MainActivity.java 文件源码

/**
 * Handles the call-back from a file chooser dialog when a file is selected. This is used for
 * communication between the {@code FileChooserDialog} and the export/import fragments. The
 * originating fragment that opened the file chooser dialog should set the "tag" of the file
 * chooser dialog to the value of the fragment tag that this activity uses to identify that
 * originating fragment. This activity will then forward this notification to that fragment,
 * which is expected to implement this same interface method.
 *
 * @param dialog
 *     The file chooser dialog that has reported the file selection.
 * @param file
 *     The file that was chosen.
 */
@Override
public void onFileSelection(@NonNull FileChooserDialog dialog, @NonNull File file) {
    // This "relay" scheme ensures that this activity is not embroiled in the gory details of
    // what the "destinationFrag" wanted with the file.
    final Fragment destinationFrag = fragmentManager.findFragmentByTag(FRAG_TAG_EXIM_DIALOG);

    if (destinationFrag instanceof FileChooserDialog.FileCallback) {
        ((FileChooserDialog.FileCallback) destinationFrag).onFileSelection(dialog, file);
    } else {
        // This is not expected unless there is a bug to be fixed.
        Log.e(TAG, "onFileSelection(): Unknown or incompatible fragment: " + destinationFrag.getTag());
    }
}