android itemtouchhelper怎样自定义动画

ItemTouchHelper 是 Android 中用于实现拖放和滑动删除功能的类。要自定义 ItemTouchHelper 的动画，你需要重写其 onItemMove() 和 onItemDismiss() 方法。以下是一个简单的示例，展示了如何自定义 ItemTouchHelper 的动画：

首先，创建一个自定义的 SimpleItemTouchHelperCallback 类，继承自 ItemTouchHelper.SimpleCallback：

import android.graphics.Canvas;
import android.view.View;
import androidx.recyclerview.widget.RecyclerView;
import com.google.android.material.card.MaterialCardView;
import com.google.android.material.snackbar.Snackbar;
import java.util.List;

public class CustomItemTouchHelperCallback extends ItemTouchHelper.SimpleCallback {

    private final OnItemMoveListener mListener;

    public CustomItemTouchHelperCallback(int dragDirs, int swipeDirs, OnItemMoveListener listener) {
        super(dragDirs, swipeDirs);
        mListener = listener;
    }

    @Override
    public boolean onItemMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        if (viewHolder != target) {
            mListener.onItemMove(viewHolder.getAdapterPosition(), target.getAdapterPosition());
        }
        return true;
    }

    @Override
    public void onItemDismiss(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
        mListener.onItemDismiss(viewHolder.getAdapterPosition());
    }

    public interface OnItemMoveListener {
        void onItemMove(int fromPosition, int toPosition);
        void onItemDismiss(int position);
    }
}

在你的 Activity 或 Fragment 中，实现 CustomItemTouchHelperCallback.OnItemMoveListener 接口，并重写 onItemMove() 和 onItemDismiss() 方法：

public class MainActivity extends AppCompatActivity implements CustomItemTouchHelperCallback.OnItemMoveListener {

    private RecyclerView mRecyclerView;
    private MyAdapter mAdapter;
    private ItemTouchHelper mItemTouchHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mRecyclerView = findViewById(R.id.recycler_view);
        mAdapter = new MyAdapter();
        mRecyclerView.setAdapter(mAdapter);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));

        mItemTouchHelper = new ItemTouchHelper(new CustomItemTouchHelperCallback(ItemTouchHelper.UP | ItemTouchHelper.DOWN, 0, this));
        mItemTouchHelper.attachToRecyclerView(mRecyclerView);
    }

    @Override
    public void onItemMove(int fromPosition, int toPosition) {
        // 在这里处理 item 移动的逻辑，例如更新数据集并刷新 RecyclerView
        mAdapter.moveItem(fromPosition, toPosition);
    }

    @Override
    public void onItemDismiss(int position) {
        // 在这里处理 item 删除的逻辑，例如更新数据集并刷新 RecyclerView
        mAdapter.removeItem(position);
    }
}

在你的 RecyclerView.Adapter 中，实现 moveItem() 和 removeItem() 方法，用于更新数据集：

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {

    private List<String> mData;

    public MyAdapter() {
        mData = new ArrayList<>();
        // 初始化数据集
    }

    public void moveItem(int fromPosition, int toPosition) {
        if (fromPosition < toPosition) {
            for (int i = fromPosition; i < toPosition; i++) {
                String temp = mData.get(i);
                mData.set(i, mData.get(i + 1));
                mData.set(i + 1, temp);
            }
        } else {
            for (int i = fromPosition; i > toPosition; i--) {
                String temp = mData.get(i);
                mData.set(i, mData.get(i - 1));
                mData.set(i - 1, temp);
            }
        }
        notifyItemMoved(fromPosition, toPosition);
    }

    public void removeItem(int position) {
        mData.remove(position);
        notifyItemRemoved(position);
    }

    // 其他适配器方法...
}

现在，你已经成功自定义了 ItemTouchHelper 的动画。你可以根据需要进一步自定义动画效果，例如改变拖动的轨迹颜色、调整滑动速度等。

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