Master-detail Using ContentResolver.applyBatch()?

问题

I was wondering if its possible to save master and detail records to a content provider using the android.content.ContentResolver.applyBatch() method in the same operation where subsequent ContentProviderOperation items in the providers parameter depend on the result of previous items.

The problem I'm having is that the actual Uri isn't known at the time that the ContentProviderOperation.newInsert(Uri) method is called and the Uri is immutable.

What I have come up with is shown below:

Master Uri: content://com.foobar.masterdetail/master
Detail Uri: content://com.foobar.masterdetail/master/#/detail

ArrayList<ContentProviderOperation> operations = new ArrayList<ContentProviderOperation>();
operations.add(ContentProviderOperation.newInsert(intent.getData())
    .withValue(Master.NAME, "")
    .withValue(Master.VALUE, "")
    .build());
operations.add(ContentProviderOperation.newInsert(intent.getData()
        .buildUpon()
        .appendPath("#") /* ACTUAL VALUE NOT KNOWN UNTIL MASTER ROW IS SAVED */
        .appendPath("detail")
        .build())
    .withValue(Detail.MASTER_ID, /* WHAT GOES HERE? */)
    .withValue(Detail.NAME, "")
    .withValue(Detail.VALUE, "")
    .build());
ContentProviderResult[] results = this.getContentResolver().applyBatch(MasterDetail.AUTHORITY, operations);
for (ContentProviderResult result : results) {
    Uri test = result.uri;
}

In my content provider, I am overriding the applyBatch() method in order to wrap the operation in a transaction.

Is this possible or is there a better way to do this?

Thanks.

回答1:

Each result produced from an item in the operations array is identified by its index in the array. Subsequent operations may reference those results via the withValueBackReference() method.

.withValue(Detail.MASTER_ID, /* WHAT GOES HERE? */)

becomes

.withValueBackReference(Detail.MASTER_ID, 0)

A complete example of this usage can be found in sample ContactManager. The 0 is the index of the ContentProviderOperation from which the value is obtained.

来源：https://stackoverflow.com/questions/3224857/master-detail-using-contentresolver-applybatch

标签

android

android-contentprovider