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Radio button are not working normally in my Recycler View. Multiple Radio Buttons got selected of the view which are not visible with the focused one

I'm using a Recycler View to show all the images from the galley or the external storage of a device in a Grid Layout Manager. And I'm using a Radio Button to show if the image is selected or not.
PROBLEM
Whenever I select or deselect a Radio Button from the visible Views in the Recycler View some other Views which are outside the Visible Screen got selected or deselected.
It is like I'm pressing on the same View of the Recycler View, but the images are different.
PROBLEM

well that's because of the recycler view concept of reusing the views instead of creating new views every time you scroll.
you see if you have 100 items you want to show in a recycler view and only 20 of them could appear to the user, recycler view creates only 20 view holder to represent the 20 items, whenever the user scroll recycler view will still have 20 view holder only but will just switch the data stored in this view holders rather than create new view holders.
now to handle selection of your items there's two ways to do this.
the naive way
hold selection in a boolean array inside the recycle view adapter.
whenever the user scrolls, the adapter calls onBindViewHolder to update the visible viewholder with the proper data.
so when onBindViewHolder gets called just set the radio button selection according the boolean array using the position sent in the method call
at the end of your usage to the recycler view you can create a getter method in the adapter to get the selection array list of boolean and pass the data based on it
public class PhotosGalleryAdapter extends RecyclerView.Adapter<PhotosGalleryViewHolder> {
ArrayList<Your_Data_ClassType> data;
ArrayList<Boolean> dataSelected ;
public PhotosGalleryAdapter(ArrayList<Your_Data_ClassType> data) {
this.data = data;
dataSelected = new ArrayList<>(data.size()) ;
}
...
#Override
public void onBindViewHolder(#NonNull PhotosGalleryViewHolder holder, int position) {
...
RadioButton radioButton = holder.getRadioButton()
radioButton.setChecked(dataSelected.get(position));
radioButton.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
dataSelected.set(holder.getAbsoluteAdapterPosition() , isChecked) ;
}
});
...
}
}
the other way is to use a selection tracker and it should be the correct way to handle selections in a recycler view.
the problem with this way is it needs a lot of editing to the code and creating new classes to include as parameters in the selection tracker, but in the end you'll find it worth the time you spent on it.
in order to start with this way you need to do the following :
firstly, decide what should be a key (String-Long-Parcelable) so the tracker should use to differentiate between your data , the safest way is either String or Parcelable as I once tried Long and ended up with lots and lots of problems (in your case I will assume it's the photo's uri which will be of type string)
secondly, you need to create two new classes, one that extends ItemDetailsLookup, and the other extends ItemKeyProvider, and should use the key as their generic type (the type that is put between <> )
your two classes should look like this (that you might copy them straight forward)
the one that extends ItemKeyProvider :
public class GalleryItemKeyProvider extends ItemKeyProvider<String>{
PhotosGalleryAdapter adapter ;
/**
* Creates a new provider with the given scope.
*
* #param scope Scope can't be changed at runtime.
*/
public GalleryItemKeyProvider(int scope,PhotosGalleryAdapter m_adapter) {
super(scope);
this.adapter = m_adapter;
}
#Nullable
#Override
public String getKey(int position) {
return adapter.getKey(position);
}
#Override
public int getPosition(#NonNull String key) {
return adapter.getPosition(key);
}
}
the one that extends ItemDetailsLookup :
public class GalleryDetailsLookup extends ItemDetailsLookup<String> {
private final RecyclerView recView ;
public GalleryDetailsLookup(RecyclerView m_recView){
this.recView = m_recView;
}
#Nullable
#Override
public ItemDetails<String> getItemDetails(#NonNull MotionEvent e) {
View view = recView.findChildViewUnder(e.getX(), e.getY());
if (view != null) {
RecyclerView.ViewHolder holder = recView.getChildViewHolder(view);
if (holder instanceof PhotosGalleryViewHolder) {
return ((PhotosGalleryViewHolder) holder).getItemDetails();
}
}
return null;
}
}
thirdly, you should include this new two methods in your adapter to be used by the above classes
public class PhotosGalleryAdapter extends RecyclerView.Adapter<PhotosGalleryViewHolder> {
...
public String getKey(int position) {
return data.get(position).getUri();
}
public int getPosition(String key) {
for (int i = 0; i < data.size(); i++) {
if (data.get(i).getUri() == key) return i;
}
return 0;
}
...
}
forthly (if there's an english word called forthly), you should initialize the tracker with all the above classes that were created before and he will handle the rest, the tracker takes as parameters
a unique selection tracker id (if that will be the only selection tracker you will use then name it anything)
the ItemKeyProvider that we created
the DetailsLookup that we created
a String-Long-Parcelable Storage to store the keys that were selected in (in our case it will be a String Storage)
a Selection predicate, it's responsible to handle the way of selection you want to do, you want it to be able to (select only one item-multiple selection with no limits- based on a weird algorithm like even only or odd only), in my case I will use a default multiple selection one but if you want to alter it with another selection algorithm you should create a new class that extends SelectionPredicates and implement your way of selection, you could also just check the other default ones might be what you're looking for.
anyway, that's how the initialization should look (you should put this code wherever you initialize your recycler view at whether it's in fragment or activity method):
private void initRecycleView() {
...
SelectionTracker<String> tracker = new SelectionTracker.Builder<>("PhotosGallerySelection",
Your_Recycler_View,
new GalleryItemKeyProvider(ItemKeyProvider.SCOPE_MAPPED, photosAdapter),
new GalleryDetailsLookup(Your_Recycler_View),
StorageStrategy.createStringStorage())
.withSelectionPredicate(SelectionPredicates.createSelectAnything())
.build();
...
}
I didn't find a way to let me initialize the adapter with data and then create the tracker inorder to make the viewholders know about their selection or not, so in this case I firstly created the tracker and then made the adapter know about it's data using a setter and notifyDataSetChanged
what I mean by that is after creating the tracker instantly set the tracker and data to the adapter, so the initRecycleView should look like this
private void initRecycleView() {
...
SelectionTracker<String> tracker = new SelectionTracker.Builder<>("PhotosGallerySelection",
Your_Recycler_View,
new GalleryItemKeyProvider(ItemKeyProvider.SCOPE_MAPPED, photosAdapter),
new GalleryDetailsLookup(Your_Recycler_View),
StorageStrategy.createStringStorage())
.withSelectionPredicate(SelectionPredicates.createSelectAnything())
.build();
photosAdapter.setTracker(tracker);
photosAdapter.setData(data);
photosAdapter.notifyDataSetChanged();
...
}
Last but no least, you should handle how the view holders should know if they were selected or not, so you should let the adapter know about the tracker and its data by creating a setter method in it, that's how the adapter should look like in the end :
public class PhotosGalleryAdapter extends RecyclerView.Adapter<PhotosGalleryViewHolder> {
ArrayList<Your_Data_Class> data;
private SelectionTracker<String> tracker;
public PhotosGalleryAdapter() {
data = new ArrayList<>();
}
public ArrayList<Your_Data_Class> getData() {
return data;
}
public void setData(ArrayList<Your_Data_Class> m_data) {
this.data = m_data;
}
#Override
public ScheduleViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
...
}
#Override
public void onBindViewHolder(#NonNull PhotosGalleryViewHolder holder, int position) {
...
boolean isSelected = tracker.isSelected(data.get(i).getUri());
RadioButton radioButton = holder.getRadioButton;
radioButton.setChecked(isSelected);
}
#Override
public int getItemCount() {
return data.size();
}
public String getKey(int position) {
return data.get(position).getUri();
}
public int getPosition(String key) {
for (int i = 0; i < data.size(); i++) {
if (data.get(i).getUri() == key) return i;
}
return 0;
}
public void setTracker(SelectionTracker<String> m_tracker) {
this.tracker = m_tracker;
}
}
(as you may notice if you initialized the adapter with its data through the constructor, when he asks the tracker if there were an item selected or not, it will result in a NullPointerException as at the moment of initializing the adapter you still didn't initialize the tracker)
that way you could keep track of your selection the way google suggests in their documentation (which I honestly don't know why the made it very complicate like that).
if you want to know all the selected item in the end of your application/fragment use, you should call tracker.getSelection() which will return a Selection List for you to iterate on
There's a tiny problem/feature with the tracker that it won't start selecting the first item until you use a long press on it, that happens only in the first item you select, if you do want this feature (start selecting mode by long press) then leave it as it is
incase you don't want it you can make the tracker select a ghost key (any unique string key that means nothing to your data) at the beginning which should later enable the selection mode with a simple click on any photo
tracker.select("");
this also the way to make a default/old selection at the beginning, you could make a for loop and call tracker.select(Key) if you do want the tracker to start with few items being selected
N.B : incase you use the Ghost Key method you should watchout that the selection array that will get returned when you call tracker.getSelection() will also contain this Ghost Key.
at the end if you do have the curiosity of reading about selection tracker in the documentation follow this link
or maybe if you know how to read kotlin follow this two links
implementing-selection-in-recyclerview
a guide to recyclerview selection
I was stuck in the selection problem for days before I figure how to do all that so I hope you find your way through it.

Omar Shawky has covered the solutions.
With my answer I will stress on the reason why someone may face this sort of an issues with recycler views and how to avoid this common issue in the future (avoiding pitfalls).
Reason:
This issue happens because RecyclerView recycles views. So a RecyclerView item's view once inflated can get reused to show another off screen (to be scrolled to) item. This helps reduces re-inflation of views which otherwise can be taxing.
So if the radio button of an item's view is selected, and the same view gets reused to show some other item, then that new item can also have a selected radio button.
Solution:
The simplest solution for such issues is to have an if else logic in your ViewHolder to provide logic for both selected and de-selected cases. We also do not rely on information from radio button itself for initial setup (we do not use radioButton.isSelected() at the time of setup)
e.g code to write inside your ViewHolder class:
private boolean isRadioButtonChecked = false; // ViewHolder class level variable. Default value is unchecked
// Now while binding in your ViewHolder class:
// Setup Radio button (assuming there is just one radio button for a recyclerView item).
// Handle both selected and de-selected cases like below (code can be simplified but elaborating for understanding):
if (isRadioButtonChecked) {
radioButton.setChecked(true);
} else {
radioButton.setChecked(false);
}
radioButton.setOnCheckedChangeListener(
(radioButton, isChecked) -> isRadioButtonChecked = isChecked);
Do not do any of the following while setting up:
private boolean isRadioButtonChecked = false; // class variable
//while binding do not only handle select case. We should handle both cases.
if (isRadioButtonChecked) { // --> Pitfall
radioButton.setChecked(true);
}
radioButton.setOnCheckedChangeListener((radioButton, isChecked) -> isRadioButtonChecked = isChecked);
OR
// During initial setup do not use radio button itself to get information.
if (radioButton.isChecked()) { // --> Pitfall
radioButton.setChecked();
}

What data type is

i've created a function and set it to onClick, so every time i hit the button this function is called. It is called, but the value of 4 other functions i can't get them in setMessage() function(when we create a dialog box). So the logic is like, after hitting the button first we check which radioId1 is equal to which id, and call the appropriate fucntion(video,cons,news,pict).These 4 funct. return some string. Then i want to add these strings to some text in my dialog box, like ....SetMessage(checkMyId() + "Some text").SetPositiveButton(...)...
but the problem is my function checkMyId is set to onClick, so it recieves an argument View v, and when i call it "mannualy" in SetMessage() it shows error, because i don't know what to put inside that parenthesis. So the question is, what type of data(or whatever) is that View ? i saw some documentation and didn't understood much or at least how to implement that in my problem.
public void checkMyId(View v) {
int radioId1 = radioGroup.getCheckedRadioButtonId();
if (radioId1 == R.id.radio_one) {
video();
} else if (radioId1 == R.id.radio_two) {
pict();
} else if (radioId1 == R.id.radio_three) {
cons();
} else news();
}
EDITED
Picture of the error

sir you have 2 way
first try this ( HINT : Don't forget to implement ONCLICK in activity )
public void checkMyId(View v) {
switch (v.getId()) {
case R.id.radio_one:
video();
break;
case R.id.radio_two:
pict();
break;
case R.id.radio_three:
cons();
break;
default:
news();
break;
}
}
sec you can use it in OnCreate ( HINT : this on radio group ) HERE
(findViewById(R.id.radio_one)).setOnCheckedChangeListener(new
OnCheckedChangeListener()
{
#Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
// checkedId is the RadioButton selected
}
});
____ READ This also for single RB

How to change EditText field for various spinner values

I want to change EditText field for each spinner selection, my EditText field should be able to take input in Feet+inch or in Cms based on the input selected by user for unit’s field, i.e. if User selects Metric System then EditText should change into cm format, for FPS system the EditText should change to Feet+inch format, something like following image
I guess I have to use onClickListener on spinner and then have to change EditText, but I don't know how to do that.

you should use this interface with your spinner. the 'position' corresponds to the spinner array item position, it your spinner array is ["inch","cm"] then case 0 correspond "inch" and 1 is "cm".
I hope it will help.
//set spinner listener
mSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
switch (position) {
case 0:
//TODO change EditText
break;
case 1:
//TODO change EditText
break;
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
});

Thank you for your time I got what I wanted , I just used a workaround,
I deploeyd three feilds Ft,In and cms; Ft for feet , In for inches and cms for centimeters, In spinner ft+in , and cms are two options, I set the visibility of non selected option as VISIBLE.GONE.

Android - default value in editText

In my app I have an edit user details page and I want to display the current name, email address etc in the corresponding editText fields and then the user can just erase that and enter a new one if they want.
Is there a way to do this? Thanks for any help

There is the hint feature? You can use the setHint() to set it, or set it in XML (though you probably don't want that, because the XML doesn't 'know' the name/adress of your user :) )

You can use EditText.setText(...) to set the current text of an EditText field.
Example:
yourEditText.setText(currentUserName);

From the xml:
android:text="yourtext"

You can use text property in your xml file for particular Edittext fields.
For example :
<EditText
android:id="#+id/ET_User"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="yourusername"/>
like this all Edittext fields contains text whatever u want,if user wants to change particular Edittext field he remove older text and enter his new text.
In Another way just you get the particular Edittext field id in activity class and set text to that one.
Another way = programmatically
Example:
EditText username=(EditText)findViewById(R.id.ET_User);
username.setText("jack");

You can do it in this way
private EditText nameEdit;
private EditText emailEdit;
private String nameDefaultValue = "Your Name";
private String emailDefaultValue = "abc#xyz.com";
and inside onCreate method
nameEdit = (EditText) findViewById(R.id.name);
nameEdit.setText(nameDefaultValue);
nameEdit.setOnTouchListener( new OnTouchListener() {
#Override
public boolean onTouch(View v, MotionEvent event) {
if (nameEdit.getText().toString().equals(nameDefaultValue)){
nameEdit.setText("");
}
return false;
}
});
nameEdit.setOnFocusChangeListener(new OnFocusChangeListener() {
#Override
public void onFocusChange(View v, boolean hasFocus) {
if(!hasFocus && TextUtils.isEmpty(nameEdit.getText().toString())){
nameEdit.setText(nameDefaultValue);
} else if (hasFocus && nameEdit.getText().toString().equals(nameDefaultValue)){
nameEdit.setText("");
}
}
});
emailEdit = (EditText)findViewById(R.id.email);
emailEdit.setText(emailDefaultValue);
emailEdit.setOnFocusChangeListener(new OnFocusChangeListener() {
#Override
public void onFocusChange(View v, boolean hasFocus) {
if(!hasFocus && TextUtils.isEmpty(emailEdit.getText().toString())){
emailEdit.setText(emailDefaultValue);
} else if (hasFocus && emailEdit.getText().toString().equals(emailDefaultValue)){
emailEdit.setText("");
}
}
});

First you need to load the user details somehow
Then you need to find your EditText if you don't have it-
EditText et = (EditText)findViewById(R.id.youredittext);
after you've found your EditText, call
et.setText(theUserName);

public class Main extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EditText et = (EditText) findViewById(R.id.et);
EditText et_city = (EditText) findViewById(R.id.et_city);
// Set the default text of second EditText widget
et_city.setText("USA");
}
}

Use android android:hint for set default value or android:text

We wish there is a default value attribute in each view of android views or group view in future versions of SDK. but to overcome that, simply before submission, check if the view is empty equal true, then assign a default value
example:
/* add 0 as default numeric value to a price field when skipped by a user,
in order to avoid parsing error of empty or improper format value. */
if (Objects.requireNonNull(edPrice.getText()).toString().trim().isEmpty())
edPrice.setText("0");

Why cant i get these calculations to display on a textview?

Im trying to make an app that converts distance/area/volume using spinners as a unit selection method. Calculations are meant be done and then the output sent to a textview based on what is entered into the EditText. But the output is only ever 0.0 and nothing else. Can anybody help with this ?
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
switch(pos){
case 0:
option1.setAdapter(length);
option2.setAdapter(length);
return;
case 1:
option1.setAdapter(area);
option2.setAdapter(area);
return;
default:
}
}
public void onNothingSelected(AdapterView<?> parent) {
// Do nothing.
}
});
option1.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
if(pos>=0) {
stringInput = edittext1.getText().toString();
if(stringInput == null || stringInput.isEmpty()) {
doubleInput = 0.0;
}
else {
doubleInput = Double.parseDouble(edittext1.getText().toString());
}
}
}
public void onNothingSelected(AdapterView<?> parent) {
// Do nothing.
}
});
option2.setOnItemSelectedListener(new OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
switch(pos) {
case 0:
miles = doubleInput * 1;
textview1.setText("" + String.valueOf(miles));
return;
case 1:
km = doubleInput * 1.609344;
textview1.setText("" + String.valueOf(km));
return;
default:
}
}
public void onNothingSelected(AdapterView<?> parent) {
// Do nothing.
}
});

At the risk of sounding like a really old man, this looks like your college homework... Is it?
Your code has changed since asking the question, which makes it pretty difficult to answer! Luckily I managed to scrape your code into Eclipse before you changed it... Anyway, in your original code your performing all your operations in the create method, at which point you haven't entered a value for edittext1 (unless it's set to some sensible default, which I presume would be 0, hence always getting zero as your answer?)
// Whilst setting up a view the create method will not have a
// reasonable value for edittext1 - or it will be your default
String stringInput = (edittext1.getText().toString());
if (stringInput.isEmpty()) {
doubleInput = 0.0; // Will always enter this line
} else {
doubleInput = Double.parseDouble(edittext1.getText().toString());
}
You've duplicated the code...
output1 = (TextView) findViewById(R.id.output1);
Actually output1 through to output10 (ie all ten lines) are duplicated.
As to your updated code, is it still giving you a problem? Are you sure that stringInput has a value? I mean have you typed something in? You could check by debugging your program..
The following is also error prone as FloatingCoder suggests, and is likely to break...
doubleInput = Double.parseDouble(edittext1.getText().toString());
A better way to do this (because it catches the exception that Java might throw) is
doubleInput = 0.0;
String inputStr = question.getText().toString();
try {
doubleInput = Double.parseDouble(inputStr);
} catch (NumberFormatException e) {
// This should probably do something more useful? i.e. tell
// the user what they've done wrong...
Log.e("Android",
"Double throws a NumberFormatException if you enter text that is not a number");
}
Oh and Android has some helper utilities for checking strings, see TextUtils, or just my example...
if (!TextUtils.isEmpty(inputStr)) { // checks for "" and null (see documentation)
doubleInput = Double.parseDouble(inputStr);
}
I'd REALLY recommend writing a simple test case for a calculation that looks incorrect, because two text boxes and a button really aren't hard to throw together and are seriously easy to debug without the need for all the spinners getting in the way... Anyway hope this helped, oh and my complete example with two edittexts and a button, I'll just post that here... Hope it helps...
private Button btnCalc;
private EditText question, answer;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
answer = (EditText) findViewById(R.id.answer);
question = (EditText) findViewById(R.id.question);
btnCalc = (Button) findViewById(R.id.btnCalc);
// The OnClickListener here will be executed outside the "Create",
// i.e., when you actually click on the button, which will give you
// a chance to enter some values in the question edittext...
btnCalc.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
double in = 0.0;
try {
String inputStr = question.getText().toString();
// if you want to check it use
if (!TextUtils.isEmpty(inputStr)) {
in = Double.parseDouble(inputStr);
}
} catch (NumberFormatException e) {
// This should probably do something more useful? i.e. tell
// the user what they've done wrong...
Log.e("Android",
"Double throws a NumberFormatException if you enter text that is not a number");
}
double miles = in * 1.6;
answer.setText(String.valueOf(miles));
}
});
}

It's a little hard to tell from the code you posted, but my guess is that you are setting doubleInput when option 1 is selected. If you are entering the number after you select option 1, it will always be 0.0, as the number was not in the text area when the spinner was changed.
Use a debugger to step through the code and see if you are ever reaching the line
doubleInput = Double.parseDouble(edittext1.getText().toString());
and to check that the number is getting set properly at that point.