MAP524/DPS924 Lecture 2

Developing on a real device

You don't need to get a special development device in order to do development work on it. Pretty much any phone or tablet can be used for regular application development, you just need to make sure it has the version of Android you need on it.

Configuring your device

To enable your phone/tablet to be used as a developement device follow these steps:

• In the "Developer options" settings you need to enable "USB debugging" to allow you to connect to the device using ADB.
  • If you don't see developer options - they are hidden by default and getting them to show varies on different devices. On a Nexus you go to "About phone" and tap "Build number" seven times.
• Then you also need to allow your phone to install the apps you build. Go to the "Security" settings and enable installing from "Unknown sources". This way you don't need to go through the trouble and expense of signing your application and publishing them on Google Play.

Note that for security reasons you shouldn't keep the USB debugging option turned on permanently. It's not easy to abuse but it can be done.

Configuring your system

If you have your own Linux system (not the ICT USB Stick) you'll have to allow your user to read and write directly to a USB device. To do this simply add this file to your /etc/udev/rules.d/ directory: 51-android.rules

If you don't do that you'll still be able to use your device, but you'll need to use it as the root user instead.

Rooting and unlocking

This is a complex topic that we don't need to dig into because you don't need a rooted or unlocked device to do development on it. But it's important for you to know what these terms mean:

• Unlocking the phone usually means unlocking it from a specific service provider. When you buy a phone from a telecom (perhaps at a discount) that phone will only work on that provider's network (it's locked to it). You can pay for a code that will unlock the device from that network and then use it with other providers.
• An unrelated thing you can unlock is the boot loader. Devices have a locked boot loader by default which means you will be unable to boot an alternate operating system or make any changes to the system image. This is accomplished with public key cryptography. The process for unlocking the boot loader is different for every device.
• A rooted phone has the "su" command, which will let you run commands as root on the phone. You need to unlock the boot loader before you can root a phone. A rooted phone is great for development if you do more system-level programming rather than just writing apps.

More command-line tools

These commands are used a lot in the real world. While developing a simple test app you may not need them - they are critical when used together with automated deployment systems and various development/QA setups.

android

This command works with the SDK Manager and the AVD Manager. Note that even though later you'll be doing all of your work from Android Studio - the SDKs and AVDs are separate from it and can be used also with Eclipse or with just the command-line.

SDK Manager

This application lets you download and delete parts of the Android development system. Specifically if you want to develop against a specific API (e.g. API 10 which is Android 2.3.3) you can download the development libraries and emulator images from that version.

Theoretically newer versions of the libraries can be used to develop against older APIs but that will give you more trouble than benefits.

AVD Manager

This application will let you create, modify, and start AVDs. These are virtual machines, the same idea as a desktop virtual machine, but specialized for phones. You can create an AVD of any Android version, and choose various hardware configurations for your virtual machine.

Project templates

You can also use the "android" command to create new projects (instead of doing it all manually as you have in the last lab).

Run this command to see the available options, you should be able to understand all the options listed:

android help

emulator

This command will let you run virtual machines you've created with the AVD Manager. For example:

$ android list avd
Available Android Virtual Devices:
    Name: myavd
    Path: /home/andrew/.android/avd/myavd.avd
  Target: Android 2.3.3 (API level 10)
 Tag/ABI: default/armeabi
    Skin: WVGA800
---------
    Name: Nexus_5_API_21
  Device: Nexus 5 (Google)
    Path: /home/andrew/.android/avd/Nexus_5_API_21.avd
  Target: Android 5.0.1 (API level 21)
 Tag/ABI: default/x86
    Skin: nexus_5
  Sdcard: 100M
Snapshot: no
$ emulator -avd Nexus_5_API_21

Remember these commands exist so you can do things (like testing) automatically. The emulator command has many options that you don't need to be concerned with. Now that you know this command exists and the type of options it has - you'll be able to find parameters you need when you need them.