In this tutorial you can learn How to build Currency Converter Application in Android. You can build a real time currency converter using YQL. RealTime Currency converter will give current exchange rates.

Step 1:- main.xml

Here we will make use of two Spinners and Define Layout of our Application.

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="@string/one"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Spinner
        android:id="@+id/spinner1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/in"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Spinner
        android:id="@+id/spinner2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/equal"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <RelativeLayout
        android:id="@+id/relativeLayout1"
        android:layout_width="match_parent"
        android:layout_height="122dp"
        android:gravity="center"
        android:background="#fff">

        <RelativeLayout
            android:id="@+id/relativeLayout2"
            android:layout_width="match_parent"
            android:layout_height="120dp"
            android:gravity="center"

            android:background="#0D0D0D">
        <TextView
            android:id="@+id/textView4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentTop="true"
            android:text="@string/result"
            android:textSize="35dp"
            />
        </RelativeLayout>

    </RelativeLayout>

    <Button
        android:id="@+id/button1"
        android:layout_marginTop="10dp"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/calculate" />
    <TextView
        android:id="@+id/tv1"
        android:layout_marginTop="10dp"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/powered"/>
</LinearLayout>
</ScrollView>

We make use of ScrollView to enable Scrolling.
Step 2:- Strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

        <string name="one">One</string>
        <string name="in">In</string>
        <string name="equal">Is Equal To</string>
        <string name="result">Click Calculate for Result</string>
        <string name="calculate">Calculate</string>
        <string name="powered">Powered By Yahoo! Finance</string>

    <string name="app_name">CurrencyConverter</string>
    <string-array name="name">
        <item >Indian Rupee</item>
        <item >US Dollar</item>
        <item >European Union Euro</item>
        <item >Canadian Dollar</item>
        <item >Australian Dollar</item>
        <item >Singapore Dollar</item>
    </string-array>
    <string-array name="value">
        <item >INR</item>
        <item >USD</item>
        <item >EUR</item>
        <item >CAD</item>
        <item >AUD</item>
        <item >SGD</item>
    </string-array>
</resources>

Here we have declared String Resources Required by our application. Here lets write Array and Other Strings Which are used by Main.xml.

Step3 :- Java Code.

package com.currency.org;
/*
 * Created by FirstAmong.com
 * License MIT
 */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

public class CurrencyConverterActivity extends Activity {
	public int to;
	public int from;
	public String [] val;
	public String s;
	public Handler handler;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Spinner s1 = (Spinner) findViewById(R.id.spinner1);
        Spinner s2 = (Spinner) findViewById(R.id.spinner2);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
                this, R.array.name, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
        val  = getResources().getStringArray(R.array.value);
        s1.setAdapter(adapter);
        s2.setAdapter(adapter);
        s1.setOnItemSelectedListener(new spinOne(1));
        s2.setOnItemSelectedListener(new spinOne(2));
        Button b = (Button) findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener(){
			public void onClick(View v) {
				TextView t = (TextView) findViewById(R.id.textView4);
				if(from == to)
				{
					Toast.makeText(getApplicationContext(), "Invalid", 4000).show();
				}
				else
				{
					  try {
						 s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
						JSONObject jObj;
						jObj = new JSONObject(s);
						String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
						t.setText(exResult);
						} catch (JSONException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
						catch (ClientProtocolException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						} catch (IOException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}	

        });
         TextView credit = (TextView) findViewById(R.id.tv1);
         credit.setOnClickListener(new OnClickListener(){

			@Override
			public void onClick(View v) {
				Intent i = new Intent(Intent.ACTION_VIEW);
				i.setData(Uri.parse("http://finance.yahoo.com"));
				startActivity(i);
			}

         });
    }
    public String getJson(String url)throws ClientProtocolException, IOException {

		StringBuilder build = new StringBuilder();
		HttpClient client = new DefaultHttpClient();
		HttpGet httpGet = new HttpGet(url);
	    HttpResponse response = client.execute(httpGet);
		HttpEntity entity = response.getEntity();
		InputStream content = entity.getContent();
		BufferedReader reader = new BufferedReader(new InputStreamReader(content));
		String con;
		while ((con = reader.readLine()) != null) {
					build.append(con);
				}
		return build.toString();
	}
    private class spinOne implements OnItemSelectedListener
    {
    	int ide;
    	spinOne(int i)
    	{
    		ide =i;
    	}
    	public void onItemSelected(AdapterView<?> parent, View view,
    			int index, long id) {
    		if(ide == 1)
    			from = index;
    		else if(ide == 2)
    			to = index;

    	}

    	public void onNothingSelected(AdapterView<?> arg0) {
    		// TODO Auto-generated method stub
    	}

    }
}

This is straight Forward. Here we parse JSON and Display results. Since we need to attribute Yahoo Finance for Data, I have added a ‘Powered By Yahoo’ link at the bottom of this Application. Thank You!!!

You Might Also Like

• Android Dynamic Autocomplete Using Wikipedia Suggest API
• Create Your Own Twitter Android Application Using PhoneGap
• Building Android Application Using HTML
• Online XML to JSON Converter
• Android 4.0 Ice Cream Sandwich is Out!
• Building QR Code Chrome Extension