使用 Item TouchHelper 实现 RecyclerView的 item 上下移动

代码如下：

package com.example.temp;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.ContextCompat;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.annotation.SuppressLint;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        RecyclerView view = findViewById(R.id.rv_demo);
        view.setLayoutManager(new LinearLayoutManager(this));
        List<String> data = new ArrayList<>();
        for (int i = 0; i < 14; i++) {
    
    
            data.add("test::" + i);
        }
        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(ItemTouchHelper.DOWN | ItemTouchHelper.UP,//item drag的条件
                ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT //item swipe 的条件
        ) {
    
    
            /**drag 时触发的事件*/
            @Override
            public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
    
    

                if (recyclerView.getAdapter() != null && recyclerView.getAdapter().getItemCount() > 0) {
    
    
                    int targetPosition = target.getAdapterPosition();
                    int viewPosition = viewHolder.getAdapterPosition();
                    Collections.swap(data, targetPosition, viewPosition);
                    recyclerView.getAdapter().notifyItemMoved(viewPosition, targetPosition);
                    return true;
                }
                return false;
            }

            /**onMove 返回true 时触发的事件*/
            @Override
            public void onMoved(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, int fromPos, @NonNull RecyclerView.ViewHolder target, int toPos, int x, int y) {
    
    
                super.onMoved(recyclerView, viewHolder, fromPos, target, toPos, x, y);
            }

            /**swipe 时触发的事件*/
            @Override
            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
    
    

            }

            /**是否可以swipe 默认为true*/
            @Override
            public boolean isItemViewSwipeEnabled() {
    
    
                return false;
            }

            /**item 被选中时触发的条件，默认是长按时触发，也可以通过 ItemTouchHelper#startDrag 或者ItemTouchHelper#startSwipe 触发*/
            @Override
            public void onSelectedChanged(@Nullable RecyclerView.ViewHolder viewHolder, int actionState) {
    
    
                super.onSelectedChanged(viewHolder, actionState);
                if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
    
    
                    viewHolder.itemView.setBackgroundColor(Color.RED);
                }
            }

          /**drag完成后调用*/
            @Override
            public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
    
    
                super.clearView(recyclerView, viewHolder);
                viewHolder.itemView.setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.design_default_color_primary));
            }
        });
        DemoAdapter demoAdapter = new DemoAdapter(data, itemTouchHelper);
        view.setAdapter(demoAdapter);
        itemTouchHelper.attachToRecyclerView(view);
    }

    static class DemoAdapter extends RecyclerView.Adapter<DemoAdapter.DemoHolder> {
    
    
        private final List<String> data;
        private final ItemTouchHelper itemTouchHelper;

        public DemoAdapter(List<String> data, ItemTouchHelper itemTouchHelper) {
    
    
            this.data = data;
            this.itemTouchHelper = itemTouchHelper;
        }

        @NonNull
        @Override
        public DemoHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    
    
            return new DemoHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_demo_item, parent, false), itemTouchHelper);
        }

        @Override
        public void onBindViewHolder(@NonNull DemoHolder holder, int position) {
    
    
            holder.bind(data.get(position));
        }

        @Override
        public int getItemCount() {
    
    
            return data.size();
        }

        static class DemoHolder extends RecyclerView.ViewHolder {
    
    
            private TextView textView;
            private Button button;

            @SuppressLint("ClickableViewAccessibility")
            public DemoHolder(@NonNull View itemView, ItemTouchHelper itemTouchHelper) {
    
    
                super(itemView);
                textView = itemView.findViewById(R.id.tv_item);
                button = itemView.findViewById(R.id.btn_move);
                button.setOnTouchListener((v, event) -> {
    
    
                    if (event.getAction() == MotionEvent.ACTION_DOWN || event.getAction() == MotionEvent.ACTION_BUTTON_PRESS)
                        //触发 drag操作
                        itemTouchHelper.startDrag(DemoHolder.this);
                    return true;
                });
            }

            public void bind(String data) {
    
    
                textView.setText(data);
            }

        }
    }
}