Question

我在android studio上有一个项目，我想将RecylerView中的图像项拖放到我的Activity上的Container ...

在我的活动中，我有一个片段容器，它显示了一个带有RecyclerView的片段，这个显示动物部分采用JSON连接，它可以拖放将图像移动到Cointainer来制作一个动物角色和发送数据到我的数据库，我怎么做???

Answer 1

您必须实施ItemTouchHelper，这是一个关于如何执行此操作的示例：

1-添加您的recyclerview

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

2 - 添加模型类

public class Customer {
private Long id;
private String name;
private String emailAddress;
private int imageId;
private String imagePath;
}

3 - 添加依赖关系

compile 'de.hdodenhof:circleimageview:2.0.0'
compile 'com.squareup.picasso:picasso:2.5.2'
compile 'com.yqritc:recyclerview-flexibledivider:1.2.6'
compile 'com.google.code.gson:gson:2.3.1'

4 - 添加互联网权限

<uses-permission android:name="android.permission.INTERNET" />

5-在活动中新建List Customer，然后将客户添加到其中。

6-创建一个名为CustomerListAdapter的新类

 package com.okason.draganddrop;

import android.content.Context;
import android.graphics.Color;
import android.support.v4.view.MotionEventCompat;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.okason.draganddrop.listeners.OnCustomerListChangedListener;
import com.okason.draganddrop.listeners.OnStartDragListener;
import com.okason.draganddrop.utilities.ItemTouchHelperAdapter;
import com.okason.draganddrop.utilities.ItemTouchHelperViewHolder;
import com.squareup.picasso.Picasso;

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

/**
 * Created by Valentine on 10/18/2015.
 */
public class CustomerListAdapter extends
        RecyclerView.Adapter<CustomerListAdapter.ItemViewHolder>
        implements ItemTouchHelperAdapter {

private List<Customer> mCustomers;
private Context mContext;
private OnStartDragListener mDragStartListener;
private OnCustomerListChangedListener mListChangedListener;

public CustomerListAdapter(List<Customer> customers, Context context,
                           OnStartDragListener dragLlistener,
                           OnCustomerListChangedListener listChangedListener){
    mCustomers = customers;
    mContext = context;
    mDragStartListener = dragLlistener;
    mListChangedListener = listChangedListener;
}


@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View rowView = LayoutInflater.from
    (parent.getContext()).inflate(R.layout.row_customer_list, parent, false);
    ItemViewHolder viewHolder = new ItemViewHolder(rowView);
    return viewHolder;
}

@Override
public void onBindViewHolder(final ItemViewHolder holder, int position) {

    final Customer selectedCustomer = mCustomers.get(position);

    holder.customerName.setText(selectedCustomer.getName());
    holder.customerEmail.setText(selectedCustomer.getEmailAddress());
    Picasso.with(mContext)
            .load(selectedCustomer.getImagePath())
            .placeholder(R.drawable.profile_icon)
            .into(holder.profileImage);



    holder.handleView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (MotionEventCompat.getActionMasked(event) == MotionEvent.ACTION_DOWN) {
                mDragStartListener.onStartDrag(holder);
            }
            return false;
        }
    });
}

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

@Override
public void onItemMove(int fromPosition, int toPosition) {
    Collections.swap(mCustomers, fromPosition, toPosition);
    mListChangedListener.onNoteListChanged(mCustomers);
    notifyItemMoved(fromPosition, toPosition);
}

@Override
public void onItemDismiss(int position) {

}

public static class ItemViewHolder extends RecyclerView.ViewHolder implements
        ItemTouchHelperViewHolder {
    public final TextView customerName, customerEmail;
    public final ImageView handleView, profileImage;


    public ItemViewHolder(View itemView) {
        super(itemView);
        customerName = (TextView)itemView.findViewById(R.id.text_view_customer_name);
        customerEmail = (TextView)itemView.findViewById(R.id.text_view_customer_email);
        handleView = (ImageView)itemView.findViewById(R.id.handle);
        profileImage = (ImageView)itemView.findViewById(R.id.image_view_customer_head_shot);
    }

    @Override
    public void onItemSelected() {
        itemView.setBahttp://valokafor.com/wp-admin/post.php?post=1804&action=edit#ckgroundColor(Color.LTGRAY);
    }

    @Override
    public void onItemClear() {
        itemView.setBackgroundColor(0);
    }
}
}

7-实施ItemTouchHelper 在您的实用程序包中，添加ItemTouchHelperAdapter.java，以下是内容：

public interface ItemTouchHelperAdapter {
/**
 * Called when an item has been dragged far enough to trigger a move. This is called every time
 * an item is shifted, and not at the end of a "drop" event.
 *
 * @param fromPosition The start position of the moved item.
 * @param toPosition   Then end position of the moved item.

 */
void onItemMove(int fromPosition, int toPosition);


/**
 * Called when an item has been dismissed by a swipe.
 *
 * @param position The position of the item dismissed.

 */
void onItemDismiss(int position);
}

在您的实用程序包中，添加ItemTouchHelperViewHolder.java，以下是内容：

public interface ItemTouchHelperViewHolder {
    /**
      * Implementations should update the item view to indicate it's active state.
     */
    void onItemSelected();


    /**
     * state should be cleared.
     */
    void onItemClear();
}

在您的实用程序包中，添加SimpleItemTouchHelperCallback.java，这是内容：

public class SimpleItemTouchHelperCallback extends ItemTouchHelper.Callback {

private final ItemTouchHelperAdapter mAdapter;

public SimpleItemTouchHelperCallback(ItemTouchHelperAdapter adapter) {
    mAdapter = adapter;
}

@Override
public boolean isLongPressDragEnabled() {
    return true;
}

@Override
public boolean isItemViewSwipeEnabled() {
    return false;
}

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

@Override
public boolean onMove(RecyclerView recyclerView, 
RecyclerView.ViewHolder source, RecyclerView.ViewHolder target) {
    mAdapter.onItemMove(source.getAdapterPosition(), target.getAdapterPosition());
    return true;
}

@Override
public void onSwiped(RecyclerView.ViewHolder viewHolder, int i) {
    mAdapter.onItemDismiss(viewHolder.getAdapterPosition());
}

@Override
public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
    if (actionState != ItemTouchHelper.ACTION_STATE_IDLE) {
        ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
        itemViewHolder.onItemSelected();
    }

    super.onSelectedChanged(viewHolder, actionState);
}

@Override
public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
    super.clearView(recyclerView, viewHolder);

    ItemTouchHelperViewHolder itemViewHolder = (ItemTouchHelperViewHolder) viewHolder;
    itemViewHolder.onItemClear();
}
}

添加一个名为listener的包，并添加一个名为OnStartDragListener.java的接口，这里是内容：

public interface OnCustomerListChangedListener {
void onNoteListChanged(List<Customer> customers);
}

实施自定义行

private RecyclerView mRecyclerView;
private CustomerListAdapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private ItemTouchHelper mItemTouchHelper;
private List<Customer> mCustomers;

在onCreate方法之后，添加此方法。然后可能在调用set Toolbar之后从onCreate（）方法调用此方法。忽略错误警告一分钟。

private void setupRecyclerView(){
        mRecyclerView = (RecyclerView) `findViewById(R.id.note_recycler_view);`
        mRecyclerView.setHasFixedSize(true);
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mCustomers = SampleData.addSampleCustomers();

        //setup the adapter with empty list
        mAdapter = new CustomerListAdapter(mCustomers, this, this, this);
        ItemTouchHelper.Callback callback = new `SimpleItemTouchHelperCallback(mAdapter);`
        mItemTouchHelper = new ItemTouchHelper(callback);
        mItemTouchHelper.attachToRecyclerView(mRecyclerView);
mRecyclerView.addItemDecoration(new  HorizontalDividerItemDecoration.Builder(this)

                .colorResId(R.color.colorPrimaryDark)
                .size(2)
                .build());
        mRecyclerView.setAdapter(mAdapter);
    }

更新MainActivity的签名，以实现我们在下面添加的两个侦听器，并使用Android Studio快速修复来实现这些方法。

public class MainActivity extends AppCompatActivity
implements OnCustomerListChangedListener,
    OnStartDragListener{

以下是其中一种方法的实现，我们将在下一节中实现另一种方法。

@Override
public void onStartDrag(RecyclerView.ViewHolder viewHolder) {
    mItemTouchHelper.startDrag(viewHolder);

}

此时，您的拖放列表应该正常工作，我们现在想要记住列表项重新组织后的位置。就像我在帖子开头提到的那样，这是通过将列表项的ID保存到SharedPreference来完成的，所以继续将以下类成员添加到文件的顶部。

private SharedPreferences mSharedPreferences;
private SharedPreferences.Editor mEditor;
public static final String LIST_OF_SORTED_DATA_ID = "json_list_sorted_data_id";
public final static String PREFERENCE_FILE = "preference_file";

在onCreate（）中实例化SharedPreference，如：

mSharedPreferences = this.getApplicationContext()
            .getSharedPreferences(PREFERENCE_FILE, Context.MODE_PRIVATE);
    mEditor = mSharedPreferences.edit();

然后继续执行另一个在列表更改时监听的方法，这里是该方法的实现：

@Override
public void onNoteListChanged(List<Customer> customers) {
    //after drag and drop operation, the new list of Customers is passed in here

    //create a List of Long to hold the Ids of the
    //Customers in the List
    List<Long> listOfSortedCustomerId = new ArrayList<Long>();

    for (Customer customer: customers){
        listOfSortedCustomerId.add(customer.getId());
    }

    //convert the List of Longs to a JSON string
    Gson gson = new Gson();
    String jsonListOfSortedCustomerIds = gson.toJson(listOfSortedCustomerId);


    //save to SharedPreference
    mEditor.putString(LIST_OF_SORTED_DATA_ID, jsonListOfSortedCustomerIds).commit();
    mEditor.commit();
}

然后，将此方法添加到MainActivity.java：

private List<Customer> getSampleData(){

    //Get the sample data
    List<Customer> customerList = SampleData.addSampleCustomers();

    //create an empty array to hold the list of sorted Customers
    List<Customer> sortedCustomers = new ArrayList<Customer>();

    //get the JSON array of the ordered of sorted customers
    String jsonListOfSortedCustomerId = mSharedPreferences.getString(LIST_OF_SORTED_DATA_ID, "");

    //check for null
    if (!jsonListOfSortedCustomerId.isEmpty()){

        //convert JSON array into a List<Long>
        Gson gson = new Gson();
        List<Long> listOfSortedCustomersId = gson.fromJson
        (jsonListOfSortedCustomerId, new TypeToken<List<Long>>(){}.getType());

        //build sorted list
        if (listOfSortedCustomersId != null && listOfSortedCustomersId.size() > 0){
            for (Long id: listOfSortedCustomersId){
                for (Customer customer: customerList){
                    if (customer.getId().equals(id)){
                        sortedCustomers.add(customer);
                        customerList.remove(customer);
                        break;
                    }
                }
            }
        }

        //if there are still customers that were not in the sorted list
        //maybe they were added after the last drag and drop
        //add them to the sorted list
        if (customerList.size() > 0){
            sortedCustomers.addAll(customerList);
        }

        return sortedCustomers;
    }else {
       return customerList;
    }
}

现在更新setupRecyclerView()中您从以下位置获取数据的行：

mCustomers = SampleData.addSampleCustomers();

为：

mCustomers = getSampleData();

Here is the source of my answer您可以找到有关每一步的更多信息和说明。

如何拖放recyclerView元素？

1 个答案: