raghav-coder
4/12/2018 - 10:07 AM

Fetching Data From Internet

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.example.android.datafrominternet;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.TextView;

import com.example.android.datafrominternet.utilities.NetworkUtils;

import java.io.IOException;
import java.net.URL;

public class MainActivity extends AppCompatActivity {

    private EditText mSearchBoxEditText;

    private TextView mUrlDisplayTextView;

    private TextView mSearchResultsTextView;

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

        mSearchBoxEditText = (EditText) findViewById(R.id.et_search_box);

        mUrlDisplayTextView = (TextView) findViewById(R.id.tv_url_display);
        mSearchResultsTextView = (TextView) findViewById(R.id.tv_github_search_results_json);
    }

    /**
     * This method retrieves the search text from the EditText, constructs
     * the URL (using {@link NetworkUtils}) for the github repository you'd like to find, displays
     * that URL in a TextView, and finally fires off an AsyncTask to perform the GET request using
     * our (not yet created) {@link GithubQueryTask}
     */
    // @@3
    private void makeGithubSearchQuery() {
        // Form a URL
        String githubQuery = mSearchBoxEditText.getText().toString();
        URL githubSearchUrl = NetworkUtils.buildUrl(githubQuery);
        mUrlDisplayTextView.setText(githubSearchUrl.toString());
        
        String githubSearchResults = null;
        try {
            // Try Fetching data 
            githubSearchResults = NetworkUtils.getResponseFromHttpUrl(githubSearchUrl);
            
            // Set the fetched data
            mSearchResultsTextView.setText(githubSearchResults);
        } catch (IOException e) {
            // Handle Error Situation
            e.printStackTrace();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int itemThatWasClickedId = item.getItemId();
        if (itemThatWasClickedId == R.id.action_search) {
            makeGithubSearchQuery();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}
/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.example.android.datafrominternet.utilities;

import android.net.Uri;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Scanner;

/**
 * These utilities will be used to communicate with the network.
 */
public class NetworkUtils {

    final static String GITHUB_BASE_URL =
            "https://api.github.com/search/repositories";

    final static String PARAM_QUERY = "q";

    /*
     * The sort field. One of stars, forks, or updated.
     * Default: results are sorted by best match if no field is specified.
     */
    final static String PARAM_SORT = "sort";
    final static String sortBy = "stars";

    /**
     * Builds the URL used to query GitHub.
     *
     * @param githubSearchQuery The keyword that will be queried for.
     * @return The URL to use to query the GitHub.
     */
    public static URL buildUrl(String githubSearchQuery) {
        Uri builtUri = Uri.parse(GITHUB_BASE_URL).buildUpon()
                .appendQueryParameter(PARAM_QUERY, githubSearchQuery)
                .appendQueryParameter(PARAM_SORT, sortBy)
                .build();

        URL url = null;
        try {
            url = new URL(builtUri.toString());
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        return url;
    }

    /**
     * This method returns the entire result from the HTTP response.
     *
     * @param url The URL to fetch the HTTP response from.
     * @return The contents of the HTTP response.
     * @throws IOException Related to network and stream reading
     */
    // @@2
    public static String getResponseFromHttpUrl(URL url) throws IOException {
        HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
        try {
            InputStream in = urlConnection.getInputStream();

            Scanner scanner = new Scanner(in);
            scanner.useDelimiter("\\A");

            boolean hasInput = scanner.hasNext();
            if (hasInput) {
                return scanner.next();
            } else {
                return null;
            }
        } finally {
            urlConnection.disconnect();
        }
    }
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          package="com.example.android.datafrominternet">

    <!-- Add the INTERNET permission-->
    // @@1
    <uses-permission android:name="android.permission.INTERNET" />

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

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

</manifest>
## Steps to fetch Data and get Network on Main Thread Exception

1. Add INTERNET permission in Android Manifest 
2. Code the getResponseFromHttpUrl()
3. Use the getResponseFromHttpUrl()