Develop Reference

How to replace AsyncTask onProgressUpdate() using Runnable callbacks

I'm trying to replace deprecated AsyncTask without using Kotlin Coroutines or others libraries, so I have
MyTask objects with following structure
public abstract class MyTask<R> implements MyCallable<R> {
#Override
public void setUiForLoading() {
//runs on ui
}
#Override
public void setDataAfterLoading(R result) {
//runs on ui
}
#Override
public R call() throws Exception {
//runs in background
return null;
}
}
MyCallable is just a simple interface
public interface MyCallable<R> extends Callable<R>{
void setDataAfterLoading(R result);
void setUiForLoading();
}
And use this MyTaskRunner to execute them
public class MyTaskRunner {
private final Handler handler = new Handler(Looper.getMainLooper());
private final Executor executor = Executors.newCachedThreadPool();
public <R> void executeAsync(MyCallable<R> callable) {
try {
callable.setUiForLoading();
executor.execute(new RunnableTask<R>(handler, callable));
} catch (Exception e) {
}
}
public static class RunnableTask<R> implements Runnable{
private final Handler handler;
private final MyCallable<R> callable;
public RunnableTask(Handler handler, MyCallable<R> callable) {
this.handler = handler;
this.callable = callable;
}
#Override
public void run() {
try {
final R result = callable.call();
handler.post(new RunnableTaskForHandler(callable, result));
} catch (Exception e) {
}
}
}
public static class RunnableTaskForHandler<R> implements Runnable{
private MyCallable<R> callable;
private R result;
public RunnableTaskForHandler(MyCallable<R> callable, R result) {
this.callable = callable;
this.result = result;
}
#Override
public void run() {
callable.setDataAfterLoading(result);
}
}
}
it works, but I cannot figure how I could replicate correctly the behaviour of publishProgress() and onProgressUpdate() of AsyncTask useful to show actual progress rather that just indeterminate

I cannot give the same code as yours but hopefully you get the idea.
Everything is self explain in code itself.
import android.app.*;
import android.graphics.*;
import android.os.*;
import android.widget.*;
import java.lang.ref.*;
public class MainActivity extends Activity
{
private static final class HeavyJob implements Runnable
{
private final WeakReference<Handler> handler;
private final Thread thread;
private boolean isAlive;
private boolean state;
private int progress;
public final HeavyJob(final Handler handler)
{
this.handler = new WeakReference<Handler>(handler);
thread = new Thread(this);
isAlive = true;
thread.setPriority(Thread.NORM_PRIORITY);
thread.start();
}
#Override
public final void run()
{
while(isAlive) {
try {
synchronized(this) {
while(!state) this.wait();
}
Thread.sleep(200L); //Let say this a heavy job which takes 200 m/s each round.
progress += 10;
final Handler hanRef = handler.get();
if(hanRef == null) {
isAlive = false;
handler.clear();
break;
}
final Message msg = Message.obtain();
msg.what = 0;
msg.arg1 = progress;
hanRef.sendMessageAtTime(msg, SystemClock.uptimeMillis()); //Update its progress each round.
} catch(final InterruptedException e) {}
}
//Finished ???
final Handler hanRef = handler.get();
if(hanRef != null) {
final Message msg = Message.obtain();
msg.what = 1;
msg.arg1 = progress; //Make your progress is 100% completed and updated.
//msg.obj = bitmap;
hanRef.sendMessageAtTime(msg, SystemClock.uptimeMillis());
}
}
public final synchronized void resume()
{
if(isAlive) {
state = true;
this.notify();
}
}
public final void suspend()
{
state = false;
thread.interrupt();
}
public final void stop()
{
isAlive = false; // In case interrupt() does nothing (Thread was not in sleep nor wait mode).
thread.interrupt();
handler.clear();
}
}
private static final class UIHandler extends Handler
{
private final WeakReference<MainActivity> activity;
public final UIHandler(final MainActivity activity)
{
super(Looper.getMainLooper());
this.activity = new WeakReference<MainActivity>(activity);
}
#Override
public final void handleMessage(final Message msg)
{
final MainActivity referent = activity.get();
if(referent != null) {
switch(msg.what) {
case 0: referent.onProgress(msg.arg1); break;
case 1: referent.onPostExecute(msg.arg1, (Bitmap)msg.obj); break;
}
}
}
}
private ProgressBar pb;
private ImageView iv;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pb = findViewById(R.id.pb);
iv = findViewById(R.id.next);
UIHandler handler = new UIHandler(this);
//Initilize the object but will not run yet.
HeavyJob hj = new HeavyJob(handler);
//Run the job
hj.resume();
//Pause the job
hj.suspend();
//Resume the job
hj.resume();
//Stop the job
hj.stop();
//Multiple jobs
for(int i=0; i<10; i++) {
new HeavyJob(handler);
}
}
public final void onProgress(final int progress) {
pb.setProgress(progress);
}
public final void onPostExecute(final int progress, Bitmap bitmap)
{
pb.setProgress(progress);
if(bitmap != null) iv.setImageBitmap(bitmap);
}
}

The best I founded to do it is:
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class MainActivity extends AppCompatActivity {
Button btn_start;
TextView text;
ProgressBar progressBar1, progressBar2;
int num = 0;
ExecutorService service;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
text = findViewById(R.id.textHello);
btn_start = findViewById(R.id.btn_start);
progressBar1 = findViewById(R.id.progressbar1);
progressBar2 = findViewById(R.id.progressBar2);
btn_start.setOnClickListener(v -> toDo());
}
private void toDo() {
service = Executors.newSingleThreadExecutor();
service.execute(() -> {
runOnUiThread(() -> {
// onPreExecute method of AsyncTask
progressBar1.setVisibility(View.VISIBLE);
progressBar2.setVisibility(View.VISIBLE);
});
// doInBackground of AsyncTask
for (int i = 1; i <= 10000; i++) {
num = i;
runOnUiThread(() -> {
// onProgressUpdate method of AsyncTask
progressUpdate(num);
});
}
runOnUiThread(() -> {
// onPostExecute method of AsyncTask
progressBar1.setVisibility(View.GONE);
progressBar2.setVisibility(View.GONE);
});
});
}
public void progressUpdate(Integer i) {
text.setText(String.valueOf(i));
progressBar2.setProgress(i);
}
}

My android app is doing too much work on the main thread but I can't help it

I'm writing a Android Whack-a-mole game. As we all know, the moles will pop up frequently on the UI and the timer text view is changed every second. So I used handlers for all of these works. I was told to use handlers instead of java.util.Timer in this question.
However, It didn't work the way I wanted it to. I mean it kind of worked but the timer text view's text changed irrationally. When I checked the logcat it said I'm doing too much work on the main thread.
Back then, when I was developing winforms programs, this problem never occurs. I was thinking about putting those handlers on another thread but as I know only the UI thread can access UI stuff, right?
Here is my countdown class:
package com.whackanandroid;
import android.os.Handler;
import android.widget.TextView;
public class CountDown {
private Handler handler;
private int timeLeft;
private TextView textView;
private boolean paused;
private CountDownListener listener;
private Runnable countDownTask = new Runnable () {
#Override
public void run() {
if (!paused) {
timeLeft--;
displayTime ();
handler.postDelayed (this, 100);
if (timeLeft == 0) {
pauseCountDown ();
if (listener != null)
listener.onCountDownFinished ();
}
}
}
};
private void displayTime () {
textView.setText (Integer.toString (timeLeft / 10));
}
public void pauseCountDown () {
paused = true;
}
public void startCountDown () {
paused = false;
handler.post (countDownTask);
}
public void setCountDownListener (CountDownListener listener) {
this.listener = listener;
}
public CountDown (TextView tv) {
textView = tv;
timeLeft = 600;
handler = new Handler ();
}
}
And here is my phone class (the "mole")
package com.whackanandroid;
import android.os.Handler;
import android.view.View;
import android.widget.ImageView;
import java.util.Random;
public class Phone {
private ImageView image;
private Handler handler;
private Random random;
private State state;
private boolean paused;
private Runnable appearTask = new Runnable () {
#Override
public void run() {
if (!paused) {
if (random.nextInt (3) < 2) {
setState (State.ANDROID);
Game.getInstance ().addScore (10);
} else {
setState (State.APPLE);
Game.getInstance ().addScore (-5);
}
handler.postDelayed (disapperTask, random.nextInt (1000) + 700);
}
}
};
private Runnable disapperTask = new Runnable () {
#Override
public void run() {
if (!paused) {
setState (State.NONE);
handler.postDelayed (appearTask, random.nextInt (2000) + 1000);
}
}
};
private View.OnClickListener imageOnClick = new View.OnClickListener () {
#Override
public void onClick(View v) {
//TODO add OnClickListener
}
};
public void setState (State value) {
state = value;
switch (state) {
case NONE:
image.setImageResource (R.drawable.phone);
break;
case ANDROID:
image.setImageResource (R.drawable.androidphone);
break;
case APPLE:
image.setImageResource (R.drawable.applephone);
break;
}
}
public State getState () {
return state;
}
public void stopTimers () {
paused = true;
}
public void startTimers () {
paused = false;
if (getState () == State.NONE) {
handler.postDelayed (appearTask, random.nextInt (2000) + 1000);
} else {
handler.postDelayed (disapperTask, random.nextInt (1000) + 700);
}
}
public Phone (ImageView view, Random r) {
view.setOnClickListener (imageOnClick);
image = view;
random = r;
handler = new Handler ();
image.setImageResource (R.drawable.phone);
}
}
I think my code just looks horrible. Hope you don't mind. If you need any more code, please tell me at once.

Spawning threads in a onSensorChanged() in Android

I'm making an app that tracks exercise movements based on orientation and accelerometer readings(the exercise movements are very slow). What I have is a strategy pattern kind of a situation where I have an abstract class for exercise movement and the concrete exercise movements implement the actual thing. Problem is, I am spawning threads to track different exercises in the onSensorChanged() method in my activity. since this is going to be called a lot of times, I don't know if my code will spawn as many threads. Do they get garbage collected?
Code:
public class WorkoutBuddy extends Activity implements SensorEventListener {
TextView t1, t2, t3, t4, t5, t6, t7;
SensorManager sensorManager;;
private Sensor sensorAccelerometer;
private Sensor sensorMagneticField;
private float[] valuesAccelerometer;
private float[] valuesMagneticField;
private float[] valuesOrientation;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.exercise_buddy);
sensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
sensorAccelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
sensorMagneticField = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
valuesAccelerometer = new float[3];
valuesMagneticField = new float[3];
valuesOrientation = new float[3];
matrixR = new float[9];
matrixI = new float[9];
matrixValues = new float[3];
//mediaPlayer = MediaPlayer.create(this, R.raw.first_position_confirmation);
}
#Override
protected void onPause() {
sensorManager.unregisterListener(this,sensorAccelerometer);
sensorManager.unregisterListener(this,sensorMagneticField);
super.onPause();
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
float[] orientation;
private float[] matrixR;
private float[] matrixI;
private float[] matrixValues;
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
valuesAccelerometer = lowPass(event.values.clone(), valuesAccelerometer);
} else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
valuesMagneticField = lowPass(event.values.clone(), valuesMagneticField);
}
if (valuesAccelerometer != null && valuesMagneticField != null) {
SensorManager.getRotationMatrix(matrixR, matrixI, valuesAccelerometer, valuesMagneticField);
if(true){
SensorManager.getOrientation(matrixR, matrixValues);
double azimuth = Math.toDegrees(matrixValues[0]);
double pitch = Math.toDegrees(matrixValues[1]);
double roll = Math.toDegrees(matrixValues[2]);
valuesOrientation[0]=(float) pitch;
valuesOrientation[1]=(float) roll;
valuesOrientation[0]=(float) azimuth;
Thread forExc1 = new Thread(new LeftShoulder(valuesAccelerometer, valuesOrientation, this));
Thread forExc2 = new Thread(new RightShoulder(valuesAccelerometer, valuesOrientation, this));
forExc1.run();
forExc2.run();
}
}
}
#Override
protected void onResume() {
sensorManager.registerListener(this,sensorAccelerometer,SensorManager.SENSOR_DELAY_NORMAL);
sensorManager.registerListener(this,sensorMagneticField,SensorManager.SENSOR_DELAY_NORMAL);
super.onResume();
}
//Low pass filter used to smooth the sensor readings
protected float[] lowPass( float[] input, float[] output ) {
float ALPHA = 0.25f;
if ( output == null ) return input;
for ( int i=0; i<input.length; i++ ) {
output[i] = output[i] + ALPHA * (input[i] - output[i]);
}
return output;
}
}
package com.example.msapp2;
public abstract class ExerciseMovement implements Runnable{
protected float[] acc, ori;
protected boolean played = false;
}
package com.example.msapp2;
import android.content.Context;
import android.media.MediaPlayer;
public class LeftShoulder extends ExerciseMovement {
MediaPlayer mediaPlayer;
public LeftShoulder(float[] accelerometer, float[] orientation, Context context){
mediaPlayer = MediaPlayer.create(context, R.raw.first_position_confirmation);
acc = accelerometer;
//this.ori = orientation;
}
public void run(){
if(acc[0]> -10 && acc[0] < -8.5 && !played){
mediaPlayer.start();
played = true;
}
}
}

If you just override OnSensorChanged and output a Log.d , you'll see it's called hundreds, if not thousands, of times per second.
I suggest you the opposite approach: Create just one thread to process in background the different received events, then feed such thread from onSensorChanged.
Implement kind of an event queue in the thread. Assume thousands of events will arrive, constantly.
SOmething like:
private class ShoulderMovementProcessorThread extends Thread {
.....
// this will be called from the UI thread, just add event to the (synchronized) queue.
public void publish (int[] valuesAccelerometer, int[] valuesWhatever) {
add_event_to_queue();
}
// this is the typical event loop where you read one from the queue, process it, then wait for the next
public void run() {
-> get event
-> process event
-> wait for next event
}
}
ShoulderMovementProcessorThread mShoulderProcessor=new ShoulderMovementProcessorThread(...);
#Override
public void onSensorChanged(SensorEvent event) {
decodeEvent (event); // fills up azimuth, roll, etc.
mShoulderProcessor.publish(valuesAccelerometer, valuesWhatever);
}
// decode an event
private void decodeEvent (SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
valuesAccelerometer = lowPass(event.values.clone(), valuesAccelerometer);
} else if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
valuesMagneticField = lowPass(event.values.clone(), valuesMagneticField);
}
if (valuesAccelerometer != null && valuesMagneticField != null) {
SensorManager.getRotationMatrix(matrixR, matrixI, valuesAccelerometer, valuesMagneticField);
if(true){
SensorManager.getOrientation(matrixR, matrixValues);
double azimuth = Math.toDegrees(matrixValues[0]);
double pitch = Math.toDegrees(matrixValues[1]);
double roll = Math.toDegrees(matrixValues[2]);
valuesOrientation[0]=(float) pitch;
valuesOrientation[1]=(float) roll;
valuesOrientation[0]=(float) azimuth;
}
}
}

I implemented something similar recently:
public class DBWorkerThread implements Runnable
{
private SensorEnum sensorType;
private LinkedBlockingQueue<float[]> sensorData;
private DBService dbService;
public DBWorkerThread(SensorEnum type, DBService dbService)
{
this.sensorType = type;
this.dbService = dbService;
this.sensorData = new LinkedBlockingQueue<float[]>();
}
/**
* Add data to queue
* #param values
*/
public void addDataToProcess(float[] values)
{
if (sensorData.size() < sensorData.remainingCapacity())
{
try
{
this.sensorData.put(values);
}
catch (Exception ex)
{
LogService.log("Error adding queue: " + ex.getMessage());
}
LogService.log("Added to queue. Size: " + sensorData.size());
}
}
/**
* Processes queue of data
*/
#Override
public void run()
{
// Moves the current Thread into the background
android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_BACKGROUND);
while (sensorData.size() > 0)
{
try
{
float[] values = sensorData.take();
storeData(values);
}
catch (Exception ex)
{
LogService.log("Error in queue: " + ex.getMessage());
}
}
}
/**
* Store data to database
* #param values
*/
private void storeData(float[] values)
{
// store data
}
}
Hopes this helps

What is wrong with my Game Thread?

I have been trying for a while to implement a Game Thread to utilise a loop to implement logic. I posted a question here not long ago, I hope no one minds the follow up.
I have managed to scrape together this code from my research:
public class GameView extends SurfaceView implements SurfaceHolder.Callback
{
class GameThread extends Thread
{
//states
public static final int STATE_LOSE = 1;
public static final int STATE_PAUSE = 2;
public static final int STATE_READY = 3;
public static final int STATE_RUNNING = 4;
private Paint m_paint;
//canvas dimensions
private int m_canvasWidth;
private int m_canvasHeight;
private long m_lastTime;
private boolean m_run = false;
private int m_mode;
public ImageView ship;
RelativeLayout.LayoutParams shipParams;
// Handle to the surface manager
private SurfaceHolder m_surfaceHolder;
public GameThread(SurfaceHolder surfaceHolder, Context context, Handler handler)
{
m_surfaceHolder = surfaceHolder;
}
//Initialise the game
public void doStart()
{
synchronized (m_surfaceHolder)
{
resetGame();
m_lastTime = System.currentTimeMillis() + 100;
setState(STATE_RUNNING);
ship = (ImageView) findViewById(R.id.imageView1);
shipParams = (RelativeLayout.LayoutParams)ship.getLayoutParams();
}
}
public void pause()
{
synchronized (m_surfaceHolder)
{
if (m_mode == STATE_RUNNING)
setState(STATE_PAUSE);
}
}
#Override
public void run()
{
while (m_run)
{
Canvas c = null;
try
{
c = m_surfaceHolder.lockCanvas(null);
synchronized (m_surfaceHolder)
{
if (m_mode == STATE_RUNNING)
{
updateGame();
}
doDraw(c);
}
}
catch(Exception e){}
finally
{
if (c != null)
{
m_surfaceHolder.unlockCanvasAndPost(c);
}
}
}
}
public void setRunning(boolean b)
{
m_run = b;
}
public void setState(int mode)
{
synchronized (m_surfaceHolder)
{
setState(mode, null);
}
}
public void setState(int mode, CharSequence message)
{
synchronized (m_surfaceHolder)
{
m_mode = mode;
}
}
public void setPlayers(boolean onePlayer)
{
}
public void setSurfaceSize(int width, int height)
{
synchronized (m_surfaceHolder)
{
m_canvasWidth = width;
m_canvasHeight = height;
}
}
public void unpause()
{
synchronized (m_surfaceHolder)
{
m_lastTime = System.currentTimeMillis() + 100;
}
setState(STATE_RUNNING);
}
private void doDraw(Canvas canvas)
{
canvas.drawARGB(255, 0, 0, 0);
}
private void updateGame()
{
long now = System.currentTimeMillis();
if (m_lastTime > now)
return;
double elapsed = (now - m_lastTime) / 1000.0;
m_lastTime = now;
System.out.print("HELLO WORLD");
shipParams.topMargin++;
ship.setLayoutParams(shipParams);
}
private boolean collided(Rect rectangle)
{
return false;
}
public boolean foundWinner()
{
return false;
}
public void resetGame()
{
}
public void handleInput(MotionEvent event)
{
}
}
private Context m_context;
private GameThread m_thread;
private Handler m_handler;
public GameView(Context context, AttributeSet attrs)
{
super(context, attrs);
SurfaceHolder holder = getHolder();
holder.addCallback(this);
m_handler = new Handler() {
#Override
public void handleMessage(Message m) {
Bundle b = m.getData();
MotionEvent e = b.getParcelable("event");
m_thread.handleInput(e);
}
};
m_thread = new GameThread(holder, context, m_handler);
setFocusable(true);
};
public GameThread getThread()
{
return m_thread;
}
#Override
public void onWindowFocusChanged(boolean hasWindowFocus)
{
if (!hasWindowFocus)
m_thread.pause();
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height)
{
m_thread.setSurfaceSize(width, height);
}
public void surfaceCreated(SurfaceHolder holder)
{
if(m_thread.getState() == State.TERMINATED)
{
m_thread = new GameThread(getHolder(), m_context, m_handler);
m_thread.setRunning(true);
m_thread.start();
m_thread.doStart();
}
else
{
m_thread.setRunning(true);
m_thread.start();
}
}
public void surfaceDestroyed(SurfaceHolder holder)
{
boolean retry = true;
m_thread.setRunning(false);
while (retry)
{
try
{
m_thread.join();
retry = false;
}
catch (InterruptedException e)
{
}
}
}
#Override
public boolean onTouchEvent(MotionEvent event)
{
return true;
}
}
I am fairly certain that my issue lies here and it is merely a logical one. Everything does seem fine to me, however and I am in need of assistance.
I have attempted to draw an image at line 47 and defined a movement to take place in the update method at line 153. I also have placed a print line for extra debug, but the line doesn't show.
I am stumped.
Any help would be great, thanks.
Here are my other codes, if neccessary:
MainActivity.java
GameSetup.java
game_setup.xml
edit: I should note that I'm not getting any kind of errors within the code, it merely doesn't respond

You are initializing m_run as false,then in the while cycle in the run() method you must have set to true. Change it to true and the thread will work normally.

set m_run to true in your doStart() procedure

How to make an android camera preview stay focused?

I am quite new to Android, thus the code is not from me since I use it only to learn.
The application I want to make has to show a camera preview. I have the preview of the camera on the surface, but it's not focused. As a work-around I made a runnable that calls auto-focus every 750ms.
I would like to know how I can make this better since whenever I call auto-focus the preview will blur until it's focused again.
Thank you for any help.
import android.app.Activity;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
public class Draw extends Activity {
private SurfaceView preview = null;
private SurfaceHolder previewHolder = null;
private Camera camera = null;
private boolean inPreview = false;
private boolean cameraConfigured = false;
private Handler handler = new Handler();;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.draw);
preview = (SurfaceView) findViewById(R.id.preview);
previewHolder = preview.getHolder();
previewHolder.addCallback(surfaceCallback);
final Runnable r = new Runnable() {
#Override
public void run() {
camera.autoFocus(autoFocusCallback);
handler.postDelayed(this, 1000);
}
};
handler.postDelayed(r, 750);
}
private AutoFocusCallback autoFocusCallback = new AutoFocusCallback() {
#Override
public void onAutoFocus(boolean autoFocusSuccess, Camera arg1) {
}
};
#Override
public void onResume() {
super.onResume();
camera = Camera.open();
startPreview();
}
#Override
public void onPause() {
if (inPreview) {
camera.stopPreview();
}
camera.release();
camera = null;
inPreview = false;
super.onPause();
}
private Camera.Size getBestPreviewSize(int width, int height, Camera.Parameters parameters) {
Camera.Size result = null;
for (Camera.Size size : parameters.getSupportedPreviewSizes()) {
if (size.width <= width && size.height <= height) {
if (result == null) {
result = size;
} else {
int resultArea = result.width * result.height;
int newArea = size.width * size.height;
if (newArea > resultArea) {
result = size;
}
}
}
}
return (result);
}
private void initPreview(int width, int height) {
if (camera != null && previewHolder.getSurface() != null) {
try {
camera.setPreviewDisplay(previewHolder);
} catch (Throwable t) {
Log.e("KritzelKunst-surfaceCallback", "Exception in setPreviewDisplay()", t);
Toast.makeText(Draw.this, t.getMessage(), Toast.LENGTH_LONG).show();
}
if (!cameraConfigured) {
Camera.Parameters parameters = camera.getParameters();
Camera.Size size = getBestPreviewSize(width, height, parameters);
if (size != null) {
parameters.setPreviewSize(size.width, size.height);
camera.setParameters(parameters);
cameraConfigured = true;
}
}
}
}
private void startPreview() {
if (cameraConfigured && camera != null) {
camera.startPreview();
inPreview = true;
}
}
SurfaceHolder.Callback surfaceCallback = new SurfaceHolder.Callback() {
#Override
public void surfaceCreated(SurfaceHolder holder) {
// no-op -- wait until surfaceChanged()
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
initPreview(width, height);
startPreview();
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
// no-op
}
};
}

Try adding
<uses-feature android:name="android.hardware.camera.autofocus" />
in your manifest.