Apps development for Android step by step

Lesson 0.8: Additional information about project structure in Android Studio: java and resources folders

Let’s look again at the project tree (if you can’t see it, just click Project tab on the left of the screen).  Previously we were navigating directly to activity_main.xml file, but now we try to look also on other folders and files. Don’t worry only on a few of them, most we would never have to touch.

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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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Lesson 0.7: Running an Android app in a real device (but you don’t need any to create an app)

It’s difficult to test your app on dozens various devices, so described in previous lesson emulators are really helpful. But if you have any real Android device, you could run on it your apps. You don’t need to register anywhere or buy anything to do it (by the way those steps are necessary to create and test iOS apps).  All you need beside your phone or tablet is a USB cable (usually delivered with device) and USB driver (available for free in Internet).

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Lesson 0.6: Running an Android app in a virtual phone or tablet

We have our first app (displaying Hello world!) without coding anything. Before we start developing something more, let’s check how this simple app works. This is very easy  – we will use built in emulator of a mobile device. The emulator is a special application which would simulate a real Android device (including original system behavior and hardware behavior) on a computer.

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Lesson 0.5 Previewing app layout on various devices and screen sizes (without having them)

The previous lesson was finished after we managed to open activity_main.xml file with a layout of our first app. You should see preview of app interface on the screen: app name, Hello word text and system menu at the bottom. This is not working app in which you could click (we would run app in the next lesson), but preview of the app layout.

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