RecyclerView是Android一個(gè)更強(qiáng)大的控件,其不僅可以實(shí)現(xiàn)和ListView同樣的效果,還有優(yōu)化了ListView中的各種不足。本文將介紹通過RecyclerView實(shí)現(xiàn)Item拖拽效果以及拖拽位置保存，感興趣的可以參考一下

基于公司產(chǎn)品的優(yōu)化需求，其中一個(gè)需求涉及到RecycleView的拖拽，以及拖拽后item位置的持久化，目的是可以用戶自定義界面偏好，并在用戶下次進(jìn)入本界面后，之前設(shè)置的偏好仍然有效。我寫了一個(gè)小Demo用作演示效果。

先看效果（只看效果，不看顏值）

步驟1、建接口文件ItemTouchHelperViewHolder，該接口文件中描述的是選中和放開當(dāng)前Item調(diào)用的方法。

public interface ItemTouchHelperViewHolder {
    void onItemSelected(); //選中item
    void onItemCleared();//放開item
}

步驟2、寫Item得ViewHolder的類，該類需要繼承RecyclerView.ViewHolder類，同時(shí)要實(shí)現(xiàn)步驟中的接口。

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);}
}

步驟3、建立接口文件ItemTouchHelperAdapter，該文件中描寫的是移動RecycleView的Item時(shí)會調(diào)用的方法。

public interface ItemTouchHelperAdapter {
    void onItemMove(int fromPosition,int toPosition);
}

步驟4、實(shí)現(xiàn)一個(gè)適配器，繼承RecyclerView.Adapter<ItemViewHolder>，同時(shí)實(shí)現(xiàn)步驟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);
            //考慮，若要更改數(shù)據(jù)源，需要怎么實(shí)現(xiàn) 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)){
            //將當(dāng)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();
    }
}

步驟5、實(shí)現(xiàn)ItemTouchHelper.Callback接口，至于什么是ItemTouchHelper，網(wǎng)上一查很多解釋，我這不做闡述了。

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();
    }
}

步驟6，現(xiàn)在就可以調(diào)用啦，基于步驟5實(shí)現(xiàn)的ItemToucherHelper.Callback實(shí)例構(gòu)建ItemTouchHelper實(shí)例，然后attach給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實(shí)現(xiàn)Item拖拽效果的詳細(xì)內(nèi)容，更多關(guān)于Android RecycleView拖拽Item的資料請關(guān)注腳本之家其它相關(guān)文章！

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