Android应用程序组件Content Provider应用实例( 九 ) _uri

在应用程序的主界面中，我们使用一个来显示文章信息条目，这个的数据源由类来提供，而类又是通过类来获得中的文章信息的。在的函数，我们还通过应用程序上下文的接口来注册了一个对象来监控中的文章信息。一旦中的文章信息发生变化，就会通过类来实时更新中的文章信息。
下面是类的实现，它实现在src/shy/luo//.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;@Overridepublic 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");}@Overridepublic 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。
程序使用到的界面文件定义在res/目录下，其中，main.xml文件定义的界面，它的内容如下所示：