How to validated fields in an Xamarin/Android app

问题

Does any one know how to make a field required in Xamarin/Android app?

I have this field and button in my Android Layout, and I'd like to make sure the info is entered before they go to the next activity.

<TextView
    android:text="Zip Code:"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/zipCodeLabel"
    android:textColor="#000000"
    android:textSize="20sp" />
<Button
    android:id="@+id/btnSearch"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/btnSearch"
    android:textSize="30sp" />

If found this for iOS, but can't find something similar for Android: https://developer.xamarin.com/recipes/ios/standard_controls/text_field/validate_input/

回答1:

There are a number of ways to validate input depending upon what your user experience requirements are.

`android:digits` to restrict input:

<EditText
    android:id="@+id/zipCodeEntry"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:digits="1234567890-"
/>

Validate after entry done and show error message:

button.Click += delegate { 
if (!ValidateZipCode(zipCodeEntry.Text))
{
    zipCodeEntry.Error = "Enter Valid USA Zip Code";
    return;
}
DoSubmit();

protected bool ValidateZipCode(string zipCode)
{
    string pattern = @"^\d{5}(\-\d{4})?$";
    var regex = new Regex(pattern);
    Log.Debug("V", regex.IsMatch(zipCode).ToString());
    return regex.IsMatch(zipCode);
}

Implement `View.IOnKeyListener` on your `Activity` and check/validate every key entry

zipCodeEntry.SetFilters(new IInputFilter[] { this });


public bool OnKey(View view, [GeneratedEnum] Keycode keyCode, KeyEvent e)
{
    if (view.Id == Resource.Id.zipCodeEntry)
    {
        Log.Debug("V", keyCode.ToString()); // Validate key by key
    }
    return false;
}

Use an `InputFilter` (Implement `IInputFilter` on your activity):

public ICharSequence FilterFormatted(ICharSequence source, int start, int end, ISpanned dest, int dstart, int dend)
{
    StringBuilder sb = new StringBuilder();
    for (int i = start; i < end; i++)
    {
        if ((Character.IsDigit(source.CharAt(i)) || source.CharAt(i) == '-'))
            sb.Append(source.CharAt(i));
    }
    return (sb.Length() == (end - start)) ? null : new Java.Lang.String(sb.ToString());
}

来源：https://stackoverflow.com/questions/38484055/how-to-validated-fields-in-an-xamarin-android-app

标签

android