Develop Reference

Simpler way to create multiple appends for a custom numpad

is there a faster/simpler way to make this:? I'm creating a numpad in my Android App which I use 10 buttons for and a delete button. Right now I'm doing it like this but like this it's gonna take a lot of code.
num0.setOnClickListener(){
editTextNumberPassword.append("0")
}
num1.setOnClickListener(){
editTextNumberPassword.append("1")
}
num2.setOnClickListener(){
editTextNumberPassword.append("3")
}

Add all views into a list and then use the index:
listOf(num0, num1, num2)
.withIndex()
.forEach { (index, view) ->
view.setOnClickListener { editTextNumberPassword.append("$index") }
}

How to get the name of view programatically such as whether it's textview or button by View params in onClick callback in Android?

In particular class, from many places call back is coming, i just want to whether it's coming text or button for example, so that I can set the data accordingly.
NOTE: I'm not talking about parent layout, I want to know exact name where the event click is happened!
If I'm doing this: Log.d("Hello", "Clicked finally: "+ view?.id)
This is coming:
D: Clicked finally: 2131296625

If you are using Kotlin, You can simply check if the View is Button or Image using is operator like:
when(view) {
is Button -> {
// a Button is clicked.
}
is AppCompatImageView -> {
// an Image is clicked.
}
else -> {
// any other view is clicked.
}
}

You can do something like this:
if (view.javaClass.simpleName == Button::class.java.simpleName) {
// it is a button
} else if (view.javaClass.simpleName == TextView::class.java.simpleName) {
// it is a text view
}
Please note that this won't work if you are using any subclass of Button or TextView. You will need to explicitly specify the class you want to check for.

Use group in ConstraintLayout to listen for click events on multiple views

Basically I'd like to attach a single OnClickListener to multiple views inside a ConstraintLayout.
Before migrating to the ConstraintLayout the views where inside one layout onto which I could add a listener. Now they are on the same layer with other views right under the ConstraintLayout.
I tried adding the views to a android.support.constraint.Group and added a OnClickListener to it programmatically.
group.setOnClickListener {
Log.d("OnClick", "groupClickListener triggered")
}
However this does not seem to work as of the ConstraintLayout version 1.1.0-beta2
Have I done something wrong, is there a way to achieve this behaviour or do I need to attach the listener to each of the single views?

The Group in ConstraintLayout is just a loose association of views AFAIK. It is not a ViewGroup, so you will not be able to use a single click listener like you did when the views were in a ViewGroup.
As an alternative, you can get a list of ids that are members of your Group in your code and explicitly set the click listener. (I have not found official documentation on this feature, but I believe that it is just lagging the code release.) See documentation on getReferencedIds here.
Java:
Group group = findViewById(R.id.group);
int refIds[] = group.getReferencedIds();
for (int id : refIds) {
findViewById(id).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
// your code here.
}
});
}
In Kotlin you can build an extension function for that.
Kotlin:
fun Group.setAllOnClickListener(listener: View.OnClickListener?) {
referencedIds.forEach { id ->
rootView.findViewById<View>(id).setOnClickListener(listener)
}
}
Then call the function on the group:
group.setAllOnClickListener(View.OnClickListener {
// code to perform on click event
})
Update
The referenced ids are not immediately available in 2.0.0-beta2 although they are in 2.0.0-beta1 and before. "Post" the code above to grab the reference ids after layout. Something like this will work.
class MainActivity : AppCompatActivity() {
fun Group.setAllOnClickListener(listener: View.OnClickListener?) {
referencedIds.forEach { id ->
rootView.findViewById<View>(id).setOnClickListener(listener)
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Referenced ids are not available here but become available post-layout.
layout.post {
group.setAllOnClickListener(object : View.OnClickListener {
override fun onClick(v: View) {
val text = (v as Button).text
Toast.makeText(this#MainActivity, text, Toast.LENGTH_SHORT).show()
}
})
}
}
}
This should work for releases prior to 2.0.0-beta2, so you can just do this and not have to do any version checks.

The better way to listen to click events from multiple views is to add a transparent view as a container on top of all required views. This view has to be at the end (i.e on top) of all the views you need to perform a click on.
Sample container view :
<View
android:id="#+id/view_container"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="#+id/view_bottom"
app:layout_constraintEnd_toEndOf="#+id/end_view_guideline"
app:layout_constraintStart_toStartOf="#+id/start_view_guideline"
app:layout_constraintTop_toTopOf="parent"/>
Above sample contains all four constraint boundaries within that, we can add views that to listen together and as it is a view, we can do whatever we want, such as ripple effect.

To complement the accepted answer for Kotlin users create an extension function and accept a lambda to feel more like the API group.addOnClickListener { }.
Create the extension function:
fun Group.addOnClickListener(listener: (view: View) -> Unit) {
referencedIds.forEach { id ->
rootView.findViewById<View>(id).setOnClickListener(listener)
}
}
usage:
group.addOnClickListener { v ->
Log.d("GroupExt", v)
}

The extension method is great but you can make it even better by changing it to
fun Group.setAllOnClickListener(listener: (View) -> Unit) {
referencedIds.forEach { id ->
rootView.findViewById<View>(id).setOnClickListener(listener)
}
}
So the calling would be like this
group.setAllOnClickListener {
// code to perform on click event
}
Now the need for explicitly defining View.OnClickListener is now gone.
You can also define your own interface for GroupOnClickLitener like this
interface GroupOnClickListener {
fun onClick(group: Group)
}
and then define an extension method like this
fun Group.setAllOnClickListener(listener: GroupOnClickListener) {
referencedIds.forEach { id ->
rootView.findViewById<View>(id).setOnClickListener { listener.onClick(this)}
}
}
and use it like this
groupOne.setAllOnClickListener(this)
groupTwo.setAllOnClickListener(this)
groupThree.setAllOnClickListener(this)
override fun onClick(group: Group) {
when(group.id){
R.id.group1 -> //code for group1
R.id.group2 -> //code for group2
R.id.group3 -> //code for group3
else -> throw IllegalArgumentException("wrong group id")
}
}
The second approach has a better performance if the number of views is large since you only use one object as a listener for all the views!

While I like the general approach in Vitthalk's answer I think it has one major drawback and two minor ones.
It does not account for dynamic position changes of the single views
It may register clicks for views that are not part of the group
It is not a generic solution to this rather common problem
While I'm not sure about a solution to the second point, there clearly are quite easy ones to the first and third.
1. Accounting position changes of element in the group
This is actually rather simple. One can use the toolset of the constraint layout to adjust the edges of the transparent view.
We simply use Barriers to receive the leftmost, rightmost etc. positions of any View in the group.
Then we can adjust the transparent view to the barriers instead of concrete views.
3. Generic solution
Using Kotlin we can extend the Group-Class to include a method that adds a ClickListener onto a View as described above.
This method simply adds the Barriers to the layout paying attention to every child of the group, the transparent view that is aligned to the barriers and registers the ClickListener to the latter one.
This way we simply need to call the method on the Group and do not need to add the views to the layout manually everytime we need this behaviour.

in Constraintlayout 2.0.0,you can use Layer to resolve multiple views click event,and also support scale animation

For the Java people out there like me:
public class MyConstraintLayoutGroup extends Group {
public MyConstraintLayoutGroup(Context context) {
super(context);
}
public MyConstraintLayoutGroup(Context context, AttributeSet attrs) {
super(context, attrs);
}
public MyConstraintLayoutGroup(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public void setOnClickListener(OnClickListener listener) {
for (int id : getReferencedIds()) {
getRootView().findViewById(id).setOnClickListener(listener);
}
}
}
This is not propagating click states to all other children however.

fun ConstraintLayout.setAllOnClickListener(listener: (View) -> Unit) {
children.forEach { view ->
rootView.findViewById<View>(view.id).setOnClickListener { listener.invoke(this) }
}
}
And then
.setAllOnClickListener {
do something
}

Programmatically hide views if it is shown. Show views if it is hidden

My button use code that shows and hides the views:
public void onClick (View v){
if (What code you need to enter here to determine hidden views or shown)
{
testActivity.setVisibility(View.VISIBLE);
}
else
{
testActivity.setVisibility(View.GONE);
}
}
What code I need to add in the "if()", so that clicking on my button was checked condition. If the activity is hidden, it should be shown, and Vice versa. If the views is shown, hide it.

I'm guessing since you are using setVisibility, that you want to check the visibility of a View , not an Activity.
In that case you just use getVisibility()
(I used != cause the visibility could be IINVISIBLE as well, change per your needs) :
public void onClick (View v){
if (testActivity.getVisibility() != View.VISIBLE)
{
testActivity.setVisibility(View.VISIBLE);
}
else
{
testActivity.setVisibility(View.GONE);
}
} });

Don't understand why, but only that removed the answer of a man who has solved my problem. Here is his response, and this code works:
public void onClick (View v){
if ((testActivity.getVisibility() == View.VISIBLE))
{
testActivity.setVisibility(View.GONE);
}
else
{
testActivity.setVisibility(View.VISIBLE);
}

Toggle button android

I want my toggle button's ON text to be large and OFF text to be small. But can't do it.. any suggestions? This is what i was trying
mf=(ToggleButton)findViewById(R.id.mf);
if(mf.isEnabled()==true)
{
mf.setTextSize(13);
}
else
mf.setTextSize(8);

Your code has to be called each time you click on your button. so use :
toggleButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (toggleButton.isChecked()) {
toggleButton.setTextSize(13.0f);
} else {
toggleButton.setTextSize(8.0f);
}
}
});
You can set OnClickListner with a easy method. In your .xml put the option
android:onClick="nameOfMethod"
And then in your code:
public void nameOfMethod(View v){
}
Where v is the togglebutton in this case ( ToggleButton mf = (ToggleButton)v; )

I put the solution here:
mf=(ToggleButton)findViewById(R.id.mf);
if(mf.isChecked())
{
mf.setTextSize(13);
}
else
mf.setTextSize(8);
Use isChecked() instead of isEnabled()

You need to do some debugging.
Firstly:
if(mf.isEnabled()==true)
can be
if (mf.isEnabled())
Does mf.setTextSize(13) on it's own work as expected?
Add some logging:
if (mf.isEnabled())
{
// Add some logging, is this line reached correctly?
mf.setTextSize(13);
}
else
// Add some logging, is this line reached correctly?
mf.setTextSize(8);
Chances are you need to change isEnabled() to isChecked(). isEnabled() means exactly that, whether it's enabled or not. You want to know whether the button has been checked.