CODEWITHSUNDEEP
androidiosmultithreadingcordovaweb-worker
Federico Squartini
Federico Squartini

Reputation: 1218

Cordova app blocking because of intensive computation

I am writing a Cordova app where at some point there are computations which are a bit too heavy (digital signatures). As a consequence when the button that launches those computations is clicked the UI freezes for an instant.

The computations are also javascript code, is there any way in Cordova to use a web worker or something equivalent and offload them to another thread?

Upvotes: 2

Views: 318

Answers (1)

DaveAlden
DaveAlden

Reputation: 30366

You can use a web worker to do the intensve JS processing on a different thread, so you don't block the UI thread. Note: you'll need to be using a modern Webview, so Crosswalk if targeting Android 4.x (Android 5+ should be fine due to self-updated Webview).

You can do something like this:

myapp.js:

var worker = new Worker('my.worker.js');

// Receive the output from the worker when it's done
worker.addEventListener('message', function (e) {
    try {
        var data = e.data;

        if(!data.success){
            handleError(data.error);
        }else{
            display(data.output);
        }        
    } catch (ex) {
        handleError(ex);
    }
}, false);

// Start the worker with some input
worker.postMessage({
    input: "something heavy to process"
});

my.worker.js:

importScripts('lib/some.dependency.js');

// Receive the input from the main UI thread
self.addEventListener('message', function(ev) {
  try{
    var data = ev.data;
    var input = data.input;

    var output = doSomeHeavyLifting(input);

    self.postMessage({
      success: true,
      output: output
    });
  }catch(ex){
    self.postMessage({
      success: false,
      error: ex
    });
  }
}, false);

Upvotes: 1

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