Android里的四大组建类到底是怎么创建的呢？是直接new出来的还是？，通过下面源码可以看到都是类加载器方式即通过反射的方式生成的（调用者都是在ActivityThread里）

//9.0源码
public class AppComponentFactory {

    public @NonNull Application instantiateApplication(@NonNull ClassLoader cl,
            @NonNull String className)
            throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        return (Application) cl.loadClass(className).newInstance();
    }


    public @NonNull Activity instantiateActivity(@NonNull ClassLoader cl, @NonNull String className,
            @Nullable Intent intent)
            throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        return (Activity) cl.loadClass(className).newInstance();
    }

   
    public @NonNull BroadcastReceiver instantiateReceiver(@NonNull ClassLoader cl,
            @NonNull String className, @Nullable Intent intent)
            throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        return (BroadcastReceiver) cl.loadClass(className).newInstance();
    }


    public @NonNull Service instantiateService(@NonNull ClassLoader cl,
            @NonNull String className, @Nullable Intent intent)
            throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        return (Service) cl.loadClass(className).newInstance();
    }

   
    public @NonNull ContentProvider instantiateProvider(@NonNull ClassLoader cl,
            @NonNull String className)
            throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        return (ContentProvider) cl.loadClass(className).newInstance();
    }

    /**
     * @hide
     */
    public static final AppComponentFactory DEFAULT = new AppComponentFactory();
}