Testing Local Web Sites with the Android Emulator

The other day I was trying to fix an issue that was reported by a user of an older Android device. I am not an Android user, and do not have an actual Android device to test with. So, I thought I’d try using the Android Emulator to reproduce the issue and verify my fix.

These instructions assume you are using  Mac OS X, but should be easy to follow with minimal changes if you are on another platform.

Install Android Studio

If you are only interested in using the Android emulator, you could skip the full Android Studio installation and just install the Android SDK Tools. But, the Android Virtual Device (AVD) Manager that comes with Android Studio looks a bit more polished than the core SDK version, so I’d recommend installing the full Android Studio.

Android Studio Download Page

Create a Dummy Project in Android Studio

I couldn’t find a way to access the AVD Manager in Android Studio without having a project open. So, create a dummy project that you can open whenever you want to access the AVD Manager. It really doesn’t matter what you set. I just clicked through with the defaults for everything.

Setup Android Virtual Devices

Open your dummy project in Android Studio. Then, go to the Tools > Android > AVD Manager menu item. This will launch the AVD Manager.

ScreenCapture at Thu Sep 3 10:41:50 EDT 2015

Depending on what you selected when you installed Android Studio, you may have an AVD already configured. If you don’t, or you need to create a customized AVD, click the + Create Virtual Device… button.

Launch AVD in the Emulator

Start your emulator from the command line by doing the following:

$ ~/Library/Android/sdk/tools/emulator -avd avdname -partition-size 512

We are launching it from the command line so that we can set a partition size. This is necessary to avoid an ‘out of memory’ error when we set the /etc/hosts file below.

It may take a while to launch, especially if it is the first time you are launching the AVD. Eventually the emulator will come up with your AVD booted in it.

ScreenCapture at Thu Sep 3 10:49:11 EDT 2015

Set /etc/hosts on AVD

So, you now have an AVD that you can use to access the web using Android’s web browser. One potential small problem… you may be developing on a local web server and have modified your local /etc/hosts file to point your hostname to your local development machine.

Example /etc/hosts file: localhost
::1 localhost example.com

So, we need to modify the /etc/hosts file on the AVD to use the same hostname mappings.

I found a good article on setting the /etc/hosts file on an Android Emulator using a Mac. Below is a quick summary.

Check which AVDs are running

$ ~/Library/Android/sdk/platform-tools/adb devices

List of devices attached
emulator-5554 device

Remount the AVD to make it writable

$ ~/Library/Android/sdk/platform-tools/adb -s emulator-5554 remount

remount succeeded

Save the current /etc/hosts file from the AVD

$ ~/Library/Android/sdk/platform-tools/adb -s emulator-5554 pull /system/etc/hosts ~/Desktop/

17 KB/s (56 bytes in 0.003s)

Make your changes to the hosts file and then save it back to the AVD

$ ~/Library/Android/sdk/platform-tools/adb -s emulator-5554 push ~/Desktop/hosts /system/etc/hosts

Now you can use the same hostname mappings you are used to on your local development machine from your AVD.

Note: You will need to push the hosts file changes to the AVD every time you launch it. So, save your modified hosts file somewhere for future use.

3 thoughts on “Testing Local Web Sites with the Android Emulator

    1. Tyler, did the step to remount the AVD filesystem as writable succeed?

      $ ~/Library/Android/sdk/platform-tools/adb -s emulator-5554 remount


    2. Yo Tyler,

      TL;DR: Do it in 2 steps. 1step) Everything until push. Don’t push the altered file. 2nd Step) Exit the emulator. Run the emulator again. Remount it again (it must succeed, as first). Quickly, push the altered file, exactly as above described. (handy to have typed the command before, to just press up sometimes and enter)

      Not sure why, the emulator is only “remountable” to read and write the first time it is launched. After any action (going to the adb shell, pushing after pulling etc) it will become read only again. And I have the feeling you have a limited time frame to do stuff after you successfully remount it. Not sure if it has something to do with SELinux enforcing stuff, it worked for me! Note that you will have to push the altered hostsfile everytime you run the emulator, so maybe it is easier to do a script to launch, remount and push.

      Thx Matt for this post.


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