@yongsheng, I have printed the value from "evaluateJavascript" in native code, it contains double quotes. 
I also tested this interface with boolean value as follows:
```
    class TestJavascriptInterface {
        @JavascriptInterface
        public boolean getBoolVaule() {
            return true;
        }
    }
    result = executeJavaScriptAndWaitForResult("testInterface.getBoolVaule()");
    assertEquals("true", result);
```
The format of value is string.