在Android RecyclerView中滑动以删除和撤消

我们已经看到许多应用程序中都包含RecyclerView，并且与此同时，我们还看到了RecyclerView中的许多功能，可通过滑动删除这些功能以及更多其他功能。我们已经在Gmail应用程序中看到了这种类型的功能，可以在其中滑动或向右或向左滑动项目以删除或添加到存档中。在本文中，我们将研究其中具有撤消功能的“滑动以删除RecyclerView”项目的实现。

我们将在本文中构建什么?

我们将构建一个简单的应用程序，在其中将显示一个简单的RecyclerView，其中显示课程列表及其说明，并且将添加用于删除和撤消功能的功能。下面给出了一个示例GIF，以了解我们将在本文中做些什么。注意，我们将使用Java语言实现该项目。

分步实施

步骤1：创建一个新项目

要在Android Studio中创建新项目，请参阅如何在Android Studio中创建/启动新项目。请注意，选择Java作为编程语言。

要实现Recycler View，需要三个子部分，它们有助于控制RecyclerView。这三个子部分包括：

• 卡片布局：卡片布局是一个XML文件，它将代表“回收者”视图内的每个单独的网格项目。
• View Holder ：View Holder类是一种Java类，用于在Card Layout中存储对UI元素的引用，并且可以在程序执行期间通过数据列表动态修改它们。
• 数据类：数据类是一个对象类，其中包含要在“回收者视图”中显示的每个“回收者”视图项中显示的信息。

步骤2：为RecyclerView卡项目创建卡布局

转到应用程序> res>布局>右键单击>新建>布局资源文件，并将文件命名为card_layout 。在此文件中，写入了与RecyclerView中的卡片项目有关的所有XML代码。以下是card_layout.xml文件的代码。

步骤3：为模态数据创建Java类

转到应用程序> Java >右键单击应用程序的包名称>新建> Java类，并将文件命名为RecyclerData 。此类将处理要显示的每个“回收者”项目的数据。以下是RecyclerData的代码。 Java文件。

Java

public class RecyclerData {
    // string for displaying 
    // title and description.
    private String title;
    private String description;
  
    // constructor for our title and description.
    public RecyclerData(String title, String description) {
        this.title = title;
        this.description = description;
    }
  
    // creating getter and setter methods.
    public String getTitle() {
        return title;
    }
  
    public void setTitle(String title) {
        this.title = title;
    }
  
    public String getDescription() {
        return description;
    }
  
    public void setDescription(String description) {
        this.description = description;
    }   
}

步骤4：为适配器创建一个新的Java类

同样，创建一个新的Java类并将文件命名为RecyclerViewAdapter。适配器是负责RecyclerView的主要类。它包含在RecyclerView中有用的所有方法。

Note: View Holder Class is also implemented in Adapter Class itself.  

这些处理“回收者视图”的方法包括：

• onCreateViewHolder ：此方法为Recycler View扩充卡片布局项目。
• onBindViewHolder ：此方法将数据设置为卡片项目的特定视图。它还处理与单击“回收者”视图中的项目有关的方法。
• getItemCount ：此方法返回RecyclerView的长度。

下面是RecyclerViewAdapter的代码。 Java文件。在代码内部添加了注释，以更详细地了解代码。

Java

import android.content.Context;
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.ArrayList;
  
public class RecyclerViewAdapter extends RecyclerView.Adapter {
  
    // creating a variable for our array list and context.
    private ArrayList courseDataArrayList;
    private Context mcontext;
  
    // creating a constructor class.
    public RecyclerViewAdapter(ArrayList recyclerDataArrayList, Context mcontext) {
        this.courseDataArrayList = recyclerDataArrayList;
        this.mcontext = mcontext;
    }
  
    @NonNull
    @Override
    public RecyclerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // Inflate Layout
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_layout, parent, false);
        return new RecyclerViewHolder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull RecyclerViewHolder holder, int position) {
        // Set the data to textview from our modal class.
        RecyclerData recyclerData = courseDataArrayList.get(position);
        holder.courseNameTV.setText(recyclerData.getTitle());
        holder.courseDescTV.setText(recyclerData.getDescription());
    }
  
    @Override
    public int getItemCount() {
        // this method returns 
          // the size of recyclerview
        return courseDataArrayList.size();
    }
  
    // View Holder Class to handle Recycler View.
    public class RecyclerViewHolder extends RecyclerView.ViewHolder {
        
        // creating a variable for our text view.
        private TextView courseNameTV;
        private TextView courseDescTV;
  
        public RecyclerViewHolder(@NonNull View itemView) {
            super(itemView);
            // initializing our text views.
            courseNameTV = itemView.findViewById(R.id.idTVCourseName);
            courseDescTV = itemView.findViewById(R.id.idTVCourseDesc);
        }
    }
}

步骤5：使用activity_main.xml文件

导航到应用程序> res>布局> activity_main.xml，然后将以下代码添加到该文件中。以下是activity_main.xml文件的代码。

步骤6：使用MainActivity。 Java文件

转到MainActivity。 Java文件并参考以下代码。下面是MainActivity的代码。 Java文件。在代码内部添加了注释，以更详细地了解代码。

Java

import android.os.Bundle;
import android.view.View;
  
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
  
import com.google.android.material.snackbar.Snackbar;
  
import java.util.ArrayList;
  
public class MainActivity extends AppCompatActivity {
      
    // creating a variable for recycler view, 
    // array list and adapter class.
    private RecyclerView courseRV;
    private ArrayList recyclerDataArrayList;
    private RecyclerViewAdapter recyclerViewAdapter;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
          
        // initializing our variables.
        courseRV = findViewById(R.id.idRVCourse);
          
        // creating new array list.
        recyclerDataArrayList = new ArrayList<>();
          
        // in below line we are adding data to our array list.
        recyclerDataArrayList.add(new RecyclerData("DSA Course", "DSA Self Paced Course"));
        recyclerDataArrayList.add(new RecyclerData("C++ Course", "C++ Self Paced Course"));
        recyclerDataArrayList.add(new RecyclerData("Java Course", "Java Self Paced Course"));
        recyclerDataArrayList.add(new RecyclerData("Python Course", "Python Slef Paced Course"));
        recyclerDataArrayList.add(new RecyclerData("Fork CPP", "Fork CPP Self Paced Course"));
        recyclerDataArrayList.add(new RecyclerData("Amazon SDE", "Amazon SDE Test Questions"));
         
        // initializing our adapter class with our array list and context.
        recyclerViewAdapter = new RecyclerViewAdapter(recyclerDataArrayList, this);
         
        // below line is to set layout manager for our recycler view.
        LinearLayoutManager manager = new LinearLayoutManager(this);
          
        // setting layout manager for our recycler view.
        courseRV.setLayoutManager(manager);
          
        // below line is to set adapter 
        // to our recycler view.
        courseRV.setAdapter(recyclerViewAdapter);
          
        // on below line we are creating a method to create item touch helper
        // method for adding swipe to delete functionality.
        // in this we are specifying drag direction and position to right
        new ItemTouchHelper(new ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT) {
            @Override
            public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
                // this method is called 
                // when the item is moved.
                return false;
            }
  
            @Override
            public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
                // this method is called when we swipe our item to right direction.
                // on below line we are getting the item at a particular position.
                RecyclerData deletedCourse = recyclerDataArrayList.get(viewHolder.getAdapterPosition());
                  
                // below line is to get the position
                // of the item at that position.
                int position = viewHolder.getAdapterPosition();
                  
                // this method is called when item is swiped.
                // below line is to remove item from our array list.
                recyclerDataArrayList.remove(viewHolder.getAdapterPosition());
                  
                // below line is to notify our item is removed from adapter.
                recyclerViewAdapter.notifyItemRemoved(viewHolder.getAdapterPosition());
                  
                // below line is to display our snackbar with action.
                Snackbar.make(courseRV, deletedCourse.getTitle(), Snackbar.LENGTH_LONG).setAction("Undo", new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        // adding on click listener to our action of snack bar.
                        // below line is to add our item to array list with a position.
                        recyclerDataArrayList.add(position, deletedCourse);
                          
                        // below line is to notify item is 
                        // added to our adapter class.
                        recyclerViewAdapter.notifyItemInserted(position);
                    }
                }).show();
            }
            // at last we are adding this 
            // to our recycler view.
        }).attachToRecyclerView(courseRV);
    }
}

现在运行您的应用程序，并查看该应用程序的输出。

输出：

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