Characteristic

No interface, running in the background

How to create

Custom class inherits Service
Rewrite onBind
Registration (manifest file)
Lifecycle oncreate() - onstartcommand - ondestore()
Starting mode
startService() -stopService(); it runs in the background all the time after startup, unless it is not related to Activity
Bindservice() - anbindservice(); when activity exits and the service is closed, you can call the method used by the service
Binding service steps
Create service
Override onBind(){new binder()}
Create binder

Code snippet implementation background network download json string

Http download tool class string is optional

public class HttpUtils {
    public static List<HashMap<String, String>> openUrl(String url){

        try {
            URL url1 = new URL(url);
            HttpURLConnection urlConnection = (HttpURLConnection) url1.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();
            if (urlConnection.getResponseCode() == 200) {
                InputStream is = urlConnection.getInputStream();
                byte[] bytes = new byte[1024];
                int len = 0;
                StringBuilder sb = new StringBuilder();
                while ((len = is.read(bytes)) != -1) {
                    String s = new String(bytes, 0, len);
                    sb.append(s);
                }
                String json = sb.toString();
                Gson gson = new Gson();
                JavaBean javaBean = gson.fromJson(json, JavaBean.class);
                List<JavaBean.DataBean> data = javaBean.getData();

                List<HashMap<String, String>> list = new ArrayList<>();

                for (int i = 0; i < data.size(); i++) {
                    JavaBean.DataBean dataBean = data.get(i);
                    String title = dataBean.getTitle();
                    String food = dataBean.getFood_str();
                    String pic = dataBean.getPic();

                    HashMap<String, String> map = new HashMap<>();
                    map.put("title", title);
                    map.put("food", food);
                    map.put("pic", pic);
                    list.add(map);
                }
                return list;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

Customized server

public class MyService extends Service {
    String url = "http://www.qubaobei.com/ios/cf/dish_list.php?stage_id=1&limit=20&page=1";

    @Override
    public IBinder onBind(Intent intent) {
        return new MyBinder();
    }

    public class MyBinder extends Binder {
        public MyService getMyService() {
            return MyService.this;
        }
    }

    public List<HashMap<String, String>> getMethod(){
        try {
            List<HashMap<String, String>> list = new MyService.MyAsyncTask().execute(url).get();
            return list;
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static class MyAsyncTask extends AsyncTask<String,Void,List<HashMap<String,String>>>{

        @Override
        protected List<HashMap<String, String>> doInBackground(String... strings) {
            return HttpUtils.openUrl(strings[0]);
        }
    }
}

Main class

public class MainActivity extends AppCompatActivity {
    Intent intent;
    MyService fuwu;
    ServiceConnection connection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            fuwu = ((MyService.MyBinder)service).getMyService();
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {

        }
    };

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

        intent = new Intent(MainActivity.this,MyService.class);
        bindService(intent,connection, Service.BIND_AUTO_CREATE);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(connection);
    }

    public void btn(View view) {
        List<HashMap<String, String>> list = fuwu.getMethod();
        Log.e("###",list.toString());
    }
}