I'm using a custom ContentProvider. For querying, there is a CancellationSignal (API 16+) which can be used to cancel a previous call to query().
My question: How can I archive that with delete()
? For clarification, my custom provider manages files on SD card, and so I want to be able to cancel delete operation inside my provider.
I solved this with a simple solution.
For example, for every call to query()
, we put a parameter pointing to the task ID, and use a SparseBooleanArray to hold that ID, like:
...
private static final SparseBooleanArray _MapInterruption = new SparseBooleanArray();
...
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
Cursor cursor = ...
int taskId = ... // obtain task ID from uri
boolean cancel = ... // obtain cancellation flag from uri
if (cancel) {
_MapInterruption.put(taskId, true);
return null; // don't return any cursor
} else {
doQuery(taskId);
if (_MapInterruption.get(taskId)) {
_MapInterruption.delete(taskId);
return null; // because the task was cancelled
}
}
...
return cursor;
}// query()
private void doQuery(int taskId) {
while (!_MapInterruption.get(taskId)) {
... // do the task here
}
}// doQuery()
Usage:
To query:
...
getContentResolver().query("content://your-uri?task_id=1", ...);
To cancel:
...
getContentResolver().query("content://your-uri?task_id=1&cancel=true", ...);
For a complete working solution, have a look at android-filechooser.
The advantage is you can use this technique in Android… 1+ and for other methods such as delete()
, update()
... While CancellationSignal is only available in API 16+ and is limited to only query()
.