DataForm for Xamarin.Android: Schema

You can set up how each property will be edited through the Property Metadata. Another way to achieve the same is through a json schema that provides the same information. This can be useful for example when editing json objects that can't be annotated with the DataFormProperty annotation.

The schema can be used not only as a replacement for the annotations for defining the metadata for each property - label, index, columnIndex, group, required, readOnly, skip, editor, editorParams, converter, validator, validatorParams - but also for data form properties like IsReadOnly, CommitMode and ValidationMode.

Here's one schema example:

{
  "commitMode": "immediate",
  "validationMode": "immediate",
  "properties":
  [
    {
      "name": "name",
      "displayName": "Your Name"
    },
    {
      "name": "age",
      "displayName": "Your Age",
      "editor": "stepper",
      "editorParams":
      {
        "minimum": 18,
        "maximum": 70
      }
    },
    {
      "name": "gender",
      "displayName": "Your Gender",
      "editor": "picker",
      "valuesProvider": ["male", "female"]
    },
    {
      "name": "email",
      "editor": "email",
      "validator": "MailValidator",
      "displayName": "Your Email"
    },
    {
      "name": "city",
      "editor": "segmentededitor",
      "valuesProvider": ["New York", "Las Vegas", "Los Angeles"]
    }
  ]
}

This schema can be used to edit the following object:

{
  "name": "John Doe",
  "age": 21,
  "gender": "Male",
  "email": "john.doe@example.com",
  "city": "New York"
}

The result would be that the name property will have a header "Your name", the age property will be edited with NumberPicker(Stepper), with available range from 18 to 70. The gender will be edited with a Picker(Spinner) with male and female as possible values, etc.

Here's how to apply the schema to the DataForm:

// The files PersonExtended.json and PersonSchema.json are
// in the Assets folder of the project
String json = LoadJSONFromAsset ("PersonExtended.json");

try {
    JSONObject jsonObject = new JSONObject (json);
    dataForm.SetEntity(jsonObject);

    String schema = LoadJSONFromAsset("PersonSchema.json");
    JSONObject jsonSchema = new JSONObject(schema);
    DataFormMetadata metadata = new DataFormMetadata(jsonSchema);
    dataForm.SetMetadata(metadata);
} catch(JSONException e) {
    Log.Error ("json", "error parsing json", e);
}

The LoadJSONFromAsset simply returns the content of file with given name. One sample implementation is provided in the Getting Started article.