• The official Android Developer webpage may be found here. To be honest, reading the entire website is essential for understanding the ecosystem and the various solutions, ideas, and technology associated with Android. You won't recall everything, but you'll know what to look for next time.
• Since May 2017, Google has officially supported Kotlin on Android as a 'first-class' language. Because fewer organisations are producing commercial apps using only Java, learning Kotlin is a must if you want to be a successful Android developer.
• Return to the official Android website and select Develop this time. The following are the two most essential sections :You can discover a number of useful examples in training courses and Codelabs. Before you start programming for real, go over all of these lessons.
• API Reference — I understand that going through all of these texts, descriptions, examples, and so on will be difficult, but it will be worthwhile. 

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