Question

在onLoadFinished（）中我使用myadapter.swapCuesor（游标），我想知道它之后是否在适配器中调用newView？它不是在android的适配器的api中写的所以我在这里问它。如果不是这样，适配器如何更新自己？

Answer 1

当您使用CursorLoader时，将为您管理Cursor。您唯一需要做的就是实现以下三种方法：

    // Called when a new Loader needs to be created
    public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // Now create and return a CursorLoader that will take care of
    // creating a Cursor for the data being displayed.
    return new CursorLoader(this, ContactsContract.Data.CONTENT_URI,
        PROJECTION, SELECTION, null, null);
   }

   // Called when a previously created loader has finished loading
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    // Swap the new cursor in.  (The framework will take care of closing the
    // old cursor once we return.)
    mAdapter.swapCursor(data);
    }

   // Called when a previously created loader is reset, making the data            unavailable
public void onLoaderReset(Loader<Cursor> loader) {
// This is called when the last Cursor provided to onLoadFinished()
// above is about to be closed.  We need to make sure we are no
// longer using it.
mAdapter.swapCursor(null);
}

您不必自己打开和关闭Cursor，加载程序会为您执行此操作。这是必须使用swapCursor的最重要原因，当它与另一个Cursor交换时，它不会关闭Cursor。

    public Cursor swapCursor(Cursor newCursor) {
    if (newCursor == mCursor) {
        return null;
    }
    Cursor oldCursor = mCursor;
    if (oldCursor != null) {
        if (mChangeObserver != null) oldCursor.unregisterContentObserver(mChangeObserver);
        if (mDataSetObserver != null) oldCursor.unregisterDataSetObserver(mDataSetObserver);
    }
    mCursor = newCursor;
    if (newCursor != null) {
        if (mChangeObserver != null) newCursor.registerContentObserver(mChangeObserver);
        if (mDataSetObserver != null) newCursor.registerDataSetObserver(mDataSetObserver);
        mRowIDColumn = newCursor.getColumnIndexOrThrow("_id");
        mDataValid = true;
        // notify the observers about the new cursor
        notifyDataSetChanged();
    } else {
        mRowIDColumn = -1;
        mDataValid = false;
        // notify the observers about the lack of a data set
        notifyDataSetInvalidated();
    }
    return oldCursor;
}

另一方面，

ChangeCursor，首先将当前光标与新光标交换，然后为您关闭它。如果您将此方法与CursorLoader一起使用，您的应用有时可能会崩溃。

    public void changeCursor(Cursor cursor) {
    Cursor old = swapCursor(cursor);
    if (old != null) {
        old.close();
      }
    }

swapCursor在完成后调用适配器中的newView

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