[TextInputLayout] Support prefix/suffix text

Is your feature request related to a problem? Please describe. Per the “Prefix and suffix text” section at https://material.io/design/components/text-fields.html material text fields should be able to display non-editable text before/after the user’s input.

Describe the solution you’d like I have no strong opinions on the API, but I would consider the minimum-viable functionality to be setting a start-justified prefix text or end-justified suffix text. It would be nice to have the ability to set the start/end gravity of the user’s input text (ex: the “55/100” example in the screenshot above), but I wouldn’t consider it essential. I assume that the hint/label animation would be omitted when prefix/suffix text is provided, otherwise the visibility will need to be coordinated.

Describe alternatives you’ve considered

• Using a TextWatcher and calculating start/end indices manually, as well as setting spans for text color. Ridiculously tedious and error-prone.

• Setting a TextDrawable on the left of the TextInputEditText. Causes the label to be misaligned when the field is focused, and also overrides the drawable tint color:

• Setting a TextDrawable as the startIconDrawable on the TextInputLayout. Does not line up with the user’s cursor, padding must be set, and also overrides the drawable tint color:

• Subclassing TextInputLayout and using a custom CollapsingTextHelper. Tedious and fragile (uses reflection); see https://stackoverflow.com/a/39568320

• Using a custom view and ignore TextInputLayout entirely. Doable but would like to avoid trying to duplicate the exact styles and positions of views, since we use TextInputLayout in many places and want a uniform experience.

[leticiarossi]

We’ve decided to start working on support for suffix/prefix on text fields

[devgen90]

seeing the alignment issues when using the prefixtext. Has this been addressed already?