我正在尝试显示在应用程序本身中创建的数据库活动的值。这些值最初是从 XML 文件中解析出来的，然后存储到数据库中。我已经进行了大量搜索并尝试了几种解决方案，但我似乎陷入了困境。如果有人可以帮助我，那就太好了！
Q，（I）一旦从 ListView 中选择了一个项目，这些值必须显示在 TextView 中。为此，我在 ListView Activity(ListRSSItemsActivity) 中设置了一个 onItemClickListener 和启动新活动的意图，并创建了相应的布局文件。我或多或少熟悉如何让 TextView 工作。但是，我不确定现在要在 New Activity(ArticleActivity) 文件中添加什么。(II) 当我点击该项目并打开新窗口时，它显示一个空白屏幕。
我已经附加了新的活动类和布局文件。
文章活动：
public class ArticleActivity extends Activity{
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.article_view);
String title, description;
title=this.getIntent().getStringExtra("TAG_TITLE");
description=this.getIntent().getStringExtra("TAG_DESCRIPTION");
}
}
article_view.xml：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<!-- Article Title -->
<TextView android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="10dp"
android:paddingBottom="8dp"
android:textSize="18sp"
android:textStyle="bold"
android:textColor="#dc6800"/>
<!-- Article Content -->
<TextView android:id="@+id/description"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:textColor="#acacac"
android:layout_below="@id/title"/>
</RelativeLayout>
ListRSSItems活动：
public class ListRSSItemsActivity extends ListActivity {
// Progress Dialog
private ProgressDialog pDialog;
// Array list for list view
ArrayList<HashMap<String, String>> rssItemList = new ArrayList<HashMap<String,String>>();
RSSParser rssParser = new RSSParser();
List<RSSItem> rssItems = new ArrayList<RSSItem>();
RSSFeed rssFeed;
public static String TAG_TITLE = "title";
private static String TAG_LINK = "link";
private static String TAG_DESCRIPTION = "description";
private static String TAG_PUBDATE = "pub_date";
private static String TAG_GUID = "guid"; // not used
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
// setContentView(R.layout.rss_item_list);
// get intent data
Intent i = getIntent();
// SQLite Row id
Integer site_id = Integer.parseInt(i.getStringExtra("id"));
// Getting Single website from SQLite
RSSDatabaseHandler rssDB = new RSSDatabaseHandler(getApplicationContext());
WebSite site = rssDB.getSite(site_id);
String rss_link = site.getRSSLink();
/**
* Calling a backgroung thread will loads recent articles of a website
* @param rss url of website
* */
new loadRSSFeedItems().execute(rss_link);
// selecting single ListView item
ListView lv = getListView();
// Launching new screen on Selecting Single ListItem
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting listview
View v = (View)view.getParent();
TextView tv = (TextView)v.findViewById(R.id.title);
String title = tv.getText().toString();
String description = ((TextView) view.findViewById(R.id.link)).getText().toString();
// Starting new intent
Intent ia = new Intent(getApplicationContext(), ArticleActivity.class);
ia.putExtra("TAG_TITLE", title);
ia.putExtra("TAG_DESCRIPTION", description);
startActivity(ia);
}
});
}
/**
* Background Async Task to get RSS Feed Items data from URL
* */
class loadRSSFeedItems extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(
ListRSSItemsActivity.this);
pDialog.setMessage("Loading recent articles...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting all recent articles and showing them in listview
* */
@Override
protected String doInBackground(String... args) {
// rss link url
String rss_url = args[0];
// list of rss items
// using GET method to obtain rssfeeditems. NOTICE: only from RSS_URL here!
rssItems = rssParser.getRSSFeedItems(rss_url);
// looping through each item
for(RSSItem item : rssItems){
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_TITLE, item.getTitle());
map.put(TAG_LINK, item.getLink());
map.put(TAG_PUBDATE, item.getPubDate());
String description = item.getDescription();
// taking only 200 chars from description
if(description.length() > 100){
description = description.substring(0, 97) + "..";
}
map.put(TAG_DESCRIPTION, description);
// adding HashList to ArrayList
rssItemList.add(map);
}
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed items into listview
* */
ListAdapter adapter = new SimpleAdapter(
ListRSSItemsActivity.this,
rssItemList, R.layout.rss_item_list_row,
new String[] { TAG_LINK, TAG_TITLE, TAG_PUBDATE, TAG_DESCRIPTION },
new int[] { R.id.page_url, R.id.title, R.id.pub_date, R.id.link });
// updating listview
setListAdapter(adapter);
}
});
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String args) {
// dismiss the dialog after getting all products
pDialog.dismiss();
}
}
}
数据库活动：
public class RSSDatabaseHandler extends SQLiteOpenHelper{
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "rssReader";
// Contacts table name
private static final String TABLE_RSS = "websites";
// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_LINK = "link";
private static final String KEY_RSS_LINK = "rss_link";
private static final String KEY_DESCRIPTION = "description";
private static final String KEY_PUBDATE = "pub_date";
public RSSDatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_RSS_TABLE = "CREATE TABLE " + TABLE_RSS + "(" + KEY_ID
+ " INTEGER PRIMARY KEY," + KEY_TITLE + " TEXT," + KEY_LINK
+ " TEXT," + KEY_RSS_LINK + " TEXT," + KEY_DESCRIPTION
+ " TEXT," + KEY_PUBDATE + " TEXT" + ")";
db.execSQL(CREATE_RSS_TABLE);
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_RSS);
// Create tables again
onCreate(db);
}
/**
* Adding a new website in websites table Function will check if a site
* already existed in database. If existed will update the old one else
* creates a new row
* */
public void addSite(WebSite site) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_TITLE, site.getTitle()); // site title
values.put(KEY_LINK, site.getLink()); // site url
values.put(KEY_RSS_LINK, site.getRSSLink()); // rss link url
values.put(KEY_DESCRIPTION, site.getDescription()); // site description
values.put(KEY_PUBDATE, site.getPubDate());
// Check if row already existed in database
if (!isSiteExists(db, site.getRSSLink())) {
// site not existed, create a new row
db.insert(TABLE_RSS, null, values);
db.close();
} else {
// site already existed update the row
updateSite(site);
db.close();
}
}
/**
* Reading all rows from database
* */
public List<WebSite> getAllSites() {
List<WebSite> siteList = new ArrayList<WebSite>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_RSS
+ " ORDER BY id DESC";
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
WebSite site = new WebSite();
site.setId(Integer.parseInt(cursor.getString(0)));
site.setTitle(cursor.getString(1));
site.setLink(cursor.getString(2));
site.setRSSLink(cursor.getString(3));
site.setDescription(cursor.getString(4));
site.setPubDate(cursor.getString(5));
// Adding contact to list
siteList.add(site);
} while (cursor.moveToNext());
}
cursor.close();
db.close();
// return contact list
return siteList;
}
/**
* Updating a single row row will be identified by rss link
* */
public int updateSite(WebSite site) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_TITLE, site.getTitle());
values.put(KEY_LINK, site.getLink());
values.put(KEY_RSS_LINK, site.getRSSLink());
values.put(KEY_DESCRIPTION, site.getDescription());
values.put(KEY_PUBDATE, site.getPubDate());
// updating row return
int update = db.update(TABLE_RSS, values, KEY_RSS_LINK + " = ?",
new String[] { String.valueOf(site.getRSSLink()) });
db.close();
return update;
}
/**
* Reading a row (website) row is identified by row id
* */
// Declaring
public WebSite getSite(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_RSS, new String[] { KEY_ID, KEY_TITLE,
KEY_LINK, KEY_RSS_LINK, KEY_DESCRIPTION, KEY_PUBDATE }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null, null);
if (cursor != null)
cursor.moveToFirst();
WebSite site = new WebSite(cursor.getString(1), cursor.getString(2),
cursor.getString(3), cursor.getString(4), cursor.getString(5));
site.setId(Integer.parseInt(cursor.getString(0)));
site.setTitle(cursor.getString(1));
site.setLink(cursor.getString(2));
site.setRSSLink(cursor.getString(3));
site.setDescription(cursor.getString(4));
site.setPubDate(cursor.getString(5));
cursor.close();
db.close();
return site;
}
/**
* Deleting single row
* */
public void deleteSite(WebSite site) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_RSS, KEY_ID + " = ?",
new String[] { String.valueOf(site.getId())});
db.close();
}
/**
* Checking whether a site is already existed check is done by matching rss
* link
* */
public boolean isSiteExists(SQLiteDatabase db, String rss_link) {
Cursor cursor = db.rawQuery("SELECT 1 FROM " + TABLE_RSS
+ " WHERE rss_link = '" + rss_link + "'", new String[] {});
boolean exists = (cursor.getCount() > 0);
return exists;
}
}