Android - Basic Steps (Service)

Service

• Run in the main thread of the hosting application
• Android can kill the Service if need the resources

Purpose

• Supporting inter-application method execution
• Performing background processing

Start a Service

• Call Context.startService(Intent intent)\
• To call from a Fragment use
• getActivity().getApplicationContext().startService( intentService);

Executing the service

• After call startService(...) 
• In the Service is executed the method onStartCommand(...)
• If the method returns the constant START_NOT_STICKY
• then Android will not restart the service automatically if the the process is killedp

Foreground

• To execute the service foreground call the method startForeground()
• Use this if the user is aware of the process

Bind to a Service

• Call the method Context.bindService(
• Intent service
• ServiceConnection con
• int flags
• )

Send Toast from the Service

• On the method onStartCommand receive the message

        public int onStartCommand(Intent intent, int flags, int startId) {

Toast.makeText(getApplicationContext(), intent.getStringExtra(MSG),

Toast.LENGTH_LONG).show();

return super.onStartCommand(intent, flags, startId);

}

Binding to Remote Services

When the client is running in a different thread

Communication

• Using Messenger class
• Manage a Hanlder
• Messages can be sent across process boundaries
• Messages are queued and process sequencially

Implementing Messages

• Service 
• Creates a Handler for processing the messages
• Creates a messenger that provides a binder to a client
• Client
• Use the binder to create its own messenger
• Send the messages to the service

Implementing AIDL

Using AIDL interface

• Define remote interface in AIDL (Android Interface Definition Language)
• Declare in .AIDL file
• AIDL defines how components can interact with the service
• Implement remote interface
• Implement Service methods
• Implement Client methods

AIDL Syntaxis

• Is like Java interface
• Cannot declare static fields
• Non-primitive remote method parameters require a directional tag
• in - transferred to the remote method
• out - return to the caller
• inout - for both

Data Types

• Java Primitive Types
• Oher AIDL (Generated interfaces)
• Classes that implement Parcelable Protocol
• List
• Generic List Supported
• Map
• Generic Map is not supported

Considerations

• When create the intent to invoke the AIDL server do it like
• Intent intent = new Intent(KeyGeneratorAidl.class.getName());
• Where KeyGeneratorAidl is the server class