• Learn how to debug your Android application as it is the single most important skill for any developer. Android Studio provides a debugger that allows you to do so many important things.
• Know about the navigations, tasks, and back stack. Android Activities are the logical construct of the screens that we want a user to navigate through. The relation that each Activity holds with respect to others is very crucial for a good user experience.

• Understanding the Context In Android Application. To develop a better Android app, we must know what context is? Context is almost everywhere in Android Development and it is the most important thing in Android Development, so we must understand to use it correctly.
• Learn about threading in detail. As the Java Virtual Machine allows an application to have multiple threads of execution running concurrently. We must know how to take advantage of a multi-threading environment correctly.

• Learn how to handle the configuration changes. Some device configurations can change during the runtime such as screen orientation, keyboard availability, and when the user enables multi-window mode. We must know how to handle these changes.
• Know about the 3rd party libraries. We have 

• Understanding the Android Core. Looper, Handler, and HandlerThread are Android’s way of solving the problems of asynchronous programming. 

• Learn about the tools to get the metrics of memory usage, CPU usage, and etc. There are a few metrics that you should measure continuously while android application development.
• Learn about creating Custom View. To develop a better Android app, we must know how to create custom views.
• Always focus more on learning techniques not so many frameworks. This helps in the longer run.

• Holding reference of objects that are not required anymore is a bad practice, freeing object’s reference after being served is helpful for the garbage collector to kill that object, that eventually helps yourself in memory leaks issues. If you keep objects reference unnecessarily, it only leads to memory leaks. Learn how to detect and fix the memory leaks in the Android application.
• Learn about the performance patterns in Android applications. How to improve the performance of your application.

• Understand Bitmaps. As it takes a huge amount of memory, can lead to OOM easily. Users love content! Especially when the content is well-formatted and looks nice. 
• Learn about Android Jetpack. It is built to make app development fast. It is the next generation of Android components that brings together the benefits of the support library, backward compatibility and immediate updates to a larger set of components. Android Jetpack manages activities like background tasks, navigation, and lifecycle management, so you can eliminate boilerplate code and focus on what makes your app great.

• Learn how to apply proguard in an Android application. It is a tool used to minify the code, obfuscate the code, and optimize the code which reduces the size of the application.
• Read about the security tips to build a secure Android application.
• Know about the Android Useful tools. These tools make the development fast and our life easier. Do not forget to explore and use these tools.
• Read others' code. This is the best thing a developer can do and learn to code in the best way. I
• Know about the Android development best practices.

• Learn Git. It is a version control system for tracking changes in computer files and coordinating work on those files among multiple people.
• Know how to improve your code with lint checks.
• Know about the Gradle Build Tool.
• Contribute to open-source projects.
• Know about Continuous Integration. It ensures that your code is building on a server that is not your own machine. Use CI like Jenkins, Circle CI, Travis, and etc.
• Become more productive in android with android studio plugins.
• Always be updated with the new technology in Android. If you miss it, you simply miss it.

• Know about database and SQL.
• Know about the REST.
• Learn about APIs.
• Learn about the content providers. They are used to share data between the applications. They provide mechanisms for defining data security and for encapsulating the data.
• Learn about RecyclerView Optimization.
• Learn about the caching implementations.
• Learn about optimizing network request frequencies.
• Learn about the Android Sensors, GPS, Acceleration.
• Learn about location and maps.
• Learn about battery improvement.
• Understand the app launch time and work on to improve it.
• Know how you can reduce the APK size.

blog.mindorks.com 

• Android Jetpack is the next generation of Android components. It manages activities like background tasks, navigation, and Lifecycle management.
• Learn about MVP architecture.