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46 lines
3.3 KiB
Markdown
46 lines
3.3 KiB
Markdown
---
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layout: editable
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title: File View Providers
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---
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A file view provider (see the [FileViewProvider](https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/psi/FileViewProvider.java) class) is a new concept in IntelliJ IDEA beginning with version 6.0. Its main purpose is managing access to multiple PSI trees within a single file.
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For example, a JSPX page has a separate PSI tree for the Java code in it (```PsiJavaFile```), a separate tree for the XML code (```XmlFile```), and a separate tree for JSP as a whole
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[JspFile](https://github.com/JetBrains/intellij-community/blob/master/java/jsp-openapi/src/com/intellij/psi/jsp/JspFile.java)).
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Each of the PSI trees covers the entire contents of the file, and contains special "outer language elements" in the places where contents in a different language can be found.
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A ```FileViewProvider``` instance corresponds to a single ```VirtualFile```, a single ```Document```, and can be used to retrieve multiple ```PsiFile``` instances.
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## How do I get one?
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* From a VirtualFile: ```PsiManager.getInstance(project).findViewProvider()```
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* From a PSI file: ```psiFile.getViewProvider()```
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## What can I do with one?
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* To get the list of all languages for which PSI trees exist in a file: ```fileViewProvider.getLanguages()```
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* To get the PSI tree for a particular language: ```fileViewProvider.getPsi(language)```, where the ```language``` parameter can take values of the
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[Language](https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/lang/Language.java)
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type defined in
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[StdLanguages](https://github.com/JetBrains/intellij-community/blob/master/platform/platform-api/src/com/intellij/lang/StdLanguages.java)
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class. For example, to get the PSI tree for XML, use ```fileViewProvider.getPsi(StdLanguages.XML)```.
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* To find an element of a particular language at the specified offset in the file: ```fileViewProvider.findElementAt(offset,language)```
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## How do I extend it?
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To create a file type that has multiple interspersing trees for different languages, your plugin must contain an extension to the _fileType.fileViewProviderFactory_
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[extension point](http://www.jetbrains.org/intellij/sdk/docs/basics/plugin_structure/plugin_extensions_and_extension_points.html)
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available in the IntelliJ Platform core.
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This extension point is declared using the
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[FileTypeExtensionPoint](https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/openapi/fileTypes/FileTypeExtensionPoint.java)
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bean class.
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To access this extension point, create a Java class that implements the
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[FileViewProviderFactory](https://github.com/JetBrains/intellij-community/blob/master/platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java)
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interface, and in this class, override the ```createFileViewProvider``` method.
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To declare the extension to the _fileType.fileViewProviderFactory_ extension point, to the <extensions> section of the plugin.xml file, add the following syntax:
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```
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<fileType.fileViewProviderFactory filetype=%file type% implementationClass=%class name%>
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</fileType.fileViewProviderFactory>
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```
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where the _%file type%_ refers to the type of the file to create (for example, to "JFS"), and the _%class name%_ refers to the name of your Java class that implements the ```FileViewProviderFactory``` interface. |