我在我的应用程序中使用ZXing Barcode Scanner 库，并且遇到以下错误：相机自动对焦仅在设备插入充电器时才有效。一旦我拔下设备，相机就会停止连续自动对焦，但一旦再次插入设备，自动对焦会立即恢复（图像每 2000 毫秒对焦一次）。测试设备的电池已充满电。
应该注意的是，来自 XZing 的示例代码可以正常工作，但是由于我在我的应用程序中使用了其中的一部分，所以我遇到了上述问题。
下面是 AutoFocusManager 类的代码：
/*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;
}
}
}
当设备连接到调试器时，LogCat 显示如下：
03-07 23:37:14.624: I/AutoFocusManager(2296): Current focus mode 'auto'; use auto focus? true
测试设备是 HTC sense，操作系统 - Cyanogenmod 10 (Android 4.1.2)。
您有什么建议吗？这种行为的原因是什么？
谢谢你。