Apps development for Android step by step

Appendix D: Comments in XML and Java – it’s crucial to create a documentation of Android app

This would be short, but very useful appendix. When you’re programing you know at that specific moment very well what for are some variables, why are you using some methods, how are you going to implement some classes and so on. But two weeks later – believe us – you will spend as much time on trying to understand your existing code as developing new one unless… you add comments.

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Appendix C: Everything about sizes and dimensions in Android

Designing Android app you have to be aware of enormous variety of devices. They have different physical sizes (from small phones to large tablets), different screen sizes (diagonal from 3 inches or less to above 5 inches), different screen resolutions (from 320×480 pixels to Full HD – 1920×1080 – or more) and different screen densities – number of pixels per inch (from 120 dpi to 480 dpi). And there is also screen orientation (landscape or portrait) to take into account.

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Appendix B: Everything about colors in Android

Android uses standard RGB (red, green and blue) color model. Each primary color value is usually represented by hexadecimal number.  At the beginning of such a color definition you have to put a pound character (#).

The simplest is just #RGB format, where #000 is black and #FFF is white. But in this format we have only 16 values per color so it gives 4096 combinations. That’s why #RRGGBB format is mainly used. In this format we have 256 values per primary color, so 16 777 216 colors in total. Black is #000000 and white is #FFFFFF.

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Appendix A: Android XML syntax – structure of XML tags and attributes

XML files are used to define layout of Android apps and store data. Tags decide what elements would be used for app interface (like strings, images and buttons), how they would look like and what values would they have.

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