For mobile UI design, it is important to note that the android app design will differ from iOS app design. In totality, the design processes are the same, however, there are a lot of differences between the user interface and experience models for both apps. These differences are imperative to create applications that are most suited for app operators irrespective of what operating system in use.
The first notable difference is the navigation. From the primary navigation to the secondary navigation buttons and the home buttons, mobile UI design for all apps are different from the iOS UI design. This can be attributed to the lack of Home-Menu-Back buttons at the bottom of the page, common to most android phones, and the middle buttons present in apple devices, i.e. until the removal in iPhone x. Navigating back and forth from each page in an application must be designed according to the operating system to essentially make it easier for users.
Another major difference in design is the screen size. Although both Android and iOS majorly use an 8dp grid to build their screen structure, the size of icons is quite different. This is so space is for the best view. Android apps design varies in regards to icon size according to the range of the phone in use. For xxxhigh DPI phones, the icon size is usually 192 x 192px compared to 120 x 120 on iPhone 11 and 8.
The font of both apps is also different. In iOS app design, Helvetica Neue font or San Francisco is chosen while in Android, Roboto is utilized. Of course, Android enables users to change their font, and is important to note this when designing your application. The space efficiency is dependent on what font is in use and chosen according to which operating system the UI design is for.
Other differences include the control design, alerts, tabs, and layout which are important to note during the application design process. Designing an app that will have an iOS variant and an Android variant is quite tedious, especially since mistakes will not go unnoticed by users. Comparing the home screen side by side and making a wireframe from the specifications on the respective operating systems, taking absolute note of the differences which exist between the two, will help in building the design of the mobile application. If this is stressful and proves tedious, there are templates specifically made for iOS app design and android app design.