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Espresso DataMatcher Selector

By delegating to Espresso's Data Matcher, we can target views that are not visible in the viewport without the need to manually scroll the Views on screen.

AdapterViews

Android apps have special types of Views called AdapterViews (e.g.: ScrollView, ListView, GridView) which have child views, but only render that child views that are on-screen. The AdapterView has "adapter" object which stores all the data for that view's children, including the views that aren't being rendered.

When using Espresso's Data Matcher, you can target views that are off-screen by writing a Hamcrest matcher that selects an item from an adapter. If the item is not in the view hierarchy, Espresso automatically scrolls it into view.

Example

This is a ListView taken from the source XML of an Android App:

<android.widget.ListView index="0" package="io.appium.android.apis" class="android.widget.ListView" checkable="false" checked="false" clickable="true" enabled="true" focusable="true" focused="false" scrollable="true" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,210][1080,1794]" resource-id="android:id/list" adapter-type="HashMap" adapters="{contentDescription=Animation, title=Animation, intent=Intent { cmp=io.appium.android.apis/.ApiDemos (has extras) }},{contentDescription=Auto Complete, title=Auto Complete, intent=Intent { cmp=io.appium.android.apis/.ApiDemos (has extras) }}, ...}">
    <android.widget.TextView index="0" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Drag and Drop" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,148][1080,274]" text="Drag and Drop" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="1" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Expandable Lists" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,277][1080,403]" text="Expandable Lists" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="2" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Focus" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,406][1080,532]" text="Focus" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="3" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Gallery" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,535][1080,661]" text="Gallery" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="4" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Game Controller Input" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,664][1080,790]" text="Game Controller Input" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="5" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Grid" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,793][1080,919]" text="Grid" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="6" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Hover Events" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,922][1080,1048]" text="Hover Events" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="7" package="io.appium.android.apis" class="android.widget.TextView" content-desc="ImageButton" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1051][1080,1177]" text="ImageButton" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="8" package="io.appium.android.apis" class="android.widget.TextView" content-desc="ImageSwitcher" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1180][1080,1306]" text="ImageSwitcher" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="9" package="io.appium.android.apis" class="android.widget.TextView" content-desc="ImageView" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1309][1080,1435]" text="ImageView" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="10" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Layout Animation" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1438][1080,1564]" text="Layout Animation" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="11" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Layouts" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1567][1080,1693]" text="Layouts" hint="false" resource-id="android:id/text1" />
    <android.widget.TextView index="12" package="io.appium.android.apis" class="android.widget.TextView" content-desc="Lists" checkable="false" checked="false" clickable="false" enabled="true" focusable="false" focused="false" scrollable="false" long-clickable="false" password="false" selected="false" visible="true" bounds="[0,1696][1080,1822]" text="Lists" hint="false" resource-id="android:id/text1" />
</android.widget.ListView>

This ListView displays menu items [Drag and Drop, Expandable Lists, ... to Lists]. This menu has several more items that aren't on-screen and can't be located with standard locators. For example, There's a menu item called TextClock that is not currently visible in the View hierarchy.

The ListView node in the above XML has an attribute called adapters that contains the data that "backs up" the ListView:

{
    contentDescription = Animation, title = Animation, intent = Intent {
        cmp = io.appium.android.apis / .ApiDemos(has extras)
    }
}, {
    contentDescription = Auto Complete,
    title = Auto Complete,
    intent = Intent {
        cmp = io.appium.android.apis / .ApiDemos(has extras)
    }
}, {
    contentDescription = Buttons,
    title = Buttons,
    intent = Intent {
        cmp = io.appium.android.apis / .view.Buttons1
    }
},
...

These items can be targeted using a datamatcher selector. Here's a code snippet that shows how to locate and click TextClock:

// Javascript example
driver.findElementById("list")
  .findElement("-android datamatcher", JSON.stringify({
    "name": "hasEntry",
    "args": ["title", "TextClock"]
  }))
  .click();
# Ruby
@driver.find_element(:id, 'list')
  .find_element(:data_matcher, {
    name: 'hasEntry',
    args: ['title', 'TextClock']
  }.to_json)
  .click
# Python
driver.find_element_by_id('list')
    .find_element_by_android_data_matcher({
        name='hasEntry',
        args=['title', 'TextClock']
    })
    .click()

This driver selector is equivalent to writing this matcher in Espresso:

// Espresso code (not Appium code)
onData(hasEntry("title", "textClock")
  .inAdapterView(withId("android:id/list))
  .perform(click());

In this example, we select the parent AdapterView using an id selector and then find a child of that view by applying a Hamcrest Matcher that matches an object with title="TextClock".

Locating the parent AdapterView is not necessary if the Activity only has one adapter view. In that case, it can be omitted.

driver.findElement("-android datamatcher", JSON.stringify({
    "name": "hasEntry",
    "args": ["title", "TextClock"]
  }))
  .click();
# Ruby
@driver.find_element(:data_matcher, {
  name: 'hasEntry',
  args: ['title', 'TextClock']
}.to_json).click
# Python
driver.find_element_by_android_data_matcher({
    name='hasEntry',
    args=['title', 'TextClock']
}).click()

Writing the Selector

The data matcher selector uses Java reflection to invoke a Hamcrest matcher that's used to locate the adapter object. The matcher is in JSON format and has this format

{
  "name": "<METHOD_NAME>",
  "args": [...],

The name is a Hamcrest matcher method name. This defaults to the org.hamcrest.Matchers namespace, but fully qualifed matcher method names can be used too (e.g.: android.support.test.espresso.matcher.CursorMatchers.withRowBlob).

The args are a list of args that the method takes (can be undefined if it takes no args). These can be strings, numbers, booleans or other hamcrest matcher JSON definitions.

JSON matcher samples

Examples of JSON matchers with the equivalent Espresso onData matcher

StartsWith

// 'startsWith' JSON
{
  "name": "startsWith",
  "args": "substr" // if it's a single arg, we don't need args to be an array
}
// Espresso 'startsWith' example
onData(startsWith("substr"));

Multiple Matchers

// 'multiple matchers' JSON
{
  "name": "allOf",
  "args": [
    {"name": "instanceOf", "args": "Map.class"},
    {"name": "hasEntry", "args": {
      "name": "equalTo", "args": "STR"
    }},
    {"name": "is", "args": "item: 50"}
  ]
}
// Espresso 'multiple matchers' example
onData(allOf(is(instanceOf(Map.class)), hasEntry(equalTo("STR"), is("item: 50"))));

Cursor Matchers

// 'cursor matchers' JSON
{
  "name": "anyOf",
  "args": [
    {
      "name": "is",
      "args": {"name": "instanceOf", "args": "Cursor.class"}
    }, {
      "name": "withRowString",
      "args": [
        "job_title",
        {"name": "is", "args": "Barista"}
      ],
      "class": "androidx.test.espresso.matcher.CursorMatchers"
    }
  ],
  "scope": {
    "name": "isDialog",
    "class": "androidx.test.espresso.matcher.RootMatchers"
  }
}
// Espresso 'cursor matchers' example
onData(
  anyOf(
    is(instanceOf(Cursor.class)),
    CursorMatchers.withRowString("job_title", is("Barista"))
  )
).inRoot(isDialog());

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