Develop Reference

Android camera preview freeze when switching the camera?

This error shows "java.lang.RuntimeException: Camera is being used after Camera.release() was called" when me switching camera. Is my way to release the camera is not the correct way? Can someone suggest me the best way to implement this?
This is my CameraActivity.java:
private Camera mCamera;
private CameraPreviewActivity mPreview;
private int cameraId = 0;
private static final int MY_PERMISSIONS_REQUEST_CAMERA = 1;
/**
* Check if this device has a camera
*/
private boolean checkCameraHardware(Context context) {
if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
/**
* A safe way to get an instance of the Camera object.
*/
// attempt to get a Camera instance
public static Camera getCameraInstance() {
Camera c = null;
try {
c = Camera.open();
} catch (Exception e) {
System.out.println("Camera not working.");
}
return c; // returns null if camera is unavailable
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.camerapreview_activity);
// Create our Preview view and set it as the content of our activity.
// Create an instance of Camera
switchCamera();
showCamera();
}
public void switchCamera() {
ToggleButton facingSwitch = (ToggleButton) findViewById(R.id.facingSwitch);
facingSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
onDestroy();
preview.removeAllViews();
if (isChecked) {
// The toggle is enabled
preview.addView(mPreview);
Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
} else {
// The toggle is disabled
preview.addView(mPreview);
Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK);
}
}
});
}
protected void onDestroy () {
super.onDestroy();
if (mCamera != null){
mCamera.stopPreview();
mCamera.release(); // release the camera for other applications
mCamera = null;
}
}
public void showCamera() {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
// Permission is not granted
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.CAMERA)) {
Toast.makeText(this, "Camera permission is needed to show the camera preview", Toast.LENGTH_SHORT).show();
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed; request the permission
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.CAMERA},
MY_PERMISSIONS_REQUEST_CAMERA);
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
else {
// Permission has already been granted
mCamera = getCameraInstance();
mPreview = new CameraPreviewActivity(this, mCamera);
FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
preview.addView(mPreview);
}
}
// Here, thisActivity is the current activity
#Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_CAMERA: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// Create our Preview view and set it as the content of our activity.
// permission was granted, yay! Do the
// contacts-related task you need to do.
showCamera();
} else {
Toast.makeText(this, "Permission was not granted", Toast.LENGTH_SHORT).show();
// permission denied, boo! Disable the
// functionality that depends on this permission.
}
return;
}
}
}
// other 'case' lines to check for other
// permissions this app might request.
And this is my CameraPreviewActivity.java
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreviewActivity(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error starting camera preview: " + e.getMessage());
}
}
}

Camera.open(1) and Camera.open(0) return a camera instance, use it to replace mCamera. This does not explain the RuntimeException.
This exception happens because your CameraPreviewActivity keeps its separate reference to the Camera instance which you opened in CameraActivity.
The best practice would be to keep the reference only in the CameraPreviewActivity class, and remove the mCamera field from CameraActivity class.

Getting Current Location on Android - Currently crashing only on first app launch [Broadcast error]

So I am trying to add a some functionality to my app so that it can allow the user to get his location in a editbox instead of having to type it.
At the moment I have a "working example" but there is a strange bug in it: The first time you launch the app and click the button to get the location, the app crashes. It doesn't happen ever again, unless you reinstall the app and again it will crash only once ever. This seems to only be happening to Android 6.0 + devices (doesn't crash at all on 4.4 and 5.0).
Also sometimes it doesn't really get the location, just keeps returning null.
I suppose there is a better way to get Location, but this is my first time trying to get user's location so I don't know it.
So my question is essentially 2 questions - is there a better way to get location that will work on Android 4.4+ and why is my application crashing with pretty strange error.
The error:
system_process E/ActivityManager: Sending non-protected broadcast projekt.substratum.APP_CRASHED from system 820:system/1000 pkg android
java.lang.Throwable
at com.android.server.am.ActivityManagerService.checkBroadcastFromSystem(ActivityManagerService.java:17973)
at com.android.server.am.ActivityManagerService.broadcastIntentLocked(ActivityManagerService.java:18545)
at com.android.server.am.ActivityManagerService.broadcastIntent(ActivityManagerService.java:18636)
at android.app.ContextImpl.sendBroadcast(ContextImpl.java:881)
at com.android.server.am.AppErrors.crashApplicationInner(AppErrors.java:370)
at com.android.server.am.AppErrors.crashApplication(AppErrors.java:305)
at com.android.server.am.ActivityManagerService.handleApplicationCrashInner(ActivityManagerService.java:13554)
at com.android.server.am.ActivityManagerService.handleApplicationCrash(ActivityManagerService.java:13536)
at android.app.ActivityManagerNative.onTransact(ActivityManagerNative.java:1660)
at com.android.server.am.ActivityManagerService.onTransact(ActivityManagerService.java:2813)
at android.os.Binder.execTransact(Binder.java:565)
The Location class that I'm using (not written by me, only minor edits done)
import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
public class ProviderLocationTracker implements LocationListener,LocationTracker {
// The minimum distance to change Updates in meters
private static final long MIN_UPDATE_DISTANCE = 10;
// The minimum time between updates in milliseconds
private static final long MIN_UPDATE_TIME = 1000 * 60;
private LocationManager lm;
public enum ProviderType{
NETWORK,
GPS
};
private String provider;
private Location lastLocation;
private long lastTime;
private boolean isRunning;
private LocationUpdateListener listener;
public ProviderLocationTracker(Context context, ProviderType type) {
lm = (LocationManager)context.getSystemService(Context.LOCATION_SERVICE);
Criteria crit = new Criteria();
crit.setAccuracy(Criteria.ACCURACY_FINE);
if(type == ProviderType.NETWORK){
provider = LocationManager.NETWORK_PROVIDER;
}
else{
provider = LocationManager.GPS_PROVIDER;
}
provider = lm.getBestProvider(crit, true);
}
public String returnProvider(){
return provider;
}
public void start(){
if(isRunning){
//Already running, do nothing
return;
}
//The provider is on, so start getting updates. Update current location
isRunning = true;
lm.requestLocationUpdates(provider, MIN_UPDATE_TIME,MIN_UPDATE_DISTANCE, this);
lastLocation = null;
lastTime = 0;
return;
}
public void start(LocationUpdateListener update) {
start();
listener = update;
}
public void stop(){
if(isRunning){
lm.removeUpdates(this);
isRunning = false;
listener = null;
}
}
public boolean hasLocation(){
if(lastLocation == null){
return false;
}
if(System.currentTimeMillis() - lastTime > 5 * MIN_UPDATE_TIME){
return false; //stale
}
return true;
}
public boolean hasPossiblyStaleLocation(){
if(lastLocation != null){
return true;
}
return lm.getLastKnownLocation(provider)!= null;
}
public Location getLocation(){
if(lastLocation == null){
return null;
}
if(System.currentTimeMillis() - lastTime > 5 * MIN_UPDATE_TIME){
return null; //stale
}
return lastLocation;
}
public Location getPossiblyStaleLocation(){
if(lastLocation != null) {
return lastLocation;
}
return lm.getLastKnownLocation(provider);
}
public void onLocationChanged(Location newLoc) {
long now = System.currentTimeMillis();
if(listener != null){
listener.onUpdate(lastLocation, lastTime, newLoc, now);
}
lastLocation = newLoc;
lastTime = now;
}
public void onProviderDisabled(String arg0) {
}
public void onProviderEnabled(String arg0) {
}
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
}
}
Getting the location on button click listener:
if (checkLocationPermission()) {
if (ContextCompat.checkSelfPermission(getContext(),
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
//Request location updates:
getLocation();
}
}
getLocation method:
public void getLocation(){
//In case we havent started it somehow, just returns if we did
location.start();
double alti;
double longti;
if(location.hasLocation()){
if (location.getLocation() != null) {
alti = location.getLocation().getLatitude();
longti = location.getLocation().getLongitude();
locationText.setText(alti +","+longti);
}else{
locationText.setText("1Couldn't get location, check your GPS/NETWORK");
}
}else{
if (location.getPossiblyStaleLocation() != null) {
alti = location.getPossiblyStaleLocation().getLatitude();
longti = location.getPossiblyStaleLocation().getLongitude();
locationText.setText(alti + "," + longti);
}else{
locationText.setText("2Couldn't get location, check your GPS/NETWORK");
}
}
}
Solved the crash, as #Giovanni Terlingen suggested, it was caused by the theme engine that I had on my phone. The problem that remains is that the GPS location getting is not always working - For older phones it doesn't get the location via GPS but the Criteria assigns GPS as provider anyway.
Is there a better way to get locations for devices from KitKat to possibly Oreo?

This seems to only be happening to Android 6.0 + device
Since Android 6.0, permissions has been introduced. Make sure that your app has location access on Android 6.0+. You should inform the user that your want to access his/her location. See this useful link:
https://developer.android.com/training/permissions/requesting.html

Application stopped unexpectedly: Fatal Exception

could anyone help my with my app code. I tryied to make an application that could send data (number or letter) to arduino through bluetooth. This is how my JAVA code look:
package com.example.btprojektas;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;
public class MainActivity extends Activity{
private static final String TAG = "btprojektas";
Button btnON, btnOFF;
BluetoothAdapter bluetoothAdapter = null;
BluetoothDevice device = null;
OutputStream outputStream = null;
BluetoothSocket socket = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
btnON = (Button) findViewById(R.id.btnON);
btnOFF = (Button) findViewById(R.id.btnOFF);
if(!bluetoothAdapter.isEnabled()){
Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBluetooth, 0);
}
loadPairedDevice();
connectBT();
btnON.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
sendData("0");
Toast.makeText(getBaseContext(), "Turn on LED", Toast.LENGTH_SHORT).show();
}
});
btnOFF.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
sendData("1");
Toast.makeText(getBaseContext(), "Turn off LED", Toast.LENGTH_SHORT).show();
}
});
}
private void connectBT() {
if (device != null) {
UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); //Standard SerialPortService ID
try {
socket = device.createRfcommSocketToServiceRecord(uuid);
socket.connect();
outputStream = socket.getOutputStream();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private void disconnect() {
try {
if (outputStream != null) outputStream.close();
if (socket != null) socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void loadPairedDevice() {
Set<BluetoothDevice> pairedDevices = bluetoothAdapter.getBondedDevices();
if (pairedDevices.size() > 0) {
Log.d(TAG, "Device found");
for (BluetoothDevice device : pairedDevices)
if (device.getName().equals("HC-06")) {
this.device = device;
break;
}
}
}
#Override
protected void onPause() {
super.onPause();
disconnect();
}
#Override
protected void onResume() {
super.onResume();
loadPairedDevice();
connectBT();
}
private void sendData(String message) {
byte[] buffer = message.getBytes();
Log.d(TAG,"Send data:"+ message);
try{
outputStream.write (buffer);
} catch (IOException e) {}
}
}
in XML I have two buttons. When the program starts I push one of those buttons and the "Applications ... stopped unexpectedly" appears with fatal exeption fault code:
01-08 15:55:15.439 15354-15354/com.example.btprojektas E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.example.btprojektas.MainActivity.sendData(MainActivity.java:122)
at com.example.btprojektas.MainActivity.access$000(MainActivity.java:22)
at com.example.btprojektas.MainActivity$1.onClick(MainActivity.java:55)
at android.view.View.performClick(View.java:2485)
at android.view.View$PerformClick.run(View.java:9080)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:130)
at android.app.ActivityThread.main(ActivityThread.java:3687)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
at dalvik.system.NativeStart.main(Native Method)
P.S. Sorry for this question I know that it is quite common but I am new at programming especially JAVA.

It's either the socket or the outputStream. In ConnectBT, you don't check if socket is not null. You directly call socket.connect() assuming socket is valid. The same applies to outputStream. You use it before making sure it's not null.
Also you call
startActivityForResult(enableBluetooth, 0);
but you don't check for the result which is whether bluetooth got enabled or not. This makes your device also suspicious.
Calling
loadPairedDevice();
connectBT();
makes sense only when bluetooth is enabled. Enabling bluetooth can take couple of seconds, but you call them right away.

A couple of tips:
you're calling loadPairedDevice() and connectBT() twice: in onCreate() and in onResume() - do it only once
before using outputStream, check if it's not null (as advised by others)
in sendData(), catch AND print your exception:
try {
if (outputStream != null) {
outputStream.write(buffer);
}
else {
Log.d("TAG", "sendData() - outputStream is null!");
}
}
catch (IOException e) {
e.printStackTrace();
}
in loadPairedDevice(), if you don't find the device "HC-06", your variable device will be null...
enabling bluetooth takes few seconds, so register and listen to ACTION_STATE_CHANGED broadcast Intent. It will contain extra field EXTRA_STATE; look for STATE_ON, and then call your loadPairedDevices() and connectBT() there:
create receiver (inside your MainActivity class):
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
//this is the action you are observing
if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR);
switch(state) {
//and the state we were looking for
//which means that bluetooth has switched on
//so now you can call your functions
//and set the flag to true, which then use in your
//onClick listeners
case BluetoothAdapter.STATE_ON:
loadPairedDevice();
connectBT();
isBluetoothOn = true;
break;
}
}
}
}
in onCreate(), create IntentFilter and register receiver with it
IntentFilter btFilter = new IntentFilter();
btFilter.addAction(BluetoothAdapter.ACTION_STATE_CHANGED);
registerReceiver(mReceiver, btFilter);
remember to unregister receiver in onPause():
unregisterReceiver(mReceiver);
disable your buttons and enable them in the above listener, when you know BT is switched on; alternatively, keep a flag and use it in your click listeners, eg.:
boolean isBluetoothOn = false;
then later in listener when you get STATE_ON
isBluetooth = true;
And in your button click listener:
//for btnON
public void onClick(View v) {
if (isBluetoothOn) {
sendData("0");
Toast.makeText(getBaseContext(), "Turn on LED", Toast.LENGTH_SHORT).show();
}
}
Do the same for btnOFF.

Enabling Camera Flash While Recording Video

I need a way to control the camera flash on an Android device while it is recording video. I'm making a strobe light app, and taking videos with a flashing strobe light would result in the ability to record objects that are moving at high speeds, like a fan blade.
The flash can only be enabled by starting a video preview and setting FLASH_MODE_TORCH in the camera's parameters. That would look like this:
Camera c = Camera.open();
Camera.Parameters p = c.getParameters();
p.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
c.setParameters(p);
c.startPreview();
Once the preview has started, I can flip that parameter back and forth to turn the light on and off. This works well until I try to record a video. The trouble is that in order to give the camera to the MediaRecorder, I first have to unlock it.
MediaRecorder m = new MediaRecorder();
c.unlock(); // the killer
m.setCamera(c);
After that unlock, I can no longer change the camera parameters and therefore have no way to change the flash state.
I do not know if it is actually possible to do this since I'm not the best at java-hacking, but here is what I do know:
Camera.unlock() is a native method, so I can't really see the mechanism behind the way it locks me out
Camera.Parameter has a HashMap that contains all of its parameters
Camera.setParameters(Parameters) takes the HashMap, converts it to a string, and passes it to a native method
I can eliminate all the parameters but TORCH-MODE from the HashMap and the Camera will still accept it
So, I can still access the Camera, but it won't listen to anything I tell it. (Which is kind of the purpose of Camera.unlock())
Edit:
After examining the native code, I can see that in CameraService.cpp my calls to Camera.setParameters(Parameters) get rejected because my Process ID does not match the Process ID the camera service has on record. So it would appear that that is my hurdle.
Edit2:
It would appear that the MediaPlayerService is the primary service that takes control of the camera when a video is recording. I do not know if it is possible, but if I could somehow start that service in my own process, I should be able to skip the Camera.unlock() call.
Edit3:
One last option would be if I could somehow get a pointer to the CameraHardwareInterface. From the looks of it, this is a device specific interface and probably does not include the PID checks. The main problem with this though is that the only place that I can find a pointer to it is in CameraService, and CameraService isn't talking.
Edit4: (several months later)
At this point, I don't think it is possible to do what I originally wanted. I don't want to delete the question on the off chance that someone does answer it, but I'm not actively seeking an answer. (Though, receiving a valid answer would be awesome.)

I encountered a similar issue. The user should be able to change the flash mode during recording to meet their needs depending on the light situation. After some investigative research i came to the following solution:
I assume, that you've already set up a proper SurfaceView and a SurfaceHolder with its necessary callbacks. The first thing i did was providing this code (not declared variables are globals):
public void surfaceCreated(SurfaceHolder holder) {
try {
camera = Camera.open();
parameters = camera.getParameters();
parameters.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(parameters);
camera.setPreviewDisplay(holder);
camera.startPreview();
recorder = new MediaRecorder();
} catch (IOException e) {
e.printStackTrace();
}
}
My next step was initializing and preparing the recorder:
private void initialize() {
camera.unlock();
recorder.setCamera(camera);
recorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
recorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
recorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
recorder.setVideoFrameRate(20);
recorder.setOutputFile(filePath);
try {
recorder.prepare();
} catch (IllegalStateException e) {
e.printStackTrace();
finish();
} catch (IOException e) {
e.printStackTrace();
finish();
}
}
It's important to note, that camera.unlock() has to be called BEFORE the whole initialization process of the media recorder. That said also be aware of the proper order of each set property, otherwise you'll get an IllegalStateException when calling prepare() or start(). When it comes to recording, i do this. This will usually be triggered by a view element:
public void record(View view) {
if (recording) {
recorder.stop();
//TODO: do stuff....
recording = false;
} else {
recording = true;
initialize();
recorder.start();
}
}
So now, i finally can record properly. But what's with that flash? Last but not least, here comes the magic behind the scenes:
public void flash(View view) {
if(!recording) {
camera.lock();
}
parameters.setFlashMode(parameters.getFlashMode().equals(Parameters.FLASH_MODE_TORCH) ? Parameters.FLASH_MODE_OFF : Parameters.FLASH_MODE_TORCH);
camera.setParameters(parameters);
if(!recording) {
camera.unlock();
}
}
Everytime i call that method via an onClick action i can change the flash mode, even during recording. Just take care of properly locking the camera. Once the lock is aquired by the media recorder during recording, you don't have to lock/unlock the camera again. It doesn't even work. This was tested on a Samsung Galaxy S3 with Android-Version 4.1.2. Hope this approach helps.

After preparing media recorder, use camera.lock(), and then set whatever parameters you want to set to camera.
But before starting recording you need to call camera.unlock(), and after you stop media recorder you need to call camera.lock() to start preview.
Enjoy!!!

Try this.. hopefully it will work.. :)
private static Torch torch;
public Torch() {
super();
torch = this;
}
public static Torch getTorch() {
return torch;
}
private void getCamera() {
if (mCamera == null) {
try {
mCamera = Camera.open();
} catch (RuntimeException e) {
Log.e(TAG, "Camera.open() failed: " + e.getMessage());
}
}
}
public void toggleLight(View view) {
toggleLight();
}
private void toggleLight() {
if (lightOn) {
turnLightOff();
} else {
turnLightOn();
}
}
private void turnLightOn() {
if (!eulaAgreed) {
return;
}
if (mCamera == null) {
Toast.makeText(this, "Camera not found", Toast.LENGTH_LONG);
button.setBackgroundColor(COLOR_WHITE);
return;
}
lightOn = true;
Parameters parameters = mCamera.getParameters();
if (parameters == null) {
button.setBackgroundColor(COLOR_WHITE);
return;
}
List<String> flashModes = parameters.getSupportedFlashModes();
if (flashModes == null) {
button.setBackgroundColor(COLOR_WHITE);
return;
}
String flashMode = parameters.getFlashMode();
Log.i(TAG, "Flash mode: " + flashMode);
Log.i(TAG, "Flash modes: " + flashModes);
if (!Parameters.FLASH_MODE_TORCH.equals(flashMode)) {
if (flashModes.contains(Parameters.FLASH_MODE_TORCH)) {
parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);
mCamera.setParameters(parameters);
button.setBackgroundColor(COLOR_LIGHT);
startWakeLock();
} else {
Toast.makeText(this, "Flash mode (torch) not supported",
Toast.LENGTH_LONG);
button.setBackgroundColor(COLOR_WHITE);
Log.e(TAG, "FLASH_MODE_TORCH not supported");
}
}
}
private void turnLightOff() {
if (lightOn) {
button.setBackgroundColor(COLOR_DARK);
lightOn = false;
if (mCamera == null) {
return;
}
Parameters parameters = mCamera.getParameters();
if (parameters == null) {
return;
}
List<String> flashModes = parameters.getSupportedFlashModes();
String flashMode = parameters.getFlashMode();
if (flashModes == null) {
return;
}
Log.i(TAG, "Flash mode: " + flashMode);
Log.i(TAG, "Flash modes: " + flashModes);
if (!Parameters.FLASH_MODE_OFF.equals(flashMode)) {
if (flashModes.contains(Parameters.FLASH_MODE_OFF)) {
parameters.setFlashMode(Parameters.FLASH_MODE_OFF);
mCamera.setParameters(parameters);
stopWakeLock();
} else {
Log.e(TAG, "FLASH_MODE_OFF not supported");
}
}
}
}
private void startPreview() {
if (!previewOn && mCamera != null) {
mCamera.startPreview();
previewOn = true;
}
}
private void stopPreview() {
if (previewOn && mCamera != null) {
mCamera.stopPreview();
previewOn = false;
}
}
private void startWakeLock() {
if (wakeLock == null) {
Log.d(TAG, "wakeLock is null, getting a new WakeLock");
PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
Log.d(TAG, "PowerManager acquired");
wakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, WAKE_LOCK_TAG);
Log.d(TAG, "WakeLock set");
}
wakeLock.acquire();
Log.d(TAG, "WakeLock acquired");
}
private void stopWakeLock() {
if (wakeLock != null) {
wakeLock.release();
Log.d(TAG, "WakeLock released");
}
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (Eula.show(this)) {
eulaAgreed = true;
}
setContentView(R.layout.main);
button = findViewById(R.id.button);
surfaceView = (SurfaceView) this.findViewById(R.id.surfaceview);
surfaceHolder = surfaceView.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
disablePhoneSleep();
Log.i(TAG, "onCreate");
}

To access the device camera, you must declare the CAMERA permission in your Android Manifest. Also be sure to include the <uses-feature> manifest element to declare camera features used by your application. For example, if you use the camera and auto-focus feature, your Manifest should include the following:
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
A sample that checks for torch support might look something like this:
//Create camera and parameter objects
private Camera mCamera;
private Camera.Parameters mParameters;
private boolean mbTorchEnabled = false;
//... later in a click handler or other location, assuming that the mCamera object has already been instantiated with Camera.open()
mParameters = mCamera.getParameters();
//Get supported flash modes
List flashModes = mParameters.getSupportedFlashModes ();
//Make sure that torch mode is supported
//EDIT - wrong and dangerous to check for torch support this way
//if(flashModes != null && flashModes.contains("torch")){
if(flashModes != null && flashModes.contains(Camera.Parameters.FLASH_MODE_TORCH)){
if(mbTorchEnabled){
//Set the flash parameter to off
mParameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
}
else{
//Set the flash parameter to use the torch
mParameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
}
//Commit the camera parameters
mCamera.setParameters(mParameters);
mbTorchEnabled = !mbTorchEnabled;
}
To turn the torch on, you simply set the camera parameter Camera.Parameters.FLASH_MODE_TORCH
Camera mCamera;
Camera.Parameters mParameters;
//Get a reference to the camera/parameters
mCamera = Camera.open();
mParameters = mCamera.getParameters();
//Set the torch parameter
mParameters.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
//Comit camera parameters
mCamera.setParameters(mParameters);
To turn the torch off, set Camera.Parameters.FLASH_MODE_OFF

How to manage Android MediaPlayer state, errors, and exceptions?

I am trying to play a short sound byte after processing a scanned bar code. My code currently works fine for as many as twenty scans. However, eventually the MediaPlayer throws the following error repeatedly even after the app has been killed:
MediaPlayer: Error (-38, 0)
MediaPlayer: Attempt to perform seekTo in wrong state: mPlayer=0xXXXXXX, mCurrentState=0
--the X's representing a random 6 digit memory address--
I originally was playing the sound byte off of the UI thread. Since I've created a handler in an attempt to mitigate the issue. This is how I access the handler:
try {
mHandler.post(mScanFeedback);
} catch (IllegalStateException e) {
System.out.println("Media player state error");
e.printStackTrace();
}
Here is the code for the handler:
private Runnable mScanFeedback = new Runnable(){
public void run() {
if(getString(R.string.working).equals(mStatusHourly)) {
final MediaPlayer mediaPlayer = MediaPlayer.create(getBaseContext(), R.raw.bleep_working);
mediaPlayer.setOnErrorListener(new OnErrorListener() {
public boolean onError(MediaPlayer mp, int what, int extra) {
mediaPlayer.reset();
System.out.println("Media Player onError callback!");
return true;
}
});
mediaPlayer.start();
try {
Thread.sleep(150);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
mediaPlayer.release();
}
} else if(getString(R.string.not_working).equals(mStatusHourly)) {
final MediaPlayer mediaPlayer = MediaPlayer.create(getBaseContext(), R.raw.bleep_not_working);
mediaPlayer.setOnErrorListener(new OnErrorListener() {
public boolean onError(MediaPlayer mp, int what, int extra) {
mediaPlayer.reset();
System.out.println("Media Player onError callback!");
return true;
}
});
mediaPlayer.start();
try {
Thread.sleep(275);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
mediaPlayer.release();
}
} else {
System.out.println("Audio feedback failed as status was indeterminate.");
}
}
};
In the beginning I didn't call release() and adding it hasn't seemed to make it work any better or worse. The onError callback is never called when the problem occurs. I've tried to reset() the media player after each time it is played but that throws an error. Right now I resort to restarting the phone to keep my Logcat from being unusable by the onslaught of the same two error lines repeated continually.
I'm using zxing's bar code scanner and there is a short beep played within that activity as confirmation that the bar code has been captured. A small part of me wonders if their isn't a conflict there.
I'm still new to programming and this is my first question on stack overflow. Let me know if I should have provided any additional information or if I should try to keep it a little more lean.
Update:
I was unable to resolve the issue with the MediaPlayer. However, I was able to work around the issue by switching to a SoundPool implementation. The class below provides the needed functionality.
import java.util.HashMap;
import android.content.Context;
import android.media.AudioManager;
import android.media.SoundPool;
public class SoundManager {
private SoundPool mSoundPool;
private HashMap mSoundPoolMap;
private AudioManager mAudioManager;
private Context mContext;
public void initSounds(Context theContext) {
mContext = theContext;
mSoundPool = new SoundPool(4, AudioManager.STREAM_MUSIC, 0);
mSoundPoolMap = new HashMap();
mAudioManager = (AudioManager)mContext.getSystemService(Context.AUDIO_SERVICE);
}
public void addSound(int index, int SoundID) {
mSoundPoolMap.put(index, mSoundPool.load(mContext, SoundID, 1));
}
public void playSound(int index) {
float streamVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
streamVolume = streamVolume / mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
mSoundPool.play(index, streamVolume, streamVolume, 1, 0, 1f);
}
public void playLoopedSound(int index) {
float streamVolume = mAudioManager.getStreamVolume(AudioManager.STREAM_MUSIC);
streamVolume = streamVolume / mAudioManager.getStreamMaxVolume(AudioManager.STREAM_MUSIC);
mSoundPool.play(index, streamVolume, streamVolume, 1, -1, 1f);
}
}
Which I then accessed from my Activity with:
mSoundManager = new SoundManager();
mSoundManager.initSounds(getBaseContext());
mSoundManager.addSound(1, R.raw.bleep_working);
mSoundManager.addSound(2, R.raw.bleep_not_working);
mSoundManager.playSound(1);
mSoundManager.playSound(2);