置灰GridView 的disable Item

如果想要disable掉GridView中的item，需要做如下两件事情：

1. override Adapter 的 areAllItemsEnabled

2. override Adapter 的 isEnabled(int position)

3. 另外如果想在disable的时候，置灰对应的item，那么只需要在getView方法中，设置对应View的alpha值即可。

比如：

class MyAdapter extends BaseAdapter {

    @Override
    public boolean isEnable(int position) {
        // return true for clickable , false for not
        return isShouldEnableItem(position);
    }

    @Override
    public boolean areAllItemsEnabled() {
        return false;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ...
        if (isEnabled(position)) {
            convertView.setAlpha(1f);
        } else {
            convertView.setAlpha(0.2f);
        }
        ...
    }
}

PS: the alpha value , 0 means the view is completely transparent and 1 means the view is completely opaque.

置灰GridView 的disable Item