Develop Reference

ArrayList Remove Object

I'm working on an app in android studio. The part of the app I'm having issues with is where the user can favourite and remove their favourite item. I do this by adding and removing the item from a list.
The thing is the add functionality works which is:
public void addFavorite(Context context, NewSubject subject) {
List<NewSubject> favorites = getFavorites(context);
if (favorites == null)
favorites = new ArrayList<NewSubject>();
favorites.add(subject);
saveFavorites(context, favorites);
}
I am passing in an object of type "NewSubject" which is just a class of getters and setters for name and id.
The problem arises when I try to remove an item from this list. Code below:
public void removeFavorite(Context context, NewSubject subject) {
ArrayList<NewSubject> favorites = getFavorites(context);
if (favorites != null) {
favorites.remove(subject);
saveFavorites(context, favorites);
}
}
I've even tried something like:
for(int i = 0; i < favorites.size(); i++){
if(favorites.get(i).getSubject_name() == subject.getSubject_name())
favorites.remove(i);
}
Even though both subject names match, the if statement never triggers as true. By changing it to ID it does remove the item but I was wondering why it doesn't work the other way. MeetTitan suggested to use "equals" operator to compare Strings and this has fixed that issue. But I'm still wondering as to why removing the item by "subject" without the FOR loop and IF statement doesn't work.
I have cleared the app's data multiple times whilst trying to debug the source of the problem.
Thank you for your time and help, it is much appreciated.

This applies if you are re-creating NewSubject twice... If you are trying to remove the exact same instance of NewSubject that you got from the collection, then I guessed wrong and this isn't the answer you are looking for.
Is it possible you haven't defined equals and hashCode in your Favorites object? Without those remove will only work with the EXACT same object instance in the collection. If you haven't, try defining them and see if remove() works the way you expect.
Without those methods defined, collections will respond this way:
Obj x=new Obj("data")
Obj y=new Obj("data")
collection.put(x)
collection.remove(y)
assert( collection.size() == 1) // was not removed because .equals didn't exist--remove reverted to == instead which failed, x != y
collection.remove(x)
assert( collection.size() == 0) // NOW it worked because you used the same instance.
if you define .equals and hashCode to compare the strings inside obj, then this will work:
collection.put(x)
collection.remove(y)
assert( collection.size() == 0) // worked because x.equals(y)!

Try
String.equalsIgnoreCase(value1,value2)
This might do your work.

From your example, it's evident that name is a String object. In java, you have to use ".equals()" or comparing two strings.
You can do this:
if(favorites.get(i).getSubject_name().equals(subject.getSubject_name())){
...
}
Or, you can override the equals() method in your NewSubject class to make this work:
favorites.remove(subject);
You can use something like this as your equals() method in the NewSubject class (considering you are only matching two NewSubject objects based on their names):
#Override
public boolean equals(Object other){
if (other == null) return false;
if (other == this) return true;
NewSubject otherSubject = (NewSubject) other;
if(this.getSubject_name().equals(otherSubject.getSubject_name()))
return true;
else
return false;
}
Update:
You may want to override hashcode() as well. If your NewSubject class ever gets used in a hash-based collection such as HashMap, overriding only equals() method will not be sufficient. For reference, this is from Effective Java by Joshua Bloch:
You must override hashCode() in every class that overrides equals().
Failure to do so will result in a violation of the general contract
for Object.hashCode(), which will prevent your class from functioning
properly in conjunction with all hash-based collections, including
HashMap, HashSet, and Hashtable.

Android: How to validate a set of fields without using TextWatcher and TextChangeListener

I have a number of EditText in an Activity. On clicking the submit button, I want to validate them, and prevent submission if there are errors in those EditText objects. I don't want to use TextWatcher because I don't want the methods to get fired at every single change. It does not make sense for an overall validation before submission. Is there a method that lets us loop through an array of the controls of the form? Thanks.

You have two options:
1) Create a Utils class with static methods for ensuring that the fields are valid.
i.e. toy example for checking email
public class Utils{
public static boolean isValidEmail(String str){
return str.contains("#");
}
}
and do so for checking the various fields (phone #, email, name, etc...). In your Activity that has the EditText(s), when you try to submit them, have something like:
public boolean validateFields(){
boolean result = true;
if(!Utils.isValidEmail(mEmailEdit.getText().toString()){
mEmailEdit.setError("Invalid email!");
result = false;
}
if(!Utils.isValidName(mEmailEdit.getText().toString()){
mNameEdit.setError("Invalid name!");
result = false;
}
return result;
}
This is a very simple idea of what you would do. Call validateFields() when clicking the submit button, and if the validateFields() method returns false, then do not proceed with the fields. If it returns true, well then all fields are valid and call another method to submit the data to w/e you are using it for.
2) (Best option for larger projects) Create an interface, call it Validator with a boolean-return function called validate(). This validator interface is extended for each various validation you wish to do, and you create a new interface like so:
public interface Validator{
public boolean validate(String s);
}
public interface EmailValidator extends Validator{
#Override
public boolean validate(String s){
return s.contains("#");
}
}
And extend a new EditText class view that has a Validator interface field, with a getter/setter. Then, in the validateFields() method, we do the same thing except call each EditText's validation interface's validate() method. There are a few more subtleties for this and I can type this all out if interested on how to do exactly. Let me know if that helps

The most straight forward way to do this is to get references to each of your sub views after you create the main view via setContentView(..). Use findViewById() to get references to each of them.
Then in your submit button click handler grab the inputs from each of them via something like nameField.getText() and do whatever validation you want. And if it fails show the error to the user in some fashion.

So, taking ideas from Lucas, creating custom components such as a DateEditText extending EditText and implementing a Validator interface, in my activity button for update onclick, I call this method that I wrote "isValidViewGroup(ViewGroup viewGroup), it will recursively go through all views, starting with the given viewGroup, and check children views, until it meets one implementing Validator and then call its isValid() method. It stops as soon as it finds an invalid one, or go through the end of views. Here's the method:
...
private boolean isValidViewGroup(ViewGroup viewGroup) {
int viewGroupChildCount = viewGroup.getChildCount();
View view = null;
for (int i = 0; i < viewGroupChildCount;i++) {
view = viewGroup.getChildAt(i);
if (view instanceof ViewGroup){
if (!isValidViewGroup((ViewGroup) view)){
return false;
}
} else {
if (view instanceof Validator){
if (!((Validator)view).isValid()){
return false;
}
}
}
}
return true;
}
...
I'm sure there could be a better, more efficient way, but for the moment that works really fine.

Unfortunately application has stopped in Android because of EditText

I have a little problem with checking length of EditText.
text = take.getText().toString();
if (text.matches("")) {
Toast.makeText(getApplicationContext(), "Enter first value", Toast.LENGTH_SHORT).show();
take is a EditText and text is a String.
When i run my app without Edittext value i got an Error:
Unfortunately "ApplicationName" has stopped.
In my Class i have
private EditText take;
private String text;
Please help me, i try to use method .equals("") or .length()==0 but stil the same.

you may have forgotten findViewById or you are calling it before setContentView of your activity!

Some time match and equal will not return proper. I prefer to use a function to check empty value.
public static String chechNullState(EditText checkTextBox) {
String makeModVal = null;
if (!TextUtils.isEmpty( checkTextBox.getText().toString() ))
{
makeModVal=checkTextBox.getText().toString();
return makeModVal;
}
else
{
return null;
}
}
Usage:
item =(EditText)findViewById(R.id.take);
String takeVal = chechNullState(item);
if ( !takeVal == null)
{
//do what ever you want;
}

Android: Edittext- get current line

In an edittext is there a method for getting the current line of the cursor? If not I will write my own method, but just wanted to check. If I do write my own method would the best method be to go through every character in the edittext until selectionstart and count the number of \n's using a For loop, or is there a better way? Thanks!

Just to let people know:
There is a better way to do this then Doug Paul has suggested by using the getLineForOffset(selection):
public int getCurrentCursorLine(EditText editText)
{
int selectionStart = Selection.getSelectionStart(editText.getText());
Layout layout = editText.getLayout();
if (!(selectionStart == -1)) {
return layout.getLineForOffset(selectionStart);
}
return -1;
}

I can't find a simple way to get this information either, so your approach seems about right. Don't forget to check for the case where getSelectionStart() returns 0. You can make the code reusable by putting it in a static utility method, like this:
private int getCurrentCursorLine(Editable editable) {
int selectionStartPos = Selection.getSelectionStart(editable);
if (selectionStartPos < 0) {
// There is no selection, so return -1 like getSelectionStart() does when there is no seleciton.
return -1;
}
String preSelectionStartText = editable.toString().substring(0, selectionStartPos);
return countOccurrences(preSelectionStartText, '\n');
}
The countOccurrences() method is from this question, but you should use one of the better answers to that question (e.g. StringUtils.countMatches() from commons lang) if feasible.
I have a full working example that demonstrates this method, so let me know if you need more help.
Hope this helps!

find the last index of "\n"using method lastindex=String.lastindexof("\n") then get a substring using method String.substring(lstindex,string.length).and you will get the last line
in two lines of code.

Android: How can I validate EditText input?

I need to do form input validation on a series of EditTexts. I'm using OnFocusChangeListeners to trigger the validation after the user types into each one, but this doesn't behave as desired for the last EditText.
If I click on the "Done" button while typing into the final EditText then the InputMethod is disconnected, but technically focus is never lost on the EditText (and so validation never occurs).
What's the best solution?
Should I be monitoring when the InputMethod unbinds from each EditText rather than when focus changes? If so, how?

Why don't you use TextWatcher ?
Since you have a number of EditText boxes to be validated, I think the following shall suit you :
Your activity implements android.text.TextWatcher interface
You add TextChanged listeners to you EditText boxes
txt1.addTextChangedListener(this);
txt2.addTextChangedListener(this);
txt3.addTextChangedListener(this);
Of the overridden methods, you could use the afterTextChanged(Editable s) method as follows
#Override
public void afterTextChanged(Editable s) {
// validation code goes here
}
The Editable s doesn't really help to find which EditText box's text is being changed. But you could directly check the contents of the EditText boxes like
String txt1String = txt1.getText().toString();
// Validate txt1String
in the same method. I hope I'm clear and if I am, it helps! :)
EDIT: For a cleaner approach refer to Christopher Perry's answer below.

TextWatcher is a bit verbose for my taste, so I made something a bit easier to swallow:
public abstract class TextValidator implements TextWatcher {
private final TextView textView;
public TextValidator(TextView textView) {
this.textView = textView;
}
public abstract void validate(TextView textView, String text);
#Override
final public void afterTextChanged(Editable s) {
String text = textView.getText().toString();
validate(textView, text);
}
#Override
final public void beforeTextChanged(CharSequence s, int start, int count, int after) { /* Don't care */ }
#Override
final public void onTextChanged(CharSequence s, int start, int before, int count) { /* Don't care */ }
}
Just use it like this:
editText.addTextChangedListener(new TextValidator(editText) {
#Override public void validate(TextView textView, String text) {
/* Validation code here */
}
});

If you want nice validation popups and images when an error occurs you can use the setError method of the EditText class as I describe here

In order to reduce the verbosity of the validation logic I have authored a library for Android. It takes care of most of the day to day validations using Annotations and built-in rules. There are constraints such as #TextRule, #NumberRule, #Required, #Regex, #Email, #IpAddress, #Password, etc.,
You can add these annotations to your UI widget references and perform validations. It also allows you to perform validations asynchronously which is ideal for situations such as checking for unique username from a remote server.
There is a example on the project home page on how to use annotations. You can also read the associated blog post where I have written sample codes on how to write custom rules for validations.
Here is a simple example that depicts the usage of the library.
#Required(order = 1)
#Email(order = 2)
private EditText emailEditText;
#Password(order = 3)
#TextRule(order = 4, minLength = 6, message = "Enter at least 6 characters.")
private EditText passwordEditText;
#ConfirmPassword(order = 5)
private EditText confirmPasswordEditText;
#Checked(order = 6, message = "You must agree to the terms.")
private CheckBox iAgreeCheckBox;
The library is extendable, you can write your own rules by extending the Rule class.

Updated approach - TextInputLayout:
Google has recently launched design support library and there is one component called TextInputLayout and it supports showing an error via setErrorEnabled(boolean) and setError(CharSequence).
How to use it?
Step 1: Wrap your EditText with TextInputLayout:
<android.support.design.widget.TextInputLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/layoutUserName">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="hint"
android:id="#+id/editText1" />
</android.support.design.widget.TextInputLayout>
Step 2: Validate input
// validating input on a button click
public void btnValidateInputClick(View view) {
final TextInputLayout layoutUserName = (TextInputLayout) findViewById(R.id.layoutUserName);
String strUsername = layoutLastName.getEditText().getText().toString();
if(!TextUtils.isEmpty(strLastName)) {
Snackbar.make(view, strUsername, Snackbar.LENGTH_SHORT).show();
layoutUserName.setErrorEnabled(false);
} else {
layoutUserName.setError("Input required");
layoutUserName.setErrorEnabled(true);
}
}
I have created an example over my Github repository, checkout the example if you wish to!

This was nice solution from here
InputFilter filter= new InputFilter() {
public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
for (int i = start; i < end; i++) {
String checkMe = String.valueOf(source.charAt(i));
Pattern pattern = Pattern.compile("[ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz123456789_]*");
Matcher matcher = pattern.matcher(checkMe);
boolean valid = matcher.matches();
if(!valid){
Log.d("", "invalid");
return "";
}
}
return null;
}
};
edit.setFilters(new InputFilter[]{filter});

I wrote a class that extends EditText which supports natively some validation methods and is actually very flexible.
Current, as I write, natively supported through xml attributes validation methods are:
alpha
alpha numeric
numeric
generic regexp
string emptyness
You can check it out here
Hope you enjoy it :)

I find InputFilter to be more appropriate to validate text inputs on android.
Here's a simple example:
How do I use InputFilter to limit characters in an EditText in Android?
You could add a Toast to feedback the user about your restrictions.
Also check the android:inputType tag out.

I needed to do intra-field validation and not inter-field validation to test that my values were unsigned floating point values in one case and signed floating point values in another. Here's what seems to work for me:
<EditText
android:id="#+id/x"
android:background="#android:drawable/editbox_background"
android:gravity="right"
android:inputType="numberSigned|numberDecimal"
/>
Note, you must not have any spaces inside "numberSigned|numberDecimal". For example: "numberSigned | numberDecimal" won't work. I'm not sure why.

This looks really promising and just what the doc ordered for me:
EditText Validator
public void onClickNext(View v) {
FormEditText[] allFields = { etFirstname, etLastname, etAddress, etZipcode, etCity };
boolean allValid = true;
for (FormEditText field: allFields) {
allValid = field.testValidity() && allValid;
}
if (allValid) {
// YAY
} else {
// EditText are going to appear with an exclamation mark and an explicative message.
}
}
custom validators plus these built in:
regexp: for custom regexp
numeric: for an only numeric field
alpha: for an alpha only field
alphaNumeric: guess what?
personName: checks if the entered text is a person first or last name.
personFullName: checks if the entered value is a complete full name.
email: checks that the field is a valid email
creditCard: checks that the field contains a valid credit card using Luhn Algorithm
phone: checks that the field contains a valid phone number
domainName: checks that field contains a valid domain name ( always passes the test in API Level < 8 )
ipAddress: checks that the field contains a valid ip address
webUrl: checks that the field contains a valid url ( always passes the test in API Level < 8 )
date: checks that the field is a valid date/datetime format ( if customFormat is set, checks with customFormat )
nocheck: It does not check anything except the emptyness of the field.

In main.xml file
You can put the following attrubute to validate only alphabatics character can accept in edittext.
Do this :
android:entries="abcdefghijklmnopqrstuvwxyz"

You can get desired behavior by listening when user hit "Done" button on keyboard, also checkout other tips about working with EditText in my post "Android form validation - the right way"
Sample code:
mTextView.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView view, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_DONE) {
validateAndSubmit();
return true;
}
return false;
}});

for email and password validation try
if (isValidEmail(et_regemail.getText().toString())&&etpass1.getText().toString().length()>7){
if (validatePassword(etpass1.getText().toString())) {
Toast.makeText(getApplicationContext(),"Go Ahead".....
}
else{
Toast.makeText(getApplicationContext(),"InvalidPassword".....
}
}else{
Toast.makeText(getApplicationContext(),"Invalid Email".....
}
public boolean validatePassword(final String password){
Pattern pattern;
Matcher matcher;
final String PASSWORD_PATTERN = "^(?=.*[0-9])(?=.*[A-Z])(?=.*
[##$%^&+=!])(?=\\S+$).{4,}$";
pattern = Pattern.compile(PASSWORD_PATTERN);
matcher = pattern.matcher(password);
return matcher.matches();
}
public final static boolean isValidEmail(CharSequence target) {
if (target == null)
return false;
return android.util.Patterns.EMAIL_ADDRESS.matcher(target).matches();
}

I have created this library for android where you can validate a material design EditText inside and EditTextLayout easily like this:
compile 'com.github.TeleClinic:SmartEditText:0.1.0'
then you can use it like this:
<com.teleclinic.kabdo.smartmaterialedittext.CustomViews.SmartEditText
android:id="#+id/passwordSmartEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:setLabel="Password"
app:setMandatoryErrorMsg="Mandatory field"
app:setPasswordField="true"
app:setRegexErrorMsg="Weak password"
app:setRegexType="MEDIUM_PASSWORD_VALIDATION" />
<com.teleclinic.kabdo.smartmaterialedittext.CustomViews.SmartEditText
android:id="#+id/ageSmartEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:setLabel="Age"
app:setMandatoryErrorMsg="Mandatory field"
app:setRegexErrorMsg="Is that really your age :D?"
app:setRegexString=".*\\d.*" />
Then you can check if it is valid like this:
ageSmartEditText.check()
For more examples and customization check the repository
https://github.com/TeleClinic/SmartEditText