RecyclerView拖動之ItemTouchHelper.Callback的使用

關於RecyclerView拖動效果

 

先看以下效果圖

 

android給了一個官方的工具ItemTouchHelper.Callback

下面上代碼，先說以下RecyclerView的使用

<android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/rv_list"/>

 

    private RecyclerView rv_list;
    private List<String> date = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rv_list = findViewById(R.id.rv_list);
        for (int i = 0; i < 8; i++) {
            date.add(String.valueOf(i+1));
        }
        LinearLayoutManager manager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        ListAdapter adapter = new ListAdapter(date, this);
        rv_list.setLayoutManager(manager);
        rv_list.setAdapter(adapter);
    

    }

適配器

 

public class ListAdapter extends RecyclerView.Adapter<ListAdapter.ListViewHolder>{

    private final LayoutInflater inflater;
    private List<String> date;
    private Context context;

    public ListAdapter(List<String> date, Context context) {
        this.date = date;
        this.context = context;
        inflater = LayoutInflater.from(context);
    }

    @NonNull
    @Override
    public ListViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        return new ListViewHolder(inflater.inflate(R.layout.list_item,viewGroup,false));
    }

    @Override
    public void onBindViewHolder(@NonNull ListViewHolder listViewHolder, int i) {
        if (!TextUtils.isEmpty(date.get(i))) {
            listViewHolder.tv.setText("條目"+i);
            if (i % 2 == 0) {
                listViewHolder.iv.setImageResource(R.mipmap.user_head_img2);
            }else {
                listViewHolder.iv.setImageResource(R.mipmap.user_head_img3);
            }
        }
    }

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

   

    class ListViewHolder extends RecyclerView.ViewHolder{
        ImageView iv;
        TextView tv;
        public ListViewHolder(@NonNull View itemView) {
            super(itemView);
            iv = itemView.findViewById(R.id.iv);
            tv = itemView.findViewById(R.id.tv);
        }
    }

}

好的。此時寫完了。效果如圖2；

 

 

下面開始拖動效果

自定義一個接口

ListItemTouchHelper

 

public interface ListItemTouchHelper {
    void itemMove(int oldIndex,int newIndex);
    void itemDelete(int index);
}

自定義回調

TouchHelperCallback

public class TouchHelperCallback extends ItemTouchHelper.Callback {
    private ListAdapter adapter;

    public TouchHelperCallback(ListAdapter adapter) {
        this.adapter = adapter;
    }

    @Override
    public int getMovementFlags(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder) {
        int dragFlags = ItemTouchHelper.UP |ItemTouchHelper.DOWN;
        int swipeFlags = ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT;
        return makeMovementFlags(dragFlags,swipeFlags);
    }

    @Override
    public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder viewHolder1) {
        adapter.itemMove(viewHolder.getAdapterPosition(),viewHolder1.getAdapterPosition());
        return false;
    }

    @Override
    public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int i) {
        adapter.itemDelete(viewHolder.getAdapterPosition());
    }
}

 

具體使用：

適配器實現接口ListItemTouchHelper

  @Override
    public void itemMove(int oldIndex, int newIndex) {
        notifyItemMoved(oldIndex, newIndex);
    }

    @Override
    public void itemDelete(int index) {
        notifyItemRemoved(index);
    }

activity設置

 

  TouchHelperCallback callback = new TouchHelperCallback(adapter);
        ItemTouchHelper helper = new ItemTouchHelper(callback);
        helper.attachToRecyclerView(rv_list);

到此就完成了這個效果了；

下面上一下activity和adapter的完整代碼。

 

    private RecyclerView rv_list;
    private List<String> date = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rv_list = findViewById(R.id.rv_list);
        for (int i = 0; i < 8; i++) {
            date.add(String.valueOf(i+1));
        }
        LinearLayoutManager manager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false);
        ListAdapter adapter = new ListAdapter(date, this);
        rv_list.setLayoutManager(manager);
        rv_list.setAdapter(adapter);
        TouchHelperCallback callback = new TouchHelperCallback(adapter);
        ItemTouchHelper helper = new ItemTouchHelper(callback);
        helper.attachToRecyclerView(rv_list);

    }

public class ListAdapter extends RecyclerView.Adapter<ListAdapter.ListViewHolder>implements ListItemTouchHelper {

    private final LayoutInflater inflater;
    private List<String> date;
    private Context context;

    public ListAdapter(List<String> date, Context context) {
        this.date = date;
        this.context = context;
        inflater = LayoutInflater.from(context);
    }

    @NonNull
    @Override
    public ListViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        return new ListViewHolder(inflater.inflate(R.layout.list_item,viewGroup,false));
    }

    @Override
    public void onBindViewHolder(@NonNull ListViewHolder listViewHolder, int i) {
        if (!TextUtils.isEmpty(date.get(i))) {
            listViewHolder.tv.setText("條目"+i);
            if (i % 2 == 0) {
                listViewHolder.iv.setImageResource(R.mipmap.user_head_img2);
            }else {
                listViewHolder.iv.setImageResource(R.mipmap.user_head_img3);
            }
        }
    }

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

    @Override
    public void itemMove(int oldIndex, int newIndex) {
        notifyItemMoved(oldIndex, newIndex);
    }

    @Override
    public void itemDelete(int index) {
        notifyItemRemoved(index);
    }

    class ListViewHolder extends RecyclerView.ViewHolder{
        ImageView iv;
        TextView tv;
        public ListViewHolder(@NonNull View itemView) {
            super(itemView);
            iv = itemView.findViewById(R.id.iv);
            tv = itemView.findViewById(R.id.tv);
        }
    }

}

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