Android应用程序组件Content Provider应用实例（3）

         下面是ArticlesAdapter类的实现，它实现在src/shy/luo/ArticlesAdapter.java文件中：

 
     
     package shy.luo.article;

 
     
     import java.util.LinkedList;

 
     
     import shy.luo.providers.articles.Articles;
 
     
     import android.content.ContentResolver;
 
     
     import android.content.ContentUris;
 
     
     import android.content.ContentValues;
 
     
     import android.content.Context;
 
     
     import android.content.IContentProvider;
 
     
     import android.database.Cursor;
 
     
     import android.net.Uri;
 
     
     import android.os.Bundle;
 
     
     import android.os.RemoteException;
 
     
     import android.util.Log;


 
     
     public class ArticlesAdapter {
 
     
             private static final String LOG_TAG = "shy.luo.article.ArticlesAdapter";

 
     
             private ContentResolver resolver = null;

 
     
             public ArticlesAdapter(Context context) {
 
     
                     resolver = context.getContentResolver();
 
     
             }

 
     
             public long insertArticle(Article article) {
 
     
                     ContentValues values = new ContentValues();
 
     
                     values.put(Articles.TITLE, article.getTitle());
 
     
                     values.put(Articles.ABSTRACT, article.getAbstract());
 
     
                     values.put(Articles.URL, article.getUrl());

 
     
                     Uri uri = resolver.insert(Articles.CONTENT_URI, values);
 
     
                     String itemId = uri.getPathSegments().get(1);

 
     
                     return Integer.valueOf(itemId).longValue();
 
     
             }

 
     
             public boolean updateArticle(Article article) {
 
     
                     Uri uri = ContentUris.withAppendedId(Articles.CONTENT_URI, article.getId());

 
     
                     ContentValues values = new ContentValues();
 
     
                     values.put(Articles.TITLE, article.getTitle());
 
     
                     values.put(Articles.ABSTRACT, article.getAbstract());
 
     
                     values.put(Articles.URL, article.getUrl());

 
     
                     int count = resolver.update(uri, values, null, null);

 
     
                     return count > 0;
 
     
             }

 
     
             public boolean removeArticle(int id) {
 
     
                     Uri uri = ContentUris.withAppendedId(Articles.CONTENT_URI, id);

 
     
                     int count = resolver.delete(uri, null, null);

 
     
                     return count > 0;
 
     
             }

 
     
             public LinkedList<Article> getAllArticles() {
 
     
                     LinkedList<Article> articles = new LinkedList<Article>();

 
     
                     String[] projection = new String[] {
 
     
                             Articles.ID,
 
     
                             Articles.TITLE,
 
     
                             Articles.ABSTRACT,
 
     
                             Articles.URL
 
     
                     };

 
     
                     Cursor cursor = resolver.query(Articles.CONTENT_URI, projection, null, null, Articles.DEFAULT_SORT_ORDER);
 
     
                     if (cursor.moveToFirst()) {
 
     
                             do {
 
     
                                     int id = cursor.getInt(0);
 
     
                                     String title = cursor.getString(1);
 
     
                                     String abs = cursor.getString(2);
 
     
                                     String url = cursor.getString(3);

 
     
                                     Article article = new Article(id, title, abs, url);
 
     
                                     articles.add(article);
 
     
                             } while(cursor.moveToNext());
 
     
                     }

 
     
                     return articles;
 
     
             }

 
     
             public int getArticleCount() {
 
     
                     int count = 0;

 
     
                     try {
 
     
                             IContentProvider provider = resolver.acquireProvider(Articles.CONTENT_URI);
 
     
                             Bundle bundle = provider.call(Articles.METHOD_GET_ITEM_COUNT, null, null);
 
     
                             count = bundle.getInt(Articles.KEY_ITEM_COUNT, 0);
 
     
                     } catch(RemoteException e) {
 
     
                             e.printStackTrace();
 
     
                     }

 
     
                     return count;
 
     
             }

 
     
             public Article getArticleById(int id) {
 
     
                     Uri uri = ContentUris.withAppendedId(Articles.CONTENT_URI, id);

 
     
                     String[] projection = new String[] {
 
     
                                     Articles.ID,
 
     
                         Articles.TITLE,
 
     
                         Articles.ABSTRACT,
 
     
                         Articles.URL
 
     
                     };

 
     
                     Cursor cursor = resolver.query(uri, projection, null, null, Articles.DEFAULT_SORT_ORDER);

 
     
                     Log.i(LOG_TAG, "cursor.moveToFirst");

 
     
                     if (!cursor.moveToFirst()) {
 
     
                             return null;
 
     
                     }

 
     
                     String title = cursor.getString(1);
 
     
                     String abs = cursor.getString(2);
 
     
                     String url = cursor.getString(3);

 
     
                     return new Article(id, title, abs, url);
 
     
             }

 
     
             public Article getArticleByPos(int pos) {
 
     
                     Uri uri = ContentUris.withAppendedId(Articles.CONTENT_POS_URI, pos);

 
     
                     String[] projection = new String[] {
 
     
                                     Articles.ID,
 
     
                         Articles.TITLE,
 
     
                         Articles.ABSTRACT,
 
     
                         Articles.URL
 
     
                     };

 
     
                     Cursor cursor = resolver.query(uri, projection, null, null, Articles.DEFAULT_SORT_ORDER);
 
     
                     if (!cursor.moveToFirst()) {
 
     
                             return null;
 
     
                     }

 
     
                     int id = cursor.getInt(0);
 
     
                     String title = cursor.getString(1);
 
     
                     String abs = cursor.getString(2);
 
     
                     String url = cursor.getString(3);

 
     
                     return new Article(id, title, abs, url);
 
     
             }
 
     
     }

         这个类首先在构造函数里面获得应用程序上下文的ContentResolver接口，然后通过就可以通过这个接口来访问ArticlesProvider中的文章信息了。成员函数insertArticle、updateArticle和removeArticle分别用来新增、更新和删除一个文章信息条目；成员函数getAllArticlese用来获取所有的文章信息；成员函数getArticleById和getArticleByPos分别根据文章的ID和位置来获得具体文章信息条目；成员函数getArticleCount直接使用ContentProvider的未公开接口call来获得文章信息条目的数量，注意，这个函数要源代码环境下编译才能通过。

 

        下面是程序主界面MainActivity类的实现，它实现在src/shy/luo/article/MainActivity.java文件中：

 
     
     package shy.luo.article;

 
     
     import shy.luo.providers.articles.Articles;
 
     
     import android.app.Activity;
 
     
     import android.content.Context;
 
     
     import android.content.Intent;
 
     
     import android.database.ContentObserver;
 
     
     import android.os.Bundle;
 
     
     import android.os.Handler;
 
     
     import android.util.Log;
 
     
     import android.view.LayoutInflater;
 
     
     import android.view.View;
 
     
     import android.view.ViewGroup;
 
     
     import android.widget.AdapterView;
 
     
     import android.widget.BaseAdapter;
 
     
     import android.widget.Button;
 
     
     import android.widget.ListView;
 
     
     import android.widget.TextView;

 
     
     public class MainActivity extends Activity implements View.OnClickListener, AdapterView.OnItemClickListener {
 
     
             private final static String LOG_TAG = "shy.luo.article.MainActivity";

 
     
             private final static int ADD_ARTICAL_ACTIVITY = 1;
 
     
             private final static int EDIT_ARTICAL_ACTIVITY = 2;

 
     
             private ArticlesAdapter aa = null;
 
     
             private ArticleAdapter adapter = null;
 
     
             private ArticleObserver observer = null;

 
     
             private ListView articleList = null;
 
     
             private Button addButton = null;

 
     
             @Override
 
     
             public void onCreate(Bundle savedInstanceState) {
 
     
                     super.onCreate(savedInstanceState);
 
     
                     setContentView(R.layout.main);

 
     
                     aa = new ArticlesAdapter(this);

 
     
                     articleList = (ListView)findViewById(R.id.listview_article);
 
     
                     adapter = new ArticleAdapter(this);
 
     
                     articleList.setAdapter(adapter);
 
     
                     articleList.setOnItemClickListener(this);

 
     
                     observer = new ArticleObserver(new Handler());
 
     
                     getContentResolver().registerContentObserver(Articles.CONTENT_URI, true, observer);

 
     
                     addButton = (Button)findViewById(R.id.button_add);
 
     
                     addButton.setOnClickListener(this);

 
     
                     Log.i(LOG_TAG, "MainActivity Created");
 
     
             }

 
     
             @Override
 
     
             public void onDestroy() {
 
     
                     super.onDestroy();
 
     
                     getContentResolver().unregisterContentObserver(observer);
 
     
             }

 
     
             @Override
 
     
             public void onClick(View v) {
 
     
                     if(v.equals(addButton)) {
 
     
                             Intent intent = new Intent(this, ArticleActivity.class);
 
     
                             startActivityForResult(intent, ADD_ARTICAL_ACTIVITY);
 
     
                     }
 
     
             }

 
     
             @Override
 
     
             public void onItemClick(AdapterView<?> parent, View view, int pos, long id) {
 
     
                     Intent intent = new Intent(this, ArticleActivity.class);

 
     
                     Article article = aa.getArticleByPos(pos);
 
     
                     intent.putExtra(Articles.ID, article.getId());
 
     
                     intent.putExtra(Articles.TITLE, article.getTitle());
 
     
                     intent.putExtra(Articles.ABSTRACT, article.getAbstract());
 
     
                     intent.putExtra(Articles.URL, article.getUrl());

 
     
                     startActivityForResult(intent, EDIT_ARTICAL_ACTIVITY);
 
     
             }

 
     
             @Override
 
     
             public void onActivityResult(int requestCode,int resultCode, Intent data) {
 
     
                     super.onActivityResult(requestCode, resultCode, data);

 
     
                     switch(requestCode) {
 
     
                     case ADD_ARTICAL_ACTIVITY: {
 
     
                             if(resultCode == Activity.RESULT_OK) {
 
     
                                     String title = data.getStringExtra(Articles.TITLE);
 
     
                                     String abs = data.getStringExtra(Articles.ABSTRACT);
 
     
                                     String url = data.getStringExtra(Articles.URL);

 
     
                                     Article article = new Article(-1, title, abs, url);
 
     
                                     aa.insertArticle(article);
 
     
                             }

 
     
                             break;
 
     
                     }

 
     
                     case EDIT_ARTICAL_ACTIVITY: {
 
     
                             if(resultCode == Activity.RESULT_OK) {
 
     
                                     int action = data.getIntExtra(ArticleActivity.EDIT_ARTICLE_ACTION, -1);
 
     
                                     if(action == ArticleActivity.MODIFY_ARTICLE) {
 
     
                                             int id = data.getIntExtra(Articles.ID, -1);
 
     
                                             String title = data.getStringExtra(Articles.TITLE);
 
     
                                             String abs = data.getStringExtra(Articles.ABSTRACT);
 
     
                                             String url = data.getStringExtra(Articles.URL);

 
     
                                             Article article = new Article(id, title, abs, url);
 
     
                                             aa.updateArticle(article);
 
     
                                     } else if(action == ArticleActivity.DELETE_ARTICLE)     {
 
     
                                             int id = data.getIntExtra(Articles.ID, -1);

 
     
                                             aa.removeArticle(id);
 
     
                                     }

 
     
                             }

 
     
                             break;
 
     
                     }
 
     
                     }
 
     
             }

 
     
             private class ArticleObserver extends ContentObserver {
 
     
                     public ArticleObserver(Handler handler) {
 
     
                             super(handler);
 
     
                     }

 
     
                     @Override
 
     
                     public void onChange (boolean selfChange) {
 
     
                             adapter.notifyDataSetChanged();
 
     
                     }
 
     
             }

 
     
             private class ArticleAdapter extends BaseAdapter {
 
     
                     private LayoutInflater inflater;

 
     
                     public ArticleAdapter(Context context){
 
     
                               inflater = LayoutInflater.from(context);
 
     
                     }

 
     
                     @Override
 
     
                     public int getCount() {
 
     
                             return aa.getArticleCount();
 
     
                     }

 
     
                     @Override
 
     
                     public Object getItem(int pos) {
 
     
                             return aa.getArticleByPos(pos);
 
     
                     }

 
     
                     @Override
 
     
                     public long getItemId(int pos) {
 
     
                             return aa.getArticleByPos(pos).getId();
 
     
                     }

 
     
                     @Override
 
     
                     public View getView(int position, View convertView, ViewGroup parent) {
 
     
                             Article article = (Article)getItem(position);

 
     
                             if (convertView == null) {
 
     
                                     convertView = inflater.inflate(R.layout.item, null);
 
     
                             }

 
     
                             TextView titleView = (TextView)convertView.findViewById(R.id.textview_article_title);
 
     
                             titleView.setText("Title: " + article.getTitle());

 
     
                             TextView abstractView = (TextView)convertView.findViewById(R.id.textview_article_abstract);
 
     
                             abstractView.setText("Abstract: " + article.getAbstract());

 
     
                             TextView urlView = (TextView)convertView.findViewById(R.id.textview_article_url);
 
     
                             urlView.setText("URL: " + article.getUrl());

 
     
                             return convertView;
 
     
                     }
 
     
             }
 
     
     }

      在应用程序的主界面中，我们使用一个ListView来显示文章信息条目，这个ListView的数据源由ArticleAdapter类来提供，而ArticleAdapter类又是通过ArticlesAdapter类来获得ArticlesProvider中的文章信息的。在MainActivity的onCreate函数，我们还通过应用程序上下文的ContentResolver接口来注册了一个ArticleObserver对象来监控ArticlesProvider中的文章信息。一旦ArticlesProvider中的文章信息发生变化，就会通过ArticleAdapter类来实时更新ListView中的文章信息。

 

        下面是ArticleActivity类的实现，它实现在src/shy/luo/article/ArticleActivity.java文件中：

 
     
     package shy.luo.article;

 
     
     import shy.luo.providers.articles.Articles;
 
     
     import android.app.Activity;
 
     
     import android.content.Intent;
 
     
     import android.os.Bundle;
 
     
     import android.util.Log;
 
     
     import android.view.View;
 
     
     import android.widget.Button;
 
     
     import android.widget.EditText;

 
     
     public class ArticleActivity extends Activity implements View.OnClickListener {
 
     
             private final static String LOG_TAG = "shy.luo.article.ArticleActivity";

 
     
             public final static String EDIT_ARTICLE_ACTION = "EDIT_ARTICLE_ACTION";
 
     
             public final static int MODIFY_ARTICLE = 1;
 
     
             public final static int DELETE_ARTICLE = 2;

 
     
             private int articleId = -1;

 
     
             private EditText titleEdit = null;
 
     
             private EditText abstractEdit = null;
 
     
             private EditText urlEdit = null;

 
     
             private Button addButton = null;
 
     
             private Button modifyButton = null;
 
     
             private Button deleteButton = null;
 
     
             private Button cancelButton = null;

 
     
             @Override
 
     
             public void onCreate(Bundle savedInstanceState) {
 
     
                     super.onCreate(savedInstanceState);
 
     
                     setContentView(R.layout.article);

 
     
                     titleEdit = (EditText)findViewById(R.id.edit_article_title);
 
     
                     abstractEdit = (EditText)findViewById(R.id.edit_article_abstract);
 
     
                     urlEdit = (EditText)findViewById(R.id.edit_article_url);

 
     
                     addButton = (Button)findViewById(R.id.button_add_article);
 
     
                     addButton.setOnClickListener(this);

 
     
                     modifyButton = (Button)findViewById(R.id.button_modify);
 
     
                     modifyButton.setOnClickListener(this);

 
     
                     deleteButton = (Button)findViewById(R.id.button_delete);
 
     
                     deleteButton.setOnClickListener(this);

 
     
                     cancelButton = (Button)findViewById(R.id.button_cancel);
 
     
                     cancelButton.setOnClickListener(this);

 
     
                     Intent intent = getIntent();
 
     
                     articleId = intent.getIntExtra(Articles.ID, -1);

 
     
                     if(articleId != -1) {
 
     
                             String title = intent.getStringExtra(Articles.TITLE);
 
     
                             titleEdit.setText(title);

 
     
                             String abs = intent.getStringExtra(Articles.ABSTRACT);
 
     
                             abstractEdit.setText(abs);

 
     
                             String url = intent.getStringExtra(Articles.URL);
 
     
                             urlEdit.setText(url);

 
     
                             addButton.setVisibility(View.GONE);
 
     
                     } else {

 
     
                             modifyButton.setVisibility(View.GONE);
 
     
                             deleteButton.setVisibility(View.GONE);
 
     
                     }

 
     
                     Log.i(LOG_TAG, "ArticleActivity Created");
 
     
             }

 
     
             @Override
 
     
             public void onClick(View v) {
 
     
                     if(v.equals(addButton)) {
 
     
                             String title = titleEdit.getText().toString();
 
     
                             String abs = abstractEdit.getText().toString();
 
     
                             String url = urlEdit.getText().toString();

 
     
                             Intent result = new Intent();
 
     
                             result.putExtra(Articles.TITLE, title);
 
     
                             result.putExtra(Articles.ABSTRACT, abs);
 
     
                             result.putExtra(Articles.URL, url);

 
     
                             setResult(Activity.RESULT_OK, result);
 
     
                             finish();
 
     
                     } else if(v.equals(modifyButton)){
 
     
                             String title = titleEdit.getText().toString();
 
     
                             String abs = abstractEdit.getText().toString();
 
     
                             String url = urlEdit.getText().toString();

 
     
                             Intent result = new Intent();
 
     
                             result.putExtra(Articles.ID, articleId);
 
     
                             result.putExtra(Articles.TITLE, title);
 
     
                             result.putExtra(Articles.ABSTRACT, abs);
 
     
                             result.putExtra(Articles.URL, url);
 
     
                             result.putExtra(EDIT_ARTICLE_ACTION, MODIFY_ARTICLE);

 
     
                             setResult(Activity.RESULT_OK, result);
 
     
                             finish();
 
     
                     } else if(v.equals(deleteButton)) {
 
     
                             Intent result = new Intent();
 
     
                             result.putExtra(Articles.ID, articleId);
 
     
                             result.putExtra(EDIT_ARTICLE_ACTION, DELETE_ARTICLE);

 
     
                             setResult(Activity.RESULT_OK, result);
 
     
                             finish();
 
     
                     } else if(v.equals(cancelButton)) {
 
     
                             setResult(Activity.RESULT_CANCELED, null);
 
     
                             finish();

 
     
                     }
 
     
             }
 
     
     }

         在ArticleActivity窗口中，我们可以执行新增、更新和删除文章信息的操作。如果启动ArticleActivity时，没有把文章ID传进来，就说明要执行操作是新增文章信息；如果启动ArticleActivity时，把文章ID和其它信自都传进来了，就说明要执行的操作是更新或者删除文章，根据用户在界面点击的是更新按钮还是删除按钮来确定。