Why can't a file be sent to the server using a stream?

Sending a file to a server using a regular thread (java.lang.Thread) is not recommended directly for several reasons related to Android architecture and performance:

• Blocking the UI thread: If the file sending is performed on the main (UI) thread, it can lead to its blocking. Long input-output operations, such as reading a file and network transmission, can cause the interface to "freeze," leading to a degraded user experience and even ANR (Application Not Responding) errors.
• Complexity of handling results: Receiving the result of the send (success/error), progress, or response data from the server back to the UI thread from a new thread requires using inter-thread communication mechanisms (Handler, runOnUiThread), which complicates the code.
• Lifecycle management: Managing the lifecycle of a regular thread in Android can be complex. If the activity or fragment that created the thread is destroyed before the operation completes, the thread may continue running, wasting resources and potentially causing memory leaks.
• Lack of built-in support: A regular Thread does not have built-in mechanisms for pausing, resuming, or canceling operations, which are important for reliable network transmission.
• Inefficient resource usage: Creating a new thread for each send can be inefficient. Thread pools (e.g., ExecutorService) are preferable for resource management.

In Android, for performing network operations and long input-output tasks, it is recommended to use specialized mechanisms:

• AsyncTask (deprecated).
• HandlerThread.
• Kotlin Coroutines.
• WorkManager.
• Libraries like Retrofit + OkHttp (for request handling and thread management).

These mechanisms provide a safer and more manageable way to perform background operations with proper handling of results in the UI thread and considering the lifecycle of Android components.