1. Working with Text

This tutorial shows how to use actions to access a caret placed in a document open in an editor. Using information about the caret, replace selected text in a document with a string.

The approach in this tutorial relies heavily on creating and registering actions. To review the fundamentals of creating and registering actions, refer to the Actions Tutorial.

Multiple examples are used from the editor_basics plugin code sample from the IntelliJ Platform SDK. It may be helpful to open that project in an IntelliJ Platform-based IDE, build the project, run it, select some text in the editor, and invoke the Editor Replace Text menu item on the editor context menu.

In this example, we access the Editor from an action. The source code for the Java class in this example is EditorIllustrationAction.

To register the action, we must add the corresponding elements to the <actions> section of the plugin configuration file plugin.xml. For more information, refer to the Registering Actions section of the Actions Tutorial. The EditorIllustrationAction action is registered in the group EditorPopupMenu so it will be available from the context menu when focus is on the editor:

<action
    id="EditorBasics.EditorIllustrationAction"
    class="org.intellij.sdk.editor.EditorIllustrationAction"
    text="Editor Replace Text"
    description="Replaces selected text with 'Replacement'."
    icon="SdkIcons.Sdk_default_icon">
  <add-to-group group-id="EditorPopupMenu" anchor="first"/>
</action>

To determine conditions by which the action will be visible and available requires EditorIllustrationAction to override the AnAction.update() method. For more information, refer to Extending the Update Method section of the Actions Tutorial.

To work with a selected part of the text, it's reasonable to make the menu action available only when the following requirements are met:

There is a Project object,
There is an instance of Editor available,
There is a text selection in Editor.

Additional steps will show how to check these conditions through obtaining instances of Project and Editor objects, and how to show or hide the action's menu items based on them.

Getting an Instance of the Active Editor from an Action Event

Using the AnActionEvent event passed into the update method, a reference to an instance of the Editor can be obtained by calling getData(CommonDataKeys.EDITOR). Similarly, to obtain a project reference, we use the getProject() method.

public class EditorIllustrationAction extends AnAction {
  @Override
  public void update(@NotNull AnActionEvent event) {
    // Get required data keys
    Project project = event.getProject();
    Editor editor = event.getData(CommonDataKeys.EDITOR);
    // ...
  }
}

Note: There are other ways to access an Editor instance:

If a DataContext object is available: CommonDataKeys.EDITOR.getData(context);
If only a Project object is available, use FileEditorManager.getInstance(project).getSelectedTextEditor()

Obtaining a Caret Model and Selection

After making sure a project is open, and an instance of the Editor is obtained, we need to check if any selection is available. The SelectionModel interface is accessed from the Editor object. Determining whether some text is selected is accomplished by calling the SelectionModel.hasSelection() method. Here's how the EditorIllustrationAction.update(AnActionEvent event) method should look:

public class EditorIllustrationAction extends AnAction {
  @Override
  public void update(@NotNull AnActionEvent event) {
    // Get required data keys
    Project project = event.getProject();
    Editor editor = event.getData(CommonDataKeys.EDITOR);

    // Set visibility only in the case of
    // existing project editor, and selection
    event.getPresentation().setEnabledAndVisible(project != null
        && editor != null && editor.getSelectionModel().hasSelection());
  }
}

Note: Editor also allows access to different models of text representation. The model classes are located in editor, and include:

Safely Replacing Selected Text in the Document

Based on the evaluation of conditions by EditorIllustrationAction.update(), the EditorIllustrationAction action menu item is visible. To make the menu item do something, the EditorIllustrationAction class must override the AnAction.actionPerformed() method. As explained below, this will require the EditorIllustrationAction.actionPerformed() method to:

Gain access to the document.
Get the character locations defining the selection.
Safely replace the contents of the selection.

Modifying the selected text requires an instance of the Document object, which is accessed from the Editor object. The Document represents the contents of a text file loaded into memory and opened in an IntelliJ Platform-based IDE editor. An instance of the Document will be used later when a text replacement is performed.

The text replacement will also require information about where the selection is in the document, which is provided by the primary Caret object, obtained from the CaretModel. Selection information is measured in terms of Offset, the count of characters from the beginning of the document to a caret location.

Text replacement could be done by calling the Document object's replaceString() method. However, safely replacing the text requires the Document to be locked and any changes performed in a write action. See the Threading Issues section to learn more about synchronization issues and changes safety on the IntelliJ Platform. This example changes the document within a WriteCommandAction.

The complete EditorIllustrationAction.actionPerformed() method is shown below:

Note the selection in the document is replaced by a string using a method on the Document object, but the method call is wrapped in a write action.
After the document change, the new text is de-selected by a call to the primary caret.

public class EditorIllustrationAction extends AnAction {
  @Override
  public void actionPerformed(@NotNull AnActionEvent event) {
    // Get all the required data from data keys
    Editor editor = event.getRequiredData(CommonDataKeys.EDITOR);
    Project project = event.getRequiredData(CommonDataKeys.PROJECT);
    Document document = editor.getDocument();

    // Work off of the primary caret to get the selection info
    Caret primaryCaret = editor.getCaretModel().getPrimaryCaret();
    int start = primaryCaret.getSelectionStart();
    int end = primaryCaret.getSelectionEnd();

    // Replace the selection with a fixed string.
    // Must do this document change in a write action context.
    WriteCommandAction.runWriteCommandAction(project, () ->
        document.replaceString(start, end, "editor_basics")
    );

    // De-select the text range that was just replaced
    primaryCaret.removeSelection();
  }
}

Last modified: 30 July 2024

IntelliJ Platform Plugin SDK Help

1. Working with Text

Creating a New Menu Action

Defining the Menu Action's Visibility

Getting an Instance of the Active Editor from an Action Event

Obtaining a Caret Model and Selection

Safely Replacing Selected Text in the Document