content: /*
   * 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.google.zxing.camera;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.concurrent.RejectedExecutionException;
  import android.annotation.SuppressLint;
  import android.content.Context;
  import android.hardware.Camera;
  import android.os.AsyncTask;
  import android.os.Build;
  import android.util.Log;
  
  public 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 stopped;
  	private boolean focusing;
  	private final boolean useAutoFocus;
  	private final Camera camera;
  	private AsyncTask<?, ?, ?> outstandingTask;
  
  	public AutoFocusManager(Context context, Camera camera) {
  		this.camera = camera;
  		String currentFocusMode = camera.getParameters().getFocusMode();
  		useAutoFocus = 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) {
  		focusing = false;
  		autoFocusAgainLater();
  	}
  
  	@SuppressLint("NewApi")
  	private synchronized void autoFocusAgainLater() {
  		if (!stopped && outstandingTask == null) {
  			AutoFocusTask newTask = new AutoFocusTask();
  			try {
  				if (Build.VERSION.SDK_INT >= 11) {
  					newTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
  				} else {
  					newTask.execute();
  				}
  				outstandingTask = newTask;
  			} catch (RejectedExecutionException ree) {
  				Log.w(TAG, "Could not request auto focus", ree);
  			}
  		}
  	}
  
  	public synchronized void start() {
  		if (useAutoFocus) {
  			outstandingTask = null;
  			if (!stopped && !focusing) {
  				try {
  					camera.autoFocus(this);
  					focusing = true;
  				} catch (RuntimeException re) {
  					// Have heard RuntimeException reported in Android 4.0.x+;
  					// continue?
  					Log.w(TAG, "Unexpected exception while focusing", re);
  					// Try again later to keep cycle going
  					autoFocusAgainLater();
  				}
  			}
  		}
  	}
  
  	private synchronized void cancelOutstandingTask() {
  		if (outstandingTask != null) {
  			if (outstandingTask.getStatus() != AsyncTask.Status.FINISHED) {
  				outstandingTask.cancel(true);
  			}
  			outstandingTask = null;
  		}
  	}
  
  	public synchronized void stop() {
  		stopped = true;
  		if (useAutoFocus) {
  			cancelOutstandingTask();
  			// Doesn't hurt to call this even if not focusing
  			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);
  			}
  		}
  	}
  
  	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
  			}
  			start();
  			return null;
  		}
  	}
  
  }
  