Error Passing java List<Double> to dart List<double>

Question

Ok, I followed completely this example: https://flutter.io/platform-channels/

and tried to modify it like so:

List<double> points;


 try {

 //Changed This 
 /*final  String  result = await platform.invokeMethod('getBatteryLevel');
 batteryLevel = 'Battery level at $result % .'; */


 //To This
 final  List<double>  result = await platform.invokeMethod('getBatteryLevel');
 points = result;
 print("Message 2");

Then In MainActivity.java, changed the getBatteryLevel function to this:

private List<Double> getBatteryLevel() {

        List<Double> list = Arrays.asList(1.38, 2.56, 4.3);
        return list;

And Lastly changed the MethodCall to this:

List<Double> batteryLevel = getBatteryLevel();

  Log.i("errors", "Message");
  result.success(batteryLevel);

But when I run the code, the Message 1 gets printed but Message 2 does not. I noticed that with simple types like Strings and Integer instead of List worked. I also tried to replace List with arrays in java, but still didn't work. The Problem is that I don't get any error any stacktraces, anything. What I thought is that in dart he's waiting for something that never comes as Lists of doubles in Dart and Java aren't the same. But it's just a thing I thought. Could it be the problem? How Can I solve it?

Answer 1

Try to receive the List without <double> because Dart assumes the type inside the List is dynamic and not primitive, so you have an error when you try to parse List<dynamic> into List<double> .

 final List result = await platform.invokeMethod('getBatteryLevel');

Should work.

Don't forget to include your imports in your MainActivity, looks like you are using Arrays and List classes, then import the following classes:

import java.util.Arrays;
import java.util.List;