我如何调用javascript函数并从javascript函数获取返回值

Question

I want to get the value from my JS function on my Java Android

Sample,

function getStringToMyAndroid(stringFromAndroid){
   var myJsString = "Hello World" + ;
   return myJsString;
}

Now I want calling function getStringToMyAndroid("This string from android") and get the returning myJsString on my Android, so I can use myJsString later on my Android;

I know I can use

WebView.loadUrl("javascript:getStringToMyAndroid('This string from android')")

to call the JS function but I want to get the string or value from JS function

NOTE: My android running on minimum SDK Android 3.0 honeycomb

Answer 1

For API Level < 19 there are only workarounds of either using a JavascriptInterface (my preferred method, below) or else hijacking the OnJsAlert method and using the alert() dialog instead. That then means you can't use the alert() function for its intended purpose.

View:

WebView.addJavascriptInterface(new JsInterface(), "AndroidApp");
WebView.loadUrl("javascript:doStringToMyAndroid('This string from android')")

JsInterface:

public class JsInterface() {
    @JavascriptInterface
    void receiveString(String value) {
        // String received from WebView
        Log.d("MyApp", value);
    }
}

Javascript:

function doStringToMyAndroid(stringFromAndroid){
   var myJsString = "Hello World" + ;
   // Call the JavascriptInterface instead of returning the value
   window.AndroidApp.receiveString(myJsString);
}

But on API Level 19+, we now have the evaluateJavascript method:

WebView.evaluateJavascript("(function() { return getStringToMyAndroid('" + myJsString + "'); })();", new ValueCallback<String>() {
    @Override
    public void onReceiveValue(String s) {
        Log.d("LogName", s); // Returns the value from the function
    }
});