Android Open Source - android-ocw Course List Activity

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License

The source code is released under:

GNU General Public License

Java Source Code

package app.ocw;
/*  ww w  . jav  a2 s  .  c  om*/
import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.message.BasicNameValuePair;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.widget.Toast;
import app.ocw.model.Course;
import app.ocw.task.SearchCoursesTask;

/**
 * Lists a collection of courses obtained through the search API.
 * Requires that a search string is passed in the calling intent.
 * 
 * @author Nick Ferraro
 *
 */
public class CourseListActivity extends Activity {
  public static final String EXTRA_SEARCH = "search";
  
  private DownloadSearchCoursesTask downloadSearchCoursesTask = new DownloadSearchCoursesTask();
  
  private String searchStr = null;
  private String searchUrl = null;
  private final List<Course> courses = new ArrayList<Course>();
  private ArrayAdapter<Course> coursesAdapter = null;
  private RelativeLayout loadingLayout = null;
  private RelativeLayout failedLayout = null;
  private ListView coursesListView = null;
  private Button retryButton = null;
  private TextView emptyText = null;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_course_list);
    
    // Get a reference to our views
    loadingLayout = (RelativeLayout)findViewById(R.id.loading_layout);
    failedLayout = (RelativeLayout)findViewById(R.id.failed_layout);
    retryButton = (Button)findViewById(R.id.retry_button);
    emptyText = (TextView)findViewById(R.id.empty_text);
    coursesListView = (ListView)findViewById(R.id.courses_list);
    coursesAdapter = new CourseAdapter(this, courses);
    coursesListView.setAdapter(coursesAdapter);
    
    // Get our search string and create our API search url
    searchStr = getIntent().getStringExtra(EXTRA_SEARCH);
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("q", searchStr));
    searchUrl = String.format("%1$s%2$s?%3$s", getString(R.string.url_base_url), getString(R.string.url_search_courses), URLEncodedUtils.format(params, "utf-8"));
    
    // Create a callback for the retry button click
    retryButton.setOnClickListener(new OnClickListener(){
      @Override
      public void onClick(View v) {
        startLoadingResults();
      }
    });
    
    // Create a callback for item selection on the courses list
    coursesListView.setOnItemClickListener(new OnItemClickListener() {
      @Override
      public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        showCourseDetails(courses.get(position));
      }
    });
    
    // Query the API for a list of courses using the search parameter
    startLoadingResults();
  }
  
  @Override
  public void onDestroy() {
    super.onDestroy();
    downloadSearchCoursesTask.cancel(true);
  }
  
  private void startLoadingResults() {
    // Hide the failed to load views and show the loading in progress views
    failedLayout.setVisibility(View.GONE);
    loadingLayout.setVisibility(View.VISIBLE);

    // Cancel, recreate, and start an async task for querying the API
    downloadSearchCoursesTask.cancel(true);
    downloadSearchCoursesTask = new DownloadSearchCoursesTask();
    downloadSearchCoursesTask.execute(searchUrl);
  }
  
  private void showCourseDetails(Course course) {
    // Launch the course details intent
    Intent courseDetailIntent = new Intent(this, CourseDetailActivity.class);
    courseDetailIntent.putExtra(CourseDetailActivity.EXTRA_COURSE, course);
    startActivity(courseDetailIntent);
  }
  
  /**
   * An async task for querying the API.
   * 
   * @author Nick Ferraro
   *
   */
  private class DownloadSearchCoursesTask extends SearchCoursesTask {
    @Override
    public void onPostExecute(List<Course> courses) {
      // Hide the loading in progress views
      loadingLayout.setVisibility(View.GONE);
      
      // If no courses were returned, an error occured, show the failed views and toast the screen
      if(courses == null) {
        failedLayout.setVisibility(View.VISIBLE);
        Toast.makeText(CourseListActivity.this, "Failed to retrieve course list", Toast.LENGTH_LONG).show();
      } else {
        // If we received courses, clear our current course list and add the new courses
        CourseListActivity.this.courses.clear();
        
        // If the course list is empty, show our empty message, otherwise update the list view
        if( courses.isEmpty() ) {
          emptyText.setVisibility(View.VISIBLE);
        } else {
          coursesListView.setVisibility(View.VISIBLE);
          CourseListActivity.this.courses.addAll(courses);
          coursesAdapter.notifyDataSetChanged();
        }
      }
    }
  }
}

Java Source Code List

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