Browser drop files event GWT

Question

I have a problem with the browser behaviour to drop files. I have a "ContentPanel" which contains a file drag and drop area. when I drag and drop a file there everything is ok but when I drop the file in some other place inside of the "ContentPanel", the browser opens the file (behaviour by default).

How can I avoid this? Nothing should happens in this last case.

Answer 1

It is necessary 2 drop handlers, one for the content panel and other for drag and drop area.

public FileUploadWidget() {

    RootPanel rootPanel = RootPanel.get();
    DropHandler dropHandlerRoot = new DropHandler(rootPanel);

    dropHandlerRoot.addFileEventHandler(new FileEventHandler() {
        @Override
        public void onFiles(FileEvent event) {
            // Nothing to do, avoid the default browser 
            // behaviour which is to open the file
        }
    });

    // Drag and drop area handler
    dropHandler = new DropHandler(dragAndDropArea);
    dropHandler.addFileEventHandler(new FileEventHandler() {
        @Override
        public void onFiles(FileEvent event) {
            JsArray<File> files = event.getFiles();

            for (int i = 0; i < files.length(); ++i) {
                File file = files.get(i);
                addFile(file);
                handleSizeChange();
            }
        }
    });
}