Book Image

Android Studio 3.5 Development Essentials - Java Edition

By : Neil Smyth
Book Image

Android Studio 3.5 Development Essentials - Java Edition

By: Neil Smyth

Overview of this book

Android applications have become an important part of our daily lives and lots of effort goes into developing an Android application. This book will help you to build you own Android applications using Java. Android Studio 3.5 Development Essentials – Java Edition first teaches you to install Android development and test environment on different operating systems. Next, you will create an Android app and a virtual device in Android Studio, and install an Android application on emulator. You will test apps on physical Android devices, then study Android Studio code editor and constraint layout, Android architecture, the anatomy of an Android app, and Android activity state changes. The book then covers advanced topics such as views and widgets implementation, multi-window support integration, and biometric authentication, and finally, you will learn to upload your app to Google Play console and handle the build process with Gradle. By the end of this book, you will have gained enough knowledge to develop powerful Android applications using Java.
Table of Contents (86 chapters)
86
Index

51.3 Returning Data from an Activity

As the example in the previous section stands, while data is transferred to ActivityB, there is no way for data to be returned to the first activity (which we will call ActivityA). This can, however, be achieved by launching ActivityB as a sub-activity of ActivityA. An activity is started as a sub-activity by starting the intent with a call to the startActivityForResult() method instead of using startActivity(). In addition to the intent object, this method is also passed a request code value which can be used to identify the return data when the sub-activity returns. For example:

startActivityForResult(i, REQUEST_CODE);

In order to return data to the parent activity, the sub-activity must implement the finish() method, the purpose of which is to create a new intent object containing the data to be returned, and then calling the setResult() method of the enclosing activity, passing through a result code and the intent containing the return...