Retrieving Data from External Site using Asynctask

Question

I'm new to Asynctask and JSon.

May i know how to start to retrieve the currency rates from this site?

http://api.fixer.io/latest?base=SGD

I did look at this post but i'm not too sure how to start..

From the rates retrieved, i'd like to add the values into this ListView, by using a custom ListView adapter class.

Codes for xml file

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0.0dp"
    android:orientation="horizontal"
    android:layout_weight="0.4"
    android:weightSum="1" >

    <LinearLayout
        android:layout_width="0.0dp"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_weight="0.8" >

        <TextView
            android:id="@+id/convertedAmtTV"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="0.00"
            android:textSize="70dp"
            android:gravity="right" />

        <EditText
            android:id="@+id/inputAmtET"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="0"
            android:textAlignment="textEnd" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="0.0dp"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_weight="0.2">

        <TextView
            android:id="@+id/convertedCurrTV"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="SGD"
            android:textSize="28dp"
            android:paddingLeft="2dp"
            android:paddingTop="29dp"
            android:paddingBottom="19dp"
            android:gravity="center_horizontal" />

        <TextView
            android:id="@+id/inputCurrTV"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="AUD"
            android:textSize="28dp"
            android:paddingLeft="2dp"
            android:layout_marginTop="3dp"
            android:gravity="center_horizontal" />

    </LinearLayout>

</LinearLayout>

<LinearLayout
    android:orientation="vertical"
    android:layout_weight="0.6"
    android:layout_width="match_parent"
    android:layout_height="0.0dp">

    <TextView
        android:text="From"
        android:textSize="21dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <ListView
        android:id="@+id/currencyLV"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

Codes for MainActivity.class

public class MainActivity extends AppCompatActivity {

CurrencyRatesDetails crd = new CurrencyRatesDetails();

CurrencyRates cr = new CurrencyRates();

TextView inputCurrTV, convertedAmtTV;
ListView currencyLV;
EditText inputAmtET;
ArrayAdapter<String> adapter;
String[] currNameArr = crd.getNames();
String[] currCodeArr = crd.getCodes();
String[] currRateArr = crd.getRates();

String[] dbName;
String[] dbCode;
String[] dbRate;

Context context;

int index = 0;

//String[] rateCurrArr = {"AUD", "BGN", "BRL", "CAD", "CHF", "CNY"};
//double[] rateArr = {0.944, 1.2824, 2.2842, 0.96158, 0.70946, 4.8624}
Menu myMenu = null;

double amtInput, finalConversion;

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


    context = this;
    //context.deleteDatabase("currency.db");

    inputAmtET = (EditText) findViewById(R.id.inputAmtET);
    convertedAmtTV = (TextView) findViewById(R.id.convertedAmtTV);
    inputCurrTV = (TextView) findViewById(R.id.inputCurrTV);
    currencyLV = (ListView) findViewById(R.id.currencyLV);

    /*for (int i = 0; i < currNameArr.length; i++) {
        cr.addToDataBase(currNameArr[i], currCodeArr[i], currRateArr[i], getApplicationContext());
    }*/

    //cr.addToDataBase(currNameArr, getApplicationContext());

    //Resources myRes = this.getResources();
    //currArr =  myRes.getStringArray(R.array.currencyList);
    //adapter = ArrayAdapter.createFromResource(this, R.array.currencyList, android.R.layout.simple_selectable_list_item);
    //adapter = new ArrayAdapter<String>(this, android.R.layout.simple_selectable_list_item, currNameArr);
    //currencyLV.setAdapter(adapter);

    dbName = cr.retrieveAllName(getApplicationContext());
    dbCode = cr.retrieveAllCode(getApplicationContext());
    dbRate = cr.retrieveAllRate(getApplicationContext());

    currencyLV.setAdapter(new CustomAdapter(this, dbName, dbCode, dbRate));

    currencyLV.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

            inputCurrTV.setText(dbCode[i]);

            index = i;

            //Getting rate based on selected currency code
            //rate = rateArr[i];

        }
    });
}

public boolean onCreateOptionsMenu(Menu menu) {
    super.onCreateOptionsMenu(menu);
    this.myMenu = menu;
    addMenuItems(menu);

    getMenuInflater().inflate(R.menu.mainmenu, menu);
    return true;
}

private void addMenuItems(Menu menu) {
    int index = 200;
    menu.add(index, index, index, "Settings");
    menu.add(index, index + 1, index + 1, "Add Custom Rate");
    menu.add(index, index + 2, index + 2, "Load Default Rates");
}

public boolean onOptionsItemSelected(MenuItem item) {

    //getOrder() to get Menu Item at this specific orderId
    if (item.getItemId() == R.id.menu_convert) {

        amtInput = Double.parseDouble(inputAmtET.getText().toString());

        //finalConversion = amtInput / rate;

        finalConversion = crd.conversion(amtInput, index);

        //Formatting converted value to 2d.p
        String finalValue = String.format("%.2f", finalConversion);

        convertedAmtTV.setText(finalValue);

    } else if (item.getItemId() == 201) {

        Intent myIntent = new Intent(MainActivity.this, CustomXchangeRate.class);
        startActivity(myIntent);

    }

    return true;
}

}

Custom ListView Adapter Class

public class CustomAdapter extends BaseAdapter{

String[] resultNames;
String[] resultCodes;
String[] resultRates;

Context context;

private static LayoutInflater inflater = null;

public CustomAdapter(CustomXchangeRate customXchangeRate, String[] names, String[] codes, String[] rates) {
    resultNames = names;
    resultCodes = codes;
    resultRates = rates;

    context = customXchangeRate;

    inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

public CustomAdapter(MainActivity mainActivity, String[] names, String[] codes, String[] rates) {
    resultNames = names;
    resultCodes = codes;
    resultRates = rates;

    context = mainActivity;

    inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}

@Override
public int getCount() {
    return resultNames.length;
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    return position;
}

public class ViewHolder{
    TextView tvName;
    TextView tvCode;
    TextView tvRate;
}

@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    ViewHolder vh = new ViewHolder();
    View rowView;

    rowView = inflater.inflate(R.layout.activity_custom_adapter, null);

    vh.tvName = (TextView) rowView.findViewById(R.id.currencyNameTV);
    vh.tvCode = (TextView) rowView.findViewById(R.id.currencyCodeTV);
    vh.tvRate = (TextView) rowView.findViewById(R.id.currencyRateTV);

    vh.tvName.setText(resultNames[position]);
    vh.tvCode.setText(resultCodes[position]);
    vh.tvRate.setText(resultRates[position]);

    return rowView;

}
}

Would appreciate any help...

Where is the `async task` you have written so far? Have you tried it? — mallaudin, Dec 15 '16 at 15:11
@mallaudin i haven't tried it yet... looking for a starting here.. i did look at certain blogs and websites but i don't get how to apply. — domster, Dec 15 '16 at 15:34
https://developer.android.com/reference/android/os/AsyncTask.html I hope this can help you. — mallaudin, Dec 15 '16 at 15:42
i did look at this but how do i apply it? and how can i get just the rates from http://api.fixer.io/latest?base=SGD with Asynctask — domster, Dec 15 '16 at 16:07
Ok use `HttpUrlConnection` for connection to network and fetching response. Later you can use json parsor e.g. `Gson` to decode the response. Example https://developer.android.com/training/basics/network-ops/connecting.html — mallaudin, Dec 15 '16 at 17:00

score 0 · Answer 1 · answered Dec 15 '16 at 15:07

0

The best way to get this JSON inside ur app will be to use Volley :

https://developer.android.com/training/volley/simple.html

Check this link you will find what ur asking for.

Cheers

answered Dec 15 '16 at 15:07

JossVAMOS

300
1
5
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my tertiary makes it obligatory that we use Asynctask, but it hasn't been taught.. appreciate it though cheers – domster Dec 15 '16 at 15:35
Oh ok sorry buddy, be carreful asynctaks seems to have memory leaks – JossVAMOS Dec 15 '16 at 15:45

Retrieving Data from External Site using Asynctask

1 Answers1