Android应用程序组件Content Provider应用实例（3）-阿里云开发者社区

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。

本文转自 Luoshengyang 51CTO博客，原文链接：http://blog.51cto.com/shyluo/966942，如需转载请自行联系原作者

Android应用程序组件Content Provider应用实例（3）

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