Android - Can I Databinding programatically? - without layout XML

Question

Below is XML equivalent of what I'm trying to achieve, but without XML

<Button
    android:id="@+id/bt_start"
    android:onClick="@{() -> vm.onClickedStart()}"
    android:text='@{vm.btStartLbl}' />

so if I have:

ConstraintLayout cl = findViewById(R.id.cl);
Button btn = new Button(MyActivity.this);

btn.setText("How to Data Bind here?");

btn.setOnClickListener(new OnClickListener (){ /* how to databind here? */ });

cl.addView(btn);

how to databind it as equivalent as xml above? is it possible?

"how to databind it as equivalent as xml above?" -- btn.setOnClickListener(() -> vm.onClickedStart()); This assumes that you have a vm in scope that has an onClickedStart() method. IOW, you do not "databind programmatically", but rather simply program. — CommonsWare
– CommonsWare, Commented Jan 22, 2018 at 16:42
Thanks, let me try - how about: android:text='@{vm.btStartLbl}' how to bind it from Java? — AnD
– AnD, Commented Jan 22, 2018 at 16:45
Call setText(vm.getBtStartLbl()) (modifying that method name to match the actual one, as there are a few possibilities). — CommonsWare
– CommonsWare, Commented Jan 22, 2018 at 16:49
I'm not sure if vm.getBtStartLbl() will update my text if variable changed, e.g: vm.label=oldVal; and getBtStartLbl(){ return this.label; } if vm.label = newVal will my button text get updated to newVal? — AnD
– AnD, Commented Jan 22, 2018 at 16:58

mlykotom · Accepted Answer · 2018-01-30 13:01:01Z

2

For automatic setting data, you could use ObservableField

Simplified version for auto-updating btn:

ObservableField<String> title = new ObservableField<>();

Observable.OnPropertyChangedCallback propertyChangeCallback = new Observable.OnPropertyChangedCallback() {
    @Override
    public void onPropertyChanged(Observable sender, int property) {
        btn.setText(title.get());
        // here what you want to automatically update
    }
};


public void onStart() {
    // activity/fragment lifecycle method
    title.addOnPropertyChangedCallback(propertyChangeCallback);
}


public void onStop() {
    // activity/fragment lifecycle method
    title.removeOnPropertyChangedCallback(propertyChangeCallback);
}

And then whenever you call title.set("some value");, it will be automatically trigger the update.

answered Jan 30, 2018 at 13:01

mlykotom

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1 Comment

AnD Over a year ago

Thanks, Let me try

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