While developing the Android application, the developer has to ensure that the development environment is set perfectly. You will have to ensure that the developer has the latest version of Android Studio with all the updates. You can create an android application using the Android Studio IDE with all the extensive features.
Major Component Files during development.
On opening the Android Studio, you will find a series of the option. The developer has to select the option ‘Start a new Android Studio Project’. You can also go the file option and choose the new project option to open up a new project template. The application name, company domain, and the project location can be changed based on the convenience. The target Android devices can be then chosen with the values, an empty activity can be chosen to begin coding. The following is the screen sample for the various activities present in the Android Studio.
By selecting the app->Java->com.example.project name>Main Activity-
This would be the main entry point for the application to be created. The system would launch an instance of this particular activity and then proceed by loading its layout. This would be the major or the home activity of the Android mobile application.
You will then have to design the activity_main.xml file. This XML file deals with the definition of the various activity’s UI. You can find this XML file in app->res->layout-activity_main.xml that would possess the entire layout of the mobile application.
The next major file would be the manifest file of the application. This is very critical as it would contain all the fundamental information and characteristics of the application with the version of packages, the version of SDK and the components get defined.
As a developer, you would also notice two files with the name build. gradle. One would be for the entire project while the other would be only for the ‘app’ module. It has to be noticed that every module will be having build. gradle file, while there will be one gradle file for the entire project.
Fundamental Components of the Mobile Application
Activities: This, being the most fundamental block of the android application, you will have to define this as an entry point for all the user’s interaction with an application that includes navigation as well. Implementation of the activity can take place easily as a subclass of the Activity class. This would provide the way for the app to get used to the user flows present between them. It would also help in keeping track of what the user currently does in a particular screen. You can know more about the possible operations of Activities with the state flows here.
This is a major application component that has the ability to do all long-running operation at the background level without the user interface. The best example would be a service designed for the purpose of handling network transactions, music playing, performing the file operations all from the background without the user interface. For creating service, the developer will have to first create a subclass of the Service or any of its already existing subclass.
The most important callback methods that should be overridden are as follows:
on Start Command()- This callback method gets invoked by the system by calling the start Service(). You will have to ensure that the service is stopped by either using stop Self() or stop Service().
on Bind()- Here this method gets invoked by calling the bind Service() when there is a need to bind with another component. In case you don’t need to allow binding, the null option should be returned.
on Create() – This callback method gets invoked in order to do the single time setup method when the service gets initially created. on Destroy() – This gets invoked when a particular service is no longer needed and destroyed. You must be declaring a service in the manifest similar to declaring the activities and components. Declaration of the Service is shown in the below figure.
Broadcast Receivers- This is a component that helps the system in providing the events that are different from the regular flow ensuring the app responds to the system. The broadcast receiver gets implemented as a subclass of the main Broadcast Receiver wherein each of the broadcast gets delivered as only an object of Intent. You can know more about the Broadcast Receiver class , its classes, constructors and methods here.
Content Providers: This is a component known for managing all the shared set of the application data present in the system. This is also in regard to the SQLite database. With the help of this, the other applications can query or do any modification to data. One example would be is the Contacts Contract.Data content provider whose major function is to read and write the information about a specific person. This is implemented as a subclass of the Content Provider and should definitely implement the API’s
Developing the Android Application
The initial step would be to set up the workspace for the android application. This can be done by opening the app->res->layout->activity_main.xml. The developer then needs to press the design tab located at the bottom and then further press the blueprint option. You can then select the default margins and also click the device for the preview on the screen.
You can add the text box by pressing the Text View present in the Component Tree window and can also add in the plain text to it. From the palette, you can choose the buttons wherein you can drag and drop and constitute towards a more intuitive user interface of the application. In addition, you can also select the design surface and then select Design. This can be done by opening the app->res->value->strings.xml. This would be the string resources file wherein you will be able to specify all the UI strings. All these will help you to develop a simple and intuitive user interface with the specific layout designs.
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The Android application’s manifest
The developer has to know that every project must definitely contain an Android Manifest.xml file. This will present at the root directory of the project and will be containing the necessary information about the application. You can know more about the android manifest element reference. The manifest file must contain the application’s package name matching with the namespace. All the components of the applications that include services, broadcast receivers, content providers and the activities must be declared in the manifest file. Another major part of the manifest file is that all the permission the application would need in order to access all the protected part of apps is declared. The following is a sample of the entire android manifest file.
Running the Android mobile application
Once the Android app gets completely developed and successfully tested with all its functionality, it can be launched. There is a possibility of running the application developed on the device as well on an emulator. To run the application on the device, you will have to do the following steps:
1. Connect the mobile device to the machine which is specific for the deployment purpose. This can be done with the help of the USB cable. The next step will be to enable the USB debugging mode in the developer options present.
2. The development mode can be enabled by opening the Settings->System->about the phone. You should then scroll through the bottom and select ‘About phone’. After which you should select the Build number 7 times continuously to enable the USB debugging mode. The following image depicts the emulator
In the Android Studio, you will have to choose the app module and then choose the Run option. This should be followed by selecting the deployment target device.
To run the Android application developed on an emulator, choose the app module -> then press the Run option. You can then choose the hardware, a phone device can be chosen. Then from the list of system image screens present, you can choose the one with the highest API level for best quality of the application. You can also know further more about running the application.