title: Fingerprint BiometricPrompt on android P from a View
body: <p>I am using <code>FingerprintManager</code> to authenticate my app with fingerprint.
  I have and android <code>View</code> with the fingerprint ui and when the <code>FingerprintManager.authenticate</code> callbacks are called I handle the callbacks in the view, e.g change fingerprint icon, error text etc. </p>
  
  <p>Now in Android P, I have to use <code>BiometricPrompt</code>, which is easy enough to use, but forces me to have an <code>Activity</code> in order to work properly</p>
  
  <p>Is there a way to make <code>BiometricPrompt</code> work in a plain android view?</p>
  
  <p>this is my working code to launch the prompt in an activity </p>
  
  <pre><code>    Signature signature = createSignature();
      biometricPrompt = new BiometricPrompt.Builder(context)
              .setDescription("Description")
              .setTitle("Title")
              .setSubtitle("Subtitle")
              .setNegativeButton("Cancel", context.getMainExecutor(), new DialogInterface.OnClickListener() {
                  @Override
                  public void onClick(DialogInterface dialogInterface, int i) {
                      Log.i(TAG, "Cancel button clicked");
                  }
              })
              .build();
  
          biometricPrompt.authenticate(new BiometricPrompt.CryptoObject(signature), cancellationSignal, context.getMainExecutor() , new BiometricPrompt.AuthenticationCallback() {...}
  </code></pre>
  
  <p>where context is an activity that without it it can not work</p>