Development Example – BNF Grammar

Static speech commands are not suitable when there are a large number of selections available to a user.

For instance, to have a speech command for entering a time would require 60 speech commands for every minute value, multiplied by the 24 hours in a day.

That would mean your application would need to register 1,440 voice commands!

To solve this issue your application can register BNF grammar to the speech engine. This allows for 2 groups of words to be combined to make a single voice command.

Once the BNF grammar has been registered the speech engine will listen for any of the possible combinations and report back the spoken command as a string for processing.

The following example allows the user to select 1 to 10 of a certain fruit. For example the user could say “2 bananas”, “8 oranges”, …

 private final String BnfString = "#BNF+EM V2.0;" + 
      "!grammar Commands;\n" + 
      "!start <Commands>;\n" + 
      "<Commands>:<global_commands>|<Hour> !optional(<Minute>);\n" + 
      "<number>:1|2|3|4|5|6|7|8|9|10;\n" + 
      "<fruit>:apples|bananas|oranges;"; 

 private final String ACTION_OVERRIDE_COMMANDS = 
      "com.realwear.wearhf.intent.action.OVERRIDE_COMMANDS"; 

 private final String EXTRA_SOURCE_PACKAGE = 
      "com.realwear.wearhf.intent.extra.SOURCE_PACKAGE"; 
 private static final String EXTRA_COMMANDS = 
      "com.realwear.wearhf.intent.extra.COMMANDS"; 

 private void textToSpeech() { 
      final Intent intent = new Intent(ACTION_OVERRIDE_COMMANDS); 
      intent.putExtra(EXTRA_SOURCE_PACKAGE, getPackageName()); 
      intent.putExtra(EXTRA_COMMANDS, BnfString); 
      sendBroadcast(intent); 
 }

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