private void validate() {
		String message = null;

		if (gradleLocalChoiceButton.getSelection()) {
			String path = gradleLocalDirText.getText().trim();
			File dir = new File(path);
			if (path.isEmpty()) {
				message = "Path to local Gradle installation must be specified.";
			}
			else if (!dir.exists()) {
				message = "Path to local Gradle installation does not exist.";
			}
			else if (!dir.isDirectory()) {
				message = "Path to local Gradle installation is not a directory.";
			}
			else if (!new File(dir, "bin/gradle").exists()) {
				message =
					"Path to local Gradle installation appears invalid.  Missing gradle binary.";
			}
		}

		if (message == null) {
			GhidraProjectCreatorPreferences.setGhidraLastGradleDistribution(
				getGradleDistribution());
		}
		else {
			GhidraProjectCreatorPreferences.setGhidraLastGradleDistribution(null);
		}

		setErrorMessage(message);
		setPageComplete(message == null);
	}
Validates the fields on the page and updates the page's status.
Should be called every time a field on the page changes.
GhidraBuild/EclipsePlugins/GhidraDev/GhidraDevPlugin/src/main/java/ghidradev/ghidraprojectcreator/wizards/pages/ConfigureGradleWizardPage.java