Adding and packaging wear module to your existing Android application

Background

Smart watches are slowing making their way into the market. They are quite expensive today but hoping prices will slash down with increase of technology. Anyway this post is aimed to add a wearable module to your existing Android app. This post expects you

1. Have an existing Android application code
2. Have it setup in latest Android Studio

So now that we have our prerequisites in place lets see how we can do this.

Step 1 : Adding a wearable  module to your Android application

If you have have your android application code opened in studio you simply need to 

1. Open module settings
2. Create on + (plus) button and select "Android Wear Module" .
3. Next give your module name (NOTE : Make sure your wear module bundle id is same as your main android app bundle id)
4. Next select activity
5. Give your activity/layout name
6. Click Finish

 Once you do this you should see a new module in your project with the name you provided during configuration. It will have its own set of java files, resource files, icons, manifest, build.gradle file etc.

You can go ahead and code your logic into this. This will run on your wearable device.

Step 2 : Packaging Wearable Apps

The way wearable app is distributed is by packaging it inside your handheld application (apk gets bundled inside) and when this app is installed on your phone/handheld device the wearable apk will get pushed to your wearable device.

To properly package a wearable module -

1. Include all the permissions declared in the manifest file of the wearable app module in the manifest file of the handheld app module. For example, if you specify the VIBRATE permission for the wearable app, you must also add that permission to the handheld app.
2. Ensure that both the wearable and handheld app modules have the same package name and version number.
3. Declare a Gradle dependency in the handheld app's build.gradle file that points to the wearable app module: 
   
   Eg.
   
   

   dependencies {
       compile fileTree(dir: 'libs', include: ['*.jar'])
       testCompile 'junit:junit:4.12'
       compile 'com.android.support:appcompat-v7:23.4.0'
       compile 'com.android.support:support-v4:23.4.0'
       compile 'com.google.android.gms:play-services:9.0.0'
       wearApp project(':flashlightwear')
   }
   

   
   
4. Click Build > Generate Signed APK.

How it works

• Your android mobile/handheld application and your wearable application (apk) should be signed using same certificate (key). 
• They must also have same package name and version number.
• When you generate a release build if your handheld application your wearable apk will get bundled in your handheld apk.
• When you install your handheld app on your mobile which is paired to your wearable device (eg smart watch) then wearable apk bundled within will be automatically pushed and installed on the wearable device.
• You cannot take a call on which ones to keep or not keep. If you have an app installed on your mobile device and it has a wear module it will be installed on your wearable device. You cannot uninstall it unless you remove the app from your phone.

You should see a notification on your wear device that app is installed.

I have added wear module to a flashlight app that I had developer sometime back just to learn this stuff. You can check it out. Its available on playstore -

• https://play.google.com/store/apps/details?id=com.osfg.flashlight

NOTES:

1. Ensure that both the wearable and handheld app modules have the same package name and version number.
2. Include all the permissions declared in the manifest file of the wearable app module in the manifest file of the handheld app module. 
3.  Your android mobile/handheld application and your wearable application (apk) should be signed using same certificate (key).
4. wearable apk gets automatically bundled with your handheld module and gets pushed to your wearable device once installed on handled device.

Related Links

•  Setting up Firebase Cloud Messaging (FCM) in Android application(OSFG)
• How to send Firebase Cloud Messaging (FCM) notification from server to client(OSFG) 
• Create a New Module
• Packaging Wearable Apps 
• How to Uninstall Apps from Android Wear(OSFG)