Question

我在Nexus 7上遇到了Android Camera2 API的问题。我在Android 4.4.4上开发了一个使用相机拍照的应用程序，我想更新它以进行Lollipop更新。我已按照此链接中的代码制作新的相机api：https://github.com/googlesamples/android-Camera2Basic/blob/master/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.java

我在Nexus 5上测试了代码，一切运行良好，但如果我在Nexus 7上试用它，就会出现问题。这是错误日志：

12-17 17:01:15.517: W/LegacyRequestMapper(24382): convertRequestMetadata - control.awbRegions setting is not supported, ignoring value
12-17 17:01:15.517: W/LegacyRequestMapper(24382): Only received metering rectangles with weight 0.
12-17 17:01:15.518: W/LegacyRequestMapper(24382): Only received metering rectangles with weight 0.
12-17 17:01:15.519: W/LegacyRequestMapper(24382): mapAeAndFlashMode - Ignore control.aeMode == ON_AUTO_FLASH;camera does not support it
12-17 17:01:15.519: W/LegacyRequestMapper(24382): convertRequestToMetadata - Ignoring android.lens.focusDistance false, only 0.0f is supported
12-17 17:01:15.955: I/CameraDeviceState(24382): Legacy camera service transitioning to state CAPTURING
12-17 17:01:21.198: I/RequestQueue(24382): Repeating capture request cancelled.
12-17 17:01:21.198: I/RequestQueue(24382): Repeating capture request set.
12-17 17:01:21.215: W/LegacyRequestMapper(24382): convertRequestMetadata - control.awbRegions setting is not supported, ignoring value
12-17 17:01:21.215: W/LegacyRequestMapper(24382): Only received metering rectangles with weight 0.
12-17 17:01:21.215: W/LegacyRequestMapper(24382): Only received metering rectangles with weight 0.
12-17 17:01:21.216: W/LegacyRequestMapper(24382): mapAeAndFlashMode - Ignore control.aeMode == ON_AUTO_FLASH;camera does not support it
12-17 17:01:21.216: W/LegacyRequestMapper(24382): convertRequestToMetadata - Ignoring android.lens.focusDistance false, only 0.0f is supported
12-17 17:01:21.495: E/AndroidRuntime(24382): FATAL EXCEPTION: CameraBackground
12-17 17:01:21.495: E/AndroidRuntime(24382): Process: com.example.newapicamera, PID: 24382
12-17 17:01:21.495: E/AndroidRuntime(24382): java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
12-17 17:01:21.495: E/AndroidRuntime(24382):    at com.example.newapicamera.Camera2BasicFragment$4.process(Camera2BasicFragment.java:285)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at com.example.newapicamera.Camera2BasicFragment$4.onCaptureCompleted(Camera2BasicFragment.java:324)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at java.lang.reflect.Method.invoke(Native Method)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at java.lang.reflect.Method.invoke(Method.java:372)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at android.hardware.camera2.dispatch.InvokeDispatcher.dispatch(InvokeDispatcher.java:39)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at android.hardware.camera2.dispatch.HandlerDispatcher$1.run(HandlerDispatcher.java:65)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at android.os.Handler.handleCallback(Handler.java:739)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at  android.os.Handler.dispatchMessage(Handler.java:95)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at android.os.Looper.loop(Looper.java:135)
12-17 17:01:21.495: E/AndroidRuntime(24382):    at android.os.HandlerThread.run(HandlerThread.java:61)
12-17 17:01:21.542: I/RequestQueue(24382): Repeating capture request cancelled.
12-17 17:01:21.580: E/BufferQueueProducer(24382): [unnamed-24382-2] dequeueBuffer: BufferQueue has been abandoned
12-17 17:01:21.580: E/BufferQueueProducer(24382): [unnamed-24382-2] dequeueBuffer: BufferQueue has been abandoned
12-17 17:01:21.596: E/BufferQueueProducer(24382): [unnamed-24382-2] queueBuffer: BufferQueue has been abandoned
12-17 17:01:21.605: W/Camera-JNI(24382): callback on dead camera object
12-17 17:01:21.620: E/BufferQueueProducer(24382): [unnamed-24382-2] queueBuffer: BufferQueue has been abandoned
12-17 17:01:21.651: E/BufferQueueProducer(24382): [unnamed-24382-2] queueBuffer: BufferQueue has been abandoned
12-17 17:01:21.688: E/BufferQueueProducer(24382): [unnamed-24382-2] queueBuffer: BufferQueue has been abandoned
12-17 17:01:21.721: E/BufferQueueProducer(24382): [unnamed-24382-2] queueBuffer: BufferQueue has been abandoned

抛出异常的行是：

int aeState = result.get(CaptureResult.CONTROL_AE_STATE);

出了什么问题？

Answer 1

使用新的camera2 API时，Nexus 7是LEGACY级别的设备，LEGACY设备相对于实现新API的有限级别或全部级别的设备有许多限制。

在CONTROL_AE_STATE的documentation中，有一条注释：

Limited capability - Present on all camera devices that report being at least HARDWARE_LEVEL_LIMITED devices in the android.info.supportedHardwareLevel key

这意味着它不能保证LEGACY设备不存在，事实上它不会，因为这些设备不会产生AE状态信息。

Answer 2

在使用Camera2 API的任何功能之前，首先需要检查设备是否支持该功能。对于您的情况，您可以检查如下：

// CONTROL_AE_STATE can be null on some devices
                        Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                        if (aeState == null ||
                                aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
                            mState = STATE_WAITING_NON_PRECAPTURE;
                            captureStillPicture();
                        } else {
                            runPrecaptureSequence();
                        }

有关详细信息，您可以在此处查看Google的官方示例代码：https://github.com/googlesamples/android-Camera2Basic

Answer 3

我今天读到，camera2 api仅在nexus 5和6版本的棒棒糖中实现。

Answer 4

我的猜测是result是一个包，get返回一个Integer对象（而不是语句左侧的int原语）。似乎CaptureResult.CONTROL_AE_STATE不在捆绑中。这可能意味着您的设备不支持某些内容，但目前还不清楚。

发生崩溃是因为Java会自动将Integer拆箱到int，但此处的Integer为null！这将抛出一个空指针异常，因为Java试图将null对象转换为int，因此警告：

Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference

更安全的方法是让aeState成为Integer，这样就不会强制java自动取消声明语句的右侧。 Java正试图帮助你，但它可能会令人困惑！

关于nexus 7的全新Android Camera2 Api

4 个答案: