RecyclerView实现拖拽效果

2024-01-06 18:44| 来源: 网络整理| 查看: 265

Google已经对RecyclerView适配好了，只需调用ItemTouchHelper，重写ItemTouchHelper.Callback再与RecyclerView即可实现拖拽效果。首先新建TestItemTouchHelperCallback.java继承ItemTouchHelper.Callback，代码如下：

package com.example.myapplication; import androidx.annotation.NonNull; import androidx.recyclerview.widget.GridLayoutManager; import androidx.recyclerview.widget.ItemTouchHelper; import androidx.recyclerview.widget.RecyclerView; import androidx.recyclerview.widget.StaggeredGridLayoutManager; public class TestItemTouchHelperCallback extends ItemTouchHelper.Callback { @Override public int getMovementFlags(RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) { if (recyclerView.getLayoutManager() instanceof GridLayoutManager || recyclerView.getLayoutManager() instanceof StaggeredGridLayoutManager) { final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN | ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT; final int swipeFlags = 0; return makeMovementFlags(dragFlags, swipeFlags); } else { final int dragFlags = ItemTouchHelper.UP | ItemTouchHelper.DOWN; final int swipeFlags = 0; return makeMovementFlags(dragFlags, swipeFlags); } } @Override public boolean onMove(@NonNull RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) { //拖拽中的viewHolder的Position int fromPosition = viewHolder.getAdapterPosition(); //当前拖拽到的item的viewHolder int toPosition = target.getAdapterPosition(); if (recyclerView.getAdapter() instanceof ItemMoveCallback) { ((ItemMoveCallback) recyclerView.getAdapter()).onItemMove(fromPosition, toPosition); } return true; } @Override public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) { } @Override public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) { super.onSelectedChanged(viewHolder, actionState); if (actionState != ItemTouchHelper.ACTION_STATE_IDLE && viewHolder instanceof ItemHolderMoveCallback) { ((ItemHolderMoveCallback) viewHolder).onItemHolderMoveStart(); } } @Override public void clearView(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) { super.clearView(recyclerView, viewHolder); if (viewHolder instanceof ItemHolderMoveCallback) { ((ItemHolderMoveCallback) viewHolder).onItemHolderMoveEnd(); } } @Override public boolean isLongPressDragEnabled() { //返回true时自动实现长按拖拽效果 return true; } }

之后再初始化ItemTouchHelper并与RecyclerView绑定

ItemTouchHelper itemTouchHelper = new ItemTouchHelper(new TestItemTouchHelperCallback()); temTouchHelper.attachToRecyclerView(mRvTest);

定义了两个回调，ItemMoveCallback和ItemHolderMoveCallback，回调拖拽状态给RecyclerView适配器处理。

public interface ItemMoveCallback { void onItemMove(int fromPosition, int toPosition); } public interface ItemHolderMoveCallback { void onItemHolderMoveStart(); void onItemHolderMoveEnd(); }

RecyclerView适配器监听ItemTouchHelper的回调，自定义RecyclerView适配器代码TestAdapter如下:

package com.example.myapplication; import android.content.Context; import android.graphics.Color; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.recyclerview.widget.RecyclerView; import java.util.Collections; import java.util.List; public class TestAdapter extends RecyclerView.Adapter implements ItemMoveCallback { private Context mContext; private List mTestList; public TestAdapter(Context mContext, List testList) { this.mContext = mContext; this.mTestList = testList; } @Override public TestViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { return new TestViewHolder(LayoutInflater.from(mContext).inflate(R.layout.item_test, null, false)); } @Override public void onBindViewHolder(final TestViewHolder holder, final int position) { holder.tvTest.setText(mTestList.get(position)); } @Override public int getItemCount() { return mTestList.size(); } @Override public void onItemMove(int fromPosition, int toPosition) { if (fromPosition Collections.swap(mTestList, i, i + 1); } } else { for (int i = fromPosition; i > toPosition; i--) { Collections.swap(mTestList, i, i - 1); } } notifyItemMoved(fromPosition, toPosition); } static class TestViewHolder extends RecyclerView.ViewHolder implements ItemHolderMoveCallback{ private TextView tvTest; public TestViewHolder(View itemView) { super(itemView); tvTest = (TextView) itemView.findViewById(R.id.tv_test); } @Override public void onItemHolderMoveStart() { tvTest.setTextSize(40); itemView.setBackgroundColor(Color.RED); } @Override public void onItemHolderMoveEnd() { tvTest.setTextSize(32); itemView.setBackgroundResource(R.color.colorAccent); } } }

TestAdapter与RecyclerView绑定：

mRvTest.setLayoutManager(gridLayoutManager); mTestList = new ArrayList(); for (int i = 0; i

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