CODEWITHSUNDEEP
android-studioandroid-asynctaskdownload
Ehsan Abbsai
Ehsan Abbsai

Reputation: 41

Download web content with Asynctask

I created this code for downloading web content and I used Asynctask, but DownloadTask class doesn't return results. However, when I get a log in this class it shows the content of website. So the DownloadTask class downloads the content but doesn't return it!

This is my code:

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutionException;

public class MainActivity extends AppCompatActivity {
    public class DownloadTask extends AsyncTask<String, Void, String> {

        @Override
protected String doInBackground(String... urls) {
            String result = "";
URL url;
HttpURLConnection urlConnection = null;

            try {
                url = new URL(urls[0]);
urlConnection = (HttpURLConnection)url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
                int data = reader.read();

                while (data != -1) {
                    char current = (char) data;
result += current;
data = reader.read();
}
                return result;
}
            catch (Exception e) {
                e.printStackTrace();
}
            return result;    

}
    }

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


DownloadTask task = new DownloadTask();
String result = null;
        try {
            result = task.execute("http://www.stackoverflow.com").get();
} catch (InterruptedException e) {
            e.printStackTrace();
} catch (ExecutionException e) {
            e.printStackTrace();
}

        Log.i("Log", "Result ...>>>>>>>" + result);
}
}

Upvotes: 1

Views: 3653

Answers (4)

Jani
Jani

Reputation: 21

//This alternative worked for me.Try the Following code

BufferedReader br = new BufferedReader(reader);
String inputLine;

while ((inputLine = br.readLine()) != null)
result += inputLine;
in.close();

//Instead of

int data = reader.read();
while (data != -1) {
char current = (char) data;
result += current;
data = reader.read();}

Upvotes: 2

Yagami
Yagami

Reputation: 11

Your code is correct but you have to add permission to connect internet 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.waleed.downloadtask">
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Upvotes: 1

Pie
Pie

Reputation: 594

First make sure that device is connected to internet.If not then logs will show error Unknown Host Exception Since your device is not connected to internet.And it cannot download content from internet.Your device should be connected to internet. Then try the following code `

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutionException;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


           DownloadTask task = new DownloadTask();
            String result = null;
            try {
                //sending utl to class method doInBackground()
                result = task.execute("http://www.ecowebhosting.co.uk").get();
            }
            catch(Exception e)
            {
                e.printStackTrace();
            }
            Log.i("Result",result);

        }

        //type of vatiable which we will send to class
        public class DownloadTask extends AsyncTask<String, Void, String> {
            @Override
            protected String doInBackground(String... urls) {
                String result="";
                URL url;
                HttpURLConnection urlConnection = null;
                try
                {
                    url=new URL(urls[0]);
                    urlConnection=(HttpURLConnection) url.openConnection();
                    InputStream in = urlConnection.getInputStream();
                    InputStreamReader reader  = new InputStreamReader(in);
                    int data = reader.read();
                    while(data!=-1)
                    {
                        char current=(char) data;
                        result+=current;
                        data=reader.read();
                    }
                    return result;
                }
                catch(Exception e)
                {
                    e.printStackTrace();
                    return "Failed";
                }
            }
        }
    }
    `

enter image description here

Upvotes: 0

Luck
Luck

Reputation: 13

did you add permission in Manifests to access the Internet? 

while (data != -1) {
char current = (char) data;
result += current;
data = reader.read();
}
            return result;
}
        catch (Exception e) {
            e.printStackTrace();
}
        return Null;       // This one should return null or something else if you 
didnt get a proper  url 

}
}

Upvotes: 0

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