原文： https://hubcarl.github.io/blog/2016/08/13/react-native-plugin/

编写自定义插件需要继承ReactContextBaseJavaModule和实现ReactPackage接口, 具体实现步骤如下：

1. 继承ReactContextBaseJavaModule接口

public class IntentModule extends ReactContextBaseJavaModule

2. 重写 getName方法,暴露给JS端调用名

@Override
public String getName() {
    return "IntentModule";
}

3. 给暴露给JS的方法添加 @ReactMethod 注解，且方法的返回值只能是void

@ReactMethod
public void backActivity(int count) {
    if (count > 0) {
        try {
            Activity currentActivity = getCurrentActivity();
            currentActivity.finish();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4.实现ReactPackage接口

public class IntentPackage implements ReactPackage {
    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
        return Arrays.<NativeModule>asList(
                new IntentModule(reactContext)
        );
    }
    @Override
    public List<Class<? extends JavaScriptModule>> createJSModules() {
        return Collections.emptyList();
    }
    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        return Collections.emptyList();
    }
}

5.在Application中注册IntentPackage

@Override
protected List<ReactPackage> getPackages() {
  return Arrays.<ReactPackage>asList(
          new MainReactPackage(),
          new IntentPackage()
  );
}

6.JavaScript调用IntentModule的backActivity方法

NativeModules.IntentModule.backActivity();