android – 在Nexus 7平板电脑中打开相机

我在 android中开发了一个Camera应用程序.它使用表面视图捕获图像.下面是我用来打开相机的代码

try {
            // attempt to get a Front Camera instance
            c = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
        } catch (Exception e) {
            // Todo Auto-generated catch block
            System.out
                    .println("fail to connect to Front Camera");
        }
        if (c == null) {
            try {
                // attempt to get a Back Camera instance
                c = Camera.open(1);
            } catch (Exception e) {
                // Todo: handle exception
                System.out
                        .println("fail to connect to Camera   with      id   =   1");
            }
        }
        if (c == null) {
            try {
                // attempt to get a Back Camera instance
                c = Camera.open(0);
            } catch (Exception e) {
                // Todo: handle exception
                System.out
                        .println("fail to connect to Camera   with      id   =   0");
            }
        }
        if (c == null) {
            try {
                // attempt to get a Back Camera instance
                c = Camera.open();
            } catch (Exception e) {
                // Todo: handle exception
                System.out
                        .println("fail to connect to Back Camera");
                return c;
            }

其中c是Camera的对象.

它在除Nexus 7平板电脑之外的其他手机中运行良好.在Nexus 7中,代码在所有情况下抛出异常,除了最后一个,即c = Camera.open();,但对象c仍为null.

这是堆栈跟踪

11-22 12:36:57.559 W/System.err(7621): java.lang.NullPointerException
11-22 12:36:57.559 W/System.err(7621): at 

com.MyPackage.OpenCamera.getFrontCameraInstance(OpenCamera.java:238)
11-22 12:36:57.559 W/System.err(7621): at 

com.MyPackage.OpenCamera.onCreate(OpenCamera.java:123)
11-22 12:36:57.559 W/System.err(7621): at 

android.app.Activity.performCreate(Activity.java:5104)
11-22 12:36:57.559 W/System.err(7621): at 

android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
11-22 12:36:57.559 W/System.err(7621): at 

android.app.ActivityThread.performlaunchActivity(ActivityThread.java:2144)
11-22 12:36:57.559 W/System.err(7621): at 

android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
11-22 12:36:57.559 W/System.err(7621): at 

android.app.ActivityThread.access$600(ActivityThread.java:141)
11-22 12:36:57.559 W/System.err(7621): at android.app.ActivityThread

$H.handleMessage(ActivityThread.java:1234)
11-22 12:36:57.559 W/System.err(7621): at 

android.os.Handler.dispatchMessage(Handler.java:99)
11-22 12:36:57.559 W/System.err(7621): at android.os.Looper.loop

(Looper.java:137)
11-22 12:36:57.559 W/System.err(7621): at android.app.ActivityThread.main

(ActivityThread.java:5039)
11-22 12:36:57.559 W/System.err(7621): at 

java.lang.reflect.Method.invokeNative(Native Method)
11-22 12:36:57.559 W/System.err(7621): at java.lang.reflect.Method.invoke

(Method.java:511)
11-22 12:36:57.559 W/System.err(7621): at 

com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run

(ZygoteInit.java:793)
11-22 12:36:57.559 W/System.err(7621): at 

com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
11-22 12:36:57.559 W/System.err(7621): at dalvik.system.NativeStart.main

(Native Method)
11-22 12:36:57.559 I/System.out(7621): Error in setting Parameter
11-22 12:36:57.609 I/ActivityManager(480): displayed 
11-22 12:36:57.679 W/System.err(7621): at 

android.location.Geocoder.getFromLocation(Geocoder.java:136)
11-22 12:36:57.679 W/System.err(7621): at com.MyPackage.OpenCamera.

$MyTimmer$1.run(OpenCamera.java:336)
11-22 12:36:57.679 W/System.err(7621): java.lang.NullPointerException
11-22 12:36:57.679 W/System.err(7621): at com.MyPackage.OpenCamera.

$MyTimmer$1.run(OpenCamera.java:344)

所以我不能用它来捕捉图像.
有什么办法吗

谢谢…

解决方法

在Nexus 7上使用以下代码时：
int cameraId = CameraInfo.CAMERA_FACING_FRONT;
但是,如您所见,cameraId为1,使用1作为参数会导致错误.
我发现使用0代替1可以工作,但每次使用后必须释放相机,所以我继续调用Camera.open(cameraId).release();
我意识到这很难看,但它似乎解决了Nexus 7的问题.

int cameraId = -1;
    boolean errorFound = false;
    boolean hasFeatCamera = getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA);

    if (hasFeatCamera) {

            try{
                 cameraId = CameraInfo.CAMERA_FACING_BACK;
                 Camera.open(cameraId).release();
                }catch(Exception e){
                    Camera.open(0).release();
                }

    } else if(CameraInfo.CAMERA_FACING_FRONT>-1){

        try{
         cameraId = CameraInfo.CAMERA_FACING_FRONT;
         Camera.open(cameraId).release();
        }catch(Exception e){
            errorFound = true;

        }

        if(errorFound){
            try{
                Camera.open(0).release(); // Put in for Nexus 7 as  CameraInfo.CAMERA_FACING_FRONT= 1 but it only loads if the id is actually 0
                cameraId = 0;
            }catch(Exception e){
                cameraId = -1;
            }
        }
    }

    if(cameraId<0){
        Toast.makeText(this,"No camera found.",Toast.LENGTH_LONG).show();
     }