Android camera auto focusing stops when unplugged from the charger

Question

I am using ZXing Barcode Scanner library in my app and I'm experiencing the following bug: camera auto focus works only if the device is plugged to the charger. As soon as I unplug the device, the camera stops continious auto focusing, but once the device is plugged again, auto focusing immidiately resumes (image focuses every 2000 milliseconds). The battery of the test device is fully charged.

It should be noted that the sample code from XZing works properly, but since I am using some part of it in my app, I am experiencing the above-mentioned issue.

Here is the code of AutoFocusManager class:

/*Copyright (C) 2012 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.myapp.utils.barcode.camera;

import android.content.Context;
import android.content.SharedPreferences;
import android.hardware.Camera;
import android.os.AsyncTask;
import android.preference.PreferenceManager;
import android.util.Log;

import java.util.ArrayList;
import java.util.Collection;

import com.myapp.utils.barcode.main.PreferencesActivity;
import com.myapp.utils.barcode.common.executor.AsyncTaskExecInterface;
import com.myapp.utils.barcode.common.executor.AsyncTaskExecManager;

final class AutoFocusManager implements Camera.AutoFocusCallback {

  private static final String TAG = AutoFocusManager.class.getSimpleName();

  private static final long AUTO_FOCUS_INTERVAL_MS = 2000L;
  private static final Collection<String> FOCUS_MODES_CALLING_AF;
  static {
    FOCUS_MODES_CALLING_AF = new ArrayList<String>(2);
    FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_AUTO);
    FOCUS_MODES_CALLING_AF.add(Camera.Parameters.FOCUS_MODE_MACRO);
  }

  private boolean active;
  private final boolean useAutoFocus;
  private final Camera camera;
  private AutoFocusTask outstandingTask;
  private final AsyncTaskExecInterface taskExec;

  AutoFocusManager(Context context, Camera camera) {
    this.camera = camera;
    taskExec = new AsyncTaskExecManager().build();
    SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(context);
    String currentFocusMode = camera.getParameters().getFocusMode();
    useAutoFocus =
        sharedPrefs.getBoolean(PreferencesActivity.KEY_AUTO_FOCUS, true) &&
        FOCUS_MODES_CALLING_AF.contains(currentFocusMode);
    Log.i(TAG, "Current focus mode '" + currentFocusMode + "'; use auto focus? " + useAutoFocus);
    start();
  }

  @Override
  public synchronized void onAutoFocus(boolean success, Camera theCamera) {
    if (active) {
      outstandingTask = new AutoFocusTask();
      taskExec.execute(outstandingTask);
    }
  }

  synchronized void start() {
    if (useAutoFocus) {
      active = true;
      try {
        camera.autoFocus(this);
      } catch (RuntimeException re) {
        // Have heard RuntimeException reported in Android 4.0.x+; continue?
        Log.w(TAG, "Unexpected exception while focusing", re);
      }
    }
  }

  synchronized void stop() {
    if (useAutoFocus) {
      try {
        camera.cancelAutoFocus();
      } catch (RuntimeException re) {
        // Have heard RuntimeException reported in Android 4.0.x+; continue?
        Log.w(TAG, "Unexpected exception while cancelling focusing", re);
      }
    }
    if (outstandingTask != null) {
      outstandingTask.cancel(true);
      outstandingTask = null;
    }
    active = false;
  }

  private final class AutoFocusTask extends AsyncTask<Object,Object,Object> {
    @Override
    protected Object doInBackground(Object... voids) {
      try {
        Thread.sleep(AUTO_FOCUS_INTERVAL_MS);
      } catch (InterruptedException e) {
        // continue
      }
      synchronized (AutoFocusManager.this) {
        if (active) {
          start();
        }
      }
      return null;
    }
  }
}

When the device is connected to debugger, the LogCat shows the following:

03-07 23:37:14.624: I/AutoFocusManager(2296): Current focus mode 'auto'; use auto focus? true

Test device is HTC sensation, OS - Cyanogenmod 10 (Android 4.1.2).

Do you have any suggestions what can be the reason of such a behaviour?

Thank you.

Answer 1

Similar happened to me too with zxing 2.1

autoFocusThread X: AF fail

on Samsung Galaxy (GT-P6200) with android 4.0.4, and Sonyericcson Xperia Neo / android 4.0.4.

Error did not occur with ZXing 2.0. You can download release 2.0 from here.

Try it, I hope solve your autofocus issue too.