Android Developing Flashlight Application

I am going to demonstrate developing a simple android application. This application is about turning on and off device flashlight / torchlight with simple touch. Please note that this app is targeted to mobile devices only, i am not sure how this app looks in tablet devices.

1) Creating new project

Create a new project in Eclipse IDE by going to File ⇒ New ⇒ Android Application Project .

2) Open your AndroidManifest.xml file and add required permissions. I also disabled landscape mode in manifest file by using android:screenOrientation=”portrait” property.

android.permission.CAMERA – required to access the camera device
android.hardware.camera – required to access camera hardware features

AndroidManifest.xml

<?xml version=”1.0″ encoding=”utf-8″?>
<manifest xmlns:android=”http://schemas.android.com/apk/res/android”
package=”com.w2class.flashlight”
android:versionCode=”1″
android:versionName=”1.0″ >

<uses-sdk
android:minSdkVersion=”8″
android:targetSdkVersion=”17″ />

<uses-permission android:name=”android.permission.CAMERA” />
<uses-feature android:name=”android.hardware.camera” />

<application
android:allowBackup=”true”
android:icon=”@drawable/ic_launcher”
android:label=”@string/app_name”
android:theme=”@style/AppTheme” >
<activity
android:name=”com.w2class.flashlight.MainActivity”
android:label=”@string/app_name”
android:screenOrientation=”portrait”>
<intent-filter>
<action android:name=”android.intent.action.MAIN” />

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

</manifest>

3) Place all the switch image files under drawable-hdpi, drawable-mdpi, drawable-ldpi folders. I named switch image files as btn_switch_off.png and btn_switch_on.png

4) Create a new xml file named radial_background.xml under res ⇒ drwable-hdpi folder and paste the following code. This file is used to create radial gradient background for the app.

radial_backbround.xml

<?xml version=”1.0″ encoding=”UTF-8″?>
<shape xmlns:android=”http://schemas.android.com/apk/res/android”>
<gradient
android:type=”radial”
android:startColor=”#343030″
android:endColor=”#151515″
android:gradientRadius=”300″
android:angle=”270″
android:centerY=”0.3″/>
</shape>

5) Now open activity_main.xml file located under res ⇒ layout folder and type the following code. This layout file acts as main screen of the application.

activity_main.xml

<RelativeLayout xmlns:android=”http://schemas.android.com/apk/res/android”
xmlns:tools=”http://schemas.android.com/tools”
android:layout_width=”match_parent”
android:layout_height=”match_parent”
android:background=”@drawable/radial_background”
tools:context=”.MainActivity” >

<ImageButton
android:id=”@+id/btnSwitch”
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_centerHorizontal=”true”
android:layout_marginTop=”100dip”
android:src=”@drawable/btn_switch_on”
android:background=”@null”
android:contentDescription=”@null”
/>
</RelativeLayout>

6)  Playing switch sound

If you are done with all the previous steps, your app will work perfectly. Here we can add an enhancement to our app by playing switch sound when user touches the switch. I downloaded two sound files from free sound libraries for switch on / switch off states and named them as light_switch_on.mp3 and light_switch_off.mp3

Under res folder create a new folder called raw and place these sound files in it. (res ⇒ raw ⇒ light_switch_on.mp3, light_switch_off.mp3)

 

7) Now open your MainActivity.java file and do the following changes.

MainActivity.java

package com.w2class.flashlight;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.media.MediaPlayer;
import android.media.MediaPlayer.OnCompletionListener;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageButton;

public class MainActivity extends Activity {

ImageButton btnSwitch;

private Camera camera;
private boolean isFlashOn;
private boolean hasFlash;
Parameters params;
MediaPlayer mp;

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

// flash switch button
btnSwitch = (ImageButton) findViewById(R.id.btnSwitch);

// First check if device is supporting flashlight or not
hasFlash = getApplicationContext().getPackageManager()
.hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);

if (!hasFlash) {
// device doesn’t support flash
// Show alert message and close the application
AlertDialog alert = new AlertDialog.Builder(MainActivity.this)
.create();
alert.setTitle(“Error”);
alert.setMessage(“Sorry, your device doesn’t support flash light!”);
alert.setButton(“OK”, new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
// closing the application
finish();
}
});
alert.show();
return;
}

// get the camera
getCamera();

// displaying button image
toggleButtonImage();

// Switch button click event to toggle flash on/off
btnSwitch.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
if (isFlashOn) {
// turn off flash
turnOffFlash();
} else {
// turn on flash
turnOnFlash();
}
}
});
}

// Get the camera
private void getCamera() {
if (camera == null) {
try {
camera = Camera.open();
params = camera.getParameters();
} catch (RuntimeException e) {
Log.e(“Camera Error. Failed to Open. Error: “, e.getMessage());
}
}
}

// Turning On flash
private void turnOnFlash() {
if (!isFlashOn) {
if (camera == null || params == null) {
return;
}
// play sound
playSound();

params = camera.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_TORCH);
camera.setParameters(params);
camera.startPreview();
isFlashOn = true;

// changing button/switch image
toggleButtonImage();
}

}

// Turning Off flash
private void turnOffFlash() {
if (isFlashOn) {
if (camera == null || params == null) {
return;
}
// play sound
playSound();

params = camera.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(params);
camera.stopPreview();
isFlashOn = false;

// changing button/switch image
toggleButtonImage();
}
}

// Playing sound
// will play button toggle sound on flash on / off
private void playSound(){
if(isFlashOn){
mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_off);
}else{
mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_on);
}
mp.setOnCompletionListener(new OnCompletionListener() {

@Override
public void onCompletion(MediaPlayer mp) {
// TODO Auto-generated method stub
mp.release();
}
});
mp.start();
}

/*
* Toggle switch button images
* changing image states to on / off
* */
private void toggleButtonImage(){
if(isFlashOn){
btnSwitch.setImageResource(R.drawable.btn_switch_on);
}else{
btnSwitch.setImageResource(R.drawable.btn_switch_off);
}
}

@Override
protected void onDestroy() {
super.onDestroy();
}

@Override
protected void onPause() {
super.onPause();

// on pause turn off the flash
turnOffFlash();
}

@Override
protected void onRestart() {
super.onRestart();
}

@Override
protected void onResume() {
super.onResume();

// on resume turn on the flash
if(hasFlash)
turnOnFlash();
}

@Override
protected void onStart() {
super.onStart();

// on starting the app get the camera params
getCamera();
}

@Override
protected void onStop() {
super.onStop();

// on stop release the camera
if (camera != null) {
camera.release();
camera = null;
}
}

}