How can I parse JSON Array and show it in ListView?

Question

MainActivity.java

package com.softjourn.redmineclient.activities;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Base64;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
import com.softjourn.redmineclient.R;
import com.softjourn.redmineclient.models.Issues;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.ProtocolException;
import java.net.URL;
import java.util.ArrayList;
import butterknife.Bind;
import butterknife.ButterKnife;

public class MainActivity extends AppCompatActivity {

private final static String URI="https://redmineng.softjourn.if.ua/issues.json?assigned_to_id=me";
@Bind(R.id.list_issues) ListView mListIssues;
Login li;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ButterKnife.bind(this);

    li = new Login();
    li.execute(URI);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

class Login extends AsyncTask<String, Void, String> implements com.softjourn.redmineclient.activities.Login {

    @Override
    protected String doInBackground(String... strings) {
        HttpURLConnection c = null;
        try {
            c = (HttpURLConnection) new URL(strings[0]).openConnection();
        } catch (IOException e) {
            e.printStackTrace();
        }
        c.setUseCaches(false);
        try {
            c.setRequestMethod("GET");
        } catch (ProtocolException e) {
            e.printStackTrace();
        }
        c.setRequestProperty("Accept", "application/json");
        c.setRequestProperty("Authorization", "basic " + Base64.encodeToString("osavchak:somepassword".getBytes(), 0));
        try {
            c.connect();
        } catch (IOException e) {
            e.printStackTrace();
        }
        BufferedReader br = null;
        try {
            br = new BufferedReader(new InputStreamReader((c.getInputStream())));
        } catch (IOException e) {
            e.printStackTrace();
        }
        StringBuilder sb = new StringBuilder();
        String output;
        try {
            while ((output = br.readLine()) != null) {
                sb.append(output);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

        return sb.toString();
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);

        JsonArray ja = new JsonParser().parse(result).getAsJsonObject().getAsJsonArray("issues");
        ArrayList<Issues> issues = new ArrayList<Issues>();

        for(JsonElement jo : ja) {
            Issues issue = new Gson().fromJson(jo, Issues.class);
            issues.add(issue);
        }

        ArrayAdapter<Issues> adapter = new ArrayAdapter<Issues>(MainActivity.this, android.R.layout.simple_list_item_1, issues);
        mListIssues.setAdapter(adapter);
    }
}
}

Issues.java

package com.softjourn.redmineclient.models;

import com.google.gson.annotations.SerializedName;

import java.util.ArrayList;


public class Issues extends ArrayList<Issues> {
@SerializedName("id")
private int id;

@SerializedName("description")
private String description;

public int getId() {
    return id;
}

public String getDescription() {
    return description;
}

public Issues(int id, String description) {
    this.id = id;
    this.description = description;
}

@Override
public String toString() {
    return "[" + this.id + "] " + this.description;
}
}

The JSON response looks like:

{"issues":[{"id":11023,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-06-08","due_date":"2015-06-08","done_ratio":0,"created_on":"2015-06-04T19:12:14Z","updated_on":"2015-06-05T08:43:35Z"},{"id":10994,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":12,"name":"Medical"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-06-03","due_date":"2015-06-03","done_ratio":0,"created_on":"2015-06-03T07:19:01Z","updated_on":"2015-06-03T08:09:21Z"},{"id":10651,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":11,"name":"Business Trip"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"U.S. visa development.","start_date":"2015-04-20","due_date":"2015-04-20","done_ratio":0,"created_on":"2015-04-09T15:58:38Z","updated_on":"2015-04-10T07:39:38Z"},{"id":10555,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-05-05","due_date":"2015-05-05","done_ratio":0,"created_on":"2015-04-03T10:24:11Z","updated_on":"2015-04-08T08:18:13Z"},{"id":10554,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-04-30","due_date":"2015-04-30","done_ratio":0,"created_on":"2015-04-03T10:19:40Z","updated_on":"2015-04-08T08:18:12Z"},{"id":10219,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"Czech visa development","start_date":"2015-03-23","due_date":"2015-03-23","done_ratio":0,"created_on":"2015-03-06T08:59:47Z","updated_on":"2015-04-06T09:20:55Z"},{"id":10199,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":12,"name":"Medical"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-03-04","due_date":"2015-03-04","done_ratio":0,"created_on":"2015-03-03T17:35:48Z","updated_on":"2015-03-04T09:27:02Z"},{"id":10183,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":12,"name":"Medical"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-03-03","due_date":"2015-03-03","done_ratio":0,"created_on":"2015-03-02T14:27:40Z","updated_on":"2015-03-02T14:34:57Z"},{"id":9791,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2015-01-09","due_date":"2015-01-09","done_ratio":0,"created_on":"2015-01-06T14:09:14Z","updated_on":"2015-01-08T11:54:55Z"},{"id":9128,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":9,"name":"Vacation"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"Vacation","start_date":"2014-11-03","due_date":"2014-11-14","done_ratio":0,"created_on":"2014-10-15T12:28:33Z","updated_on":"2014-10-16T09:17:31Z"},{"id":7921,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":9,"name":"Vacation"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"Vacation for two weeks","start_date":"2014-08-11","due_date":"2014-08-21","done_ratio":0,"created_on":"2014-06-03T14:04:15Z","updated_on":"2014-06-05T10:01:23Z"},{"id":7698,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":12,"name":"Medical"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"Medical on Monday","start_date":"2014-05-12","due_date":"2014-05-12","done_ratio":0,"created_on":"2014-05-11T10:18:58Z","updated_on":"2014-05-13T08:21:08Z"},{"id":7337,"project":{"id":52,"name":"Our Vacations and Days Off"},"tracker":{"id":10,"name":"Day Off"},"status":{"id":12,"name":"Accepted"},"priority":{"id":1,"name":"Normal"},"author":{"id":186,"name":"Savchak Orest"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Orest Savchak","description":"","start_date":"2014-02-27","due_date":"2014-02-28","done_ratio":0,"created_on":"2014-02-11T12:34:16Z","updated_on":"2014-02-17T15:15:30Z"},{"id":6823,"project":{"id":138,"name":"Orest Savchak tasks"},"tracker":{"id":2,"name":"User Story"},"status":{"id":1,"name":"New"},"priority":{"id":1,"name":"Normal"},"author":{"id":42,"name":"Vershynin Yevgeniy"},"assigned_to":{"id":186,"name":"Savchak Orest"},"subject":"Authomatization testing","description":"Testing for IMAX Android app.","start_date":"2013-12-04","done_ratio":0,"created_on":"2013-12-04T16:16:16Z","updated_on":"2014-01-21T16:29:49Z","story_points":null}],"total_count":14,"offset":0,"limit":25}

And when I run my application it crashes with 'com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT'

How can I fix it?

Answer 1

The problem is you're telling Gson you have an object of your type when in fact you have an array of objects of your type.

Try this way instead:

Type collectionType = new TypeToken < List<Issues>>(){}.getType();

List<Issues> issues = (List<Issues>) new Gson().fromJson( json_response, collectionType);