问题
I was searching over the internet for how to perform the new cool android data-binding over the RadioGroup
and I didn't find a single blog post about it.
Its a simple scenario, based on the radio button selected, I want to attach a callback event using android data binding. I don't find any method on the xml part which allows me to define a callback.
Like here is my RadioGroup:
<RadioGroup
android:id="@+id/split_type_radio"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:checkedButton="@+id/split_type_equal"
android:gravity="center"
<!-- which tag ? -->
android:orientation="horizontal">
...
</RadioGroup>
How do I attach a handler method which will be called on RadioGroup
's checkChnged
event will fire using data-binding?
I have tried using onClick
(don't know if it is the same) in layout file and defining method in the Activity and located it using this in the layout file:
<variable
name="handler"
type="com.example.MainActivity"/>
...
<RadioGroup
android:onClick="handler.onCustomCheckChanged"
.. >
And defined method onCustomCheckChanged
like this:
public void onCustomCheckChanged(RadioGroup radio, int id) {
// ...
}
But, it gives me the compilation error:
Error:(58, 36) Listener class android.view.View.OnClickListener with method onClick did not match signature of any method handler.onCustomCheckChanged
I have seen many blogs mentioning it is possible with RadioGroup
but non of them really say how. How can I handle this with data-binding
?
回答1:
After digging to the bunch of methods, I found this question on SO which helped me understand how to bind single methods of listeners.
Here is what to do with RadioGroup:
In RadioGroup
listener you have a method onCheckedChanged(RadioGroup g, int id)
. So you can directly bound that method to your handler or your activity by passing an instance of it as a variable in layout file and calling a method with the same signature.
So call on layout file like this:
<RadioGroup
android:id="@+id/split_type_radio"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="10dp"
android:checkedButton="@+id/split_type_equal"
android:gravity="center"
android:onCheckedChanged="@{handler.onSplitTypeChanged}"
android:orientation="horizontal">
...
</RadioGroup>
And in my activity or handler, I need to simply provide the method with same name and signature like this:
public void onSplitTypeChanged(RadioGroup radioGroup,int id) {
// ...
}
Just make sure method is public.
NOTE: This works for any (most of, I have not tried all) listener methods. Like for EditText
you can provide android:onTextChanged
and so on.
回答2:
I am using a string, and in this case I have bindable based on viewModel.getCommuteType() viewModel.setCommuteType(String)
<RadioGroup
android:orientation="horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<RadioButton
android:checked="@{viewModel.commuteType.equals(Commute.DRIVING)}"
android:onClick="@{()->viewModel.setCommuteType(Commute.DRIVING)}"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="D"/>
<RadioButton
android:checked="@{viewModel.commuteType.equals(Commute.BICYCLE)}"
android:onClick="@{()->viewModel.setCommuteType(Commute.BICYCLE)}"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="B"/>
<RadioButton
android:checked="@{viewModel.commuteType.equals(Commute.WALKING)}"
android:onClick="@{()->viewModel.setCommuteType(Commute.WALKING)}"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="W"/>
<RadioButton
android:checked="@{viewModel.commuteType.equals(Commute.BUS)}"
android:onClick="@{()->viewModel.setCommuteType(Commute.BUS)}"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="T"/>
回答3:
After some hours I found easy way: two-way databinding in android. It's base skeleton with livedata and Kotlin. Also you can use ObservableField()
- Set your viewmodel to data
- Create your radiogroup with buttons as you like. Important: set all radio buttons id !!!
- Set in your radio group two-way binding to checked variable (use viewmodel variable)
- Enjoy)
layout.xml
<data>
<variable
name="VM"
type="...YourViewModel" />
</data>
<LinearLayout
android:id="@+id/settings_block_env"
...
>
<RadioGroup
android:id="@+id/env_radioGroup"
android:checkedButton="@={VM.radio_checked}">
<RadioButton
android:id="@+id/your_id1"/>
<RadioButton
android:id="@+id/your_id2" />
<RadioButton
android:id="@+id/your_id3"/>
<RadioButton
android:id="@+id/your_id4"/>
</RadioGroup>
</LinearLayout>
class YourViewModel(): ViewModel {
var radio_checked = MutableLiveData<Int>()
init{
radio_checked.postValue(R.id.your_id1)//def value
}
//other code
}
回答4:
Often you care more about what was actually checked instead of "something was checked". In such case alternative solution is to ignore RadioGroup and bind all items as below:
<RadioGroup (...) >
<RadioButton (...)
android:checked="@={viewModel.optionA}"/>
<RadioButton (...)
android:checked="@={viewModel.optionB}"/>
<RadioButton (...)
android:checked="@={viewModel.optionC}"/>
</RadioGroup>
where optionA, optionB and optionC are defined in ViewModel like below:
public final ObservableBoolean optionA = new ObservableBoolean();
public final ObservableBoolean optionB = new ObservableBoolean();
public final ObservableBoolean optionC = new ObservableBoolean();
This is usually enough, however if you want to react immediately on click then you can add callBacks and use them like that:
OnPropertyChangedCallback userChoosedA = new OnPropertyChangedCallback() {
@Override
public void onPropertyChanged(Observable sender, int propertyId) {
(...) // basically propertyId can be ignored in such case
}
};
optionA.addOnPropertyChangedCallback(userChoosedA);
Advantage of such approach is that you don't need to compare and track "id".
回答5:
In my current project, I did it like this. I have three currency in the project and I choose one of them via RadioGroup.
It's enum with currencies:
enum class Currency(val value: Byte) {
USD(0),
EUR(1),
RUB(2);
companion object Create {
fun from(sourceValue: Byte): Currency = values().first { it.value == sourceValue }
fun from(sourceValue: String): Currency = values().first { it.toString() == sourceValue }
}
}
A piece of my ViewModel:
class BaseCurrencyViewModel : ViewModelBase<BaseCurrencyModelInterface>() {
/**
* Selected currency
*/
val currency: MutableLiveData<Currency> = MutableLiveData()
/**
*
*/
init {
currency.value = Currency.USD // Init value
}
}
Part of my layout (pay attention to binding in RadioGroup and tags of RadioButton):
<RadioGroup
android:id="@+id/currencySwitchers"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:selectedCurrency = "@{viewModel.currency}"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintEnd_toEndOf="parent">
<RadioButton
android:id="@+id/usdSwitcher"
android:text="USD"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:tag="USD"
/>
<RadioButton
android:id="@+id/eurSwitcher"
android:text="EUR"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:tag="EUR"
/>
<RadioButton
android:id="@+id/rubSwitcher"
android:text="RUB"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:tag="RUB"
/>
</RadioGroup>
And the final part - binding adapter.
@BindingAdapter("selectedCurrency")
fun setSelectedCurrency(view: View, value: MutableLiveData<Currency>?) {
view.getParentActivity()?.let { parentActivity ->
value?.observe(parentActivity, Observer { value ->
view.findViewWithTag<RadioButton>(value.toString())
?.also {
if(!it.isChecked) {
it.isChecked = true
}
}
}
)
(view as RadioGroup).setOnCheckedChangeListener { radioGroup, checkedId ->
val currency = Currency.from(radioGroup.findViewById<RadioButton>(checkedId).tag as String)
if(value != null && value.value != currency) {
value.value = currency
}
}
}
}
In this way, I got two-way binding between RadioGroup and a property in my ViewModel.
来源:https://stackoverflow.com/questions/39427178/how-to-bind-method-on-radiogroup-on-checkchanged-event-with-data-binding