Retrieving MySQL data dynamically and plotting on android using retrofit and MPAndroidChart

问题

I am following to plot following this example. Things work if I have a static JSON and it will plot the data like shown in the website. However, I am retrieving data from MySQL and they are being updated every hour (I had look into this; create a button and potential to call the URL every hour), but I am not too sure if that's the efficient approach.
My question is if I have a MySQL table/data that is being every hour, how do I retrieve them and plot (retain old values as well as plot the new ones)? I have the following

Api Client with URL:

public class ApiClient {

    private static Retrofit retrofit = null;

private static OkHttpClient buildClient() {
    return new OkHttpClient
            .Builder()
            .addInterceptor(new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY))
            .build();
}

public static Retrofit getClient() {
    if (retrofit == null) {
        retrofit = new Retrofit.Builder()
                .client(buildClient())
                .addConverterFactory(GsonConverterFactory.create())

                /**
                 *
                 *  base url here for api
                 */

                .baseUrl("https://xxx")       //retrieve data from MySQL 
                .build();
    }
    return retrofit;
}
}

MainActivity:

public class BarchartRetrofit extends AppCompatActivity {
    
    
        public ApiInterface apiInterface;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        apiInterface = ApiClient.getClient().create(ApiInterface.class);

        /**
         *  api call to get some data from server
         *
         */
        getData();

    }


    private void getData() {
        Call<PiChart> piChartCall = apiInterface.init();
        piChartCall.enqueue(new Callback<PiChart>() {
            @Override
            public void onResponse(Call<PiChart> call, Response<PiChart> response) {
                Log.d("CHART_RESPONSE", "" + response.body().getBarMonths().toString());
                setData(response.body());
            }

            @Override
            public void onFailure(Call<PiChart> call, Throwable t) {

            }
        });
    }

   

     private void setData(PiChart piChart) {
    
            ArrayList<BarDataSet> dataSets = null;
    
            ArrayList<BarEntry> completed = new ArrayList<>();
    
            for (int i = 0; i < piChart.getBarCompleted().size(); i++) {
                BarEntry value = new BarEntry(piChart.getBarCompleted().get(i), i); // Jan
                completed.add(value);
            }
    
            BarDataSet completeData = new BarDataSet(completed, "Completed Issue");
            completeData.setColor(Color.rgb(0, 155, 0));
    
            ArrayList<BarEntry> pending = new ArrayList<>();
            for (int i = 0; i < piChart.getBarCompleted().size(); i++) {
                BarEntry value = new BarEntry(piChart.getBarPending().get(i), i); // Jan
                pending.add(value);
            }
    
            BarDataSet pendingdata = new BarDataSet(pending, "Pending Issue");
            pendingdata.setColor(Color.rgb(253, 129, 0));
    
            ArrayList<BarEntry> rejected = new ArrayList<>();
            for (int i = 0; i < piChart.getBarCompleted().size(); i++) {
                BarEntry value = new BarEntry(piChart.getBarRejected().get(i), i); // Jan
                rejected.add(value);
            }
    
    
            BarDataSet rejectedData = new BarDataSet(rejected, "Rejected Issue");
            pendingdata.setColor(Color.rgb(255, 0, 0));
    
            dataSets = new ArrayList<>();
            dataSets.add(completeData);
            dataSets.add(pendingdata);
            dataSets.add(rejectedData);
            
            ArrayList<String> xAxis = new ArrayList<>();
            for (String months : piChart.getBarMonths()) {
                Log.d("CHART_RESPONSE", "month: " + months.toString());
                xAxis.add(months);
            }
    
            com.github.mikephil.charting.charts.BarChart chart = (com.github.mikephil.charting.charts.BarChart) findViewById(R.id.barchart);
    
            
            BarData data = new BarData(xAxis, dataSets);
            
            chart.setData(data);
            chart.setDescription("Bar chart");
            chart.invalidate();
    
        }
    }

Create JSON POJO:

public class Example {

@SerializedName("success")
@Expose
private boolean success;
@SerializedName("bar_months")
@Expose
private List<String> barMonths = null;
@SerializedName("bar_pending")
@Expose
private List<Integer> barPending = null;
@SerializedName("bar_rejected")
@Expose
private List<Integer> barRejected = null;
@SerializedName("bar_completed")
@Expose
private List<Integer> barCompleted = null;

public boolean isSuccess() {
return success;
}

public void setSuccess(boolean success) {
this.success = success;
}

public List<String> getBarMonths() {
return barMonths;
}

public void setBarMonths(List<String> barMonths) {
this.barMonths = barMonths;
}

public List<Integer> getBarPending() {
return barPending;
}

public void setBarPending(List<Integer> barPending) {
this.barPending = barPending;
}

public List<Integer> getBarRejected() {
return barRejected;
}

public void setBarRejected(List<Integer> barRejected) {
this.barRejected = barRejected;
}

public List<Integer> getBarCompleted() {
return barCompleted;
}

public void setBarCompleted(List<Integer> barCompleted) {
this.barCompleted = barCompleted;
}

}

The JSON is:

{
 
  "success": true,
  
  
  "bar_months":[
  "jan",
  "feb",
  "mar"
],
  
  "bar_pending":[
    100,
    200,
    300
  ],
  
   "bar_rejected":[
    140,
    220,
    340
  ],
  
  
   "bar_completed":[
    170,
    290,
    310
  ]
  
}

So basically, my data in bar_months,bar_pending, bar_rejected and bar_completed will changed instead of a static value, wondering what suggestions/ examples that I can try to retrain the dynamic data every hour. Thanks in advance for reading and helping!

回答1:

In order to schedule your getData() task as recurring (even when your app is not in the foreground) you can use a workmanager. In this specific case, you'll need a PeriodicWorkRequestBuilder (link). The first step is defining the work you want to run periodically, extend the Worker class to do so:

class ExampleWorker(
    appContext: Context,
    workerParams: WorkerParameters
) :
    Worker(appContext, workerParams) {
    override fun doWork(): Result {
        getData()
        // Indicate whether the work finished successfully with the Result
        return Result.success()
    }

    private fun getData() {
        val piChartCall: Call<PiChart> = apiInterface.init()
        piChartCall.enqueue(object : Callback<PiChart?>() {
            fun onResponse(call: Call<PiChart?>?, response: Response<PiChart?>) {
                Log.d("CHART_RESPONSE", "" + response.body().getBarMonths().toString())
                setData(response.body())
            }

            fun onFailure(call: Call<PiChart?>?, t: Throwable?) {}
        })
    }
}

The second step will be to schedule this work in a recurring way, PeriodicWorkRequestBuilder function can help you:

private fun schedulePeriodicWork(context: Context) {
    val request =
        PeriodicWorkRequestBuilder<ExampleWorker>(1, TimeUnit.HOURS).build()
    WorkManager.getInstance(context).enqueueUniquePeriodicWork(
        "charSync",
        ExistingPeriodicWorkPolicy.REPLACE, request
    )
}

Probably it would be a wise choice to put the scheduling function call in the onCreate() method of your Application class

来源：https://stackoverflow.com/questions/65912445/retrieving-mysql-data-dynamically-and-plotting-on-android-using-retrofit-and-mpa