I am trying to use data binding in my app, but nothing is shown.
This is what I did:
I created an New Project with an Empty Activity.
I added
dataBinding {
enabled = true
}
to my build.gradle
This is my activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable name="game" type="my.name.bar.Bar"/>
</data>
<android.support.constraint.ConstraintLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="my.name.bar.MainActivity">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{game.GetFoo()}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>
</layout>
And this is my Bar class
public class Bar {
private String str;
public Bar() {
str = "Foo";
}
public String GetFoo() {
return str;
}
}
But I am only getting a white screen. If I replace the binding with just "Hello World!" then everything works fine. What am I doing wrong?
(promoted from the comment)
You must bind the value. In your case, it is something like this:
ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
binding.setGame(new Bar());
Related
I read a few posts to convert from String to Integer and tried to do the same to convert string to double using two-way binding but was unable to do it.
SampleViewModel.kt
class SampleViewModel: ViewModel() {
val weight = MutableLiveData<Double>()
fun validateFields() {
Log.i("SAMPLE_VIEW_MODEL", "validateFields: ${weight.value}")
}
}
TypeConverters.kt
object TypeConverters {
#InverseMethod("stringToDouble")
#JvmStatic
fun doubleToString(value: Double?): String {
return value?.toString() ?: ""
}
#JvmStatic
fun stringToDouble(value: String): Double? {
if (TextUtils.isEmpty(value)) {
return null
}
return value.toDoubleOrNull()
}
}
fragment_sample.xml
<?xml version="1.0" encoding="utf-8"?>
<layout>
<data>
<variable
name="viewModel"
type="com.example.sampleapp.SampleViewModel" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
...
<com.google.android.material.textfield.TextInputLayout
android:id="#+id/til_weight"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_margin="#dimen/_10sdp"
android:hint="#string/hint_weight"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintBottom_toBottomOf="#+id/tilName">
<com.google.android.material.textfield.TextInputEditText
android:id="#+id/tiet_weight"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:text="#={TypeConverters.doubleToString(viewModel.weight)}"/>
</com.google.android.material.textfield.TextInputLayout>
...
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
The example above does not let me enter the proper value on UI like "56.78". I tried to follow this post but doesn't work for me. Another way is to take string value and then convert it into double and vice versa accordingly. I would like to know which is the correct way.
In your TextInputEditText, update this line
android:text="#={String.valueOf(viewModel.weight)}"
See Results
<com.google.android.material.textfield.TextInputEditText
android:id="#+id/tiet_weight"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="numberDecimal"
android:text="#={String.valueOf(viewModel.weight)}"/>
I'm trying to call a function from my Data Binding layout, but I'm always receiving some error. I'm trying to set the text on my textView using MyUtilClass's function which I have created. here's my code:
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<import type="com.example.testapp.User"/>
<import type="com.example.testapp.MyUtilClass"/>
<variable
name="user"
type="User" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{MyUtilClass.Companion.changeText(user.firstName)}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
MyUtilClass
class MyUtilClass {
companion object {
#JvmStatic
fun changeText(text: String): String {
return text
}
}
}
User
data class User(
val firstName: String,
val lastName: String,
val age: Int,
val loggedIn: Boolean
)
MainActivity.java
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val myUser = User("John", "Doe", 25, true)
binding.user = myUser
}
}
Error:
C:\Users\Stefan\AndroidStudioProjects\TestApp\app\build\generated\source\kapt\debug\com\example\testapp\DataBinderMapperImpl.java:9:
error: cannot find symbol import
com.example.testapp.databinding.ActivityMainBindingImpl;
^ symbol: class ActivityMainBindingImpl location: package
com.example.testapp.databinding
cannot find method changeText(java.lang.String) in class
com.example.testapp.MyUtilClass.Companion Open File
Adding JvmStatic to the changeText() method in MyUtilClass automatically makes it static.
Therefore, you can access it like this in your layout file:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">
<data>
<import type="com.example.testapp.User"/>
<import type="com.example.testapp.MyUtilClass"/>
<variable
name="user"
type="User" />
</data>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{MyUtilClass.changeText(user.firstName)}"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</layout>
You can check this link to find out more:
Kotlin DataBinding pass static function into layout xml
This is the change I made, and it worked. I basically removed class keyword and added object instead.
object MyUtilClass {
#JvmStatic
fun changeText(text: String): String {
return text
}
}
I have a test project where I want to bind the press of a button to trigger a function via the DataBinding Libray and add:command.
Unfortunately, I'm getting the error:
Found data binding errors.
****/ data binding error ****msg:Could not resolve com.example.ckleineidam.testproject.ViewModel.testButton as an accessor or listener on the attribute.
MainActivity:
public class MainActivity extends AppCompatActivity {
ViewModel mModel;
ActivityMainBinding binding;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_main);
binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
mModel = new ViewModel(this);
binding.setViewModel(mModel);
}
}
ViewModel:
public class ViewModel extends BaseObservable {
private static final String TAG = "VIEW_MODEL";
private Context mActivity;
public ViewModel(Context context) {
this.mActivity=context;
}
public void testButton(){
Log.i(TAG, "Button Click");
}
}
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<layout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
tools:context=".MainActivity">
<data>
<variable
name="ViewModel"
type="com.example.ckleineidam.testproject.ViewModel" />
</data>
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="title"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="#+id/activation_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Test Button"
android:background="?android:attr/selectableItemBackground"
app:command="#{ViewModel.testButton}"
app:layout_constraintTop_toBottomOf="#id/title" />
</android.support.constraint.ConstraintLayout >
</layout>
The code is also as an example project at Github.
You are getting this error because there is no attribute app:command on a button.
If you are trying to achieve an onClick functionality, you can use android:onClick="#{ViewModel.testButton}" and change your function signature to void testButton(View view).
To use custom attributes, you need to define a binding adapter
I googled but still didn't find solution for me.
This is my xml:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">
<data>
<import
alias="noteViewModel"
type="com.app.screen.createnote.CreateNoteViewModel" />
</data>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<EditText
android:id="#+id/etNote"
style="#style/JWidget.EditText.Grey"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="start"
android:inputType="textMultiLine"
android:scrollbars="vertical"
android:text="#={noteViewModel.note.description}" />
</LinearLayout>
</layout>
This is my ViewModel code:
public class CreateNoteViewModel extends BaseObservable {
private Note note;
#Bindable
public Note getNote() {
return note;
}
public void setNote(Note note) {
this.note = note;
notifyPropertyChanged(BR.note);
}
}
But when I try run my app I got it:
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
java.lang.RuntimeException: Found data binding errors.
****/ data binding error ****msg:Could not find accessor com.justsafe.tmgr.justsafe.screen.createnote.CreateNoteViewModel.note
file:C:\android\work\JustSafeTmgr\app\src\main\res\layout\activity_create_note.xml
loc:44:33 - 44:62
****\ data binding error ****
P.S. In other place in my app it work, but there I get problem.
Try to change the <import> tag to a <variable> tag:
<data>
<variable
name="noteViewModel"
type="com.app.screen.createnote.CreateNoteViewModel" />
</data>
build.gradle -- app
android {
dataBinding {
enabled = true
}
}
dependencies {
def life_versions = "1.1.1"
// Lifecycle components
implementation "android.arch.lifecycle:extensions:$life_versions"
annotationProcessor "android.arch.lifecycle:compiler:$life_versions"
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="LoginViewModel"
type="com.keshav.mvvmdemokeshav.viewModel.LoginViewModel" />
</data>
<!-- TODO Your XML File-->
</layout>
The 2 main questions are :
Why ViewDataBinding doesn't have a method like getVariable("variableName") that will look up for a variable and returns it or null if no variable with this name exists.
Is their any way/workaround to achieve this kind of behavior?
So to be more explicit : if I don't know the type of my ViewDataBinding, is their a way to get its variable or I must know its type?
Here is how it is working actually :
I havea layout called my_layout.xml :
<layout>
<data>
<variable
android:name="myVaribale"
android:type="String"/>
</variable>
</data>
<RelativeLayout
android:id="#+id/root_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="#{myVariable}"/>
</RelativeLayout>
<layout>
I inflate an instance of its ViewDataBinding :
MyLayoutBinding binding = (MyLayoutBinding) DataBindingUtil.inflate(inflater, R.layout.my_layout, root, false);
I can get its variable by calling the appropriate method :
String myVariable = binding.getMyVariable();
So this was how to get a variable when we know the type of the ViewDataBinding.
My problem is here :
Let's imagine I have 3 layouts called my_layout_1, my_layout_2, my_layout_3 and those 3 layouts are surrounded by a <layout> tag.
Those 3 layouts has also the same variable (myVariable).
So here are the layouts :
my_layout_1
<layout>
<data>
<variable
android:name="myVariable"
android:type="String"/>
</variable>
</data>
<RelativeLayout
android:id="#+id/root_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="#{myVariable}"
style="#style/my_style_1"/>
</RelativeLayout>
<layout>
my_layout_2
<layout>
<data>
<variable
android:name="myVariable"
android:type="String"/>
</variable>
</data>
<RelativeLayout
android:id="#+id/root_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="#{myVariable}"
style="#style/my_style_2"/>
</RelativeLayout>
<layout>
my_layout_3
<layout>
<data>
<variable
android:name="myVariable"
android:type="String"/>
</variable>
</data>
<RelativeLayout
android:id="#+id/root_view"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:text="#{myVariable}"
style="#style/my_style_3"/>
</RelativeLayout>
<layout>
So the different layout represent a text with a different style (I know it can be achieved by others way but the goal is just to explain why I need this function getVariable(variableName).
Imagine now that I got a layout called my_text_container which will randomly contain one of the 3 layouts.
my_text_container
<layout>
<FrameLayout
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<layout>
So I'll add a text by doing something like this (again, it's just for demonstration purpose) :
MyTextContainerBinding textContainerBinding = (MyTextContainerBinding) DataBindingUtil.inflate(inflater, R.layout.my_text_container, root, false);
int textLayoutRes;
int randomNumber = generateNumberBetween0and2();
switch(randomNumber) {
case 0: textLayoutRes = R.layout.my_layout_1;
break;
case 1: textLayoutRes = R.layout.my_layout_2;
break;
case 2: textLayoutRes = R.layout.my_layout_3;
break;
}
textContainerBinding.getRoot().addView(DataBindingUtil.inflate(inflater, textLayoutRes, root, false));
And finally I want to retrieve myVariable but I don't know if it's a layout 1, 2 or 3. Basically what could be done now is to use instanceof operator to check whether its a type MyLayoutBinding1, MyLayoutBinding2 or MylayoutBinding3. But as I said this use-case is only for demonstration purpose and I could have 999 different layouts.
So what I would like to do is :
ViewDataBinding myLayout = DataBindingUtil.getBinding(textContainerBinding.getRoot().getChildAt(0));
String myVariable = myLayout.getVariable("myVariable");
if(myVariable != null)
Log.d(TAG, "myLayout was MylayoutBinding1 or myLayoutBinding2 or myLayoutBinding3");
else
Log.d(TAG, "mylayout was not one of the 3 layouts");
Sorry for this (very) long post but thank's for reading it and for any future answers !
I am not sure if I get it but what I do is I declare a variable in the layout like this:
<data>
<variable
name="variableName"
type="bla.bla.VariableType"/>
</data>
Then first you get your layout binding in onCreate:
binding = DataBindingUtil.inflate(inflater, R.layout.your_layout, container, false);
Then you should send a variable to the layout in code like:
binding.setVariableName(yourVariable);
Then you can retrieve it like:
binding.getVariableName();
why ViewDataBinding Doesn't have getMethodVariable?
consider the normal scenario without binding. you have a text container layout. how will you include another layout inside it in a normal activity.
my_text_container.xml:(Normal activity)
You inflate this layout to your java file using R.layout.my_text_container, you won't inflate every layout to a different view to access textview inside it. just one inflate and go with it.
So the same procedure is followed in DataBinding as well, when you use include tag ,the respective fields will be inside MyTextContainerLayoutBinding.
you don't have to inflate it again and again with activity name like MyLayout1Binding, MyLayout2Binding. that's why getting variable name become unnecessary over here.
I think adding variability to Binding , will be more helpful in a place where you just want to display data. Data from one model across multiple included layouts,more helpful with Listviews,Recyclerviews(where layout use data from models).
you can't provide different type for different layouts ,if you are going include one layout to another.(Remember that this binds both layout to single name (parent_activity in your case container)).
Eg:
UserProfileModel:
public class UserProfileModel {
String firstname;
String lastname;
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public String getFirstname() {
return firstname;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
}
my_layout_1.xml;
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<data>
<variable name="user"
type="com.hourglass.lingaraj.bindingusingvariables.UserProfileModel" />
</data>
<LinearLayout
android:orientation="vertical"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:visibility="visible"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{user.firstname}"
style="#style/mystyle_1"/>
<include layout ="#layout/my_layout_2"
app:user="#{user}" />
</LinearLayout>
</layout>
my_layout_2.xml:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="user"
type="com.hourglass.lingaraj.bindingusingvariables.UserProfileModel"/>
</data>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:visibility="visible"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#{user.lastname}"
style="#style/mystyle_2"/>
</RelativeLayout>
</layout>
MainActivity.java:
public class MainActivity extends AppCompatActivity {
MyLayout1Binding layout_binding;
UserProfileModel data_model;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_layout_1);
data_model = new UserProfileModel();
data_model.setFirstname("Lingaraj");
data_model.setLastname("Sankaravelu");
layout_binding = DataBindingUtil.inflate(getLayoutInflater(),R.layout.my_layout_1,null,false);
layout_binding = DataBindingUtil.setContentView(this,R.layout.my_layout_1);
layout_binding.setUser(data_model);
}
}
As you see we are using only one model to populate data across included layout. So there is no need get Variable name to verify which model is loaded as it's Binded to single layout.
There is no workaround to achieve this, us of I have tried.
So my answer will be No you can't get a variable name from binding
References.
No More findViewById
Android Data Binding: That Thing
Android Data Binding: Adding some variability
Android Data Binding: Express Yourself