When click on an item in a tree, it makes the vertical scroll bar jump up

问题

Look at this simple code

 Tree testTree=new Tree(); 
 TreeItem testTreeItem=new TreeItem("test");
 TreeItem testTreeItem2=new TreeItem("test2");
 more TreeItem....

 testTree.addItem(testTreeItem1);
 testTree.addItem(testTreeItem2);
 ........

Now, resize your browser so that you can see the vertical scroll bar on the right hand-side. Now click on a tree item at the very bottom ex testTreeItem10, you will see the the vertical scroll bar jump up instead of staying in the current position.

This error also happens when using UiBinder

<g:Tree ui:field="myTree"> 
<g:TreeItem text="Item 1" /> 
<g:TreeItem text="Item 2" /> .....
</g:Tree>

Also, addItem of Tree got deprecated, so how to solve this problem?

回答1:

This hacking code may work, but i am not sure it is the right way or elegant way to fix?

Could this hacking code break in the future?

By the way, just modify the Tree a bit:

    Tree testTree=new Tree(){

        public void onBrowserEvent(Event event) {
            if (DOM.eventGetType(event) == Event.ONCLICK) {

                return;
            }

            if (DOM.eventGetType(event) == Event.ONMOUSEDOWN) {
                //int s = scrollPanel.getVerticalScrollPosition();
                int scrollLeftInt = Window.getScrollLeft();
                int scrollTopInt = Window.getScrollTop();
                DOM.setStyleAttribute(this.getElement(), "position",
                        "fixed");
                super.onBrowserEvent(event);
                DOM.setStyleAttribute(this.getElement(), "position",
                        "static");

                //scrollPanel.setVerticalScrollPosition(s);
                Window.scrollTo(scrollLeftInt,scrollTopInt);
                return;
            }

            super.onBrowserEvent(event);
        }

    };

回答2:

I was solving this problem some time ago. This code did the trick for me.

private Tree gwtTree = new Tree(){
        @Override
        public void setFocus(boolean focus) {
            //Do not do anything!
        }
    };

来源：https://stackoverflow.com/questions/19131318/when-click-on-an-item-in-a-tree-it-makes-the-vertical-scroll-bar-jump-up