这是我第一次在该网站上发帖,希望这将是一次积极的经历.我有一个Android sqlite / ContentProvider问题,在过去3个小时中,我一直在犹豫不决.以下是ContentProvider代码：
public class IncidentProvider extends ContentProvider {
private static final UriMatcher sUriMatcher;
private static final HashMap<String,String> projectionMap;
private static final int INCIDENTS = 1;
public static final String AUTHORITY = "com.test.providers.IncidentsProvider";
public static final String TABLE_NAME = "incidents";
private static class DatabaseHelper extends sqliteOpenHelper {
public DatabaseHelper(Context context) {
super(context,context.getString(R.string.database_name),null,Integer.parseInt(context.getString(R.string.database_version)));
}
@Override
public void onCreate(sqliteDatabase db) {
db.execsql("CREATE TABLE " + TABLE_NAME + " ("
+ Incidents.INCIDENT_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"
+ Incidents.NAME + " VARCHAR(30),"
+ Incidents.CREATE_TIME + " LONG,"
+ Incidents.LAST_UPDATE + " LONG,"
+ Incidents.IS_ACTIVE + " VARCHAR(30)" + ");");
}
@Override
public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
db.execsql("DROP TABLE IF EXISTS " + TABLE_NAME );
onCreate(db);
}
}
private DatabaseHelper dbHelper;
/**
* Delete a row from the database
*/
@Override
public int delete(Uri uri,String where,String[] whereArgs) {
sqliteDatabase db = dbHelper.getWritableDatabase();
int count;
switch(sUriMatcher.match(uri)) {
case INCIDENTS:
count = db.delete(TABLE_NAME,where,whereArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
getContext().getContentResolver().notifyChange(uri,null);
db.close();
return count;
}
/**
* Return the content type managed by this ContentProvider
*/
@Override
public String getType(Uri uri) {
switch(sUriMatcher.match(uri)) {
case INCIDENTS:
return Incidents.CONTENT_TYPE;
default:
throw new IllegalArgumentException("UNKNOWN URI " + uri);
}
}
/**
* Insert new content into a row in the database
*/
@Override
public Uri insert(Uri uri,ContentValues initialValues) {
if(sUriMatcher.match(uri) != INCIDENTS)
throw new IllegalArgumentException("UNKNOWN URI " + uri);
ContentValues values;
if(initialValues != null) {
values = new ContentValues(initialValues);
} else {
values = new ContentValues();
}
sqliteDatabase db = dbHelper.getWritableDatabase();
long rowId = db.insert(TABLE_NAME,Incidents.NAME,values);
if(rowId > 0) {
Uri incidentUri = ContentUris.withAppendedId(Incidents.CONTENT_URI,rowId);
getContext().getContentResolver().notifyChange(incidentUri,null);
db.close();
return incidentUri;
}
db.close();
throw new sqlException("Failed to insert row into " + uri);
}
/**
* Called when creating this ContentProvider
*/
@Override
public boolean onCreate() {
dbHelper = new DatabaseHelper(getContext());
return false;
}
/**
* Called when making a query to this content provider
*/
@Override
public Cursor query(Uri uri,String[] projection,String selection,String[] selectionArgs,String sortOrder) {
sqliteQueryBuilder qb = new sqliteQueryBuilder();
switch(sUriMatcher.match(uri)) {
case INCIDENTS:
qb.setTables(TABLE_NAME);
qb.setProjectionMap(projectionMap);
break;
default:
throw new IllegalArgumentException("UNKNOWN URI " + uri);
}
sqliteDatabase db = dbHelper.getWritableDatabase();
Cursor c = qb.query(db,projection,selection,selectionArgs,sortOrder);
c.setNotificationUri(getContext().getContentResolver(),uri);
db.close();
return c;
}
/**
* Called when updating a row through this content provider
*/
@Override
public int update(Uri uri,ContentValues values,String[] whereArgs) {
sqliteDatabase db = dbHelper.getWritableDatabase();
int count;
switch(sUriMatcher.match(uri)) {
case INCIDENTS:
count = db.update(TABLE_NAME,values,whereArgs);
break;
default:
throw new IllegalArgumentException("UNKNOWN URI " + uri);
}
getContext().getContentResolver().notifyChange(uri,null);
db.close();
return count;
}
static {
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
sUriMatcher.addURI(AUTHORITY,TABLE_NAME,INCIDENTS);
projectionMap = new HashMap<String,String>();
projectionMap.put(Incidents.INCIDENT_ID,Incidents.INCIDENT_ID);
projectionMap.put(Incidents.NAME,Incidents.NAME);
projectionMap.put(Incidents.CREATE_TIME,Incidents.CREATE_TIME);
projectionMap.put(Incidents.LAST_UPDATE,Incidents.LAST_UPDATE);
projectionMap.put(Incidents.IS_ACTIVE,Incidents.IS_ACTIVE);
}
}
我还编写了一个db helper类,以使其易于与ContentProvider进行交互. 2个示例DBHelper方法如下(1用于插入,1用于查询).
/**
* Adds a new incident to the database
**/
public void addNewIncident(ContentResolver contentResolver,Incident incident) {
ContentValues contentValues = new ContentValues();
contentValues.put(Incidents.NAME,incident.getName());
contentValues.put(Incidents.CREATE_TIME,incident.getCreateTime());
contentValues.put(Incidents.LAST_UPDATE,incident.getLastUpdate());
contentValues.put(Incidents.IS_ACTIVE,incident.isActive()?"true":"false");
contentResolver.insert(Incidents.CONTENT_URI,contentValues);
}
/**
* Retrieves all incidents from the database
**/
public ArrayList<Incident> getIncidents(ContentResolver contentResolver) {
Cursor c = contentResolver.query(Incidents.CONTENT_URI,null);
ArrayList<Incident> returnList = new ArrayList<Incident>();
if(c!=null && c.moveToNext()) {
for(int i=0; i<c.getCount(); i++) {
c.moveToPosition(i);
Incident incident = new Incident(c.getString(c.getColumnIndex(Incidents.NAME)));
incident.setCreateTime(c.getLong(c.getColumnIndex(Incidents.CREATE_TIME)));
incident.setLastUpdate(c.getLong(c.getColumnIndex(Incidents.LAST_UPDATE)));
incident.setActive(c.getString(c.getColumnIndex(Incidents.IS_ACTIVE)).equalsIgnoreCase("true"));
returnList.add(incident);
}
c.close();
}
return returnList;
}
好的！所以这是我的问题.我可以毫无问题地插入数据库！如果我通过adb shell查询数据库,则可以看到所有正在插入的记录.当我使用sqliteQueryBuilder或sqliteDatabase.rawQuery或任何其他查询方法进行查询时,返回的游标以-1返回.无论查询单个记录还是查询整个数据库都没有关系.查询仍然返回-1.
有任何想法吗？我错过了一件非常简单的事情吗？
在此先感谢任何愿意帮助沮丧的人的人！
更新：
/**
* Following db insert works
*/
IncidentsDB db = IncidentsDB.getInstance();
workingIncident.setLastUpdate(System.currentTimeMillis()); // isActive,and createTime set in constructor
db.addNewIncident(this.getContentResolver(),workingIncident);
/**
* Following db queries do not work,cursor ends up with mCount=-1
*/
Cursor c = IncidentsDB.getInstance().getIncidents(this.getContentResolver());
最佳答案
好吧,看来我已经解决了.事实证明,最好使用finalize方法关闭数据库,而不是像上面发布的代码中那样在每个delete,insert,query和update方法中打开和关闭.这是像我一样遇到此问题的人员的代码片段：
// add sqliteDatabase member variable to content provider
private sqliteDatabase db;
/**
* Delete a row from the database
*/
@Override
public int delete(Uri uri,String[] whereArgs) {
// use Content Provider's db member variable in the following code block
int count;
switch(sUriMatcher.match(uri)) {
case INCIDENTS:
count = db.delete(TABLE_NAME,null);
return count;
}
@Override
protected void finalize() throws Throwable {
super.finalize();
db.close();
}