Question

A non-UI thread in my Android application contains a Handler object, and I add implementations of Runnable to this Handler using the post() method.

From reading the API, it seems that Handler uses a queue. Does this mean that if I post() 2 Runnables to the queue, that the second one will only start executing on completion of the first Runnable’s run method?

Just wanted to confirm this as I am seeing some multi-threading issues in my application.

Thanks

Answer 1

(As per I understand your question)

As per the API reference, Handler using a MessageQueue, The 2nd runnable execution starts after completion of the first,

A Handler allows you to send and process Message and Runnable objects associated with a thread’s MessageQueue. Each Handler instance is associated with a single thread and that thread’s message queue. When you create a new Handler, it is bound to the thread / message queue of the thread that is creating it — from that point on, it will deliver messages and runnables to that message queue and execute them as they come out of the message queue.

There are two main uses for a Handler: (1) to schedule messages and runnables to be executed as some point in the future; and (2) to enqueue an action to be performed on a different thread than your own.