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我有兩個加載程序，每個加載程序都加載來自不同內容提供程序的數據。加載程序不返回數據或空遊標
片段被提供有來自第一內容提供者的藥物ID，並且第一加載器加載與該藥物相關的所有信息。第二個加載器應該向第二個內容提供者查詢與該藥物相關的所有警報。
第一個加載程序工作正常，並返回所有正確的數據。但是，第二個加載器似乎返回空遊標，儘管我知道表中有大量數據應該是相關的。我說「出現」是因爲對第二個加載器的onLoadFinished中的數據使用getCount（）會導致我的應用程序崩潰，並且我認爲會發生這種情況的唯一原因是光標爲空。
無論如何，這是我的裝載機代碼。如果你需要，我可以給你任何你想要的代碼。
/**
* Initializes the loaders.
*/
@Override
public Loader<Cursor> onCreateLoader(int loaderId, Bundle bundle) {
CursorLoader loader = null;
long id = getArguments().getLong(ARG_MED_ID);
switch(loaderId) {
case 0: // MedList Loader
Log.d("MedManager", "Loading med data");
Uri singleUri = ContentUris.withAppendedId(MedProvider.CONTENT_URI, id);
String[] projection = { MedTable.MED_ID,
MedTable.MED_NAME,
MedTable.MED_DOSAGE,
MedTable.MED_DATE_FILLED,
MedTable.MED_DURATION };
loader = new CursorLoader(getActivity(), singleUri,
projection, null, null,
MedTable.MED_NAME + " COLLATE LOCALIZED ASC");
break;
case 1: // AlarmList Loader
Log.d("MedManager", "Theoretically loading alarm list");
Uri baseUri = AlarmProvider.CONTENT_URI;
// Create and return a CursorLoader that will take care of
// creating a Cursor for the data being displayed.
String[] alarmProjection = { DailyAlarmTable.ALARM_ID,
DailyAlarmTable.ALARM_MEDNUM,
DailyAlarmTable.ALARM_TIME };
String select = "((" + DailyAlarmTable.ALARM_MEDNUM + " NOTNULL) AND ("
+ DailyAlarmTable.ALARM_MEDNUM + " = " + id + "))";
loader = new CursorLoader(getActivity(), baseUri,
alarmProjection, select, null,
DailyAlarmTable.ALARM_TIMESTAMP + " ASC");
break;
}
return loader;
}
/**
* Customizes the various TextViews in the layout to match
* the values pulled from the MedTable, or swaps the alarm cursor
* into the adapter.
*/
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
switch(loader.getId()) {
case 0:
setUpMedDetails(data);
break;
case 1:
Log.d("MedManager", "Alarm finished loading");
/*
* these lines are commented out because their presence causes
* the app to crash.
*/
/*
boolean isEmpty = data.getCount() < 1;
if(isEmpty) {
Log.d("MedManager", "No results");
}
*/
mAdapter.swapCursor(data);
break;
}
}
@Override
public void onLoaderReset(Loader<Cursor> arg0) {
// TODO Auto-generated method stub
if(arg0.getId() == 1) {
mAdapter.swapCursor(null);
}
}
編輯：爲了完整性，又因爲可能性總是存在的，我很乾脆忽視的東西明顯了大規模的白癡，這裏是由我添加警報到表中的代碼：
/**
* This function will turn the hour and day into an "HH:mm AM/PM" string,
* calculate the timestamp, and then inserts them into the table.
*/
@Override
public void onTimePicked(int hourOfDay, int minute) {
Log.d("MedManager", "onTimePicked triggered");
// Convert the hour and minute into a string
String alarmString = formatAlarmString(hourOfDay, minute);
// Convert the hour and minute into a timestamp
long alarmTimestamp = getAlarmTimestamp(hourOfDay, minute);
// Define the URI to receive the results of the insertion
Uri newUri = null;
// Define a contentValues object to contain the new Values
ContentValues mValues = new ContentValues();
// Add medId;
long medId = getIntent().getLongExtra(MedDetailFragment.ARG_MED_ID, 0);
mValues.put(DailyAlarmTable.ALARM_MEDNUM, medId);
// Add the timestamp
mValues.put(DailyAlarmTable.ALARM_TIMESTAMP, alarmTimestamp);
// Add the time string
mValues.put(DailyAlarmTable.ALARM_TIME, alarmString);
// Insert the new alarm
Toast.makeText(getApplicationContext(), "medNum = " + medId, Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(), "time = " + alarmString, Toast.LENGTH_SHORT).show();
newUri = getContentResolver().insert(AlarmProvider.CONTENT_URI, mValues);
String uriStr = newUri.toString();
Toast.makeText(getApplicationContext(), "Uri = " + uriStr, Toast.LENGTH_SHORT).show();
}
按照要求，這是我的AlarmProvider類。
package com.gmail.jfeingold35.medicationmanager.alarmprovider;
import java.util.Arrays;
import java.util.HashSet;
import com.gmail.jfeingold35.medicationmanager.database.AlarmDatabaseHelper;
import com.gmail.jfeingold35.medicationmanager.database.DailyAlarmTable;
import android.content.ContentProvider;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;
public class AlarmProvider extends ContentProvider {
// Database
private AlarmDatabaseHelper database;
// Used for the UriMatcher
private static final int ALARMS = 10;
private static final int ALARM_ID = 20;
private static final String AUTHORITY = "com.gmail.jfeingold35.medicationmanager.alarmprovider";
private static final String BASE_PATH = "medicationmanager";
public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY
+ "/" + BASE_PATH);
public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE
+ "/alarms";
public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE
+ "/alarm";
private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
sUriMatcher.addURI(AUTHORITY, BASE_PATH, ALARMS);
sUriMatcher.addURI(AUTHORITY, BASE_PATH + "/#", ALARM_ID);
}
@Override
public boolean onCreate() {
database = new AlarmDatabaseHelper(getContext());
return false;
}
/**
* Perform a query from the alarm database
*/
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// Using SQLiteQueryBuilder instead of the query() method
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
// Check if the caller requested a column which doesn't exist
checkColumns(projection);
// Set the table
queryBuilder.setTables(DailyAlarmTable.TABLE_ALARM);
int uriType = sUriMatcher.match(uri);
switch(uriType) {
case ALARMS:
break;
case ALARM_ID:
// Adding the ID to the original query
queryBuilder.appendWhere(DailyAlarmTable.ALARM_ID + "="
+ uri.getLastPathSegment());
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
SQLiteDatabase db = database.getWritableDatabase();
Cursor cursor = queryBuilder.query(db, projection, selection,
selectionArgs, null, null, sortOrder);
// Make sure that potential listeners are getting notified
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return null;
}
/**
* Delete from the alarm database
*/
public int delete(Uri uri, String selection, String[] selectionArgs) {
int uriType = sUriMatcher.match(uri);
SQLiteDatabase db = database.getWritableDatabase();
int rowsDeleted = 0;
switch(uriType) {
case ALARMS:
rowsDeleted = db.delete(DailyAlarmTable.TABLE_ALARM, selection,
selectionArgs);
break;
case ALARM_ID:
String id = uri.getLastPathSegment();
if(TextUtils.isEmpty(selection)) {
rowsDeleted = db.delete(DailyAlarmTable.TABLE_ALARM,
DailyAlarmTable.ALARM_ID + "=" + id, null);
} else {
rowsDeleted = db.delete(DailyAlarmTable.TABLE_ALARM,
DailyAlarmTable.ALARM_ID + "=" + id + " and " + selection,
selectionArgs);
}
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return rowsDeleted;
}
@Override
public String getType(Uri uri) {
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
int uriType = sUriMatcher.match(uri);
SQLiteDatabase db = database.getWritableDatabase();
long id = 0;
switch(uriType) {
case ALARMS:
id = db.insert(DailyAlarmTable.TABLE_ALARM, null, values);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return Uri.parse(BASE_PATH + "/" + id);
}
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
int uriType = sUriMatcher.match(uri);
SQLiteDatabase db = database.getWritableDatabase();
int rowsUpdated = 0;
switch(uriType) {
case ALARMS:
rowsUpdated = db.update(DailyAlarmTable.TABLE_ALARM,
values,
selection,
selectionArgs);
break;
case ALARM_ID:
String id = uri.getLastPathSegment();
if(TextUtils.isEmpty(selection)) {
rowsUpdated = db.update(DailyAlarmTable.TABLE_ALARM,
values,
DailyAlarmTable.ALARM_ID + "=" + id,
null);
} else {
rowsUpdated = db.update(DailyAlarmTable.TABLE_ALARM,
values,
DailyAlarmTable.ALARM_ID + "=" + id + " and " + selection,
selectionArgs);
}
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return rowsUpdated;
}
/**
* Confirms that the columns the user requested exist.
* @param projection
*/
public void checkColumns(String[] projection) {
String[] available = { DailyAlarmTable.ALARM_ID,
DailyAlarmTable.ALARM_MEDNUM,
DailyAlarmTable.ALARM_TIMESTAMP,
DailyAlarmTable.ALARM_TIME };
if(projection != null) {
HashSet<String> requestedColumns = new HashSet<String>(Arrays.asList(projection));
HashSet<String> availableColumns = new HashSet<String>(Arrays.asList(available));
// Check if all columns which are requested are available
if(!availableColumns.containsAll(requestedColumns)) {
throw new IllegalArgumentException("Unknown columsn in projection");
}
}
}
}
您可以發佈您的AlarmProvider類嗎？ – hieuxit
它在清單中正確註冊。我剛剛檢查過。 – Feingat35