Android data binding — 2
Binding user event
The first section introduced simple data mapping sample. This section is about event binding
In this example, we add a button in main activity, then handle event when user click on this button
First, in ViewModel, we need define a function to handle event
onClick then will be mapped to layout:
①: Map button text to viewModel. By default (on Android studio designer view, show “Click_Me”)
②: Map onClick event to onClick function of viewModel
That’s it. Now when user click on Button, the Toast will be show.
However, the problem is we wanna separate between ViewModel & View. When user click on Button, 2 separated tasks should be done:
- Update some states in ViewModel, and data Model (handle by ViewModel)
- Do some task on UI, should handle by View (e.g Toast should be handled by View — activity class)
So we need a method that let View also know about this event.
In this sample, we define ISampleViewModelEventListener as an interface, then when onClick fired, we also call listener.onClickButton(); to raise event to View.
For View class (Activity class in this sample), we implement ISampleViewModelEventListener
And that’s it. If we need more view-model-2-view event, just define more function in ISampleViewModelEventListener.
