Android Jetpack Compose – Delete Data in Firebase Firestore

In the previous article, we have taken a look at How to add, read and update data from our application in Firebase Firestore. In this article, we will take a look at How to implement a functionality in our application so that we will be able to delete data from Firebase Firestore in our android application using Jetpack Compose. A sample video is given below to get an idea about what we are going to do in this article.

Step by Step Implementation

As we have implemented Read and write operation in the previous article which is given below :

• Android Jetpack Compose – Adding data to Firebase Firestore
• Android Jetpack Compose – Reading data from Firebase Firestore
• Android Jetpack Compose – Updating data from Firebase Firestore

Check out the project link for the part 1, part 2, and part 3. Now we will move towards deleting the data inside our Firebase Database in Android. For deleting the data we have to simply update our UpdateCourse.kt file. 

Step 1: Working with UpdateCourse.kt file

Navigate to app>java>your app’s package name>UpdateCourse.kt file and add the below code to it. Comments are added in the code to get to know it in detail. 

Kotlin

package com.example.firebaseproject

import android.content.Context
import android.content.Intent
import android.os.Bundle
import android.text.TextUtils
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.*
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import com.example.firebaseproject.ui.theme.FirebaseProjectTheme
import com.example.firebaseproject.ui.theme.greenColor
import com.google.android.gms.tasks.OnCompleteListener
import com.google.firebase.firestore.FirebaseFirestore

class UpdateCourse : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            FirebaseProjectTheme {
                // A surface container using the
                // 'background' color from the theme
                Surface(
                    // on below line we are specifying
                    // modifier and color for our app
                    modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background
                ) {
                    // on the below line we are specifying
                    // the theme as the scaffold.
                    Scaffold(
                        // in scaffold we are specifying the top bar.
                        topBar = {
                            // inside top bar we are
                            // specifying background color.
                            TopAppBar(backgroundColor = greenColor,
                                // along with that we are specifying
                                // title for our top bar.
                                title = {
                                    // in the top bar we are
                                    // specifying tile as a text
                                    Text(
                                        // on below line we are specifying
                                        // text to display in top app bar
                                        text = "GFG",
                                        // on below line we are specifying
                                        // modifier to fill max width
                                        modifier = Modifier.fillMaxWidth(),
                                        // on below line we are specifying
                                        // text alignment
                                        textAlign = TextAlign.Center,
                                        // on below line we are specifying
                                        // color for our text.
                                        color = Color.White
                                    )
                                })
                        }) {

                        // on below line getting data from our database
                        // on below line we are calling method to display UI
                        firebaseUI(
                            LocalContext.current,
                            intent.getStringExtra("courseName"),
                            intent.getStringExtra("courseDuration"),
                            intent.getStringExtra("courseDescription"),
                            intent.getStringExtra("courseID")
                        )
                    }
                }
            }
        }
    }

    @Composable
    fun firebaseUI(
        context: Context,
        name: String?,
        duration: String?,
        description: String?,
        courseID: String?
    ) {

        // on below line creating variable for course name,
        // course duration and course description.
        val courseName = remember {
            mutableStateOf(name)
        }

        val courseDuration = remember {
            mutableStateOf(duration)
        }

        val courseDescription = remember {
            mutableStateOf(description)
        }

        // on below line creating a column
        Column(
            // adding modifier for our column
            modifier = Modifier
                .fillMaxHeight()
                .fillMaxWidth()
                .background(Color.White),
            // on below line adding vertical and
            // horizontal alignment for column.
            verticalArrangement = Arrangement.Center,
            horizontalAlignment = Alignment.CenterHorizontally
        ) {


            TextField(
                // on below line we are specifying
                // value for our course name text field.
                value = courseName.value.toString(),

                // on below line we are adding on
                // value change for text field.
                onValueChange = { courseName.value = it },

                // on below line we are adding place holder
                // as text as "Enter your course name"
                placeholder = { Text(text = "Enter your course name") },

                // on below line we are adding modifier to it
                // and adding padding to it and filling max width
                modifier = Modifier
                    .padding(16.dp)
                    .fillMaxWidth(),

                // on below line we are adding text style
                // specifying color and font size to it.
                textStyle = TextStyle(color = Color.Black, fontSize = 15.sp),

                // on below line we are adding
                // single line to it.
                singleLine = true,
            )

            Spacer(modifier = Modifier.height(10.dp))

            TextField(
                // on below line we are specifying
                // value for our course duration text field.
                value = courseDuration.value.toString(),

                // on below line we are adding on
                // value change for text field.
                onValueChange = { courseDuration.value = it },

                // on below line we are adding place holder
                // as text as "Enter your course duration"
                placeholder = { Text(text = "Enter your course duration") },

                // on below line we are adding modifier to it
                // and adding padding to it and filling max width
                modifier = Modifier
                    .padding(16.dp)
                    .fillMaxWidth(),

                // on below line we are adding text style
                // specifying color and font size to it.
                textStyle = TextStyle(color = Color.Black, fontSize = 15.sp),

                // on below line we are adding
                // single line to it.
                singleLine = true,
            )

            Spacer(modifier = Modifier.height(10.dp))

            TextField(
                // on below line we are specifying
                // value for our course description text field.
                value = courseDescription.value.toString(),

                // on below line we are adding on
                // value change for text field.
                onValueChange = { courseDescription.value = it },

                // on below line we are adding place holder
                // as text as "Enter your course description"
                placeholder = { Text(text = "Enter your course description") },

                // on below line we are adding modifier to it
                // and adding padding to it and filling max width
                modifier = Modifier
                    .padding(16.dp)
                    .fillMaxWidth(),

                // on below line we are adding text style
                // specifying color and font size to it.
                textStyle = TextStyle(color = Color.Black, fontSize = 15.sp),

                // on below line we are adding
                // single line to it.
                singleLine = true,
            )

            Spacer(modifier = Modifier.height(10.dp))

            // on below line creating button to add data
            // to firebase firestore database.
            Button(
                onClick = {
                    // on below line we are validating user input parameters.
                    if (TextUtils.isEmpty(courseName.value.toString())) {
                        Toast.makeText(context, "Please enter course name", Toast.LENGTH_SHORT)
                            .show()
                    } else if (TextUtils.isEmpty(courseDuration.value.toString())) {
                        Toast.makeText(
                            context,
                            "Please enter course Duration",
                            Toast.LENGTH_SHORT
                        )
                            .show()
                    } else if (TextUtils.isEmpty(courseDescription.value.toString())) {
                        Toast.makeText(
                            context,
                            "Please enter course description",
                            Toast.LENGTH_SHORT
                        )
                            .show()
                    } else {
                        // on below line adding data
                        // to firebase firestore database.
                        updateDataToFirebase(
                            courseID,
                            courseName.value,
                            courseDuration.value,
                            courseDescription.value,
                            context
                        )
                    }
                },
                // on below line we are
                // adding modifier to our button.
                modifier = Modifier
                    .fillMaxWidth()
                    .padding(16.dp)
            ) {
                // on below line we are adding text for our button
                Text(text = "Update Data", modifier = Modifier.padding(8.dp))
            }

            Spacer(modifier = Modifier.height(10.dp))

            // on below line creating button to delete the course.
            Button(
                onClick = {
                    // on below line calling delete course
                    // method to delete our course.
                    deleteDataFromFirebase(courseID, context)
                },
                // on below line we are
                // adding modifier to our button.
                modifier = Modifier
                    .fillMaxWidth()
                    .padding(16.dp)
            ) {
                // on below line we are adding text for our button
                Text(text = "Delete Course", modifier = Modifier.padding(8.dp))
            }

        }
    }

    private fun deleteDataFromFirebase(courseID: String?, context: Context) {

        // getting our instance from Firebase Firestore.
        val db = FirebaseFirestore.getInstance();

        // below line is for getting the collection
        // where we are storing our courses.
        db.collection("Courses").document(courseID.toString()).delete().addOnSuccessListener {
            // displaying toast message when our course is deleted.
            Toast.makeText(context, "Course Deleted successfully..", Toast.LENGTH_SHORT).show()
            context.startActivity(Intent(context, CourseDetailsActivity::class.java))
        }.addOnFailureListener {
            // on below line displaying toast message when
            // we are not able to delete the course
            Toast.makeText(context, "Fail to delete course..", Toast.LENGTH_SHORT).show()
        }

    }


    private fun updateDataToFirebase(
        courseID: String?,
        name: String?,
        duration: String?,
        description: String?,
        context: Context
    ) {
        // inside this method we are passing our updated
        // values inside our object class and later on we
        // will pass our whole object tofirebase Firestore.
        val updatedCourse = Course(courseID, name, duration, description)

        // getting our instance from Firebase Firestore.
        val db = FirebaseFirestore.getInstance();
        db.collection("Courses").document(courseID.toString()).set(updatedCourse)
            .addOnSuccessListener {
                // on below line displaying toast message and
                // opening new activity to view courses.
                Toast.makeText(context, "Course Updated successfully..", Toast.LENGTH_SHORT).show()
                context.startActivity(Intent(context, CourseDetailsActivity::class.java))
                finish()

            }.addOnFailureListener {
                Toast.makeText(context, "Fail to update course : " + it.message, Toast.LENGTH_SHORT)
                    .show()
            }
    }
}

Now run your project to see the output of it. 

Output: