PageKeyedDataSource.LoadInitialCallback
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android
abstract class PageKeyedDataSource.LoadInitialCallback<Key : Any?, Value : Any?>
Callback for loadInitial to return data and, optionally, position/count information.
A callback can be called only once, and will throw if called again.
If you can compute the number of items in the data set before and after the loaded range, call the five parameter onResult to pass that information. You can skip passing this information by calling the three parameter onResult, either if it's difficult to compute, or if LoadInitialParams.placeholdersEnabled is false, so the positioning information will be ignored.
It is always valid for a DataSource loading method that takes a callback to stash the callback and call it later. This enables DataSources to be fully asynchronous, and to handle temporary, recoverable error states (such as a network error that can be retried).
| Parameters | |
|---|---|
<Key : Any?> |
Type of data used to query pages. |
<Value : Any?> |
Type of items being loaded. |
Summary
Public constructors |
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<Key : Any?, Value : Any?> LoadInitialCallback() |
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Public functions |
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abstract Unit |
Called to pass loaded data from a DataSource. |
android
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abstract Unit |
onResult(Called to pass initial load state from a DataSource. |
android
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Public constructors
Public functions
onResult
abstract fun onResult(data: List<Value>, previousPageKey: Key?, nextPageKey: Key?): Unit
Called to pass loaded data from a DataSource.
Call this from loadInitial to initialize without counting available data, or supporting placeholders.
It is always valid to pass a different amount of data than what is requested. Pass an empty list if there is no more data to load.
| Parameters | |
|---|---|
data: List<Value> |
List of items loaded from the |
previousPageKey: Key? |
Key for page before the initial load result, or |
nextPageKey: Key? |
Key for page after the initial load result, or |
onResult
abstract fun onResult(
data: List<Value>,
position: Int,
totalCount: Int,
previousPageKey: Key?,
nextPageKey: Key?
): Unit
Called to pass initial load state from a DataSource.
Call this method from your DataSource's loadInitial function to return data, and inform how many placeholders should be shown before and after. If counting is cheap to compute (for example, if a network load returns the information regardless), it's recommended to pass data back through this method.
It is always valid to pass a different amount of data than what is requested. Pass an empty list if there is no more data to load.
| Parameters | |
|---|---|
data: List<Value> |
List of items loaded from the |
position: Int |
Position of the item at the front of the list. If there are |
totalCount: Int |
Total number of items that may be returned from this DataSource. Includes the number in the initial |