What is "DataBindingComponent" class in android databinding? -

i have seen databindingcomponent in official api doc.

https://developer.android.com/reference/android/databinding/databindingutil.html

this interface generated during compilation contain getters used instance bindingadapters. when bindingadapter instance method, instance of class implementing method must instantiated. interface generated getter each class name get* * simple class name of declaring bindingadapter class/interface. name collisions resolved adding numeric suffix getter.

an instance of class may passed static or instance bindingadapters first parameter.

if using dagger 2, developer should extend interface , annotate extended interface component.

however, cannot find example usage of class in web. can know , how use it.

i tried make simple code , debug see what's showed null variable on a variable.

protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     activitymainbinding binding= databindingutil.setcontentview(this,r.layout.activity_main);     android.databinding.databindingcomponent = databindingutil.getdefaultcomponent();     setcontentview(binding.getroot()); } 

from documentation know

this interface generated during compilation contain getters used instance bindingadapters. when bindingadapter instance method, instance of class implementing method must instantiated. interface generated getter each class name get* * simple class name of declaring bindingadapter class/interface. name collisions resolved adding numeric suffix getter.

an instance of class may passed static or instance bindingadapters first parameter.

if using dagger 2, developer should extend interface , annotate extended interface component.

this tells interface used , generated injecting factory instances implementing custom @bindingadapter methods. can configure data bindings different situations or layouts or supply more general state. if have @ default databindingcomponent class in android studio find located in build/generated/source/apt/dev.

the methods can use databindingcomponent are

• databindingutil.setdefaultcomponent()
• databindingutil.inflate()
• databindingutil.bind()

considering define interface like

public interface foo {     @bindingadapter("foobar")     void foobar(view view, string baz); } 

an android.databinding.databindingcomponent interface gets generated

public interface databindingcomponent {     di.pkg.foo getfoo(); } 

this @bindingadapter host gets used in data bindings, need implement interface , use 1 of methods given above like

databindingutil.setdefaultcomponent(new databindingcomponent(){     @override     public foo getfoo() {         return new foo() {             @override             public void foobar(view view, string baz) {                 if (view instanceof textview) ((textview) view).settext(baz);             }         };     } }); 

in example null databindingutil.getdefaultcomponent() because you've never set default component yourself.