CODEWITHSUNDEEP
androidandroid-contentprovider
Hugo Zapata
Hugo Zapata

Reputation: 4474

understanding the use of ContentUris.appendId to query the calendar provider

The code i'm working on lists the events from the calendar, i need to limit the range of dates, and in the examples i see this code:

// Construct the query with the desired date range.
Uri.Builder builder = Instances.CONTENT_URI.buildUpon();
ContentUris.appendId(builder, startMillis);
ContentUris.appendId(builder, endMillis);

I don't understand why appendId is used in this way. startMillis and endMillis are not ids, i would expect that the parameter name had to be provided eg "startdate" , It's not clear to me why this works, and what other parameters could be specified this way. Are there more parameters supported by appenedId? How can i know?

Upvotes: 2

Views: 1155

Answers (2)

Darnst
Darnst

Reputation: 91

I too have been trying to understand more about ContentUris as I had a section of code that wasn't working within the CalendarContract Instances table. This is strange because I didn't need to pass these in for the Calendars or Events table queries that I have developed.

So I added the appendId statements and passed in the current time in UTC for both values and the code now works. The actual query in my code is using the current time to looking for current events - please see the code below. If I take the appendID statements out an exception is raised - I think it was something like Content Provider URL not found.

String instanceQuery = "EVENT_ID = " + event_id + 
                    " AND begin <= " + now +
                    " AND end >= " +  now;


Uri.Builder eventsUriBuilder = CalendarContract.Instances.CONTENT_URI.buildUpon();
ContentUris.appendId(eventsUriBuilder, now);
ContentUris.appendId(eventsUriBuilder, now);
Uri eventsUri = eventsUriBuilder.build();
Cursor instanceCursor = null; 
instanceCursor = ctx.getContentResolver().query(eventsUri, 
    new String[] {  CalendarContract.Instances.EVENT_ID,
    CalendarContract.Instances.BEGIN,
    CalendarContract.Instances.END},
    instanceQuery,
    null,
    null);

My code is working but I would like to know what impact the appendID statements actually have, e.g. do the values add any constraints. It looks like my actual query is overriding any implied range that is passed in and I really don't understand why they are required.

Hopefully a brief explanation from someone who understands this more would benefit the developer community....

Upvotes: 0

Nebula
Nebula

Reputation: 1057

What appendId actually does is add a /# to your uri where # is a number. In your example (assuming startMillis = 1000 and endMillis = 3000 and the uri content://com.google.calendar/) this would mean your uri could end up like this:

content://com.google.calendar/1000/3000

This is something that a uri parser can pickup:

URIMatcher.addURI(AUTHORITY, calendar + "/#/#", DATE_RANGE);

Long story short: appendId is just a convenient and type-safe way to add an integer to your uri path.

Upvotes: 3

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