如何在以下代码 Android API 服务中添加自动刷新

Question

如何使后台刷新间隔为 5 秒。根据我的代码，当我发布新名称时它不会显示，因此当我重新打开应用程序时它会显示，所以我需要自动刷新。

我应该改变什么或应该添加什么。

MainActivity

    public class MainActivity extends AppCompatActivity {

        ListView listView;

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

            listView = (ListView) findViewById(R.id.listViewHeroes);

            //calling the method to display the heroes
            getHeroes();
        }

        private void getHeroes() {
            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(Api.BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create()) //Here we are using the GsonConverterFactory to directly convert json data to object
                    .build();

            Api api = retrofit.create(Api.class);

            Call<List<Hero>> call = api.getHeroes();

            call.enqueue(new Callback<List<Hero>>() {
                @Override
                public void onResponse(Call<List<Hero>> call, Response<List<Hero>> response) {
                    List<Hero> heroList = response.body();

                    //Creating an String array for the ListView
                    String[] heroes = new String[heroList.size()];

                    //looping through all the heroes and inserting the names inside the string array
                    for (int i = 0; i < heroList.size(); i++) {
                        heroes[i] = heroList.get(i).getName();
                    }


                    //displaying the string array into listview
                    listView.setAdapter(new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, heroes));

                }

                @Override
                public void onFailure(Call<List<Hero>> call, Throwable t) {
                    Toast.makeText(getApplicationContext(), t.getMessage(), Toast.LENGTH_SHORT).show();
                }
            });
        }
    }

Answer 1

查看更改，基本上使用Handler 进行周期性的事情-

public class MainActivity extends AppCompatActivity {

    ListView listView;

    Handler handler = new Handler();
    int apiDelayed = 5*1000; //1 second=1000 milisecond, 5*1000=5seconds
    Runnable runnable;

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

        listView = (ListView) findViewById(R.id.listViewHeroes);

        //calling the method to display the heroes
        getHeroes();
    }

    @Override
    protected void onResume() {
        super.onResume();

        handler.postDelayed( runnable = new Runnable() {
            public void run() {
                //do your function;
                getHeroes();
                handler.postDelayed(runnable, apiDelayed);
            }
        }, apiDelayed); // so basically after your getHeroes(), from next time it will be 5 sec repeated
    }
    @Override
    protected void onPause() {
        super.onPause();
        handler.removeCallbacks(runnable); //stop handler when activity not visible
    }

    private void getHeroes() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(Api.BASE_URL)
                .addConverterFactory(GsonConverterFactory.create()) //Here we are using the GsonConverterFactory to directly convert json data to object
                .build();

        Api api = retrofit.create(Api.class);

        Call<List<Hero>> call = api.getHeroes();

        call.enqueue(new Callback<List<Hero>>() {
            @Override
            public void onResponse(Call<List<Hero>> call, Response<List<Hero>> response) {
                List<Hero> heroList = response.body();

                //Creating an String array for the ListView
                String[] heroes = new String[heroList.size()];

                //looping through all the heroes and inserting the names inside the string array
                for (int i = 0; i < heroList.size(); i++) {
                    heroes[i] = heroList.get(i).getName();
                }


                //displaying the string array into listview
                listView.setAdapter(new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, heroes));

            }

            @Override
            public void onFailure(Call<List<Hero>> call, Throwable t) {
                Toast.makeText(getApplicationContext(), t.getMessage(), Toast.LENGTH_SHORT).show();
            }
        });
    }
}