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Cloud Vision Android Sample

So you want to use the Google Cloud Vision API from Android? Then this sample is for you. It's a minimal single-activity sample that shows you how to make a call to the Cloud Vision API with an image picked from your device's gallery.

Prerequisites

  • An API key for the Cloud Vision API (See the docs to learn more)
  • An Android device running Android 5.0 or higher
  • Android Studio, with a recent version of the Android SDK.

Quickstart

  • Download the CloudVision directory from this repository.
  • In Android Studio, open the CloudVision directory as an existing Android Studio project.
  • Open MainActivity.java and set the constant CLOUD_VISION_API_KEY to the API key obtained above.
  • Run the sample.

Running the app

  • As with all Google Cloud APIs, every call to the Vision API must be associated with a project within the Google Cloud Console that has the Vision API enabled. This is described in more detail in the getting started doc, but in brief:

  • Download the CloudVision directory from this repository.

    The easiest way to do this from GitHub is to fetch the entire repository. If you have git installed, you can do this by executing the following command:

      $ git clone https://github.com/GoogleCloudPlatform/cloud-vision.git

    This will download the repository of samples into the directory cloud-vision.

    Otherwise, GitHub offers an auto-generated zip file of the master branch, which you can download and extract.

    Either method will include the desired directory at cloud-vision/android/CloudVision.

  • Open Android Studio, and navigate to open an existing project. When prompted, open this project's root directory cloud-vision/android/CloudVision.

  • Within Android Studio, open the MainActivity java file within the app, and look for where the constant CLOUD_VISION_API_KEY is set. Replace the string value with the api key obtained from the cloud console above.

    This constant is the credential used in the callCloudVision method to authenticate all requests to the Vision API. Calls to the API are thus associated with the project you created above, for access and billing purposes.

  • You are now ready to build and run the project. As per usual for Android Studio projects, you can run the project by clicking the green 'Play' button, or going to Run | Run 'app'. The app should build and run on your connected Android device or emulator.

  • You will be presented with the single-activity app.

    • Click the floating red action button to select the image to send to the API.
      • This executes the onClickListener that's set in onCreate, which creates an Intent for selecting the content to send to the API.
    • Select an image from your device.
      • Control is handed back to the MainActivity and is handled by onActivityResult, which does a little bit of processing on the selected image and hands it to the callCloudVision method.
      • The callCloudVision method creates and executes a label detection request to the Vision API using the google-api-services-vision java client library. This library is declared as a dependency in app/build.gradle, and is used to simplify making API calls to the Google Cloud Vision API.
      • Notice that the CLOUD_VISION_API_KEY is set as part of this request, to authenticate the request and associate it with your project.
    • When the API responds, the convertResponseToString method extracts the labels from the response object and constructs a String to display.
    • The onPostExecute callback fires, with the constructed result, and populates the image_details TextView with the labels returned by the Vision API.