android 2: a first project kirk scott 1. 2 2.1 creating a new, example android application project...

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Android 2: A First Project

Kirk Scott

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• 2.1 Creating a New, Example Android Application Project in Eclipse

• 2.2 Creating a Virtual Device, an Emulator• 2.3 Running an App on the Emulator in Eclipse• 2.4 Running the Project on an Attached

Device Instead of an Emulator

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2.1 Creating a New, Example Android Application Project in Eclipse

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• These overheads give a general overview of what is involved in getting a sample application to work—without even looking at its code, how it works, or what Android features it is making use of or depends on

• This is the initial monkey work mentioned in the previous set of overheads

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• These overheads are based on the initial example app that is given in the tutorial on the Android developer’s Web site

• If you discover that something in the overheads doesn’t seem to work, it means you can go directly to the tutorial for additional information

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A New Android Application

• In the Eclipse menu take the option File, New, Android Application Project

• The result of this is shown in the screenshot on the following overhead

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• In the first box, type in the following:• My First App• The other boxes will auto-complete as shown

in the following screenshot• (If the other boxes don’t auto-complete, this is

the first stage where you will have to go fish)

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• If things auto-completed as hoped, then you click the Next > button

• I will not show the next screenshots for the wizard• Just keep on accepting the defaults and taking

Next until you reach the Finish option• Notice how this is an area where you’re just doing

monkey work• God knows what all of the options mean at this

point

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• Once you click finish “things will happen”• They may happen slowly• I have a reasonably powerful machine and it

takes things a while to happen• There is a progress bar at the bottom which

gives you some indication of what’s going on

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• The initial Welcome screen may remain visible• If so, it covers up what has happened• Minimize anything in the way, and with luck,

what you will see in the Eclipse environment will look more or less like the screenshot on the following overhead

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• There are several things to notice in this screenshot

• The simplest and most reassuring is that if you can actually read the fine print, you will see that My First App is a Hello World app

• Whenever a new app is created using the defaults, this Hello World layout is provided by default

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• Obviously you’re not looking at code• The name of the file that is being shown has an

XML extension• What you’re seeing is the layout of the output

of the app• What you’re seeing is a representation of the

layout as provided in the development environment

• This is not the output showing in the emulator

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• You might notice that this screenshot of the editor doesn’t look quite like the one given earlier

• It doesn’t show the tools mentioned in the previous set of overheads, but it’s not exactly the same

• The toolbar happens to have disappeared• It’s not a big cause for concern• You can cause it to appear again or you can access

the tools through the menu

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2.2 Creating a Virtual Device, an Emulator

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Running the Project on a Virtual Device, an Emulator

• If you want to run the project using the emulator, you need to use the Android Virtual Device Manager to create a new virtual device

• If you take the Android Virtual Device Manager tool (or menu option) you should arrive at something similar to the screenshot shown on the following overhead

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• Click the New button to create an Android Virtual Device

• The window shown in the screenshot on the following overhead comes up

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• It’s shown on the following overhead with the drop down list for Device expanded

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• I tried using various devices• For initial test purposes I finally settled on the

device at the bottom of the list• My theory was that emulation for older,

simpler devices might work better or faster than for newer devices

• On the following overhead the form is shown filled out with representative values for that simple device

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Using Snapshot

• Another mystery:• Certain reference sources waffle on the

desirability of the Snapshot option• If you do select Snapshot and then make other

changes, you may have troubles later• Without Snapshot things might run more

slowly, but again, for the first time, try it without Snapshot

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Warning

• Here is an example of what can go wrong• I also tried making a virtual device that was a

Nexus tablet (the real hardware I’m working with)

• The memory option defaulted to a RAM value of 1024

• Unfortunately, when I continued with that value of 1024, I got a mystery error

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• My Web search informed me that if I changed the RAM value to 512, things should be OK

• For the device I’ve chosen to illustrate with, I took memory size values of 256

• For whatever reason, these values worked, and for the time being, that’s good enough for me

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Continuing with Virtual Device Creation

• Once you’ve got the parameters set, click on OK

• The system can drag on for a noticeable amount of time creating the virtual device

• Successful completion is indicated by the appearance of the device in the list as shown in the screenshot on the following overhead

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• There is no final OK step after virtual device creation

• You’re done—and you have to close this window

• If you just minimize it, it sits there but is still the active window

• To go on from here, close this window

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2.3 Running an App on the Emulator in Eclipse

• There are several different ways of running an app in the emulator

• Later on you will find out that you can create run configurations and debug configurations which are linked to a project

• This is a fine way of doing business, but more complicated than necessary initially

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• Starting the emulator can take a lot of time• Trying to run the app and having that process

start the emulator doesn’t seem to be the best plan

• The alternative is to start the emulator and then run the app in it

• This second approach is a better way to do it initially

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Starting the Emulator

• The Android Virtual Device screen is shown again on the following overhead with the created virtual device in it

• The screenshot shows the device as being selected and you’ll note a Start… button on the right hand side

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• If you click the Start button the following screen should appear

• This is the magic moment• Click Launch

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• After clicking launch, you should see the screen with the progress bar shown on the following overhead

• So far so good

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• Even before the previous screen goes away, or at the very least, as soon as it finishes, you should see the emulator on the screen

• It’s conceivable that you’ll have to close some things to find it

• It may be hidden• In any case, the initial stage of launch shouldn’t

take a long time, and this is what you should see

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Even If Things are Going OK, This is the Painful Part

• What you need now is patience (potentially a lot of it) and faith

• The Android message on the emulated device will flash white for an indeterminate period of time

• The emulator is still launching• As long as that process is going on, there’s

nothing else that you should do• Find something to kill a little time with, because a

watched pot never boils

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Edging Towards Success

• Eventually, with good luck, the emulator will look as shown on the following overhead

• In the screenshot that is shown, the emulator screen is grayed out

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• If your emulator is grayed out, click and drag over the emulator screen with the mouse

• This should wake it up, as shown on the following overhead

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• Click on the circle as directed• If the apps are shown, as they are in the

following screenshot, you have been successful

• The emulator has been launched and is running

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Running the Project in the Emulator

• If you want to run the project (without setting up run or debug) configurations, you need a source file for the project open in the Eclipse environment

• The screenshot on the following overhead shows the explorer on the left tracing the path to the MyFirstApp.java file, with that file open in the editor in the middle

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• By default, the project is likely to have been built, or will be built when you opt to run

• In the interests of thoroughness, you can also build the project yourself

• In the menu you would take Project, Build All

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• To run the app, go to the Run menu in the menu bar and take the Run option in it

• Or, there is a Run tool in the toolbar which you can click on

• There’s no need to take the dropdown option on the tool

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• The first time you to try to run it, you may get another dialog box asking what kind of thing you’re trying to run

• You’re given a list of choices, and the choice you want to make is “Android application”

• This dialog is shown on the following overhead

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• After choosing the right run type, once again there may be a certain amount of waiting, but with luck, when you look at the emulator, you’ll see what’s shown in the screen shot on the following overhead

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• Click and drag over the emulator screen, and it comes to life, as shown on the following overhead

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2.4 Running the Project on an Attached Device Instead of an Emulator

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• If you haven’t yet run a homemade app on your device, there are essentially 3 steps:

• Getting the Device Ready– You have to get into developer mode so that you it’s

possible to transfer the app to the device• Downloading and Installing the Driver– You need a USB driver in order to transfer through a

USB port• Running the App on the Device– Then you can run the app on the device

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• For reference purposes, these overheads were prepared with the following:

• Windows 7• Eclipse, as already described• A Nexus 7 tablet• The fact that it was the Nexus 7 tablet is

relevant to the specific instructions for getting the device ready

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Getting the Device Ready

• On the running device, go to the App screen• Tap on Settings• Under System, find About tablet• Tap Build number 7 times• When you return from doing this you should

find Developer options under System

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• Take Developer options• Under Debugging, enable USB debugging• You can now connect the device to your

system using a USB cable

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Downloading and Installing the Driver

• For information on the Nexus 7 USB driver, if you want any, go to the Android Web site:

• http://developer.android.com• A search on “USB driver” will take you to a

page that has information on the driver• The driver is only necessary when developing

in a Windows environment

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• You have a choice on getting the driver• Either you can download from this page• Or you can use the Android SDK Manager

from the ADT bundle in Eclipse• If you’re following this set of overheads and

not using your own development environment, using the SDK Manager is easier

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• Using the manager is so easy, there’s not much to say about it

• Click on the tool in the Eclipse environment• Find the line for the driver• Click and follow any instructions

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• If for some reason you want to download and install this the hard way, here is a brief list of the steps involved:

• Note which folder the driver is saved in• Right click on the “computer” icon on your

machine• Take the Manage option• Select the Device Manager on the left• Find and expand the Other devices

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• Find the Nexus 7 device in the list• You may find the Nexus 7 device somewhere

else depending on your situation• When you find the Nexus 7 device, right click on

it• Take the Update Driver Software… option• Follow the directions and browse to the location

where the driver was saved to• Blah blah blah

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Running the App on the Device

• The assumption is that you successfully installed the driver and your device is attached with a USB cable

• Open your app in Eclipse• Take the Run tool or the Run option in the menu• This should cause the Android Device Chooser to

appear on the screen, with the Nexus 7 device in the list

• This is shown on the following overhead

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• Select your device and click OK• The magic should happen• The app should run on your device• In addition to running, it will effectively be

installed on the device• If you go to the apps screen you’ll find the

little green Android icon for it and you can run it from there in the future

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Summary and Mission

• This is the end of the description of the first project

• As noted, it was only about nuts and bolts• The presentation had nothing to do with code

or the components of the app• Those topics will be pursued in the following

sets of overheads

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• You have two missions, neither of which are graded homework:

• 1. Get “Hello World” to work on an emulated virtual device in whatever development environment you’re using

• 2. Get “Hello World” to work on a real attached Android device

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The End