private boolean initialize() {
mContext = getContext();
mContentResolver = mContext.getContentResolver();
mOpenHelper = DatabaseHelper.getInstance(mContext);
try {
mDb = mOpenHelper.getWritableDatabase();
} catch (SQLiteException ex) {
mDb = mOpenHelper.getReadableDatabase();
}
return true;
}
@SuppressLint("SimpleDateFormat")
@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
// 新增,故uri只能为collection
if (sUriMatch.match(uri) != HISTORY_COLLECTION_URI_INDICATOR) {
throw new IllegalArgumentException("URI =" + uri);
}
// 允许插入空行
ContentValues cv;
if (values == null) {
cv = new ContentValues();
} else {
cv = new ContentValues(values);
}
//
if (cv.containsKey(ChatHistoryTable.CHAT_TIME)) {
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd-HH:mm:ss");
String now = sdf.format(new Date(System.currentTimeMillis()));
cv.put(ChatHistoryTable.CHAT_TIME, now);
}
mDb = mOpenHelper.getWritableDatabase();
long rowId = mDb.insert(ChatHistoryTable.TABLE_NAME, null, cv);
if (rowId > 0) {
Uri insertUri = ContentUris.withAppendedId(ChatHistoryTable.CONTENT_URI, rowId);
mContentResolver.notifyChange(insertUri, null);
return insertUri;
}
throw new SQLiteException("Failed to insert!!!");
}
@Override
public Cursor query(
Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
// check uri
// first 通过SQLiteQueryBuilder,设置数据库查询的信息.Uri有两种情况,一种是collect,
// 一种已经指定某个item,两者需要区别对待,item将获取_ID,并在where中增加一个匹配条件.
SQLiteQueryBuilder dbQuery = new SQLiteQueryBuilder();
final int match = sUriMatch.match(uri);
switch (match) {
case HISTORY_COLLECTION_URI_INDICATOR:
dbQuery.setTables(ChatHistoryTable.TABLE_NAME);
dbQuery.setProjectionMap(sHistoryProjectionMap);
break;
case HISTORY_ITEM_URI_INDICATION:
dbQuery.setTables(ChatHistoryTable.TABLE_NAME);
dbQuery.setProjectionMap(sHistoryProjectionMap);
dbQuery.appendWhere(ChatHistoryTable._ID + "=" + uri.getPathSegments().get(1));
break;
default:
throw new IllegalArgumentException("Unknow uri=" + uri);
}
// second v 对排序进行缺省设置
// String order = TextUtils.isEmpty(sortOrder) ? HistoryTable.DEFAULE_SORT_ORDER : sortOrder;
SQLiteDatabase db = mOpenHelper.getReadableDatabase();
// third start query
final Cursor c = dbQuery.query(db, projection, selection, selectionArgs, null, null, sortOrder);
// fourth 向系统注册通知:观察所要查询的数据,即Uri对应的数据是否发生变化
// 开发者通过provider接口获取数据,可通过通知获知数据已经发生变更
if (c != null) {
c.setNotificationUri(mContentResolver, ChatHistoryTable.CONTENT_URI);
}
return c;
}