如何在Android的Firebase Firestore中更新数据？

在上一篇文章中，我们了解了如何在Android的Firebase Firestore中添加数据，如何在Android的Firebase Firestore中读取数据。现在，我们将看到如何在Firebase Firestore中更新此添加的数据。现在，我们将着手在Android Firebase中实现此更新数据。

我们将在本文中构建什么?

我们将创建一个与添加数据时类似的屏幕，并在此屏幕中，在Firebase Firestore中更新数据，并且该数据也将在我们的应用程序中更新。

分步实施

步骤1：创建新的Activity以更新数据

要创建新的Activity，请导航至应用程序> res>布局>右键单击它，然后单击New>然后单击Empty Activity以创建一个新的Activity ，我们将其命名为UpdateCourse 。创建新的活动后，导航至应用程序> res>布局> activity_update_course.xml ，并将以下代码添加到其中。

第2步：更新存储数据的模态类

在以前的文章中，我们已经看到了创建Modal类。在本文中，我们将更新Modal类，以便可以将对象类从适配器传递到活动中进行导航。除了可序列化的实现之外，我们还必须创建一个新的字符串变量，并为该变量创建一个getter和setter方法。我们将使用该变量存储文档的ID。以下是更新后的课程的代码。 Java类。在代码内部添加了注释，以便更详细地了解。

Java

import com.google.firebase.firestore.Exclude;
  
import java.io.Serializable;
  
// we have to implement our modal class
// with serializable so that we can pass
// our object class to new activity on
// our item click of recycler view.
public class Courses implements Serializable {
  
    // getter method for our id
    public String getId() {
        return id;
    }
  
    // setter method for our id
    public void setId(String id) {
        this.id = id;
    }
  
    // we are using exclude because
    // we are not saving our id
    @Exclude
    private String id;
      
    // variables for storing our data.
    private String courseName, courseDescription, courseDuration;
  
    public Courses() {
        // empty constructor required for Firebase.
    }
  
    // Constructor for all variables.
    public Courses(String courseName, String courseDescription, String courseDuration) {
        this.courseName = courseName;
        this.courseDescription = courseDescription;
        this.courseDuration = courseDuration;
    }
  
    // getter methods for all variables.
    public String getCourseName() {
        return courseName;
    }
  
    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }
  
    public String getCourseDescription() {
        return courseDescription;
    }
  
    // setter method for all variables.
    public void setCourseDescription(String courseDescription) {
        this.courseDescription = courseDescription;
    }
  
    public String getCourseDuration() {
        return courseDuration;
    }
  
    public void setCourseDuration(String courseDuration) {
        this.courseDuration = courseDuration;
    }
}

步骤3：为我们的RecyclerView项目添加onClickListener()

正如我们在上一篇文章中创建了Adapter类之后，该类用于在Recycler View中显示课程列表。在本文中，我们将在该Adapter类内为RecyclerView项目单击侦听器添加onClickListener() 。将以下代码段添加到CourseRVAdapter。 Java文件。

Java

// here we are adding on click listener
// for our item of recycler view.
itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    
                    // after clicking of the item of recycler view.
                    // we are passing our course object to the new activity.
                    Courses courses = coursesArrayList.get(getAdapterPosition());
  
                    // below line is creating a new intent.
                    Intent i = new Intent(context, UpdateCourse.class);
  
                    // below line is for putting our course object to our next activity.
                    i.putExtra("course", courses);
  
                    // after passing the data we are starting our activity.
                    context.startActivity(i);
           }
    });

下面是CourseRVAdapter的更新代码。 Java文件。

Java

import android.content.Context;
import android.content.Intent;
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 CourseRVAdapter extends RecyclerView.Adapter {
    // creating variables for our ArrayList and context
    private ArrayList coursesArrayList;
    private Context context;
  
    // creating constructor for our adapter class
    public CourseRVAdapter(ArrayList coursesArrayList, Context context) {
        this.coursesArrayList = coursesArrayList;
        this.context = context;
    }
  
    @NonNull
    @Override
    public CourseRVAdapter.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // passing our layout file for displaying our card item
        return new ViewHolder(LayoutInflater.from(context).inflate(R.layout.course_item, parent, false));
    }
  
    @Override
    public void onBindViewHolder(@NonNull CourseRVAdapter.ViewHolder holder, int position) {
        // setting data to our text views from our modal class.
        Courses courses = coursesArrayList.get(position);
        holder.courseNameTV.setText(courses.getCourseName());
        holder.courseDurationTV.setText(courses.getCourseDuration());
        holder.courseDescTV.setText(courses.getCourseDescription());
    }
  
    @Override
    public int getItemCount() {
        // returning the size of our array list.
        return coursesArrayList.size();
    }
  
    class ViewHolder extends RecyclerView.ViewHolder {
        // creating variables for our text views.
        private final TextView courseNameTV;
        private final TextView courseDurationTV;
        private final TextView courseDescTV;
  
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            // initializing our text views.
            courseNameTV = itemView.findViewById(R.id.idTVCourseName);
            courseDurationTV = itemView.findViewById(R.id.idTVCourseDuration);
            courseDescTV = itemView.findViewById(R.id.idTVCourseDescription);
  
            // here we are adding on click listener
            // for our item of recycler view.
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    
                    // after clicking of the item of recycler view.
                    // we are passing our course object to the new activity.
                    Courses courses = coursesArrayList.get(getAdapterPosition());
  
                    // below line is creating a new intent.
                    Intent i = new Intent(context, UpdateCourse.class);
  
                    // below line is for putting our course object to our next activity.
                    i.putExtra("course", courses);
  
                    // after passing the data we are starting our activity.
                    context.startActivity(i);
                }
            });
        }
    }
}

步骤4：更新CourseDetails中的代码。 Java文件

由于我们在模态类中创建了一个用于存储文档ID的新变量，因此我们必须初始化该变量并将文档ID传递到该变量中。为了传递该文档ID，我们必须更新CourseDetails的代码。显示我们已添加的所有课程列表的Java文件。将以下代码段添加到CourseRVAdapter。 Java文件。

Java

// below is the updated line of code which we have to
// add to pass the document id inside our modal class.
// we are setting our document id with d.getId() method
c.setId(d.getId());

以下是CourseDetails的更新代码。 Java文件。

Java

import android.os.Bundle;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;
  
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
  
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.DocumentSnapshot;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.QuerySnapshot;
  
import java.util.ArrayList;
import java.util.List;
  
public class CourseDetails extends AppCompatActivity {
  
    // creating variables for our recycler view,
    // array list, adapter, firebase firestore
    // and our progress bar.
    private RecyclerView courseRV;
    private ArrayList coursesArrayList;
    private CourseRVAdapter courseRVAdapter;
    private FirebaseFirestore db;
    ProgressBar loadingPB;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_course_details);
  
        // initializing our variables.
        courseRV = findViewById(R.id.idRVCourses);
        loadingPB = findViewById(R.id.idProgressBar);
  
        // initializing our variable for firebase
        // firestore and getting its instance.
        db = FirebaseFirestore.getInstance();
  
        // creating our new array list
        coursesArrayList = new ArrayList<>();
        courseRV.setHasFixedSize(true);
        courseRV.setLayoutManager(new LinearLayoutManager(this));
  
        // adding our array list to our recycler view adapter class.
        courseRVAdapter = new CourseRVAdapter(coursesArrayList, this);
  
        // setting adapter to our recycler view.
        courseRV.setAdapter(courseRVAdapter);
  
        // below line is use to get the data from Firebase Firestore.
        // previously we were saving data on a reference of Courses
        // now we will be getting the data from the same reference.
        db.collection("Courses").get()
                .addOnSuccessListener(new OnSuccessListener() {
                    @Override
                    public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                        // after getting the data we are calling on success method
                        // and inside this method we are checking if the received
                        // query snapshot is empty or not.
                        if (!queryDocumentSnapshots.isEmpty()) {
                            // if the snapshot is not empty we are
                            // hiding our progress bar and adding
                            // our data in a list.
                            loadingPB.setVisibility(View.GONE);
                            List list = queryDocumentSnapshots.getDocuments();
                            for (DocumentSnapshot d : list) {
                                // after getting this list we are passing
                                // that list to our object class.
                                Courses c = d.toObject(Courses.class);
  
                                // below is the updated line of code which we have to
                                // add to pass the document id inside our modal class.
                                // we are setting our document id with d.getId() method
                                c.setId(d.getId());
  
                                // and we will pass this object class
                                // inside our arraylist which we have
                                // created for recycler view.
                                coursesArrayList.add(c);
                            }
                            // after adding the data to recycler view.
                            // we are calling recycler view notifuDataSetChanged
                            // method to notify that data has been changed in recycler view.
                            courseRVAdapter.notifyDataSetChanged();
                        } else {
                            // if the snapshot is empty we are displaying a toast message.
                            Toast.makeText(CourseDetails.this, "No data found in Database", Toast.LENGTH_SHORT).show();
                        }
                    }
                }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                // if we do not get any data or any error we are displaying
                // a toast message that we do not get any data
                Toast.makeText(CourseDetails.this, "Fail to get the data.", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

步骤5：现在，我们将着手实施UpdateCourses。 Java文件

更新我们的适配器类后，导航至应用程序> Java >您的应用程序的程序包名称> UpdateCourses。 Java文件，并向其中添加以下代码。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.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
  
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
  
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.firebase.firestore.FirebaseFirestore;
  
public class UpdateCourse extends AppCompatActivity {
  
    // creating variables for our edit text
    private EditText courseNameEdt, courseDurationEdt, courseDescriptionEdt;
  
    // creating a strings for storing our values from Edittext fields.
    private String courseName, courseDuration, courseDescription;
  
    // creating a variable for firebasefirestore.
    private FirebaseFirestore db;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update_course);
        Courses courses = (Courses) getIntent().getSerializableExtra("course");
  
        // getting our instance from Firebase Firestore.
        db = FirebaseFirestore.getInstance();
  
        // initializing our edittext and buttons
        courseNameEdt = findViewById(R.id.idEdtCourseName);
        courseDescriptionEdt = findViewById(R.id.idEdtCourseDescription);
        courseDurationEdt = findViewById(R.id.idEdtCourseDuration);
  
        // creating variable for button
        Button updateCOurseBtn = findViewById(R.id.idBtnUpdateCourse);
  
        courseNameEdt.setText(courses.getCourseName());
        courseDescriptionEdt.setText(courses.getCourseDescription());
        courseDurationEdt.setText(courses.getCourseDuration());
  
  
        updateCOurseBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                courseName = courseNameEdt.getText().toString();
                courseDescription = courseDescriptionEdt.getText().toString();
                courseDuration = courseDurationEdt.getText().toString();
  
                // validating the text fields if empty or not.
                if (TextUtils.isEmpty(courseName)) {
                    courseNameEdt.setError("Please enter Course Name");
                } else if (TextUtils.isEmpty(courseDescription)) {
                    courseDescriptionEdt.setError("Please enter Course Description");
                } else if (TextUtils.isEmpty(courseDuration)) {
                    courseDurationEdt.setError("Please enter Course Duration");
                } else {
                    // calling a method to update our course.
                    // we are passing our object class, course name,
                    // course description and course duration from our edittext field.
                    updateCourses(courses, courseName, courseDescription, courseDuration);
                }
            }
        });
    }
  
    private void updateCourses(Courses courses, String courseName, String courseDescription, String courseDuration) {
        // inside this method we are passing our updated values
        // inside our object class and later on we
        // will pass our whole object to firebase Firestore.
        Courses updatedCourse = new Courses(courseName, courseDescription, courseDuration);
  
        // after passing data to object class we are
        // sending it to firebase with specific document id.
        // below line is use to get the collection of our Firebase Firestore.
        db.collection("Courses").
                // below line is use toset the id of
                // document where we have to perform
                // update operation.
                document(courses.getId()).
  
                // after setting our document id we are
                // passing our whole object class to it.
                set(updatedCourse).
  
                // after passing our object class we are
                // calling a method for on success listener.
                addOnSuccessListener(new OnSuccessListener() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        // on successful completion of this process
                        // we are displaying the toast message.
                        Toast.makeText(UpdateCourse.this, "Course has been updated..", Toast.LENGTH_SHORT).show();
                    }
                }).addOnFailureListener(new OnFailureListener() {
            // inside on failure method we are
            // displaying a failure message.
            @Override
            public void onFailure(@NonNull Exception e) {
                Toast.makeText(UpdateCourse.this, "Fail to update the data..", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

输出：

想要一个节奏更快，更具竞争性的环境来学习Android的基础知识吗?

单击此处，前往由我们的专家精心策划的指南，以使您立即做好行业准备！