How to wait for a callback without blocking main thread

Question

I need to use a WebView in a custom renderer for Android and need to get a Value with EvaluateJavascript:

class ValueCallback : Java.Lang.Object, IValueCallback
{
    public Java.Lang.Object Value
    {
        get;
        set;
    }

    public void OnReceiveValue(Java.Lang.Object value)
    {
        Value = value;
    }
}

This is called from a Method in the Renderer, which in Turn gets called from a Property like Duration

public double Duration;

Get Duration from Webview:

var callback = new ValueCallback();
View.EvaluateJavascript(jsToExecute, callback);
//How to wait here without blocking the MainThread?

The Problem is that EvaluateJavascript can only be called from the MainThread and the Property is also called from MainThread. So when I use something like AutoResetEvent to wait for the Script to finish, the result is a Deadlock.

Answer 1

You're asking how to block the main thread without blocking the main thread. The answer is quite simple, you can't .

If you don't want to block the main thread you're going to need to not wait , and instead do whatever you want to have happen after the callback executes in the callback rather than waiting for it.