Android中的拖拽

傷城~ 2022-05-28 03:48 272阅读 0赞

转载请注明链接：[https://blog.csdn.net/feather\_wch/article/details/79736307][https_blog.csdn.net_feather_wch_article_details_79736307]

# Android中的拖拽 #

版本:2018/3/29-1(15:31)-3/30(11:05)

*  Android中的拖拽
    
     *  简单实例：将一个控件拖拽到一个布局中
     *  实例：从RecyclerViewA中将Item拖拽到另一个RecyclerViewB中
     *  参考和学习资料

这样一个效果该如何实现？  
“我想要拖拽一个控件到另一个布局中，手一松就添加到了该布局中”。

主要的方法有通过View的滑动(如改变控件的布局参数等方法)，滑动到目标区域即可。可以参考教程：[https://blog.csdn.net/feather\_wch/article/details/78679327][https_blog.csdn.net_feather_wch_article_details_78679327]

本文的方法是通过给控件设置`OnDragListener(拖拽监听器)`直接完成该效果，更为简单。

## 简单实例：将一个控件拖拽到一个布局中 ##

> 主要思路：  
> 1. 给被拖拽控件添加点击事件监听器，并在内部转交给`View.startDrag`方法去实现拖拽。  
> 2. 给接收方添加`OnDrageListener`，会监听到发生在自身区域内的`拖拽事件`，在拖拽完成的回调中将`被拖拽控件`添加进来

被拖拽控件：

mAddButton.setOnTouchListener(new View.OnTouchListener() {
                @Override
                public boolean onTouch(View view, MotionEvent event) {
                    if(event.getAction() == MotionEvent.ACTION_DOWN){
                        //1. 剪切板可以保存数据
                        ClipData data = ClipData.newPlainText("", "");
                        //2. 影子
                        View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
                        //3. 震动反馈，不需要震动权限
                        view.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS, HapticFeedbackConstants.FLAG_IGNORE_GLOBAL_SETTING);
                        //4. 拖拽
                        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                            view.startDragAndDrop(data, shadowBuilder, view, 0);
                        }else{
                            view.startDrag(data, shadowBuilder, view, 0);
                        }
                        return true;
                    }else{
                        return false;
                    }
                }
            });

目标布局接收拖拽的控件：

mRelativeLayout.setOnDragListener(new View.OnDragListener() {
                @Override
                public boolean onDrag(View v, DragEvent event) {
                    switch (event.getAction()){
                        case DragEvent.ACTION_DROP:
                            //1. 响应拖拽，将控件安置到该位置
                            View otherView = (View) event.getLocalState();
                            ViewGroup owner = (ViewGroup) otherView.getParent();
                            owner.removeView(otherView);
                            RelativeLayout relativeLayout = (RelativeLayout) v;
                            relativeLayout.addView(otherView);
                            otherView.setVisibility(View.VISIBLE);
                            break;
                    }
                    return true;
                }
            });

## 实例：从RecyclerViewA中将Item拖拽到另一个RecyclerViewB中 ##

> 主要思路也就是和上面的一样。  
> 区别在于：接收方和被拖拽方都是`RecyclerView`，需要通过特定的方法去完成`拖拽和添加Item`的功能。

1、RVA中需要实现onDrag拖拽和onItemLongclick长按开始拖拽的两种监听器

public interface RecyclerViewOnItemLongClickListenr{ 
        public boolean onLongClick(View view, ItemDataBean data);
    }
    public class RecyclerViewOnTouchAndDragListener implements View.OnDragListener, RecyclerViewOnItemLongClickListenr { 
        int fromPosition = -1;
        int toPosition = 0;
        RecyclerView mRecyclerView;
        RVAdapter mAdapter;
    
        public int getFromPosition() {
            return fromPosition;
        }
    
        public void setFromPosition(int fromPosition) {
            this.fromPosition = fromPosition;
        }
    
        public int getToPosition() {
            return toPosition;
        }
    
        public RecyclerViewOnTouchAndDragListener(){
        }
        public RecyclerViewOnTouchAndDragListener(RecyclerView recyclerView, RVAdapter adapter) {
            mRecyclerView = recyclerView;
            mAdapter = adapter;
        }
        @Override
        public boolean onDrag(View v, DragEvent event) {
            if (mRecyclerView == null || mAdapter == null) {
                return false;
            }
            final int action = event.getAction();
            switch (action) {
                /**======================================================= * 1. 开始拖拽需要确定当前点击的ItemView * 2. 如果点击在界外，则fromPosition= -1, 需要在其他阶段确定点击的Item *=========================================================*/
                case DragEvent.ACTION_DRAG_STARTED:
                    View itemView = mRecyclerView.findChildViewUnder(event.getX(), event.getY());
                    if (itemView != null) {
                        RecyclerView.ViewHolder startViewHolder = mRecyclerView.getChildViewHolder(itemView);
                        fromPosition = startViewHolder.getAdapterPosition();
                        //点击的ItemView不可见, 如同已经被拖走
                        startViewHolder.itemView.setVisibility(View.INVISIBLE);
                    }
                    return true;
                /**======================================================= * 2. 拖拽进入了当前控件的区域, 如果第一阶段没有确定ItemView，该阶段补充确定 *=========================================================*/
                case DragEvent.ACTION_DRAG_ENTERED:
                    if (fromPosition == -1) {
                        itemView = mRecyclerView.findChildViewUnder(event.getX(), event.getY());
                        if (itemView != null) {
                            RecyclerView.ViewHolder startViewHolder = mRecyclerView.getChildViewHolder(itemView);
                            fromPosition = startViewHolder.getAdapterPosition();
                            //点击的ItemView不可见
                            startViewHolder.itemView.setVisibility(View.INVISIBLE);
                        }
                    }
                    return true;
                /**======================================================= * 3. 拖拽过程中对RecyclerView里面的ItemView顺序进行切换 *=========================================================*/
                case DragEvent.ACTION_DRAG_LOCATION:
                    //1. 获取目标View的VeiwHolder
                    itemView = mRecyclerView.findChildViewUnder(event.getX(), event.getY());
                    if (itemView != null) {
                        RecyclerView.ViewHolder toViewHolder = mRecyclerView.getChildViewHolder(itemView);
                        //2. 获得目标View的Position
                        toPosition = toViewHolder.getAdapterPosition();
                        //3. 可能开始拖拽的位置不在RecylcerView中
                        if (fromPosition == -1) {
                            fromPosition = toPosition;
                        }
                        //4. from 和 to 之间进行位置变换
                        if (fromPosition < toPosition) {
                            for (int i = fromPosition; i < toPosition; i++) {
                                Collections.swap(mAdapter.getCitys(), i, i + 1);
                            }
                        } else {
                            for (int i = fromPosition; i > toPosition; i--) {
                                Collections.swap(mAdapter.getCitys(), i, i - 1);
                            }
                        }
                        mAdapter.notifyItemMoved(fromPosition, toPosition);
                        //5. 已经完成了位置交换
                        fromPosition = toPosition;
                    }
                    return true;
                case DragEvent.ACTION_DRAG_EXITED:
                    v.invalidate();
                    return true;
                /**======================================================= * 4. 拖拽行为停止，将之前不可见的子Item的View重新可见 *=========================================================*/
                case DragEvent.ACTION_DROP:
                    mRecyclerView.findViewHolderForAdapterPosition(fromPosition).itemView.setVisibility(View.VISIBLE);
                    return true;
                case DragEvent.ACTION_DRAG_ENDED:
                    return true;
                default:
                    break;
            }
            return false;
        }
    
        /**======================================================= * 长按进入拖拽状态，并将控件的数据保存到“剪切板”中 *=========================================================*/
        @Override
        public boolean onLongClick(View view, ItemDataBean data) {
            //1. 将数据序列化-通过剪切板传输
            Bundle bundle = new Bundle();
            bundle.putParcelable("data", data);
            Intent intent = new Intent();
            intent.putExtra("bundle", bundle);
            ClipData clipData = ClipData.newIntent("intent", intent);
            //2. 影子
            View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
            //3. 震动反馈，不需要震动权限
            view.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS, HapticFeedbackConstants.FLAG_IGNORE_GLOBAL_SETTING);
            //4. 拖拽
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                view.startDragAndDrop(clipData, shadowBuilder, view, 0);
            } else {
                view.startDrag(clipData, shadowBuilder, view, 0);
            }
            return true;
        }
    }

2、RecyclerView的Adapter，将ItemView的长按监听的具体实现转移到我们的点击接口中(只有核心代码)

private RecyclerViewOnItemLongClickListenr mOnItemLongClickListenr;
    public void setOnItemLongClickListener(RecyclerViewOnItemLongClickListenr onItemLongClickListener) {
        mOnItemLongClickListenr = onItemLongClickListener;
    }
    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
        final ViewHolder viewHolder = (ViewHolder) holder;
        viewHolder.mTextView.setText(citys.get(position));
        /** * 借助OnLongClickListenr将点击事件转移到自定义的Item长按事件接口 **/
        if(mOnItemLongClickListenr != null){
            viewHolder.itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View v) {
                    ItemDataBean itemData = new ItemDataBean();
                    itemData.text =  viewHolder.mTextView.getText().toString();
                    return mOnItemLongClickListenr.onLongClick(v, itemData);
                }
            });
        }
    }

3、需要通过序列化传给目标RV的数据实体类

public class ItemDataBean implements Parcelable { 
        public String text;
    
        @Override
        public int describeContents() {
            return 0;
        }
    
        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeString(this.text);
        }
    
        public ItemDataBean() {
        }
    
        protected ItemDataBean(Parcel in) {
            this.text = in.readString();
        }
    
        public static final Parcelable.Creator<ItemDataBean> CREATOR = new Parcelable.Creator<ItemDataBean>() {
            @Override
            public ItemDataBean createFromParcel(Parcel source) {
                return new ItemDataBean(source);
            }
    
            @Override
            public ItemDataBean[] newArray(int size) {
                return new ItemDataBean[size];
            }
        };
    }

4、目标RVB接收拖拽控件的代码

mRecyclerView2.setOnDragListener(new View.OnDragListener() {
        @Override
        public boolean onDrag(View v, DragEvent event) {
            switch (event.getAction()) {
                /**============================ * 接收其他的控件放置到该RV内部 *============================*/
                case DragEvent.ACTION_DROP:
                    //1. 层层获取到传递来的数据(通过Parcelable序列化)
                    ClipData clipData = event.getClipData();
                    ClipData.Item clipDataItem= clipData.getItemAt(0);
                    Intent intent = clipDataItem.getIntent();
                    Bundle bundle = intent.getBundleExtra("bundle");
                    bundle.setClassLoader(getClass().getClassLoader());
                    ItemDataBean itemData = bundle.getParcelable("data");
    
                    //2. 获取到想要加入的位置
                    View childView = mRecyclerView2.findChildViewUnder(event.getX(), event.getY());
                    if(childView != null){
                        RecyclerView.ViewHolder toViewHolder = mRecyclerView2.getChildViewHolder(childView);
                        int targetPosition = toViewHolder.getAdapterPosition();
    
                        //3. 将控件添加到本控件内部
                        mRVAdapter2.getCitys().add(targetPosition, itemData.text);
                        mRVAdapter2.notifyItemInserted(targetPosition);
                        mRecyclerView2.scrollToPosition(targetPosition);
    
                        //4. 让第一个RV删除掉移动过来的Item
                        int fromPosition = mViewOnTouchAndDragListener.getFromPosition();
                        if(fromPosition != -1){
                            mRVAdapter.getCitys().remove(fromPosition);
                            mRVAdapter.notifyItemRemoved(fromPosition);
                            mViewOnTouchAndDragListener.setFromPosition(-1); //归零防止出问题
                        }
                    }
                    break;
                default:
                    break;
            }
            return true;
        }
    });

5、给RVA设置两种监听器

//1. 相应拖拽：自动排序效果
    mRecyclerView.setOnDragListener(mViewOnTouchAndDragListener = new RecyclerViewOnTouchAndDragListener(mRecyclerView, mRVAdapter));
    //2. 长按开启拖拽
    mRVAdapter.setOnItemLongClickListener(new RecyclerViewOnTouchAndDragListener());

## 参考和学习资料 ##

1.  [ 玩玩Andoid的拖拽——实现一款万能遥控器][_Andoid]
2.  [Android开发之Drag&Drop框架实现拖放手势][Android_Drag_Drop]
3.  [剪贴板框架：ClipData解析][ClipData]

[https_blog.csdn.net_feather_wch_article_details_79736307]: https://blog.csdn.net/feather_wch/article/details/79736307
[https_blog.csdn.net_feather_wch_article_details_78679327]: https://blog.csdn.net/feather_wch/article/details/78679327
[_Andoid]: https://blog.csdn.net/qq_17766199/article/details/79466506
[Android_Drag_Drop]: https://www.cnblogs.com/jerehedu/p/4427588.html
[ClipData]: http://www.iot-online.com/art/2017/021746450.html