Example to start AsyncTask when button clicked

This exercise demonstrate how to start AsyncTask when button clicked. It will achieve the same function of "Get yweather:forecast from Yahoo! Weather RSS Feed using Thread with Runnable", but using AsyncTask when button clicked.

Example to start AsyncTask when button clicked


Modify layout to add a button to start AsyncTask loading.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />
<Button
android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Load yahoo Weather" />
<ScrollView
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:id="@+id/weather"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</ScrollView>

</LinearLayout>


Java code of MainActivity.java
package com.example.androidyahooweatherdom;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;
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.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

public class MyTask extends AsyncTask<Void, Void, Void> {

MyWeather weatherResult;

@Override
protected Void doInBackground(Void... arg0) {
String weatherString = QueryYahooWeather();
Document weatherDoc = convertStringToDocument(weatherString);
weatherResult = parseWeather(weatherDoc);
return null;
}

@Override
protected void onPostExecute(Void result) {
weather.setText(weatherResult.toString());
super.onPostExecute(result);
}
}

MyTask myTask;

Button buttonLoad;
TextView weather;

class MyWeather{
String description;
String city;
String region;
String country;

String windChill;
String windDirection;
String windSpeed;

String sunrise;
String sunset;

String conditiontext;
String conditiondate;

String numberOfForecast;
String forecast;

public String toString(){

return "\n- " + description + " -\n\n"
+ "city: " + city + "\n"
+ "region: " + region + "\n"
+ "country: " + country + "\n\n"

+ "Wind\n"
+ "chill: " + windChill + "\n"
+ "direction: " + windDirection + "\n"
+ "speed: " + windSpeed + "\n\n"

+ "Sunrise: " + sunrise + "\n"
+ "Sunset: " + sunset + "\n\n"

+ "Condition: " + conditiontext + "\n"
+ conditiondate +"\n"

+ "\n"
+ "number of forecast: " + numberOfForecast + "\n"
+ forecast;

}
}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
weather = (TextView)findViewById(R.id.weather);

buttonLoad = (Button)findViewById(R.id.start);
buttonLoad.setOnClickListener(new OnClickListener(){

@Override
public void onClick(View arg0) {
weather.setText("Loading...");
myTask = new MyTask();
myTask.execute();
}});

}

private MyWeather parseWeather(Document srcDoc){

MyWeather myWeather = new MyWeather();

//<description>Yahoo! Weather for New York, NY</description>
myWeather.description = srcDoc.getElementsByTagName("description")
.item(0)
.getTextContent();

//<yweather:location.../>
Node locationNode = srcDoc.getElementsByTagName("yweather:location").item(0);
myWeather.city = locationNode.getAttributes()
.getNamedItem("city")
.getNodeValue()
.toString();
myWeather.region = locationNode.getAttributes()
.getNamedItem("region")
.getNodeValue()
.toString();
myWeather.country = locationNode.getAttributes()
.getNamedItem("country")
.getNodeValue()
.toString();

//<yweather:wind.../>
Node windNode = srcDoc.getElementsByTagName("yweather:wind").item(0);
myWeather.windChill = windNode.getAttributes()
.getNamedItem("chill")
.getNodeValue()
.toString();
myWeather.windDirection = windNode.getAttributes()
.getNamedItem("direction")
.getNodeValue()
.toString();
myWeather.windSpeed = windNode.getAttributes()
.getNamedItem("speed")
.getNodeValue()
.toString();

//<yweather:astronomy.../>
Node astronomyNode = srcDoc.getElementsByTagName("yweather:astronomy").item(0);
myWeather.sunrise = astronomyNode.getAttributes()
.getNamedItem("sunrise")
.getNodeValue()
.toString();
myWeather.sunset = astronomyNode.getAttributes()
.getNamedItem("sunset")
.getNodeValue()
.toString();

//<yweather:condition.../>
Node conditionNode = srcDoc.getElementsByTagName("yweather:condition").item(0);
myWeather.conditiontext = conditionNode.getAttributes()
.getNamedItem("text")
.getNodeValue()
.toString();
myWeather.conditiondate = conditionNode.getAttributes()
.getNamedItem("date")
.getNodeValue()
.toString();

//Added to get elements of <yweather:forecast.../>
NodeList forecastList = srcDoc.getElementsByTagName("yweather:forecast");

myWeather.forecast = "";
if(forecastList.getLength() > 0){
myWeather.numberOfForecast = String.valueOf(forecastList.getLength());
for(int i = 0; i < forecastList.getLength(); i++){
Node forecastNode = forecastList.item(i);
myWeather.forecast +=
forecastNode
.getAttributes()
.getNamedItem("date")
.getNodeValue()
.toString() + " " +
forecastNode
.getAttributes()
.getNamedItem("text")
.getNodeValue()
.toString() +
" High: " + forecastNode
.getAttributes()
.getNamedItem("high")
.getNodeValue()
.toString() +
" Low: " + forecastNode
.getAttributes()
.getNamedItem("low")
.getNodeValue()
.toString() + "\n";
}
}else{
myWeather.numberOfForecast = "No forecast";
}

return myWeather;
}

private Document convertStringToDocument(String src){

Document dest = null;
DocumentBuilderFactory dbFactory =
DocumentBuilderFactory.newInstance();
DocumentBuilder parser;

try {
parser = dbFactory.newDocumentBuilder();
dest = parser.parse(new ByteArrayInputStream(src.getBytes()));
} catch (ParserConfigurationException e1) {
e1.printStackTrace();
Toast.makeText(MainActivity.this,
e1.toString(), Toast.LENGTH_LONG).show();
} catch (SAXException e) {
e.printStackTrace();
Toast.makeText(MainActivity.this,
e.toString(), Toast.LENGTH_LONG).show();
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(MainActivity.this,
e.toString(), Toast.LENGTH_LONG).show();
}

return dest;
}

private String QueryYahooWeather(){

String qResult = "";
String queryString = "http://weather.yahooapis.com/forecastrss?w=2459115";

HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(queryString);

try {
HttpEntity httpEntity = httpClient.execute(httpGet).getEntity();

if (httpEntity != null){
InputStream inputStream = httpEntity.getContent();
Reader in = new InputStreamReader(inputStream);
BufferedReader bufferedreader = new BufferedReader(in);
StringBuilder stringBuilder = new StringBuilder();

String stringReadLine = null;

while ((stringReadLine = bufferedreader.readLine()) != null) {
stringBuilder.append(stringReadLine + "\n");
}

qResult = stringBuilder.toString();
}
} catch (ClientProtocolException e) {
e.printStackTrace();
Toast.makeText(MainActivity.this,
e.toString(), Toast.LENGTH_LONG).show();
} catch (IOException e) {
e.printStackTrace();
Toast.makeText(MainActivity.this,
e.toString(), Toast.LENGTH_LONG).show();
}

return qResult;
}

}


Permission of "android.permission.INTERNET" is need.

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