Let's say I have this view model with methods:
public int getValueA() {
return a;
}
public int getValueB() {
return b;
}
#BindingAdapter("valueA")
public void setupSomething(View view, int valueA) {
// do something with a
}
#BindingAdapter({"valueA", "valueB"})
public void setupSomethingElse(View view, int valueA, int valueB) {
// do something with a and b
}
and I bind this to a view:
<View
android:layout_width="match_parent"
android:layout_height="wrap_content"
bind:valueA="#{viewmodel.valueA}"
bind:valueB="#{viewmodel.valueB}"/>
How can I call both BindingAdapter methods? Right now data binding is just calling the later. I guess I could just call setSomething from within setSomethingElse but this smells a little fishy to me (and partially defeats the purpose of databinding).
It's like you're suggesting yourself: you need to call setupSomething() from setupSomethingElse. It's just fine doing so and how databindings work. Only the best fitting #BindingAdapter will be used for your attributes.
Alternatively you can use the requireAll() field of #BindingAdapter. But this is only feasible if you can handle the Java default value (in your case 0) for your values.
Whether every attribute must be assigned a binding expression or if some can be absent. When this is false, the BindingAdapter will be called when at least one associated attribute has a binding expression. The attributes for which there was no binding expression (even a normal XML value) will cause the associated parameter receive the Java default value. Care must be taken to ensure that a default value is not confused with a valid XML value.
#BindingAdapter({"valueA", "valueB"}, requireAll = false)
public void setupSomethingElse(View view, int valueA, int valueB) {
if (valueA != 0) {
// do something with a
if (valueB != 0) {
// do something with a and b
}
}
}
So you don't need setupSomething() anymore. But personally I like the first approach better.
Related
My goal is to 2-way databind material.Slider view to MutableLiveData from my viewmodel:
<com.google.android.material.slider.Slider
...
android:value="#={viewmodel.fps}"
...
/>
Of course, it's not working because there is no databinding adapter for Slider in androidx.databinding library
[databinding] Cannot find a getter for <com.google.android.material.slider.Slider android:value> that accepts parameter type <java.lang.Integer>. If a binding adapter provides the getter, check that the adapter is annotated correctly and that the parameter type matches.
But, they have one for SeekBar: /androidx/databinding/adapters/SeekBarBindingAdapter.java
As I understand, 2-way databinding should work only with "progress" attribute, and 1-way databinding requires two attributes: "onChanged" and "progress"
I made a try to adapt SeekBarBindingAdapter for Slider:
#InverseBindingMethods({
#InverseBindingMethod(type = Slider.class, attribute = "android:value"),
})
public class SliderBindingAdapter {
#BindingAdapter("android:value")
public static void setValue(Slider view, int value) {
if (value != view.getValue()) {
view.setValue(value);
}
}
#BindingAdapter(value = {"android:valueAttrChanged", "android:onValueChange"}, requireAll = false)
public static void setOnSliderChangeListener(Slider view, final Slider.OnChangeListener valChanged, final InverseBindingListener attrChanged) {
if (valChanged == null)
view.addOnChangeListener(null);
else
view.addOnChangeListener((slider, value, fromUser) -> {
if (valChanged != null)
valChanged.onValueChange(slider, value, fromUser);
});
if (attrChanged != null) {
attrChanged.onChange();
}
}
#Override
public void onValueChange(#NonNull Slider slider, float value, boolean fromUser) {
}
It's not building:
Could not find event android:valueAttrChanged on View type Slider
but why it looks for valueAttrChanged if I only use
android:value="#={viewmodel.fps}"
?
How do I find the right attribute to add to BindingAdapter, if I don't see valueAttrChanged in Slider class?
Let's look at SeekBarBindingAdapter's setOnSeekBarChangeListener() method. It adds four different attributes: {"android:onStartTrackingTouch", "android:onStopTrackingTouch", "android:onProgressChanged", "android:progressAttrChanged"} but only the last one is used by two-way databinding.
But why there are four attributes? If you look at SeekBar class, it has setOnSeekBarChangeListener() method which allows you to set and remove a listener. The problem is that SeekBar can only have one listener, and that listener provides different callbacks: onProgressChanged, onStartTrackingTouch and onStopTrackingTouch.
SeekBarBindingAdapter registers its own listener which means that no one can register another listener without removing the existing one. It's why SeekBarBindingAdapter provides onStartTrackingTouch, onStopTrackingTouch and onProgressChanged attributes, so you can listen to these events without registering your own OnSeekBarChangeListener.
Actually the Slider adapter can be much simpler than SeekBarBindingAdapter, because the Slider allows you to add and remove listeners using addOnChangeListener() and removeOnChangeListener(). So a two-way databinding adapter can register its own listener and anyone else can register other listeners without removing previous ones.
It allows us to define a pretty concise adapter. I created a kotlin example, hope you can translate it to java:
#InverseBindingAdapter(attribute = "android:value")
fun getSliderValue(slider: Slider) = slider.value
#BindingAdapter("android:valueAttrChanged")
fun setSliderListeners(slider: Slider, attrChange: InverseBindingListener) {
slider.addOnChangeListener { _, _, _ ->
attrChange.onChange()
}
}
And the layout:
...
<com.google.android.material.slider.Slider
...
android:value="#={model.count}" />
...
You can find the full sources here.
Update Android Java
Data binding
<variable
name="device"
type=".....Device" />
Trong file binding
#InverseBindingAdapter(attribute = "android:value")
public Float getSlider(Slider slider) {
return slider.getValue();
}
#BindingAdapter("app:valuesAttrChanged")
public void setSliderListeners(Slider slider, InverseBindingListener attrChange) {
slider.addOnChangeListener(new Slider.OnChangeListener() {
#Override
public void onValueChange(#NonNull Slider slider, float value, boolean fromUser) {
attrChange.onChange();
}
});
}
Trong file xml thêm dòng
android:value="#{device.data}"
data is value change
I'm still new to all this MVVM and Android Architecture Components. I have a few screens (Login and Register) that have inputs for email, password, name etc and a 'continue' button that's only enabled when the required fields are filled out correctly. There's also text views for messages such as "password must be..." and "not a valid email...". I'm trying to use a binding adapter and viewmodel to pull some of this validation logic out of my MainActivity and away from my business logic, but I'm struggling. I'm not even sure if this is the best way to do it. My thought with the ViewModel is that it would hold it's state on rotation/activity changes.
RegisterActivity is an Activity that simply holds a ViewPager with 3 fragments (email/password, first/last name, validation code).
Binding Adapter
#BindingAdapter("app:onTextChanged")
public static void onTextChanged(TextInputEditText view, TextViewBindingAdapter.OnTextChanged listener) {
}
Layout
<TextView
android:id="#+id/tv_error_message"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="16dp"
android:text="#string/register_email_requirement"
android:textColor="#color/moenPrimaryError"
android:textSize="18sp"
android:visibility="#{viewModel.emailValidationVisible ? View.VISIBLE: View.GONE}"
app:layout_constraintBottom_toTopOf="#id/input_layout_password"
app:layout_constraintEnd_toEndOf="#+id/input_layout_email_address"
app:layout_constraintStart_toStartOf="#+id/input_layout_email_address"
app:layout_constraintTop_toBottomOf="#+id/input_layout_email_address"
app:layout_goneMarginTop="16dp" />
<com.google.android.material.textfield.TextInputEditText
android:id="#+id/input_email_address"
style="#style/MoenTextInputEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="textEmailAddress"
app:onTextChanged="#{viewModel.onTextChanged}"
app:onFocusChange="#{inputLayoutEmailAddress}">
</com.google.android.material.textfield.TextInputEditText>
ViewModel
public class RegisterFragmentViewModel extends BaseObservable {
private boolean emailValidationVisible = false;
#Bindable
public boolean getEmailValidationVisible() {
return this.emailValidationVisible;
}
public void toggle() {
this.emailValidationVisible = !this.emailValidationVisible;
notifyPropertyChanged(BR.viewModel);
}
public void onTextChanged(CharSequence s, int start, int before, int count) {
Log.w("tag", "onTextChanged " + s);
this.toggle();
}
}
This is just a test I have. My thought was that I could bind the TextView visibility to a boolean that I can toggle/manipulate with a onTextChanged listener, but I don't know how to wire up the Binding Adapter. Am I on the right path? Is there a better/easier way to do this?
Am I on the right path? Is there a better/easier way to do this?
it is a way of doing it. I would remove the ternary operator from this line
android:visibility="#{viewModel.emailValidationVisible ? View.VISIBLE: View.GONE}"
and create a simple function in your VM that returns it. EG:
#Bindable
public int getVisibility() {
return emailValidationVisible ? View.VISIBLE: View.GONE
}
and in toggle(), you will have something like
public void toggle() {
this.emailValidationVisible = !this.emailValidationVisible;
notifyPropertyChanged(BR.visibility);
}
which will call the getter for you. Your xml will have to be changed like follow
android:visibility="#{viewModel.getVisibility()}"
Alternately you could create a BindingAdapter that takes a Boolean and change the visibility accordingly to it
I got JSON response which have elementId and flag for hide/show that element
Call function using this(From JSON Response)
displayView(templateDefinationItem.getTemplateDefinationId(), templateDefinationItem.isActive());
I have created one function for hide the views
public void displayView(final int elementId, boolean isVisible) {
try {
View view = findViewById(elementId);
if (isVisible) {
view.setVisibility(View.VISIBLE);
} else {
view.setVisibility(View.GONE);
}
} catch (Exception e) {
e.printStackTrace();
}
}
In above code i passed elementId and true/false value for the operation, where
elementId of(EditTextId,TextView,LinearLayout,Buttons etc.)
Error
i got error in this line View view = findViewById(elementId); getting null.
What i want
is there any way to bind any type of element? Or any generic view for same?
in my case i used this View view = findViewById(elementId); for binding but i got null.
Rather passing view id you should pass view in display method that is more convenient.
First Views Ids are generated automatically so if things you are storing this ids some Where and later used to get views it not right thing because Ids are generated and it different device to device and might change any time when application closed and start again.
You can do it by getIdentifier()
try {
String buttonID = elementId;//String name of id
int resID = getResources().getIdentifier(buttonID, "id", getPackageName());
View view = findViewById(resID);
if (isVisible) {
view.setVisibility(View.VISIBLE);
} else {
view.setVisibility(View.GONE);
} catch (Exception e) {
e.printStackTrace();
}
as above we are passing view id with combination of i and j values and then using getIdentifier() method to make Views objects .
I thing above code is solution towards your problem.
I would suggest using Kotlin instead of Java, and additionally using the core ktx library (it's a library of usefull Kotlin extensions for Android).
With it, you can do something like this:
view.isVisible = true sets the view to View.VISIBLE, whereas view.isVisible = false sets it to View.GONE
Similarly you have view.isInvisible which toggles between Invisible and Visible, and view.isGone which toggles between Gone and Visible.
In case you need the documentation of these methods, you can find it here.
Also, if you're using Kotlin instead of Java, you don't need to do findViewById(R.id.xxx), you can simply do a static import of any View.
I have a list of items. In each item's row I have 2 EditTexts side-by-side. EditText-2 depends on EditText-1's value. This list is bound with data-binding values in HashMap<String, ItemValues>
For Example:
Total _____1000____
Item A __1__ __200__
Item B __1__ __200__
Item C __1__ __200__
Item D __2__ __400__
First EditText is the share and the second value is its value calculated based on total and share. So, in example if I change any 1 share, all the values will be changed. So, shown in example total no of shares are = 1+1+1+2 = 5. So amount per share = 1000/5 = 200 and is calculated and shown in next EditText.
I have bound this values with two-way data binding like this:
As, this is a double value, I have added 2 binding adapters for this like this:
#BindingAdapter("android:text")
public static void setShareValue(EditText editText, double share) {
if (share != 0) {
editText.setText(String.valueOf(share));
} else {
editText.setText("");
}
}
#InverseBindingAdapter(attribute = "android:text")
public static double getShareValue(EditText editText) {
String value = editText.getText().toString();
if (!value.isEmpty()) {
return Double.valueOf(value);
} else
return 0;
}
Now, to calculate new values, I need to re-calculate whole thing after any share value is changed. So, I added android:onTextChagned method to update Calculations. But it gets me an infinite loop.
<EditText
android:text="#={items[id].share}"
android:onTextChanged="handler.needToUpdateCalculations"
.... />
public void needToUpdateCalculations(CharSequence charSequence, int i, int i1, int i2) {
updateCalculations();
}
This gets an infinete loop because when data changes, it is rebound to the EditText, and each EditText has an onTextChanged attached it will fire again and it will get really large - infinite loop.
It also updates the value of itself, ended up loosing the cursor as well.
I have also tried several other methods like adding TextWatcher when on focus and removing when losses focus. But at least it will update it self and will loose the cursor or infinite loop.
Unable to figure this problem out. Thank you for looking into this problem.
EDIT:
I have tried with the below method. But, it doesn't allow me to enter . (period).
#BindingAdapter("android:text")
public static void setDoubleValue(EditText editText, double value) {
DecimalFormat decimalFormat = new DecimalFormat("0.##");
String newValue = decimalFormat.format(value);
String currentText = editText.getText().toString();
if (!currentText.equals(newValue)) {
editText.setText("");
editText.append(newValue);
}
}
The reason you stated is correct and it will make a infinite loop definitely. And there is a way to get out from the infinite loop of this problem, android official provided a way to do so (But it is not quite obvious.)(https://developer.android.com/topic/libraries/data-binding/index.html#custom_setters)
Binding adapter methods may optionally take the old values in their
handlers. A method taking old and new values should have all old
values for the attributes come first, followed by the new values:
#BindingAdapter("android:paddingLeft")
public static void setPaddingLeft(View view, int oldPadding, int newPadding) {
if (oldPadding != newPadding) {
view.setPadding(newPadding,
view.getPaddingTop(),
view.getPaddingRight(),
view.getPaddingBottom());
}
}
You can use the old value and new value comparison to make the setText function called conditionally.
#BindingAdapter("android:text")
public static void setShareValue(EditText editText, double oldShare,double newShare) {
if(oldShare != newShare)
{
if (newShare!= 0) {
editText.setText(String.valueOf(newShare));
} else {
editText.setText("");
}
}
}
I have a View object on my Activity and I'd like to change the background resource of the view. More specifically, I'd like to toggle it.
So I'll need some logic like this:
if (myView.getBackgroundResource() == R.drawable.first) {
myView.setBackgroundResource(R.drawable.second);
}
else {
myView.setBackgroundResource(R.drawable.first);
}
The issue here being that there is no getBackgroundResource() method.
How can I obtain the resource a View is using for its background?
I don't think the View remembers what resource it is using after it gets the Drawable from the resource.
Why not use an instance variable in your Activity, or subclass the View and add an instance variable to it?
Wouldn't it be easier to just have a control variable that maintains the state? Lets you be flexible and allows you any number of drawables.
int[] backgrounds = {
R.drawable.first,
R.drawable.second,
R.drawable.third
};
int currentBg;
void switch() {
currentBg++;
currentBg %= backgrounds.length;
myView.setBackgroundResource(backgrounds[currentBg]);
}
You could use a flag to keep track of which was last set
private static final int FIRST_BG = 0;
private static final int SECOND_BG = 1;
private int mCurrentBg;
...
if (mCurrentBg == FIRST_BG) {
myView.setBackgroundResource(R.drawable.second);
mCurrentBg = SECOND_BG;
}
else {
myView.setBackgroundResource(R.drawable.first);
mCurrentBg = FIRST_BG;
}
You would have to initialize mCurrentBg wherever the background is initially set though.
You can get the ID of a resource via the getResources().getIdentifier("filename", "drawable", "com.example.android.project"); function. As you can see you will need the filename, the type of resource (drawable, layout or whatever) and the package it is in.
EDIT: Updated my logic fail.
I think you might be able to put the setTag() and getTag() methods to use here:
//set the background and tag initially
View v = (View)findViewById(R.id.view);
v.setBackgroundResource(R.drawable.first);
v.setTag(R.drawable.first);
if(v.getTag().equals(R.drawable.first)) {
v.setBackgroundResource(R.drawable.second);
v.setTag(R.drawable.second);
} else {
v.setBackgroundResource(R.drawable.first);
v.setTag(R.drawable.first);
}
I have not tested this, but I think it should work, in theory. The downside is that you add a little overhead by having to manually tag it the first time, but after the initial tagging, you shouldn't have to worry about keeping track of flags.