[Android] measure not returning values unless element has onLayout property

[oblador]

I have something similar to this:

handleSomething: function() {
  this._root.measure((ox, oy, width, height, px, py) => {
    console.log({ox, oy, width, height, px, py});
  });
},
render: function() {
  return (<View ref={component => this._root = component}>...</View>);
}

This code works flawlessly on iOS, but on android the measure callback will always be called with undefined arguments – unless I put an empty callback on the onLayout property.

[foghina]

@oblador what happens if, instead of logging arguments, you log ox, oy etc.?

[oblador]

@foghina: they log as undefined, logging arguments is just shorter to write.

[oblador]

@foghina: in case you don't know of arguments: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/arguments

[foghina]

@oblador I know about arguments, we just ran into this internally and it turned out arguments was wrong for some reason, but logging the arguments by name worked.

Can you try wrapping the measure call in requestAnimationFrame? E.g.:

this.requestAnimationFrame(() => {
  this._root.measure((ox, oy, width, height, px, py) => {
    console.log(arguments);
  });
});

[ide]

@foghina "arguments" in an arrow function refers to the enclosing non-arrow function's arguments (same scoping as "this"). Maybe that was the issue you were seeing.

[foghina]

@ide that does not explain why it works on iOS :-/

[ide]

There was a timing change with how iOS does measurement that may have fixed this issue. Haven't really looked into it in detail, but it might be related? aa62a5e

[oblador]

I've updated the issue to not confuse anybody. It works as expected on iOS for all I know, but not on android. Wasn't aware of arrow functions inheriting the arguments object, but it's unrelated to this issue.

[ide]

@oblador does wrapping the call in a rAF callback help?

[oblador]

@ide haven't tried, but don't really understand why it would make a difference. handleSomething is supposed to be a Touchable* callback.

[ide]

Yeah you're probably right.

[marcshilling]

I'm also experiencing this. Along with onLayout, I've found that setting renderToHardwareTextureAndroid={true} on the view also makes measure return values.