Android: Can a JavascriptInterface function have default parameters?-CodePudding

I'm making my first steps in android webapp development.
I wrote some android functions and made them accessible to javascript, it works like a charm (set pref, read pref...).

My question: is it possible to declare default value for function arguments?

As an illustration:
showToast() hereunder is available from within javadcript in the WebView webView1.
But it can't be called with a single argument (lengthLong: Boolean = true seems to have no effect js-side).

class CallableFromWebViewJS(context: Context) {
    private val context: Context

    init {
        this.context= context
    }

    @JavascriptInterface
    fun showToast(message: String?, lengthLong: Boolean = true) {
        Toast.makeText(context, message, if (lengthLong) Toast.LENGTH_LONG else Toast.LENGTH_SHORT)
          .show()
    }
}

...

/* Then somewhere in my main activity: */
webView1.addJavascriptInterface(CallableFromWebViewJS(this), "appInterface");

In the JS script:

appInterface.showToast("Foo bar", true); //this works
appInterface.showToast("Foo bar");       //this does NOT work

Can I achieve this, and if yes, how?

CodePudding user response：

You can force Android JavascriptInterface interpreter to create both javascript methods like the code below.

@JavascriptInterface
 fun showToast(message: String?) {
     // here, you can define the default value
     showToast(message, true)
 }

 @JavascriptInterface
 fun showToast(message: String?, lengthLong: Boolean) {
     Toast.makeText(
       context, 
       message, 
       if (lengthLong) Toast.LENGTH_LONG else Toast.LENGTH_SHORT
     )
     .show()
 }

If you need to send complex data you can use simply json.

const someObject = {
  message: "hello world",
  isLong: false,
}

const toSend = JSON.stringify(someObject);

// send to Android web interface
appInterface.complex(toSend);

@JavascriptInterface
fun complex(jsonStr: String) {
    val json = JSONObject(jsonStr)

    println(json.getString("message"))
    println(json.getBoolean("isLong"))

    // or use as you want
}

Hope it helps