Android RecycleView实现Item拖拽效果

基于公司产品的优化需求，其中一个需求涉及到recycleview的拖拽，以及拖拽后item位置的持久化，目的是可以用户自定义界面偏好，并在用户下次进入本界面后，之前设置的偏好仍然有效。我写了一个小demo用作演示效果。

先看效果（只看效果，不看颜值）

步骤1、建接口文件itemtouchhelperviewholder，该接口文件中描述的是选中和放开当前item调用的方法。

public interface itemtouchhelperviewholder {
    void onitemselected(); //选中item
    void onitemcleared();//放开item
}

步骤2、写item得viewholder的类，该类需要继承recyclerview.viewholder类，同时要实现步骤中的接口。

public class itemviewholder extends recyclerview.viewholder implements itemtouchhelperviewholder {
 
    private textview tvname;
 
    public textview gettvname() {
        return tvname;
    }
 
    public void settvname(textview tvname) {
        this.tvname = tvname;
    }
 
    public itemviewholder(@nonnull view itemview) {
        super(itemview);
        tvname = itemview.findviewbyid(r.id.tv_item_name);
    }
 
    @override
    public void onitemselected() {
        tvname.setbackgroundcolor(color.gray);
    }
 
    @override
    public void onitemcleared() {
        tvname.setbackgroundcolor(color.yellow);}
}

步骤3、建立接口文件itemtouchhelperadapter，该文件中描写的是移动recycleview的item时会调用的方法。

public interface itemtouchhelperadapter {
    void onitemmove(int fromposition,int toposition);
}

步骤4、实现一个适配器，继承recyclerview.adapter<itemviewholder>，同时实现步骤3的接口。

public class recyclergridadapter extends recyclerview.adapter<itemviewholder> implements itemtouchhelperadapter {
    private arraylist<string> localdataset;
    private sharedpreferences sp;
    private sharedpreferences.editor speditor;
    final static  string save_key = "star_sort";
    final static string user_preference = "user_preference";
    private context context;
 
    public recyclergridadapter(arraylist<string> dataset,context context) {
        string defaultstr = dataset.tostring();
        if(context != null){
            this.context = context;
            sp = context.getsharedpreferences(user_preference,context.mode_private);
            speditor = sp.edit();
            string savestring = sp.getstring(save_key,defaultstr);
            //考虑，若要更改数据源，需要怎么实现 todo
            string[] splitstr = savestring.replace("[","").replace("]","").replace(" ","").split(",");
            localdataset = new arraylist();
            localdataset.addall(arrays.aslist(splitstr));
        }
    }
 
 
    @nonnull
    @override
    public itemviewholder oncreateviewholder(@nonnull viewgroup parent, int viewtype) {
        view view = layoutinflater.from(parent.getcontext()).inflate(r.layout.item_view_holder_layout, parent, false);
        return new itemviewholder(view);
    }
 
    @override
    public void onbindviewholder(@nonnull itemviewholder holder, int position) {
        holder.gettvname().settext(localdataset.get(position));
    }
 
    @override
    public int getitemcount() {
        return localdataset.size();
    }
 
    @override
    public void onitemmove(int fromposition, int toposition) {
        string prve = localdataset.remove(fromposition);
        if((toposition > fromposition) && (localdataset.size() <= toposition)){
            //将当前item移至最后一位
            localdataset.add(prve);
        }else{
            localdataset.add(toposition, prve);
        }
        notifyitemmoved(fromposition, toposition);
        speditor.putstring(save_key,localdataset.tostring());
        speditor.apply();
    }
}

步骤5、实现itemtouchhelper.callback接口，至于什么是itemtouchhelper，网上一查很多解释，我这不做阐述了。

public class simpleitemtouchhelpercallback extends itemtouchhelper.callback {
 
    private itemtouchhelperadapter adapter;
 
    public simpleitemtouchhelpercallback(itemtouchhelperadapter adapter) {
        this.adapter = adapter;
    }
 
    @override
    public int getmovementflags(@nonnull recyclerview recyclerview, @nonnull recyclerview.viewholder viewholder) {
        final int dragflags = itemtouchhelper.up | itemtouchhelper.down | itemtouchhelper.left | itemtouchhelper.right;
        return makeflag(itemtouchhelper.action_state_drag, dragflags);
    }
 
    @override
    public boolean onmove(@nonnull recyclerview recyclerview, @nonnull recyclerview.viewholder viewholder, @nonnull recyclerview.viewholder target) {
        if (viewholder.getitemviewtype() != target.getitemviewtype()) {
            return false;
        }
        adapter.onitemmove(viewholder.getadapterposition(), target.getadapterposition());
        return true;
    }
 
    @override
    public void onswiped(@nonnull recyclerview.viewholder viewholder, int direction) {
 
    }
 
 
    @override
    public void onselectedchanged(@nullable recyclerview.viewholder viewholder, int actionstate) {
        if (actionstate == itemtouchhelper.action_state_drag) {
            itemtouchhelperviewholder itemtouchhelperviewholder = (itemtouchhelperviewholder) viewholder;
            itemtouchhelperviewholder.onitemselected();
        }
        super.onselectedchanged(viewholder, actionstate);
    }
 
    @override
    public void clearview(@nonnull recyclerview recyclerview, @nonnull recyclerview.viewholder viewholder) {
        super.clearview(recyclerview, viewholder);
        itemviewholder itemviewholder = (itemviewholder) viewholder;
        itemviewholder.onitemcleared();
    }
}

步骤6，现在就可以调用啦，基于步骤5实现的itemtoucherhelper.callback实例构建itemtouchhelper实例，然后attach给recycleview就好啦。

class mainactivity : appcompatactivity() {
    override fun oncreate(savedinstancestate: bundle?) {
        super.oncreate(savedinstancestate)
        val viewbinding = databindingutil.setcontentview<activitymainbinding>(this,r.layout.activity_main)
        with(viewbinding){
            var data = arraylist<string>()
            var index = 10
            while (index-- >0){
                data.add(index.tostring())
            }
            var adapter = recyclergridadapter(data,this@mainactivity)
            recycletest.layoutmanager = gridlayoutmanager(this@mainactivity,4)
            recycletest.adapter = adapter
            var callback = simpleitemtouchhelpercallback(adapter)
            var itemtouchhelper = itemtouchhelper(callback)
            itemtouchhelper.attachtorecyclerview(recycletest)
        }
    }
}

以上就是android recycleview实现item拖拽效果的详细内容，更多关于android recycleview拖拽item的资料请关注其它相关文章！