How to turn ON the Torch!

 Do you wonder how can we lit the light of our Android Phone's Torch?

Here we have a very small code to do that!

We only need just one permission in our AndroidManifest.xml to turn ON the light:

<uses-feature
    android:name="android.hardware.camera"
    android:required="false" />
<uses-permission android:name="android.permission.CAMERA" />

So after adding this, the AndroidManifest.xml looks like this:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-feature
        android:name="android.hardware.camera"
        android:required="false" />
    <uses-permission android:name="android.permission.CAMERA" />

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Torch">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Then in the activity_main.xml, create a button for user interaction:

<Button
    android:id="@+id/torchButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Toggle Flashlight" />

Here is the full content of the activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:gravity="center">

    <Button
        android:id="@+id/torchButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Toggle Flashlight" />
</LinearLayout>

Finally in the MainActivity.java we have to do multiple thing:

1. Create object of CameraManager which is used to interact with the camera hardware, in this case, to control the flashlight.

2. Create a String object cameraId which holds the ID of the camera (typically used to refer to the back camera here).

3. Create a boolean isTorchOn to track whether the torch is currently on or off.

private CameraManager cameraManager;
private String cameraId;
private boolean isTorchOn = false;

4. The getSystemService(CAMERA_SERVICE) call retrieves a system-level service to access the camera hardware.

cameraManager = (CameraManager) getSystemService(CAMERA_SERVICE);

5. Add a try catch block:

• This block attempts to get a list of camera IDs using cameraManager.getCameraIdList(). The first item in the list ([0]) corresponds to the back camera.

• If there’s an error in accessing the camera, it catches the CameraAccessException and prints the stack trace.

try {
    cameraId = cameraManager.getCameraIdList()[0]; // Use the back camera
} catch (CameraAccessException e) {
    e.printStackTrace();
}

6. Set up the Button for Toggling Torch:

A Button named torchButton is found using findViewById(R.id.torchButton), which references the button element defined in the XML layout file.

The setOnClickListener method attaches a click listener to the button, so when it’s clicked, the toggleTorch() method will be called.

Button torchButton = findViewById(R.id.torchButton);
torchButton.setOnClickListener(view -> toggleTorch());

7. toggleTorch() Method: This method toggles the flashlight (torch) on and off.

It checks the isTorchOn flag:

If the torch is on (isTorchOn is true), it calls cameraManager.setTorchMode(cameraId, false) to turn the flashlight off.

If the torch is off (isTorchOn is false), it calls cameraManager.setTorchMode(cameraId, true) to turn it on.

After toggling the torch, it updates the isTorchOn flag accordingly.

private void toggleTorch() {
    try {
        if (isTorchOn) {
            // Turn off the torch
            cameraManager.setTorchMode(cameraId, false);
            isTorchOn = false;
        } else {
            // Turn on the torch
            cameraManager.setTorchMode(cameraId, true);
            isTorchOn = true;
        }
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

So the complete code of MainActivity.java will be:

package com.prashantsj.apps.torch;

import android.app.Activity;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.os.Bundle;
import android.widget.Button;

public class MainActivity extends Activity {

    private CameraManager cameraManager;
    private String cameraId;
    private boolean isTorchOn = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Initialize the CameraManager
        cameraManager = (CameraManager) getSystemService(CAMERA_SERVICE);

        // Get the camera ID (for the back camera)
        try {
            cameraId = cameraManager.getCameraIdList()[0]; // Use the back camera
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

        // Button to toggle torch
        Button torchButton = findViewById(R.id.torchButton);
        torchButton.setOnClickListener(view -> toggleTorch());
    }

    private void toggleTorch() {
        try {
            if (isTorchOn) {
                // Turn off the torch
                cameraManager.setTorchMode(cameraId, false);
                isTorchOn = false;
            } else {
                // Turn on the torch
                cameraManager.setTorchMode(cameraId, true);
                isTorchOn = true;
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
}