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ContentQueryMap


android.content

Class ContentQueryMap



  • public class ContentQueryMap
    extends Observable
    Caches the contents of a cursor into a Map of String->ContentValues and optionally keeps the cache fresh by registering for updates on the content backing the cursor. The column of the database that is to be used as the key of the map is user-configurable, and the ContentValues contains all columns other than the one that is designated the key.

    The cursor data is accessed by row key and column name via getValue().

    • Constructor Detail

      • ContentQueryMap

        public ContentQueryMap(Cursor cursor,
                       String columnNameOfKey,
                       boolean keepUpdated,
                       Handler handlerForUpdateNotifications)
        Creates a ContentQueryMap that caches the content backing the cursor
        Parameters:
        cursor - the cursor whose contents should be cached
        columnNameOfKey - the column that is to be used as the key of the values map
        keepUpdated - true if the cursor's ContentProvider should be monitored for changes and the map updated when changes do occur
        handlerForUpdateNotifications - the Handler that should be used to receive notifications of changes (if requested). Normally you pass null here, but if you know that the thread that is creating this isn't a thread that can receive messages then you can create your own handler and use that here.
    • Method Detail

      • setKeepUpdated

        public void setKeepUpdated(boolean keepUpdated)
        Change whether or not the ContentQueryMap will register with the cursor's ContentProvider for change notifications. If you use a ContentQueryMap in an activity you should call this with false in onPause(), which means you need to call it with true in onResume() if want it to be kept updated.
        Parameters:
        keepUpdated - if true the ContentQueryMap should be registered with the cursor's ContentProvider, false otherwise
      • getValues

        public ContentValues getValues(String rowName)
        Access the ContentValues for the row specified by rowName
        Parameters:
        rowName - which row to read
        Returns:
        the ContentValues for the row, or null if the row wasn't present in the cursor
      • requery

        public void requery()
        Requeries the cursor and reads the contents into the cache
      • close

        public void close()
      • finalize

        protected void finalize()
                         throws Throwable
        Description copied from class: Object
        Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

        Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

        If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

        Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

        Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

        Overrides:
        finalize in class Object
        Throws:
        Throwable


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