Android文档指出LOADERS - 它们监视数据源并在内容更改时提供新结果。我已将CursorAdapter更改为适用于SQLite数据库。
import android.content.ContentResolver;
import android.content.Context;
import android.database.ContentObserver;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v4.content.AsyncTaskLoader;
import android.support.v4.content.Loader.ForceLoadContentObserver;
import android.util.Log;
public class SimpleCursorLoader extends AsyncTaskLoader<Cursor> {
final ForceLoadContentObserver mObserver;
String mTable;
String[] mColumns;
String mSelection;
String[] mSelectionArgs;
String mGroupBy;
String mHaving;
String mOrderBy;
String mLimit;
Cursor mCursor;
SQLiteDatabase mDb;
/**
* Creates an empty unspecified CursorLoader. You must follow this with
* calls to {@link #setUri(Uri)}, {@link #setSelection(String)}, etc
* to specify the query to perform.
*/
public SimpleCursorLoader(Context context) {
super(context);
mObserver = new ForceLoadContentObserver();
}
/**
* Creates a fully-specified SimpleCursorLoader. See
* {@link ContentResolver#query(Uri, String[], String, String[], String)
* ContentResolver.query()} for documentation on the meaning of the
* parameters. These will be passed as-is to that call.
*/
public SimpleCursorLoader(Context context,String table, String[] columns, String selection,
String[] selectionArgs, String groupBy, String having, String orderBy, String limit, SQLiteDatabase db) {
super(context);
mObserver = new ForceLoadContentObserver();
mTable = table;
mColumns = columns; //copying array
mSelection = selection;
mSelectionArgs = selectionArgs;
mGroupBy = groupBy;
mHaving = having;
mOrderBy = orderBy;
mLimit = limit;
mDb = db;
}
/* Runs on a worker thread */
@Override
public Cursor loadInBackground() {
Cursor cursor = mDb.query(mTable, mColumns, mSelection, mSelectionArgs, mGroupBy, mHaving, mOrderBy, mLimit);
if (cursor != null) {
// Ensure the cursor window is filled
cursor.getCount();
Log.d("SimpleCursorLoader","Cursor.getCount()= " + String.valueOf(cursor.getCount()));
registerContentObserver(cursor, mObserver);
}
return cursor;
}
/**
* Registers an observer to get notifications from the content provider
* when the cursor needs to be refreshed.
*/
void registerContentObserver(Cursor cursor, ContentObserver observer) {
cursor.registerContentObserver(mObserver);
}
/* Runs on the UI thread */
@Override
public void deliverResult(Cursor cursor) {
Log.d("Gaurav","Inside SimpleCursorLoader - deliverResult");
if (isReset()) {
// An async query came in while the loader is stopped
if (cursor != null) {
cursor.close();
}
return;
}
Cursor oldCursor = mCursor;
mCursor = cursor;
if (isStarted()) {
super.deliverResult(cursor);
}
if (oldCursor != null && oldCursor != cursor && !oldCursor.isClosed()) {
oldCursor.close();
}
}
/**
* Starts an asynchronous load of the contacts list data. When the result is ready the callbacks
* will be called on the UI thread. If a previous load has been completed and is still valid
* the result may be passed to the callbacks immediately.
*
* Must be called from the UI thread
*/
@Override
protected void onStartLoading() {
Log.d("Gaurav", "onStartLoading");
if (mCursor != null) {
deliverResult(mCursor);
}
if (takeContentChanged() || mCursor == null) {
forceLoad();
}
}
/**
* Must be called from the UI thread
*/
@Override
protected void onStopLoading() {
// Attempt to cancel the current load task if possible.
cancelLoad();
}
@Override
public void onCanceled(Cursor cursor) {
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
}
@Override
protected void onReset() {
super.onReset();
// Ensure the loader is stopped
onStopLoading();
if (mCursor != null && !mCursor.isClosed()) {
mCursor.close();
}
mCursor = null;
}
}
CursorLoader在ListFragment中使用自定义适配器，该适配器扩展SimpleCursor Adapter并在构造函数中传递FLAG_REGISTER_CONTENT_OBSERVER，但当列表中使用的响应更改基础数据时，游标会发生更改。
答案 0 :(得分：0)
虽然我使用的是与你不同的实现，但我遇到了同样的问题。我能够通过明确地将通知URI声明为不太具体的东西来纠正我的问题。我确信我的代码还有其他问题导致我需要这样做，但它解决了我的问题。所以，我的内容提供商中的Cursor查询来自：
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
................
................
................
Cursor cursor = queryBuilder.query(mDB.getReadableDatabase(),
projection, selection, selectionArgs, null, null, sortOrder);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
cursor.setNotificationUri(getContext().getContentResolver(), uri;)
到
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
................
................
................
Cursor cursor = queryBuilder.query(mDB.getReadableDatabase(),
projection, selection, selectionArgs, null, null, sortOrder);
cursor.setNotificationUri(getContext().getContentResolver(), uri);
cursor.setNotificationUri(getContext().getContentResolver(), MYURI;)
其中MYURI是URI类型的变量，我知道它将覆盖我正在观看的所有内容。
希望这可以帮助别人。
答案 1 :(得分：-6)
您需要覆盖转储方法。
@Override
public void dump(String prefix, FileDescriptor fd, PrintWriter writer, String[] args) {
super.dump(prefix, fd, writer, args);
writer.print(prefix); writer.print("mTable="); writer.println(mTable);
writer.print(prefix); writer.print("mDB=");writer.println(mDb);
writer.print(prefix); writer.print("mProjection=");
writer.println(Arrays.toString(mProjection));
writer.print(prefix); writer.print("mSelection="); writer.println(mSelection);
writer.print(prefix); writer.print("mSelectionArgs=");
writer.println(Arrays.toString(mSelectionArgs));
writer.print(prefix); writer.print("mSortOrder="); writer.println(mSortOrder);
writer.print(prefix); writer.print("mCursor="); writer.println(mCursor);
writer.print(prefix); writer.print("mContentChanged="); writer.println(mContentChanged);
}