Idea Plugin Dev - File Type Definition

File Type

public class SimpleFileType extends LanguageFileType {
    public static final SimpleFileType INSTANCE = new SimpleFileType();

    private SimpleFileType() {
        super(SimpleLanguage.INSTANCE);
    }

    @NotNull
    @Override
    public String getName() {
        return "Simple file";
    }

    @NotNull
    @Override
    public String getDescription() {
        return "Simple language file";
    }

    @NotNull
    @Override
    public String getDefaultExtension() {
        return "simple";
    }

    @Nullable
    @Override
    public Icon getIcon() {
        return SimpleIcon.FILE;
    }
}

Factory

public class SimpleFileTypeFactory extends FileTypeFactory {

    @Override
    public void createFileTypes(@NotNull FileTypeConsumer fileTypeConsumer) {
        fileTypeConsumer.consume(SimpleFileType.INSTANCE, "simple");
    }

}

Registration

In plugin.xml, via platform extension

<idea-plugin version="2">
  <!-- ....... -->
  <extensions defaultExtensionNs="com.intellij">
    <fileTypeFactory implementation="com.gerardnico.SimpleFileTypeFactory"/>    
  </extensions>
</idea-plugin>

Test

Run the project, create a file with the same extension and verify that this the good Icon