Android Autofill

Android Autofill is a component that provides functionality to use alternative Autofill providers, such as the Android Autofill framework.

It is used exclusively by the //android_webview embedder (and some deprecated uses inside of Weblayer).

High-level architecture

The below diagram shows the main classes involved in //android_autofill.

                                   ┌───────────────────────┐             ┌──────────────────────────┐
                                   │                       │             │                          │
                                   │AwContents             │             │AwContents.java           │
                                   │                       │             │                          │
                                   └───┬─────────▲─────────┘             └───┬──────────────────────┘
                                       │         │                           │
                                       │owns 1   │raw ref                    │
┌──────────────────────┐           ┌───▼─────────┴─────────┐                 │
│ContentAutofillDriver │           │                       │                 │
│(1 per RFH,           │           │WebContents            │                 │
│ see c/autofill)      │           │                       │                 │
└───┬──────────────────┘           └───┬───────────────────┘                 │
    │                                  │                                     │
    │owns                              │owns                                 │owns
┌───▼──────────────────┐           ┌───▼───────────────────┐              ┌──▼──────────────────────┐     ┌────────────────────────────┐
│                      │           │AutofillProviderAndroid├─events──────►│                         │     │AutofillManagerWrapper.java │
│AndroidAutofillManager├─events───►│implements             │              │AutofillProvider.java    │owns─►(wraps Android's            │
│                      │           │AutofillProvider       │◄─ask-to-fill─┤                         │     │ AutofillManager)           │
└──────────────────────┘           └───┬───────────────────┘              └──┬──────────────────────┘     └────────────────────────────┘
                                       │                                     │
                                       │                                     │owns at most 1
                                       │                                  ┌──▼──────────────────────┐
                                       │                                  │                         │
                                       │                                  │AutofillRequest.java     │
                                       │                                  │                         │
                                       │                                  └──┬──────────────────────┘
                                       │                                     │
                                       │owns at most 1                       │owns 1
                                   ┌───▼───────────────────┐              ┌──▼──────────────────────┐
                                   │FormDataAndroid        │              │                         │
                                   │(wraps a FormData)     ◄──updates─────►FormDataAndroid.java     │
                                   │                       │  & references│                         │
                                   └───┬───────────────────┘              └──┬──────────────────────┘
                                       │                                     │
                                       │owns 0 to N                          │owns 0 to N
                                   ┌───▼───────────────────┐              ┌──▼──────────────────────┐
                                   │                       │              │                         │
                                   │FormFieldDataAndroid   ◄──updates─────►FormFieldDataAndroid.java│
                                   │                       │  & references│                         │
                                   └───────────────────────┘              └─────────────────────────┘

To edit the diagram, copy-paste it to asciiflow.com.

Responsibilities of the main classes

C++ classes

• AndroidAutofillManager:
  • One instance per RenderFrameHost, i.e. potentially multiple instances per WebContents.
  • Implements AutofillManager to receive information for various OnX() events.
  • Responsibilities:
    • Forward all information from various OnX() implementations to the AutofillProvider of the WebContents (if one exists).
    • Conversely, receive fill requests from AutofillProvider and forward them to ContentAutofillDriver.
• AutofillProviderAndroid:
  • One instance per WebContents.
  • Implements AutofillProvider (and is currently the only class to do).
  • Owns at most one FormDataAndroid, the one related to the current autofill session
  • Responsibilities:
    • Start an Autofill session. An Autofill session is initiated e.g. if a user interacts with a form field and OnAskForValuesToFill is called. The purpose of an Autofill session is to keep Android's AutofillManager informed about the state of the currently focused form such as its field structure, its field positions, the currently focused field, etc. Autofill sessions are tied to a form in a frame and are represented by AutofillRequests.java on the Java side.
    • If there is an ongoing autofill session, update the FormDataAndroid object it owns to keep it in sync with changes on the page.
    • Forward information from OnX() methods to its AutofillProvider.java sibling.
• FormDataAndroid:
  • Is created based from a FormData object and creates a copy of it, which continues to be updated by its parent AutofillProviderAndroid.
  • Owns 0 to N FormFieldDataAndroid objects that represent the form field elements in the form.
  • Responsibilities:
    • Form a wrapper around FormData and propagate updates to and from its sibling class FormDataAndroid.java.
• FormFieldDataAndroid:
  • Responsibilities:
    • Forms a wrapper around FormFieldData and propagate updates to and from its sibling class FormFieldDataAndroid.java.

Java classes

• AutofillProvider.java:
  • One instance per embedder wrapper of WebContents, i.e. AwContents.
  • Owns up to one AutofillRequest.java, one AutofillManagerWrapper.java and multiple helper classes (e.g. for metrics collection).
  • Responsibilities:
    • Orchestrate Autofill logic on the Java and form the glue between its C++ siblings, AutofillManagerWrapper.java, and various metrics/helper classes.
    • Create an AutofillRequest.java when a new Autofill session is started and forwards updates to it.
    • Use AutofillRequest.java to fill virtual view structures for use in Android Autofill.
    • Propagate selection choices to its C++ sibling.
• AutofillRequest.java: Responsibilities:
  • Package information about the view structure of the current session's form for use by Android's Autofill framework.
• FormDataAndroid.java and FormFieldDataAndroid.java: Pure data classes and siblings to the C++ classes of the same name.