Is it possible to show a chart by using MpAndroid from web server api?

Question

I am newbie android developer and i have a list of different currency items and I should open a new screen with chart of clicked item.

when user clicks on a list item a new screen should be opened which shows the exchange rate chart of the selected currency for the last 7 days based on USD. I should request every time the currency data gets updated for the last 7 days.

Example request for getting currency history in a given period between USD and CAD:

https://api.exchangeratesapi.io/history?start_at=2019-11-27&end_at=2019-12-03&base=USD&symbols=CAD

Here is My code:

MainActivity

 public class MainActivity extends AppCompatActivity {
        private ProgressBar progressBar;


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

            progressBar = findViewById(R.id.progress_bar);
            new GetServerData(this).execute();

        }

        private static class GetServerData extends AsyncTask<Integer, Void, List<CurrencyRate>> {
            private static final int TIMEOUT = 30000;
            private static final String BASE_URL = "https://api.exchangeratesapi.io/latest?base=USD";
            private WeakReference<MainActivity> activityReference;

            GetServerData(MainActivity context) {
                activityReference = new WeakReference<>(context);
            }

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                MainActivity activity = activityReference.get();
                if (activity == null || activity.isFinishing()) {
                    return;
                }
                activity.progressBar.setVisibility(View.VISIBLE);
            }

            @Override
            protected List<CurrencyRate> doInBackground(Integer... integers) {
                List<CurrencyRate> currencyList = new ArrayList<>();
                OkHttpClient client = new OkHttpClient().newBuilder()
                        .readTimeout(TIMEOUT, TimeUnit.SECONDS)
                        .connectTimeout(TIMEOUT, TimeUnit.SECONDS)
                        .writeTimeout(TIMEOUT, TimeUnit.SECONDS)
                        .retryOnConnectionFailure(true)
                        .build();
                Request request = new Request.Builder()
                        .url(BASE_URL)
                        .build();
                try {
                    Response response = client.newCall(request).execute();
                    Log.d("Response", response.toString());
                    long tx = response.sentRequestAtMillis();
                    long rx = response.receivedResponseAtMillis();
                    System.out.println("response time : " + (rx - tx) + " ms");
                    JSONObject object = new JSONObject(Objects.requireNonNull(response.body()).string());
                    JSONObject rates = object.getJSONObject("rates");
                    Iterator<String> iterator = rates.keys();
                    while (iterator.hasNext()) {
                        String key = iterator.next();
                        String value = rates.getString(key);
                        CurrencyRate data = new CurrencyRate(key, value);
                        currencyList.add(data);
                    }
                } catch (IOException | JSONException e) {
                    e.printStackTrace();
                    Log.d("MainActivity", e.toString());
                }
                return currencyList;
            }

            @Override
            protected void onPostExecute(final List<CurrencyRate> result) {
                final MainActivity activity = activityReference.get();
                if (activity == null || activity.isFinishing()) {
                    return;
                }
                ListView listView = activity.findViewById(R.id.list_view);
                CurrencyAdapter adapter = new CurrencyAdapter(activity, result);
                listView.setAdapter(adapter);
                listView.smoothScrollToPosition(0);
                adapter.notifyDataSetChanged();
                activity.progressBar.setVisibility(View.GONE);
                listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                        Toast.makeText(activity.getApplicationContext(), result.get(i).getName()+" Clicked", Toast.LENGTH_SHORT).show();
                        /*Which code should be here to open a new screen with exchange chart for last 7 days of clicked item??*/
                    }
                });
            }
        }

    }

CurrencyRate class

public class CurrencyRate {
    private String name;
    private String value;

    public CurrencyRate(String name, String value) {
        super();
        this.name = name;
        this.value = value;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }

}

My emulator screen

so as you see the items,i want to show chart of clicked item (chart of currency in a given period 7 days between USD and Clicked item)

Answer 1

I think that i should format the value by using XAxis like that xAxis.setValueFormatter(here i should use a class);

Elaborating on my answer to your other question and not knowing MPAndoirdChart, it would seem to me from the documentation that you need to make your own subclass of ValueFormatter and override getFormattedValue(float) to return something like LocalDate.ofEpochDay(Math.round(value)).toString(). Instead of toString you may want to use a DateTimeFormatter.

Here’s a quick attempt, not tested:

public class DateValueFormatter extends ValueFormatter {

    @Override
    String getFormattedValue(float value) {
        int epochDay = Math.round(value);
        LocalDate date = LocalDate.ofEpochDay(epochDay);
        return date.toString();
    }

}

My humble and tentative suggestion is that you instantiate an object of this class and pass it to xAxis.setValueFormatter().

Links

• My answer to your question java.lang.NumberFormatException: For input string: “2019-11-27”
• Documentation of com.github.mikephil.charting.formatter.ValueFormatter
• Documentation of DateTimeFormatter