Develop Reference

to create variables, loops in kotlin?

I create app for Android on Kotlin,I need to create 55 variables to work with them in code,how to do it using a for loop?
Variables should be look like this:
val EditText0: EditText = findViewById(R. id.et0)
val EditText1: EditText = findViewById(R. id.et1)
and so on

You should use getIdentifier()
for(int i=0; i<some_value; i++) {
for(int j=0; j<some_other_value; j++) {
String buttonID = "btn" + i + "-" + j;
int resID = getResources().getIdentifier(buttonID, "id", getPackageName());
buttons[i][j] = ((Button) findViewById(resID));
buttons[i][j].setOnClickListener(this);
}
}
This is Java but same logic for kotlin.

When you have many of a similar kind of variable like this, you really should have a single List variable for all of them.
If they have consistent names like this, you can generate the IDs using resources.getIdentifier. It's easier using a List constructor than a for loop.
// In an Activity:
val myEditTexts: List<EditText> = List(55) { index ->
val id = resources.getIdentifier("et$index", "id", packageName)
findViewById<EditText>(id)
}
// In a Fragment's onViewCreated function:
val myEditTexts: List<EditText> = with(requireContext()) {
List(55) { index ->
val id = resources.getIdentifier("et$index", "id", packageName)
view.findViewById<EditText>(id)
}
}
If you don't want to keep all of them in a single list, then you should use View Binding to let the properties be generated for you.

How to iterate controls to get their value in a loop in Android

I have many controls in an activity layout in Android, and
i want to get their value in a simple for, the problem is that
Eclipse assigns the ID randomy, so I cannot get controls ID in a
sequential way to access the controls in a for loop because
they are not sequential IDs.
Here is why I am trying to do:
int visibleId = R.id.fieldVisible1;
int editId = R.id.editField2;
int spinnerId = R.id.spinner1;
for(int nIndex = 0; nIndex < 12; nIndex++)
{
CheckBox checkBox = (CheckBox)findViewById(visibleId + nIndex);
checkBox.setChecked(_fieldsInfoArray.get(nIndex).getVisible() == 1);
EditText edit = (EditText)findViewById(editId );
edit.setText(_fieldsInfoArray.get(nIndex).getName());
Spinner spinner = (Spinner)findViewById(spinnerId + nIndex);
spinner.setSelection(_fieldsInfoArray.get(nIndex).getOffset());
}
how can I make Eclipse to assign sequential IDs to controls so I can
just increment by 1 the id in a loop?

A better way of doing this may possibly to look into the use of:
int children = layout.getChildCount();
for (int i=0; i < children; i++){
View v = ll.getChildAt(i);
}
This would allow you to loop over all views inside the layout without needing to know their IDs.

Properly implementing/initializing lots of new variables, taken from RadioGroups and Spinners

I am developing a simple questionnaire-like app which includes lots of radio buttons joined into groups and spinners. I have multiple activities (6); some of them having RBs and some Spinners to let the user answer the questions.
The following step, which I have trouble with, is how to fetch lots of selections (of all the radio buttons/choices) and possibly do that in a for loop (so I don't have to initialize each new variable 30+ times in a row for just one activity). I've already assigned IDs to all of the views, but am having a hard time how to actually fetch the selection, initialize a new var corresponding to the selection (let's say radio button 1 in radio group 1 gives me a new variable with a value of 1) and then make the variables available to all of the activities (should I use global when initializing?).
My failed attempt on generating 10 variables for the first "page"
public void goTo2(View v) {
checkRB();
Intent intent1 = new Intent(Vprasalnik1.this, Vprasalnik2.class);
startActivity(intent1);
finish();
}
public void checkRB()
{
for (int i=0;i<9;i++)
{
RadioButton "vRB" + i; //I'd like to loop and initialize vars by adding a number to them (vRB1, vRB2, ...)
}
}

Put variables into array like a
int size = 9;
RadioButton[] views = new RadioButton[size];
public static checkRB()
{
for(int i=0;i<size;i++)
{
views[i] = (RadioButton)findViewByID(...);//For example
}
}
Or make a structure :
public class Choise
{
int mRadioButtonChoise;
int mSpinnerChoise;
}
And use something like this:
...
Choise c = new Choise();
c.mRadioButtonChoise = yourRadioButtonID;
c.mSpinnerChoise = youtSpinnerChoiseID;
...

Using a variable to identify a resource:
RadioButton[] rb = new RadioButton[size];
public static checkRB()
{
for(int i=0;i<size;i++)
{
int id = context.getResources().getIdentifier("vRB" + i, "id", context.getPackageName())
rb[i] = (RadioButton)findViewByID(id);
}
}

If you have an array of RadioButtons then you can get all the values at the same time, however initializing them will have to be manual.
RadioButton rb[];
boolean rbc[];
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
rbc=new boolean[200];
rb=new RadioButton[200]();
rb[0]=(RadioButton)findViewById(R.id.rb1);
rb[1]=(RadioButton)findViewById(R.id.rb2);
rb[2]=(RadioButton)findViewById(R.id.rb3);
rb[3]=(RadioButton)findViewById(R.id.rb4);
// many more.
}
public void checkRB()
{
for (int i=0;i<9;i++)
{
rbc[i]=rb.isChecked(); //I'd like to loop and initialize vars by adding a number to them (vRB1, vRB2, ...)
}
}
Then before starting your intent add all relevant data to it.

So I've managed to cramp up the radio buttons activity, so that it finally works. If anyone is interested - I've used tags in xml code to properly assign values (1, 2 and 3 for each group of buttons) and managed to get an output in my testToast. At least I didn't have to initialize all of the variables manually - I've been saving the values into an ArrayList and then appended to them via StringBuilder.
Thanks to everyone who tried to help - it turned out I've needed a bit more research, testing and teasing my half-awake brain.
btn = (Button) findViewById(R.id.v3_btn1);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
for(int i = 1; i <= 36; i++)
{
tmpRGid = "radioGroup_v3q" + i;
tmp2RGid = getResources().getIdentifier(tmpRGid, "id", getPackageName());
RGid = (RadioGroup) findViewById(tmp2RGid);
selectedOption = RGid.getCheckedRadioButtonId();
RBid = (RadioButton) findViewById(selectedOption);
addToIDList.add((String)RBid.getTag());
}
String testToast = "";
StringBuilder builder = new StringBuilder();
builder.append("Vaša izbira (");
for (int z=0; z < addToIDList.size(); z++) {
testToast = addToIDList.get(z);
builder.append(testToast + ", ");
}
builder.setLength(builder.length() - 2);
builder.append(") je bila shranjena.");
Toast.makeText(Vprasalnik3.this, builder, Toast.LENGTH_LONG).show();

Dynamic Button Onclick Listener

I am trying to create dynamic buttons. When clicking a button it should go to the specified url assigned to the text of the button.
For testing, first I tried to get that ID, if it is equal it prints the value of i. But whenever I clicked any one button, instead of telling that particular i value, it enters into whole loop, and prints all the values of i starting from 1 to 19 (the number of buttons that are dynamically created)
And after printing all values from 1 to 19, the program is getting force closed saying Null pointer exception.
I even tried by placing the handler code outside onCreate(), but I'm still getting the same error.
for ( i = 0; i <itemList.getTitle().size()-1; i++) {
title[i] = new TextView(this);
title[i].setTextColor( -16711936 );
title[i].setTextSize(18);
title[i].setText("Title = "+itemList.getTitle().get(i));
description[i] = new TextView(this);
description[i].setTextColor(-16776961);
description[i].setText("Description = "+itemList.getDescription().get(i)+"......");
more[i]=new Button(this);
more[i].setText(itemList.getLink().get(i));
layout.addView(title[i]);
System.out.println("Title view is set");
layout.addView(description[i]);
//System.out.println("Description view is set");
layout.addView(more[i]);
more[i].setOnClickListener(listener);
}
private OnClickListener listener=new OnClickListener(){
public void onClick(View arg) {
int index = 0;
for (i = 0; i < more.length; i++)
{
if (more[i].getId() == arg.getId())
{
index = i;
System.out.println("Value of i onclick is"+i);
}
}
//System.out.println("Vlaue of I in onclick"+i);
//Uri uri=Uri.parse(itemList.getLink().get(i));
//startActivity(new Intent(Intent.ACTION_VIEW,uri));
//Toast.makeText(getApplicationContext(), "This button is clicked"+i+more[i].getText()+itemList.getLink().get(i),Toast.LENGTH_LONG).show();
}
}

You can use setTag() and getTag() method of View to identify different button.
for (i = 0; i < itemList.getTitle().size()-1; i++) {
...
more[i].setTag(i); // Use index of itemList as the tag
}
In onClick:
int index = (Integer)arg.getTag();

you can also set the id of button
more[i].setid(i);

int index = 0;
for (i = 0; i < more.length; i++)
{
if (more[i].getId() == arg.getId())
{
index = i;
System.out.println("Value of i onclick is"+i);
}
}
As you can see here, i is still in your for loop.
Put the System.out.println("Value of i onclick is"+i); outside of your for loop and it should work
PS: format your code, it's easier to read that way and you'll notice small mistakes like these more easily

I think this will help you..
set button tag also dynamic like
more[i].setId(i);
and also changed condition like
if (more[i].getId() == i) {
index = i;
}
hope this will help you...

Android: Using findViewById() with a string / in a loop

I'm making an android application, where there is a view composed of hundreds of buttons, each with a specific callback. Now, I'd like to set these callbacks using a loop, instead of having to write hundreds of lines of code (for each one of the buttons).
My question is: How can I use findViewById without statically having to type in each button id?
Here is what I would like to do:
for(int i=0; i<some_value; i++) {
for(int j=0; j<some_other_value; j++) {
String buttonID = "btn" + i + "-" + j;
buttons[i][j] = ((Button) findViewById(R.id.buttonID));
buttons[i][j].setOnClickListener(this);
}
}
Thanks in advance!

You should use getIdentifier()
for(int i=0; i<some_value; i++) {
for(int j=0; j<some_other_value; j++) {
String buttonID = "btn" + i + "-" + j;
int resID = getResources().getIdentifier(buttonID, "id", getPackageName());
buttons[i][j] = ((Button) findViewById(resID));
buttons[i][j].setOnClickListener(this);
}
}

You can try making an int[] that holds all of your button IDs, and then iterate over that:
int[] buttonIDs = new int[] {R.id.button1ID, R.id.button2ID, R.id.button3ID, ... }
for(int i=0; i<buttonIDs.length; i++) {
Button b = (Button) findViewById(buttonIDs[i]);
b.setOnClickListener(this);
}

Take a look at these answers:
Android and getting a view with id cast as a string
Array of ImageButtons, assign R.view.id from a variable

you can Use tag if you want to access.
in onClick
int i=Integer.parseInt(v.getTag);
But you cant access that button like this.
simply create button programatically
by Button b=new Button(this);

create Custom Button in java code rather in Xml as i shown below
Button bs_text[]= new Button[some_value];
for(int z=0;z<some_value;z++)
{
try
{
bs_text[z] = (Button) new Button(this);
}
catch(ArrayIndexOutOfBoundsException e)
{
Log.d("ArrayIndexOutOfBoundsException",e.toString());
}
}

If your top level view only has those button views as children, you could do
for (int i = 0 ; i < yourView.getChildCount(); i++) {
Button b = (Button) yourView.getChildAt(i);
b.setOnClickListener(xxxx);
}
If there are more views present you'd need to check if the selected one is one of your buttons.

If for some reason you can't use the getIdentifier() function and/or you know the possible id's beforehand, you could use a switch.
int id = 0;
switch(name) {
case "x":
id = R.id.x;
break;
etc.etc.
}
String value = findViewById(id);

To put it simply, here's a function for it
public View findViewByArrayName (String name, int i) {
buttonID = name + Integer.toString(i);
resID = getResources().getIdentifier(buttonID, "id", getPackageName());
return findViewById(resID);
}
Also unlike Python, Java is a compiled language, so it probably makes sense that there aren't any chances for dynamic variable names. Unless achieved through a certain approach like this one.