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      1 /*
      2  * Copyright (C) 2009 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.camera;
     18 
     19 import static com.android.camera.Util.Assert;
     20 
     21 import android.hardware.Camera.CameraInfo;
     22 import android.hardware.Camera.Parameters;
     23 import android.os.Build;
     24 import android.os.Handler;
     25 import android.os.HandlerThread;
     26 import android.os.Looper;
     27 import android.os.Message;
     28 import android.util.Log;
     29 
     30 import java.io.IOException;
     31 
     32 /**
     33  * The class is used to hold an {@code android.hardware.Camera} instance.
     34  *
     35  * <p>The {@code open()} and {@code release()} calls are similar to the ones
     36  * in {@code android.hardware.Camera}. The difference is if {@code keep()} is
     37  * called before {@code release()}, CameraHolder will try to hold the {@code
     38  * android.hardware.Camera} instance for a while, so if {@code open()} is
     39  * called soon after, we can avoid the cost of {@code open()} in {@code
     40  * android.hardware.Camera}.
     41  *
     42  * <p>This is used in switching between {@code Camera} and {@code VideoCamera}
     43  * activities.
     44  */
     45 public class CameraHolder {
     46     private static final String TAG = "CameraHolder";
     47     private android.hardware.Camera mCameraDevice;
     48     private long mKeepBeforeTime = 0;  // Keep the Camera before this time.
     49     private final Handler mHandler;
     50     private int mUsers = 0;  // number of open() - number of release()
     51     private int mNumberOfCameras;
     52     private int mCameraId = -1;  // current camera id
     53     private int mBackCameraId = -1, mFrontCameraId = -1;
     54     private CameraInfo[] mInfo;
     55 
     56     // We store the camera parameters when we actually open the device,
     57     // so we can restore them in the subsequent open() requests by the user.
     58     // This prevents the parameters set by the Camera activity used by
     59     // the VideoCamera activity inadvertently.
     60     private Parameters mParameters;
     61 
     62     // Use a singleton.
     63     private static CameraHolder sHolder;
     64     public static synchronized CameraHolder instance() {
     65         if (sHolder == null) {
     66             sHolder = new CameraHolder();
     67         }
     68         return sHolder;
     69     }
     70 
     71     private static final int RELEASE_CAMERA = 1;
     72     private class MyHandler extends Handler {
     73         MyHandler(Looper looper) {
     74             super(looper);
     75         }
     76 
     77         @Override
     78         public void handleMessage(Message msg) {
     79             switch(msg.what) {
     80                 case RELEASE_CAMERA:
     81                     synchronized (CameraHolder.this) {
     82                         // In 'CameraHolder.open', the 'RELEASE_CAMERA' message
     83                         // will be removed if it is found in the queue. However,
     84                         // there is a chance that this message has been handled
     85                         // before being removed. So, we need to add a check
     86                         // here:
     87                         if (CameraHolder.this.mUsers == 0) releaseCamera();
     88                     }
     89                     break;
     90             }
     91         }
     92     }
     93 
     94     private CameraHolder() {
     95         HandlerThread ht = new HandlerThread("CameraHolder");
     96         ht.start();
     97         mHandler = new MyHandler(ht.getLooper());
     98         mNumberOfCameras = android.hardware.Camera.getNumberOfCameras();
     99         mInfo = new CameraInfo[mNumberOfCameras];
    100         for (int i = 0; i < mNumberOfCameras; i++) {
    101             mInfo[i] = new CameraInfo();
    102             android.hardware.Camera.getCameraInfo(i, mInfo[i]);
    103             if (mBackCameraId == -1 && mInfo[i].facing == CameraInfo.CAMERA_FACING_BACK) {
    104                 mBackCameraId = i;
    105             }
    106             if (mFrontCameraId == -1 && mInfo[i].facing == CameraInfo.CAMERA_FACING_FRONT) {
    107                 mFrontCameraId = i;
    108             }
    109         }
    110     }
    111 
    112     public int getNumberOfCameras() {
    113         return mNumberOfCameras;
    114     }
    115 
    116     public CameraInfo[] getCameraInfo() {
    117         return mInfo;
    118     }
    119 
    120     public synchronized android.hardware.Camera open(int cameraId)
    121             throws CameraHardwareException {
    122         Assert(mUsers == 0);
    123         if (mCameraDevice != null && mCameraId != cameraId) {
    124             mCameraDevice.release();
    125             mCameraDevice = null;
    126             mCameraId = -1;
    127         }
    128         if (mCameraDevice == null) {
    129             try {
    130                 Log.v(TAG, "open camera " + cameraId);
    131                 mCameraDevice = android.hardware.Camera.open(cameraId);
    132                 mCameraId = cameraId;
    133             } catch (RuntimeException e) {
    134                 Log.e(TAG, "fail to connect Camera", e);
    135                 throw new CameraHardwareException(e);
    136             }
    137             mParameters = mCameraDevice.getParameters();
    138         } else {
    139             try {
    140                 mCameraDevice.reconnect();
    141             } catch (IOException e) {
    142                 Log.e(TAG, "reconnect failed.");
    143                 throw new CameraHardwareException(e);
    144             }
    145             mCameraDevice.setParameters(mParameters);
    146         }
    147         ++mUsers;
    148         mHandler.removeMessages(RELEASE_CAMERA);
    149         mKeepBeforeTime = 0;
    150         return mCameraDevice;
    151     }
    152 
    153     /**
    154      * Tries to open the hardware camera. If the camera is being used or
    155      * unavailable then return {@code null}.
    156      */
    157     public synchronized android.hardware.Camera tryOpen(int cameraId) {
    158         try {
    159             return mUsers == 0 ? open(cameraId) : null;
    160         } catch (CameraHardwareException e) {
    161             // In eng build, we throw the exception so that test tool
    162             // can detect it and report it
    163             if ("eng".equals(Build.TYPE)) {
    164                 throw new RuntimeException(e);
    165             }
    166             return null;
    167         }
    168     }
    169 
    170     public synchronized void release() {
    171         Assert(mUsers == 1);
    172         --mUsers;
    173         mCameraDevice.stopPreview();
    174         releaseCamera();
    175     }
    176 
    177     private synchronized void releaseCamera() {
    178         Assert(mUsers == 0);
    179         Assert(mCameraDevice != null);
    180         long now = System.currentTimeMillis();
    181         if (now < mKeepBeforeTime) {
    182             mHandler.sendEmptyMessageDelayed(RELEASE_CAMERA,
    183                     mKeepBeforeTime - now);
    184             return;
    185         }
    186         mCameraDevice.release();
    187         mCameraDevice = null;
    188         // We must set this to null because it has a reference to Camera.
    189         // Camera has references to the listeners.
    190         mParameters = null;
    191         mCameraId = -1;
    192     }
    193 
    194     public synchronized void keep() {
    195         // We allow (mUsers == 0) for the convenience of the calling activity.
    196         // The activity may not have a chance to call open() before the user
    197         // choose the menu item to switch to another activity.
    198         Assert(mUsers == 1 || mUsers == 0);
    199         // Keep the camera instance for 3 seconds.
    200         mKeepBeforeTime = System.currentTimeMillis() + 3000;
    201     }
    202 
    203     public int getBackCameraId() {
    204         return mBackCameraId;
    205     }
    206 
    207     public int getFrontCameraId() {
    208         return mFrontCameraId;
    209     }
    210 }
    211