Edit text validation library using MVVM

by androidexample

ValidationEditText

This is a simple library that facilitates text validation and error handling in a user-friendly way on EditText with (TextInputLayout support). For MVVM + data binding stack

Integration

To add ValidationEditText to your project, first make sure that in root build.gradle you have specified the following repository:

    repositories {
        jcenter()
    }

Note: by creating a new project in Android Studio there will be jcenter repository specified by default, so you do not need add it manually.
Once you make sure that you have jcenter repository in your project, all you need to do is to add the following line in dependencies section of your project build.gradle.
See the latest library version 

implementation 'com.github.vitaliyptitsyn:validationedittext:X.X.X'

Usage description

Usage of ValidationEditText is quite simple. Just like regular data binding events. Need to bind LiveData that connect model with UI and provide validation rules.

binding

You can connect with ui in 2 ways: by VET_validation_result or VET_validation_text.
In VET_validation_text you will have text from the view, and only user error will be shown.
In VET_validation_result yo have to bind ValidateResult in you live data. And
app:VET_validation_result="@={vm.liveName} at layout.

data class ValidateResult(
    val originalText: String, //Text delivered to View   app:VET_validation_result="@={vm.liveName}"
    val errorText: String? = null, //Text shown on  the view. 
    val isValid: Boolean = false
)

rules

There are 2 ways to provide rules:
To provide the list VET_validationRules that accepts List<ValidationRule> (List of validator may dynamic)
Or Use list attributes for common validator. You can combine them differently. (Validators from the xml)

        <data>
            <import type="com.pvitaliy.validationtext.rules.ContentValidation" />
        </data>

        <com.google.android.material.textfield.TextInputEditText
                        <!--    ...     -->
                  app:VET_show_error_mode="@{vm.liveShowOnEdit}"
                  app:VET_validation_content="@{ContentValidation.NOT_EMPTY}"
                  app:VET_validation_result="@={vm.liveName}"
                  tools:text="18,6" />

Validator text:

Name Behavior
VET_validation_content Take ContentValidation field Email or NotEmpty.
VET_validation_length_min VET_validation_length_max (may accept only one) Validate min and max Length
VET_validation_rule Take 1 custom rule
VET_validate_equal (optional)VET_validate_equal_on_both Take another View, to compare text equality. If VET_validate_equal_on_both=@{true} error will be delivered to both views.

Error showing

You can customize error showing on user view by choosing one ErrorMode. Also you can dynamically change error mode.
For example. When user clicks on Sing up need to validate input (email, and password) and show exception to user.
To do it set VET_show_error_mode to ErrorMode.Once, validation will be immediately triggered and after change validation mode to nextMode from the validator (see the sample project)

Name Behavior
ErrorMode.None Error is not shown on EditText.
ErrorMode.OnUserInput Shown only when view has focus and on user's typing.
ErrorMode.Always always validates result (Event if you send value in runtime).
ErrorMode.Once The most interesting format. It validates text once, than sets mode accordingly to nextMode field.

Customize error and message

To make you own validation Rule, implement ValidationRule and throw ValidationException in validate func when the validation failed.
Then ValidationConverter handles the error and shows it on the EditText.
ValidationException has 3 child classes.
In custom validation rules, the handiest way is to throw ResException or StringException

open class ErrorCodeException(
    open val errorCode: Int,
    open vararg val args: Any?
) : ValidationException()

open class StringException(val reason: String) : ValidationException()

open class ResException(
    @StringRes val resString: Int,
    vararg val args: Any?
) : ValidationException()

To override error message, provide custom ValidationConvector by VET_validation_converter

GitHub