Android Interview Preparation Guide

Download PDF

Android allows the system to protect the applications that are not responsive for a period of time by displaying a status called as ANR (Application not responding). Methods should use the main thread for work, as it takes long time for the main thread to complete the task. The work should be divided and another thread named as child thread be used for executing more tasks, as it takes less time. Main thread should provide a handler for child threads to post back upon completion.

Android is rich in file features and it provides lots of variations in them as well. The file features are as follows:
Intent filters: includes bundle of information which describes a desired action.

Icons and Labels: includes information for small icon and a text label that can be displayed to users. These are set for an intent filter and are used to represent a component which fulfills the function advertised by the filter.

Permissions: it is a restriction or limitation access to a part of code or data on the device. It is given as:-android.permission.CALL_EMERGENCY_NUMBERS

Libraries: it includes the basic packages for building and developing applications.

AOSP stands for Android Open-source project that maintains Android software and keep track of the new versions. It can be used for any purpose including the devices that are not compatible with other devices. It is related to the Android Compatibility Program as it defines the implementation of Android that is compatible with the third party apps.

Android provides many options for storage of persistent data. It provides the solution according to your need. The storages which have been provided in Android are as follows:-

Shared Preferences: Store private primitive data in key-value pairs

Internal Storage: Store private data on the device memory.

External Storage: Store public data on the shared external storage.

SQLite Databases: Store structured data in a private database.

Network Connection: Store data on the web with your own network server.

Localization is a way of representing the products in different languages. Android is an operating system which runs in many regions, so to reach different users localization is a must. Localization in Android can be achieved by incorporating different languages in the application which you are using. To do this knowledge of Java, XML elements, Activity lifecycle and general principles of internationalization and localization are required.

Android application architecture allows the simplification and reuse of any application. It provides a better way to publish the capabilities of the application so that any other application can make good use of those capabilities. This architecture includes the following components:

Intent: perform some operation on some activity and service

Resource Externalization - such as strings and graphics

Notification signaling users - light, sound, icon etc.

Content Providers – sharing of data between various applications

There are 4 dialog boxes which have been supported by Android. These are as follows:
AlertDialog: it supports 0 to 3 buttons with a list of selectable elements that includes check boxes and radio buttons.

-ProgressDialog: it displays the progress of any dialog or application. It is an extension of AlertDialog and supports adding buttons.
-DatePickerDialog: it is used to give provision to the user to select the date
- TimePickerDialog: it is used to give provision to the user to select the time

APK termed as Application package file is a format that is used to distribute and install the application software for android, and middleware on the android operating system. To make an APK file, first android is compiled and then all of its parts are grouped in one file termed as package. The package consists of the entire program’s code (.dex files), resources, manifest file etc. The file is saved with .apk extension.

Intent is basically an abstract description of an operation that has to be performed for communication. Sticky Intent is also a type of intent which allows the communication between a function and a service. For example: sendStickyBroadcast() performs send Broadcast(Intent) which stays even after the broadcast is complete. It helps in retrieving the data quickly. The message ACTION_BATTERY_CHANGED of an operating system is an example of it.

Android uses Google translator to translate data from one language into another language using XAMPP. XAMPP is used to transmit the data. The steps which have to be followed are: Type the message in your language, go to the language setting, a list will be displayed there, select the language from the list to convert your text.