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/*
* Copyright (C) 2009 The Android Open Source Project
*
* 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.android.camera;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import java.io.IOException;
import static com.android.camera.Util.Assert;
//
// CameraHolder is used to hold an android.hardware.Camera instance.
//
// The open() and release() calls are similar to the ones in
// android.hardware.Camera. The difference is if keep() is called before
// release(), CameraHolder will try to hold the android.hardware.Camera
// instance for a while, so if open() call called soon after, we can avoid
// the cost of open() in android.hardware.Camera.
//
// This is used in switching between Camera and VideoCamera activities.
//
public class CameraHolder {
private static final String TAG = "CameraHolder";
private android.hardware.Camera mCameraDevice;
private long mKeepBeforeTime = 0; // Keep the Camera before this time.
private Handler mHandler;
private int mUsers = 0; // number of open() - number of release()
// Use a singleton.
private static CameraHolder sHolder;
public static synchronized CameraHolder instance() {
if (sHolder == null) {
sHolder = new CameraHolder();
}
return sHolder;
}
private static final int RELEASE_CAMERA = 1;
private class MyHandler extends Handler {
MyHandler(Looper looper) {
super(looper);
}
@Override
public void handleMessage(Message msg) {
switch(msg.what) {
case RELEASE_CAMERA:
releaseCamera();
break;
}
}
}
private CameraHolder() {
HandlerThread ht = new HandlerThread("CameraHolder");
ht.start();
mHandler = new MyHandler(ht.getLooper());
}
public synchronized android.hardware.Camera open() {
Assert(mUsers == 0);
if (mCameraDevice == null) {
mCameraDevice = android.hardware.Camera.open();
} else {
try {
mCameraDevice.reconnect();
} catch (IOException e) {
Log.e(TAG, "reconnect failed.");
}
}
++mUsers;
mHandler.removeMessages(RELEASE_CAMERA);
mKeepBeforeTime = 0;
return mCameraDevice;
}
public synchronized void release() {
Assert(mUsers == 1);
--mUsers;
mCameraDevice.stopPreview();
releaseCamera();
}
private synchronized void releaseCamera() {
Assert(mUsers == 0);
Assert(mCameraDevice != null);
long now = System.currentTimeMillis();
if (now < mKeepBeforeTime) {
mHandler.sendEmptyMessageDelayed(RELEASE_CAMERA,
mKeepBeforeTime - now);
return;
}
mCameraDevice.release();
mCameraDevice = null;
}
public synchronized void keep() {
// We allow (mUsers == 0) for the convenience of the calling activity.
// The activity may not have a chance to call open() before the user
// choose the menu item to switch to another activity.
Assert(mUsers == 1 || mUsers == 0);
// Keep the camera instance for 3 seconds.
mKeepBeforeTime = System.currentTimeMillis() + 3000;
}
}
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