Lesson 2 Running app android

Running Your App PREVIOUS NEXT
If you followed the previous lesson
to create an Android project, it
includes a default set of "Hello
World" source files that allow you to
immediately run the app.
How you run your app depends on
two things: whether you have a real
Android-powered device and whether
you're using Eclipse. This lesson
shows you how to install and run
your app on a real device and on the
Android emulator, and in both cases
with either Eclipse or the command
line tools.
Before you run your app, you should
be aware of a few directories and
files in the Android project:
AndroidManifest.xml
The manifest file describes the
fundamental characteristics of the
app and defines each of its
components. You'll learn about
various declarations in this file as
you read more training classes.
One of the most important elements
your manifest should include is the
<uses-sdk> element. This declares
your app's compatibility with
different Android versions using the
android:minSdkVersion and
android:targetSdkVersion
attributes. For your first app, it
should look like this:
<manifest xmlns:android = "http://schemas.android.com/apk/res/android" ... >
<uses-sdk android:minSdkVersion ="8" android:targetSdkVersion = "17" />
...
</manifest>
You should always set the
android:targetSdkVersion as
high as possible and test your app
on the corresponding platform
version. For more information, read
Supporting Different Platform
Versions.
src/
Directory for your app's main source
files. By default, it includes an
Activity class that runs when your
app is launched using the app icon.
res/
Contains several sub-directories for
app resources. Here are just a few:
drawable-hdpi/
Directory for drawable objects (such
as bitmaps) that are designed for
high-density (hdpi) screens. Other
drawable directories contain assets
designed for other screen densities.
layout/
Directory for files that define your
app's user interface.
values/
Directory for other various XML files
that contain a collection of
resources, such as string and color
definitions.
When you build and run the default
Android app, the default Activity
class starts and loads a layout file
that says "Hello World." The result is
nothing exciting, but it's important
that you understand how to run your
app before you start developing.
Run on a Real Device
If you have a real Android-powered
device, here's how you can install
and run your app:
1. Plug in your device to your
development machine with a USB
cable. If you're developing on
Windows, you might need to install
the appropriate USB driver for your
device. For help installing drivers,
see the OEM USB Drivers document.
2. Enable USB debugging on your
device.
On most devices running Android
3.2 or older, you can find the option
under Settings > Applications >
Development .
On Android 4.0 and newer, it's in
Settings > Developer options .
Note: On Android 4.2 and newer,
Developer options is hidden by
default. To make it available, go to
Settings > About phone and tap
Build number seven times. Return
to the previous screen to find
Developer options.
To run the app from Eclipse:
1. Open one of your project's files and
click Run from the toolbar.
2. In the Run as window that appears,
select Android Application and click
OK .
Eclipse installs the app on your
connected device and starts it.
Or to run your app from a command
line:
1. Change directories to the root of
your Android project and execute:
ant debug
2. Make sure the Android SDK
platform-tools/ directory is
included in your PATH environment
variable, then execute:
adb install bin/MyFirstApp-debug.apk
3. On your device, locate MyFirstActivity
and open it.
That's how you build and run your
Android app on a device! To start
developing, continue to the next
lesson.
Run on the Emulator
Whether you're using Eclipse or the
command line, to run your app on
the emulator you need to first create
an Android Virtual Device (AVD). An
AVD is a device configuration for the
Android emulator that allows you to
model different devices.
To create an AVD:
1. Launch the Android Virtual Device
Manager:
a. In Eclipse, click Android Virtual
Device Manager from the
toolbar.
b. From the command line, change
directories to <sdk>/tools/
and execute:
android avd
2. In the Android Virtual Device
Manager panel, click New .
3. Fill in the details for the AVD. Give
it a name, a platform target, an SD
card size, and a skin (HVGA is
default).
4. Click Create AVD .
5. Select the new AVD from the Android
Virtual Device Manager and click
Start .
6. After the emulator boots up, unlock
the emulator screen.
To run the app from Eclipse:
1. Open one of your project's files and
click Run from the toolbar.
2. In the Run as window that appears,
select Android Application and click
OK .
Eclipse installs the app on your AVD
and starts it.
Or to run your app from the
command line:
1. Change directories to the root of
your Android project and execute:
ant debug
2. Make sure the Android SDK
platform-tools/ directory is
included in your PATH environment
variable, then execute:
adb install bin/MyFirstApp-debug.apk
3. On the emulator, locate
MyFirstActivity and open it.
That's how you build and run your
Android app on the emulator! To
start developing, continue to the
next lesson .