file_view_providers.md: cleanup

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Yann Cébron 2019-12-03 11:44:07 +01:00
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title: File View Providers
---
A file view provider (see the [`FileViewProvider`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProvider.java) class) was introduced in *IntelliJ IDEA* 6.0. Its main purpose is to manage access to multiple PSI trees within a single file.
A file view provider ([`FileViewProvider`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProvider.java)) manages access to multiple PSI trees within a single file.
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 [`JspFile`](upsource:///java/jsp-openapi/src/com/intellij/psi/jsp/JspFile.java)).
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.
A [`FileViewProvider`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProvider.java) instance corresponds to a single `VirtualFile`, a single `Document`, and can be used to retrieve multiple `PsiFile` instances.
A `FileViewProvider` instance corresponds to a single `VirtualFile`, a single `Document`, and can be used to retrieve multiple `PsiFile` instances.
## How do I get an FVP?
## How do I get a FileViewProvider?
* From a VirtualFile: `PsiManager.getInstance(project).findViewProvider()`
* From a PSI file: `psiFile.getViewProvider()`
* From a `VirtualFile`: `PsiManager.getInstance(project).findViewProvider()`
* From a `PsiFile`: `psiFile.getViewProvider()`
## What can I do with an FVP?
## What can I do with a FileViewProvider?
* To get the set of all languages for which PSI trees exist in a file: `fileViewProvider.getLanguages()`
* To get the PSI tree for a particular language: `fileViewProvider.getPsi(language)`, where the `language` parameter can take values of the [`Language`](upsource:///platform/core-api/src/com/intellij/lang/Language.java) type defined in [StdLanguages](upsource:///platform/platform-api/src/com/intellij/lang/StdLanguages.java) class. For example, to get the PSI tree for XML, use `fileViewProvider.getPsi(StdLanguages.XML)`.
* To get the PSI tree for a particular language: `fileViewProvider.getPsi(language)`. For example, to get the PSI tree for XML, use `fileViewProvider.getPsi(XMLLanguage.INSTANCE)`.
* To find an element of a particular language at the specified offset in the file: `fileViewProvider.findElementAt(offset, language)`
## How do I extend the FileViewProvider?
To create a file type that has multiple interspersing trees for different languages, your plugin must contain an extension to the `fileType.fileViewProviderFactory` [extension point](/basics/plugin_structure/plugin_extensions_and_extension_points.md) available in the *IntelliJ Platform* core.
To create a file type that has multiple interspersing trees for different languages, a plugin must contain an extension to the `com.intellij.fileType.fileViewProviderFactory` extension point.
This extension point is declared using the [`FileTypeExtensionPoint`](upsource:///platform/core-api/src/com/intellij/openapi/fileTypes/FileTypeExtensionPoint.java)
bean class.
To access this extension point, create a Java class that implements the [`FileViewProviderFactory`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java) interface, and in this class, override the `createFileViewProvider` method.
To declare the extension to the `fileType.fileViewProviderFactory` extension point, add the following syntax to the `<extensions>` section of the `plugin.xml` file:
Implement [`FileViewProviderFactory`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java) and return your `FileViewProvider` implementation from `createFileViewProvider()` method.
Register as follows in `plugin.xml`:
```xml
<extensions>
<fileType.fileViewProviderFactory filetype="%file_type%" implementationClass="%class_name%" />
<fileType.fileViewProviderFactory filetype="%file_type%" implementationClass="com.plugin.MyFileViewProviderFactory" />
</extensions>
```
Where `%file_type%` refers to the type of the file being created (for example, "JFS"), and the `%class_name%` refers to the name of your Java class that implements the [`FileViewProviderFactory`](upsource:///platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java) interface.
Where `%file_type%` refers to the type of the file being created (for example, "JFS").