i know that the android app runs in the main thread means UI thread.I want to know what is need of main thread to run an app? What happens if we do not use the main thread to run app.Why main thread is necessary?
From this link:
What is the need of main thread?
When an Android application is first started, the runtime system creates a single thread in which all application components will run by default. This thread is generally referred to as the main thread. The primary role of the main thread is to handle the user interface in terms of event handling and interaction with views in the user interface. Any additional components that are started within the application will, by default, also run on the main thread.
Why is main thread necessary?
Any component within an application that performs a time-consuming task using the main thread will cause the entire application to appear to lock up until the task is completed. This will typically result in the operating system displaying an “Application is unresponsive” warning to the user. Clearly, this is far from the desired behavior for any application. In such a situation, this can be avoided simply by launching the task to be performed in a separate thread, allowing the main thread to continue unhindered with other tasks.
Please refer to the link to understand more about main thread with an example.
For more details, you can follow this link.