【Android 事件分发】ItemTouchHelper 简介 ( 拖动/滑动事件 | ItemTouchHelper.Callback 回调 )（三）

package kim.hsl.recyclerview;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
    /**
     * 数据源
     */
    private ArrayList<String> names = new ArrayList<String>();
    /**
     * 当前的 RecyclerView 列表
     */
    private RecyclerView recycler_view;
    /**
     * 布局管理器
     */
    private LinearLayoutManager layoutManager;
    /**
     * 适配器
     */
    private Adapter adapter;
    /**
     * 添加拖动处理
     */
    private ItemTouchHelper mItemTouchHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 初始化数据
        initData();
        //1 . 从布局中获取 RecyclerView
        recycler_view = findViewById(R.id.recycler_view);
        //2 . 创建并设置布局管理器
        //创建布局管理器
        layoutManager = new LinearLayoutManager(
                this,
                RecyclerView.VERTICAL,
                false);
        //设置布局管理器
        recycler_view.setLayoutManager(layoutManager);
        // 设置边距
        recycler_view.addItemDecoration(new ItemDecoration());
        //3 . 创建并设置列表适配器
        adapter = new Adapter();
        recycler_view.setAdapter(adapter);
        //4. 添加拖动事件
        Callback callback = new Callback();
        mItemTouchHelper = new ItemTouchHelper(callback);
        //mItemTouchHelper.attachToRecyclerView(recycler_view);
    }
    /**
     * 初始化数据
     */
    private void initData(){
        names.add("宋江");
        names.add("卢俊义");
        names.add("吴用");
        names.add("公孙胜");
        names.add("关胜");
        names.add("林冲");
        names.add("秦明");
        names.add("呼延灼");
        names.add("花荣");
        names.add("柴进");
        names.add("李应");
        names.add("朱仝");
        names.add("鲁智深");
        names.add("武松");
        names.add("董平");
        names.add("张清");
        names.add("杨志");
        names.add("徐宁");
        names.add("索超");
    }
    /**
     * RecyclerView 适配器
     */
    public class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View root_view = LayoutInflater.from(MainActivity.this)
                    .inflate(R.layout.item_recyclerview, parent, false);
            return new ViewHolder(root_view);
        }
        @Override
        public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
            holder.text.setText("" + names.get(position));
        }
        @Override
        public int getItemCount() {
            return names.size();
        }
        public class ViewHolder extends RecyclerView.ViewHolder {
            TextView text;
            public ViewHolder(@NonNull View itemView) {
                super(itemView);
                text = itemView.findViewById(R.id.text);
            }
        }
    }
}

package kim.hsl.recyclerview;
import android.graphics.Canvas;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.RecyclerView;
public class Callback extends ItemTouchHelper.Callback {
    @Override
    public boolean isLongPressDragEnabled() {
        return super.isLongPressDragEnabled();
    }
    @Override
    public boolean isItemViewSwipeEnabled() {
        return super.isItemViewSwipeEnabled();
    }
    @Override
    public void onSelectedChanged(@Nullable RecyclerView.ViewHolder viewHolder, int actionState) {
        super.onSelectedChanged(viewHolder, actionState);
    }
    @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);
    }
    /**
     * 设置上下左右动作
     * 只有在此处打开了指定方向的设置 , 才可以应用具体方向的拖动
     * @param recyclerView
     * @param viewHolder
     * @return
     */
    @Override
    public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
        /*
            设置拖动方向, 此处设置上下拖动事件
         */
        int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN;
        /*
            设置滑动方向, 此处设置左右侧滑事件
         */
        int swipeFlags = ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
        // 应用 拖动 和 滑动 设置
        return makeMovementFlags(dragFlags, swipeFlags);
    }
    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
        return false;
    }
    @Override
    public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
    }
    @Override
    public void onChildDraw(@NonNull Canvas c, @NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }
    @Override
    public void onChildDrawOver(@NonNull Canvas c, @NonNull RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, float dX, float dY, int actionState, boolean isCurrentlyActive) {
        super.onChildDrawOver(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive);
    }
}