warning message. To simplify application code, PySide.QtCore.QXmlStreamReader contains a PySide.QtCore.QXmlStreamReader.raiseError() mechanism that lets you raise custom errors that trigger the same error handling described.
QXmlStream 书签范例 illustrates how to use the recursive descent technique to read an XML bookmark file (XBEL) with a stream reader.
QXmlStream understands and resolves XML namespaces. E.g. in case of a StartElement , PySide.QtCore.QXmlStreamReader.namespaceUri() returns the namespace the element is in, and PySide.QtCore.QXmlStreamReader.name() returns the element's local name. The combination of namespaceUri and name uniquely identifies an element. If a namespace prefix was not declared in the XML entities parsed by the reader, the namespaceUri is empty.
If you parse XML data that does not utilize namespaces according to the XML specification or doesn't use namespaces at all, you can use the element's PySide.QtCore.QXmlStreamReader.qualifiedName() instead. A qualified name is the element's PySide.QtCore.QXmlStreamReader.prefix() followed by colon followed by the element's local PySide.QtCore.QXmlStreamReader.name() - exactly like the element appears in the raw XML data. Since the mapping namespaceUri to prefix is neither unique nor universal, PySide.QtCore.QXmlStreamReader.qualifiedName() should be avoided for namespace-compliant XML data.
In order to parse standalone documents that do use undeclared namespace prefixes, you can turn off namespace processing completely with the PySide.QtCore.QXmlStreamReader.namespaceProcessing() 特性。
PySide.QtCore.QXmlStreamReader is an incremental parser. It can handle the case where the document can't be parsed all at once because it arrives in chunks (e.g. from multiple files, or over a network connection). When the reader runs out of data before the complete document has been parsed, it reports a PrematureEndOfDocumentError . When more data arrives, either because of a call to PySide.QtCore.QXmlStreamReader.addData() or because more data is available through the network PySide.QtCore.QXmlStreamReader.device() , the reader recovers from the PrematureEndOfDocumentError error and continues parsing the new data with the next call to PySide.QtCore.QXmlStreamReader.readNext() .
For example, if your application reads data from the network using a network access manager , you would issue a network request to the manager and receive a network reply in return. Since a PySide.QtNetwork.QNetworkReply 是 PySide.QtCore.QIODevice , you connect its PySide.QtNetwork.QNetworkReply.readyRead() signal to a custom slot, e.g. slotReadyRead() in the code snippet shown in the discussion for PySide.QtNetwork.QNetworkAccessManager . In this slot, you read all available data with PySide.QtNetwork.QNetworkReply.readAll() and pass it to the XML stream reader using PySide.QtCore.QXmlStreamReader.addData() . Then you call your custom parsing function that reads the XML events from the reader.
| 参数： |
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构造流读取器。
创建的新流读取器读取自 device .
创建的新流读取器读取自 data .
另请参阅
PySide.QtCore.QXmlStreamReader.addData() PySide.QtCore.QXmlStreamReader.clear() PySide.QtCore.QXmlStreamReader.setDevice()
创建的新流读取器读取自 data .
另请参阅
PySide.QtCore.QXmlStreamReader.addData() PySide.QtCore.QXmlStreamReader.clear() PySide.QtCore.QXmlStreamReader.setDevice()
创建的新流读取器读取自 data .
此枚举指定不同错误情况
| 常量 | 描述 |
|---|---|
| QXmlStreamReader.NoError | 没有发生错误。 |
| QXmlStreamReader.CustomError | 引发自定义错误采有 PySide.QtCore.QXmlStreamReader.raiseError() |
| QXmlStreamReader.NotWellFormedError | The parser internally raised an error due to the read XML not being well-formed. |
| QXmlStreamReader.PrematureEndOfDocumentError | The input stream ended before a well-formed XML document was parsed. Recovery from this error is possible if more XML arrives in the stream, either by calling PySide.QtCore.QXmlStreamReader.addData() or by waiting for it to arrive on the PySide.QtCore.QXmlStreamReader.device() . |
| QXmlStreamReader.UnexpectedElementError | The parser encountered an element that was different to those it expected. |
此枚举指定读取器刚刚读取的令牌类型。
| 常量 | 描述 |
|---|---|
| QXmlStreamReader.NoToken | 读取器尚未读取任何内容。 |
| QXmlStreamReader.Invalid | 发生错误，报告在 PySide.QtCore.QXmlStreamReader.error() and PySide.QtCore.QXmlStreamReader.errorString() . |
| QXmlStreamReader.StartDocument | The reader reports the XML version number in PySide.QtCore.QXmlStreamReader.documentVersion() , and the encoding as specified in the XML document in PySide.QtCore.QXmlStreamReader.documentEncoding() . If the document is declared standalone, PySide.QtCore.QXmlStreamReader.isStandaloneDocument() returns true; otherwise it returns false. |
| QXmlStreamReader.EndDocument | The reader reports the end of the document. |
| QXmlStreamReader.StartElement | The reader reports the start of an element with PySide.QtCore.QXmlStreamReader.namespaceUri() and PySide.QtCore.QXmlStreamReader.name() . Empty elements are also reported as StartElement , followed directly by EndElement . The convenience function PySide.QtCore.QXmlStreamReader.readElementText() can be called to concatenate all content until the corresponding EndElement . Attributes are reported in PySide.QtCore.QXmlStreamReader.attributes() , namespace declarations in PySide.QtCore.QXmlStreamReader.namespaceDeclarations() . |
| QXmlStreamReader.EndElement | The reader reports the end of an element with PySide.QtCore.QXmlStreamReader.namespaceUri() and PySide.QtCore.QXmlStreamReader.name() . |
| QXmlStreamReader.Characters | The reader reports characters in PySide.QtCore.QXmlStreamReader.text() . If the characters are all white-space, PySide.QtCore.QXmlStreamReader.isWhitespace() returns true. If the characters stem from a CDATA section, PySide.QtCore.QXmlStreamReader.isCDATA() returns true. |
| QXmlStreamReader.Comment | 读取器报告注释按 PySide.QtCore.QXmlStreamReader.text() . |
| QXmlStreamReader.DTD | The reader reports a DTD in PySide.QtCore.QXmlStreamReader.text() , notation declarations in PySide.QtCore.QXmlStreamReader.notationDeclarations() , and entity declarations in PySide.QtCore.QXmlStreamReader.entityDeclarations() . Details of the DTD declaration are reported in in PySide.QtCore.QXmlStreamReader.dtdName() , PySide.QtCore.QXmlStreamReader.dtdPublicId() ，和 PySide.QtCore.QXmlStreamReader.dtdSystemId() . |
| QXmlStreamReader.EntityReference | The reader reports an entity reference that could not be resolved. The name of the reference is reported in PySide.QtCore.QXmlStreamReader.name() , the replacement text in PySide.QtCore.QXmlStreamReader.text() . |
| QXmlStreamReader.ProcessingInstruction | The reader reports a processing instruction in PySide.QtCore.QXmlStreamReader.processingInstructionTarget() and PySide.QtCore.QXmlStreamReader.processingInstructionData() . |
此枚举指定不同行为在 PySide.QtCore.QXmlStreamReader.readElementText() .
| 常量 | 描述 |
|---|---|
| QXmlStreamReader.ErrorOnUnexpectedElement | Raise an UnexpectedElementError and return what was read so far when a child element is encountered. |
| QXmlStreamReader.IncludeChildElements | Recursively include the text from child elements. |
| QXmlStreamReader.SkipChildElements | 跳过子级元素。 |
注意
该枚举在 Qt 4.6 引入或被修改
| 参数： | data – str |
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添加更多 data for the reader to read. This function does nothing if the reader has a PySide.QtCore.QXmlStreamReader.device() .
| 参数： | data – unicode |
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添加更多 data for the reader to read. This function does nothing if the reader has a PySide.QtCore.QXmlStreamReader.device() .
| 参数： | data – PySide.QtCore.QByteArray |
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添加更多 data for the reader to read. This function does nothing if the reader has a PySide.QtCore.QXmlStreamReader.device() .
| 参数： | extraNamespaceDeclaraction – PySide.QtCore.QXmlStreamNamespaceDeclaration |
|---|
添加 extraNamespaceDeclaration . The declaration will be valid for children of the current element, or - should the function be called before any elements are read - for the entire XML document.
| 参数： | extraNamespaceDeclaractions – |
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| 返回类型： | PySide.QtCore.bool |
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Returns true if the reader has read until the end of the XML document, or if an PySide.QtCore.QXmlStreamReader.error() has occurred and reading has been aborted. Otherwise, it returns false.
当 PySide.QtCore.QXmlStreamReader.atEnd() and PySide.QtCore.QXmlStreamReader.hasError() return true and PySide.QtCore.QXmlStreamReader.error() 返回 PrematureEndOfDocumentError , it means the XML has been well-formed so far, but a complete XML document has not been parsed. The next chunk of XML can be added with PySide.QtCore.QXmlStreamReader.addData() , if the XML is being read from a PySide.QtCore.QByteArray , or by waiting for more data to arrive if the XML is being read from a PySide.QtCore.QIODevice . Either way, PySide.QtCore.QXmlStreamReader.atEnd() will return false once more data is available.
| 返回类型： | PySide.QtCore.QXmlStreamAttributes |
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返回属性为 StartElement .
| 返回类型： | PySide.QtCore.qint64 |
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返回当前字符偏移，从 0 开始。
移除任何 PySide.QtCore.QXmlStreamReader.device() or data from the reader and resets its internal state to the initial state.
| 返回类型： | PySide.QtCore.qint64 |
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返回当前列号，从 0 开始。
| 返回类型： | PySide.QtCore.QIODevice |
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返回被当前设备关联的 PySide.QtCore.QXmlStreamReader , or 0 if no device has been assigned.
| 返回类型： | PySide.QtCore.QStringRef |
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若 state() is StartDocument , this function returns the encoding string as specified in the XML declaration. Otherwise an empty string is returned.
| 返回类型： | PySide.QtCore.QStringRef |
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若 state() is StartDocument , this function returns the version string as specified in the XML declaration. Otherwise an empty string is returned.
| 返回类型： | PySide.QtCore.QStringRef |
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若 state() is DTD ，此函数返回 DTD 名称。否则返回空字符串。
| 返回类型： | PySide.QtCore.QStringRef |
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若 state() is DTD , this function returns the DTD's public identifier. Otherwise an empty string is returned.
| 返回类型： | PySide.QtCore.QStringRef |
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若 state() is DTD , this function returns the DTD's system identifier. Otherwise an empty string is returned.
| 返回类型： |
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若 state() is DTD , this function returns the DTD's unparsed (external) entity declarations. Otherwise an empty vector is returned.
QXmlStreamEntityDeclarations class is defined to be a QVector of PySide.QtCore.QXmlStreamEntityDeclaration .
| 返回类型： | PySide.QtCore.QXmlStreamEntityResolver |
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Returns the entity resolver, or 0 if there is no entity resolver.
| 返回类型： | PySide.QtCore.QXmlStreamReader.Error |
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返回当前错误的类型，或 NoError 若没有发生错误。
| 返回类型： | unicode |
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返回错误消息，设置采用 PySide.QtCore.QXmlStreamReader.raiseError() .
| 返回类型： | PySide.QtCore.bool |
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返回 true 若有发生错误，否则 false .
| 返回类型： | PySide.QtCore.bool |
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Returns true if the reader reports characters that stem from a CDATA section; otherwise returns false.
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 Characters ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 Comment ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 DTD ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 EndDocument ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 EndElement ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 EntityReference ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 ProcessingInstruction ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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Returns true if this document has been declared standalone in the XML declaration; otherwise returns false.
If no XML declaration has been parsed, this function returns false.
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 StartDocument ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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返回 true 若 PySide.QtCore.QXmlStreamReader.tokenType() 等于 StartElement ；否则返回 false。
| 返回类型： | PySide.QtCore.bool |
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Returns true if the reader reports characters that only consist of white-space; otherwise returns false.
| 返回类型： | PySide.QtCore.qint64 |
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返回当前行号，从 1 开始。
| 返回类型： | PySide.QtCore.QStringRef |
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返回本地名称为 StartElement , EndElement ，或 EntityReference .
| 返回类型： |
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若 state() is StartElement , this function returns the element's namespace declarations. Otherwise an empty vector is returned.
PySide.QtCore.QXmlStreamNamespaceDeclaration class is defined to be a QVector of PySide.QtCore.QXmlStreamNamespaceDeclaration .
| 返回类型： | PySide.QtCore.bool |
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| 返回类型： | PySide.QtCore.QStringRef |
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返回 namespaceUri 为 StartElement or EndElement .
| 返回类型： |
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若 state() is DTD , this function returns the DTD's notation declarations. Otherwise an empty vector is returned.
QXmlStreamNotationDeclarations class is defined to be a QVector of PySide.QtCore.QXmlStreamNotationDeclaration .
| 返回类型： | PySide.QtCore.QStringRef |
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返回前缀为 StartElement or EndElement .
| 返回类型： | PySide.QtCore.QStringRef |
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返回数据为 ProcessingInstruction .
| 返回类型： | PySide.QtCore.QStringRef |
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Returns the target of a ProcessingInstruction .
| 返回类型： | PySide.QtCore.QStringRef |
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Returns the qualified name of a StartElement or EndElement ;
A qualified name is the raw name of an element in the XML data. It consists of the namespace prefix, followed by colon, followed by the element's local name. Since the namespace prefix is not unique (the same prefix can point to different namespaces and different prefixes can point to the same namespace), you shouldn't use PySide.QtCore.QXmlStreamReader.qualifiedName() , but the resolved PySide.QtCore.QXmlStreamReader.namespaceUri() and the attribute's local PySide.QtCore.QXmlStreamReader.name() .
| 参数： | message – unicode |
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引发自定义错误采用可选错误 message .
| 参数： | behaviour – PySide.QtCore.QXmlStreamReader.ReadElementTextBehaviour |
|---|---|
| 返回类型： | unicode |
Convenience function to be called in case a StartElement was read. Reads until the corresponding EndElement and returns all text in-between. In case of no error, the current token (see PySide.QtCore.QXmlStreamReader.tokenType() ) after having called this function is EndElement .
函数串联 PySide.QtCore.QXmlStreamReader.text() when it reads either Characters or EntityReference 令牌，但跳过 ProcessingInstruction and Comment . If the current token is not StartElement , an empty string is returned.
behaviour defines what happens in case anything else is read before reaching EndElement . The function can include the text from child elements (useful for example for HTML), ignore child elements, or raise an UnexpectedElementError and return what was read so far.
| 返回类型： | unicode |
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此函数重载 PySide.QtCore.QXmlStreamReader.readElementText() .
Calling this function is equivalent to calling readElementText( ErrorOnUnexpectedElement ).
| 返回类型： | PySide.QtCore.QXmlStreamReader.TokenType |
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读取下一令牌并返回其类型。
With one exception, once an PySide.QtCore.QXmlStreamReader.error() is reported by PySide.QtCore.QXmlStreamReader.readNext() , further reading of the XML stream is not possible. Then PySide.QtCore.QXmlStreamReader.atEnd() returns true, PySide.QtCore.QXmlStreamReader.hasError() returns true, and this function returns QXmlStreamReader.Invalid .
The exception is when PySide.QtCore.QXmlStreamReader.error() 返回 PrematureEndOfDocumentError . This error is reported when the end of an otherwise well-formed chunk of XML is reached, but the chunk doesn't represent a complete XML document. In that case, parsing can be resumed by calling PySide.QtCore.QXmlStreamReader.addData() to add the next chunk of XML, when the stream is being read from a PySide.QtCore.QByteArray , or by waiting for more data to arrive when the stream is being read from a PySide.QtCore.QXmlStreamReader.device() .
| 返回类型： | PySide.QtCore.bool |
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Reads until the next start element within the current element. Returns true when a start element was reached. When the end element was reached, or when an error occurred, false is returned.
The current element is the element matching the most recently parsed start element of which a matching end element has not yet been reached. When the parser has reached the end element, the current element becomes the parent element.
You can traverse a document by repeatedly calling this function while ensuring that the stream reader is not at the end of the document:
<Code snippet "doc/src/snippets/xml/streamreader/traverse.cpp:traverse document" not found>
This is a convenience function for when you're only concerned with parsing XML elements. The QXmlStream 书签范例 makes extensive use of this function.
| 参数： | device – PySide.QtCore.QIODevice |
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把当前设备设为 device 。设置设备将流重置到其初始状态。
| 参数： | resolver – PySide.QtCore.QXmlStreamEntityResolver |
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Makes resolver the new PySide.QtCore.QXmlStreamReader.entityResolver() .
The stream reader does not take ownership of the resolver. It's the callers responsibility to ensure that the resolver is valid during the entire life-time of the stream reader object, or until another resolver or 0 is set.
| 参数： | arg__1 – PySide.QtCore.bool |
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Reads until the end of the current element, skipping any child nodes. This function is useful for skipping unknown elements.
The current element is the element matching the most recently parsed start element of which a matching end element has not yet been reached. When the parser has reached the end element, the current element becomes the parent element.
| 返回类型： | PySide.QtCore.QStringRef |
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Returns the text of Characters , Comment , DTD ，或 EntityReference .
| 返回类型： | unicode |
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以字符串形式返回读取器的当前令牌。
| 返回类型： | PySide.QtCore.QXmlStreamReader.TokenType |
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返回当前令牌类型。
当前令牌也可以查询采用方便函数 PySide.QtCore.QXmlStreamReader.isStartDocument() , PySide.QtCore.QXmlStreamReader.isEndDocument() , PySide.QtCore.QXmlStreamReader.isStartElement() , PySide.QtCore.QXmlStreamReader.isEndElement() , PySide.QtCore.QXmlStreamReader.isCharacters() , PySide.QtCore.QXmlStreamReader.isComment() , PySide.QtCore.QXmlStreamReader.isDTD() , PySide.QtCore.QXmlStreamReader.isEntityReference() ，和 PySide.QtCore.QXmlStreamReader.isProcessingInstruction() .