Retrieving data from firebase

Question

I keep getting the stacktrace error below each time I implement

GenericTypeIndicator> t = new GenericTypeIndicator

        

Answer 1

Looking at your data structure:

"Driver name" : {
  "-Js6OJniEqVZAYSNhqbB" : "gvvb",
  "-Js7GjPMGNOLurrKk9rC" : "iggvv",
  "-Js7GlUlCwIoljJxpFbZ" : "iiggv",
  "-Js7GnBCRogiFUfn-ncZ" : "ihccvv",
  "-Js7GqGxH2vLYK5tsjjP" : "hhvv",
  "-Js7Gs80AoB5eeWci6jW" : "hhgc",
  "-Js7Gtm6AGh_QaTUK6fQ" : "ugghh",
  "-Js7GyomOIzjtVo3-PVg" : "tyygff",
  "-JsPxEhf4tx7O4v7JWMc" : "",
  "-JsQBoMqVBF4SzOHF3WA" : "rr",
  "-JsQC6TuGqHrBBkdalik" : "eed"
}

You try to deserialize this into a List<String>. But it actually is a Map<String,String>. So:

@Override
public void onDataChange(DataSnapshot snapshot) {
    GenericTypeIndicator<Map<String,String>> mapType = new GenericTypeIndicator<Map<String, String>>() { };
    Map<String,String>  namelist =  snapshot.child("Driver name").getValue(mapType);
    Map<String,String> carlist =  snapshot.child("Drivers car").getValue(mapType);
    if (namelist!=null & carlist!=null) {
        for (String name: namelist.values()) {
            System.out.println(name);
        }
    }
}

Note that I have no idea how you're trying to match up a driver and their car. I highly recommend that you reconsider this data structure before you continue to code.

One possible structure:

"DriversList": {
  "-Js6OJniEqVZAYSNhqbB" : {
    "name": "puf",
    "available": false,
    "car": "Toyota RAV4"
  },
  "-Js7GjPMGNOLurrKk9rC" : {
    "name": "manon",
    "available": false,
    "car": "Toyota Matrix"
  },
  ...
}

To read/write these, you'll need a Driver class:

public class Driver {
  String name;
  Boolean available;
  String car;

  public Driver() {}

  public String getName() { return name; }
  public Boolean getAvailable() { return available; }
  public String getCar() { return car; }
}

And then:

public void onDataChange(DataSnapshot snapshot) {
    GenericTypeIndicator<Map<String,Driver>> mapType = new GenericTypeIndicator<Map<String, Driver>>() { };
    Map<String,Driver> drivers = snapshot.getValue(mapType);
    if (drivers!=null) {
        for (Driver driver: drivers.values()) {
            System.out.println(driver.name);
        }
    }
}