For example, when your device boots up or switched on system generates a broadcast to all apps.
Principle app android android#
Android Intents can be used to deliver broadcasts to other apps. Android Broadcast is a message which spreads out when any event occurs. We know little bit about activity, service but what this broadcast chap is all about? Let’s find out this in next few lines. Now this is residential address is what we refer to be as fully qualified name. For example, if you want to call your best friend you would do it by name and if he/she is not with you then you would definitely know the residential address. These elements are started by their name i.e.
Explicit intents: These are generally used to start a new element of your own application. Implicit Intents: These are used to declare general actions to be performed so that part of another app can handle it. A broadcast can be sent to other apps by passing intents. A service can be started by passing intent to perform a single operation. Android Intent can be used to instantiate a new activity or get result from another activity. It can be used to query an action from another app component. i.e., app components send messages to one another like you do with your friends. Android Intents and Broadcast ReceiversĪndroid Intents are the communication medium. For example, custom searches on device require content providers.ġ.4.4. These content providers are internal to android applications. Android has content providers which manages video, audio, etc. It is this object which is going to receive the requests retrieves the results and returns the result. For accessing data in a content provider an object has to be created and this object acts as a client whereas content provider act as a server. It provides gateway to access data from a structured set. Content providers as the name indicates provides content of one process to another hence it acts as an interface. These Android components bring the object oriented functionality to the system. After the destruction of component, service terminates. Multiple components can be bound to this type of service. Inter process communication is achieved through this service. Requests can be send, receive requests, and return result to the user. This type of service provides a client-server like interface. Bound: In this case, a component is bound to a service so that a particular task can be completed. After the task is completed, it should terminate itself. Started: After a service starts, it can run indefinitely and usually performs single operation. You get the notification of new e-mail even if you are not using the e-mail app or doing something else. For example, when you receive your email updates in inbox it is a service. A service can be connected to a component which can even do inter process communication (IPC). Service doesn’t terminate even if the component which initiated it got terminated or switched to another application. It does long running operations in background. ServiceĪnother important component of an android application is service. A stack has a structure like a book shelf where you arrange your books but unlike a book shelf, only one item can be inserted and deleted from stack respectively. 
Adding an item to this is called push operation. A stack is data structure in which computer organizes its data in the memory. If you are a novice or don’t have computer’s background, you might be thinking what the heck is this stack, push and pop kind of things. When you press back key, it should resume the previous activity right!! Previous activity was your own home screen. Now previous activity resumes.įor example, when you send SMS, you open the messenger and send message. As soon as the back key of your device is pressed, new activity is popped out of stack and destroyed. Whenever, there is a new window is started, previous activity is pushed to the back stack and it is stopped until the new activity is done. All other activities are child activities. Generally, every Android application has more than one activity. A window is provided to each activity where user interfacing is done. everything is done by interacting with a window and that very window is provided by an activity. For example, opening a contact, dialing a caller, etc. It provides the space to the user for doing anything and everything. 1.4.1 ActivityĪn activity is the first stepping stone is building an Android user application. We shall deal with them in details in next chapters. Let us go through a brief introduction of these components. The basic components of any android application are the following:
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