DemoPlugin.java

package com.equaleyes.demoplugin;

import org.gradle.api.*;

@NonNullApi
public class DemoPlugin implements Plugin<Project> {
	private static final String TRANSFORM_CLASS = "com.android.build.api.transform.Transform";
    private static final String ERROR_PLUGIN_REQUIRED = "'com.android.application' or 'com.android.library' plugin required";
    private static final String ERROR_PLUGIN_OUTDATED = "Gradle plugin 1.5.0 or later is required.";

    Project project;

    @Override
    public void apply(Project project) {
        this.project = project;
        requireAndroidPlugins();
        requireTransformAvailable();
    }

    void requireAndroidPlugins() {
        boolean missingAndroid = project.getPlugins().withType(AppPlugin.class).isEmpty();
        boolean missingLibrary = project.getPlugins().withType(LibraryPlugin.class).isEmpty();

        if (missingAndroid && missingLibrary) {
            throw new GradleException(ERROR_PLUGIN_REQUIRED);
        }
    }

    void requireTransformAvailable() {
        try {
            Class.forName(TRANSFORM_CLASS);
        } catch (ClassNotFoundException e) {
            throw new GradleException(ERROR_PLUGIN_OUTDATED);
        }
    }
}