Hello Android 之 Events 实例

 

1. EventsData 创建events.db数据库文件

public class EventsData extends SQLiteOpenHelper { private static final String DATABASE_NAME = "events.db"; private static final int DATABASE_VERSION = 1; /** Create a helper object for the Events database */ public EventsData(Context ctx) { super(ctx, DATABASE_NAME, null, DATABASE_VERSION); } //首次访问数据库时，Helper发现其不存在则调用onCreate创建数据库文件。 @Override public void onCreate(SQLiteDatabase db) { db.execSQL("CREATE TABLE " + TABLE_NAME + " (" + _ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + TIME + " INTEGER," + TITLE + " TEXT NOT NULL);"); } // 当Helper检测到实用的是旧版本的数据库文件时调用onUpgrade. @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); onCreate(db); } }   

2.  实现Provider (EventsProvider)

public class EventsProvider extends ContentProvider { private static final int EVENTS = 1; private static final int EVENTS_ID = 2; /** The MIME type of a directory of events */ private static final String CONTENT_TYPE = "vnd.android.cursor1.dir/vnd.example.event"; /** The MIME type of a single event */ private static final String CONTENT_ITEM_TYPE = "vnd.android.cursor1.item/vnd.example.event"; private static final String TAG = "EventsProvider"; private EventsData events; private UriMatcher uriMatcher; // ... @Override public boolean onCreate() { uriMatcher = new UriMatcher(UriMatcher.NO_MATCH); uriMatcher.addURI(AUTHORITY, "events", EVENTS); uriMatcher.addURI(AUTHORITY, "events/#", EVENTS_ID); events = new EventsData(getContext()); return true; } @Override public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String orderBy) { if (uriMatcher.match(uri) == EVENTS_ID) { long id = Long.parseLong(uri.getPathSegments().get(1)); selection = appendRowId(selection, id); } // Get the database and run the query SQLiteDatabase db = events.getReadableDatabase(); Cursor cursor = db.query(TABLE_NAME, projection, selection, selectionArgs, null, null, orderBy); // Tell the cursor what uri to watch, so it knows when its // source data changes cursor.setNotificationUri(getContext().getContentResolver(), uri); return cursor; } @Override public String getType(Uri uri) { Log.v(TAG, " getType: Uri = " + uri ); switch (uriMatcher.match(uri)) { case EVENTS: return CONTENT_TYPE; case EVENTS_ID: return CONTENT_ITEM_TYPE; default: throw new IllegalArgumentException("Unknown URI " + uri); } } @Override public Uri insert(Uri uri, ContentValues values) { SQLiteDatabase db = events.getWritableDatabase(); // Validate the requested uri if (uriMatcher.match(uri) != EVENTS) { throw new IllegalArgumentException("Unknown URI " + uri); } // Insert into database long id = db.insertOrThrow(TABLE_NAME, null, values); // Notify any watchers of the change Uri newUri = ContentUris.withAppendedId(CONTENT_URI, id); getContext().getContentResolver().notifyChange(newUri, null); return newUri; } @Override public int delete(Uri uri, String selection, String[] selectionArgs) { SQLiteDatabase db = events.getWritableDatabase(); Log.v(TAG, " uriMatcher.match(uri) = " + uriMatcher.match(uri) + " uri = " + uri); int count; switch (uriMatcher.match(uri)) { case EVENTS: count = db.delete(TABLE_NAME, selection, selectionArgs); break; case EVENTS_ID: long id = Long.parseLong(uri.getPathSegments().get(1)); count = db.delete(TABLE_NAME, appendRowId(selection, id), selectionArgs); break; default: throw new IllegalArgumentException("Unknown URI " + uri); } // Notify any watchers of the change getContext().getContentResolver().notifyChange(uri, null); return count; } @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { SQLiteDatabase db = events.getWritableDatabase(); int count; switch (uriMatcher.match(uri)) { case EVENTS: count = db.update(TABLE_NAME, values, selection, selectionArgs); break; case EVENTS_ID: long id = Long.parseLong(uri.getPathSegments().get(1)); count = db.update(TABLE_NAME, values, appendRowId( selection, id), selectionArgs); break; default: throw new IllegalArgumentException("Unknown URI " + uri); } // Notify any watchers of the change getContext().getContentResolver().notifyChange(uri, null); return count; } /** Append an id test to a SQL selection expression */ private String appendRowId(String selection, long id) { return _ID + "=" + id + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""); } }

 AndroidManifest.xml添加provider支持

 

<provider android:name=".EventsProvider" android:authorities="org.example.events" />

 

3. 在Activity(Events)中使用 Provider(EventsProvider)

public class Events extends ListActivity { private static String[] FROM = { _ID, TIME, TITLE, }; private static int[] TO = { R.id.rowid, R.id.time, R.id.title, }; private static String ORDER_BY = TIME + " DESC"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); addEvent("Hello, Android!"); Cursor cursor = getEvents(); showEvents(cursor); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { // TODO Auto-generated method stub if ( keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) { Uri uri = Uri.parse("content://" + AUTHORITY + "/" + TABLE_NAME + "/64"); getContentResolver().delete(uri, null, null ); } else if ( keyCode == KeyEvent.KEYCODE_VOLUME_UP) addEvent("Hello, Android!"); return super.onKeyDown(keyCode, event); } private void addEvent(String string) { // Insert a new record into the Events data source. // You would do something similar for delete and update. ContentValues values = new ContentValues(); values.put(TIME, System.currentTimeMillis()); values.put(TITLE, string); getContentResolver().insert(CONTENT_URI, values); } private Cursor getEvents() { // Perform a managed query. The Activity will handle closing // and re-querying the cursor when needed. return managedQuery(CONTENT_URI, FROM, null, null, ORDER_BY); } private void showEvents(Cursor cursor) { // Set up data binding SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.item, cursor, FROM, TO); setListAdapter(adapter); } }