Java Android API 23(Android 6+)上摄像头不工作的表面视图
我想用SurfaceView上的摄像头制作一个背景,我成功地使用了低于23的android API。尽管我之前在API 23的应用程序中请求摄像头许可,但以下错误仍然出现在我的Nexus 5和Android 6上: java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.hardware.Camera.setPreviewDisplayandroid.view.SurfaceHolder” 位于com.package.name.CameraPreview.surfaceCreatedCameraPreview.java:31 我的代码是:Java Android API 23(Android 6+)上摄像头不工作的表面视图,java,android,android-studio,camera,Java,Android,Android Studio,Camera,我想用SurfaceView上的摄像头制作一个背景,我成功地使用了低于23的android API。尽管我之前在API 23的应用程序中请求摄像头许可,但以下错误仍然出现在我的Nexus 5和Android 6上: java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“void android.hardware.Camera.setPreviewDisplayandroid.view.SurfaceHolder” 位于com.package.name.Ca
import android.content.Context;
import android.hardware.Camera;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import java.io.IOException;
/** A basic Camera preview class */
public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
private SurfaceHolder mHolder;
private Camera mCamera;
public CameraPreview(Context context, Camera camera) {
super(context);
mCamera = camera;;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
public void surfaceCreated(SurfaceHolder holder) {
// The Surface has been created, now tell the activity_hologram where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
mCamera.setDisplayOrientation(90);
} catch (IOException e) {
Log.d("", "Error setting activity_hologram preview: " + e.getMessage());
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
// empty. Take care of releasing the Camera preview in your activity.
}
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
// ignore: tried to stop a non-existent preview
}
// set preview size and make any resize, rotate or
// reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d("", "Error starting activity_hologram preview: " + e.getMessage());
}
}
}
错误在mCamera.setPreviewDisplayholder处跳转 我的主要活动代码:
public class MainActivity extends AppCompatActivity {
private static Context mContext;
private Camera mCamera;
private CameraPreview mPreview;
private FrameLayout layout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mContext = getApplicationContext();
layout = (FrameLayout) findViewById(R.id.camera_preview);
mCamera = getCameraInstance();
mPreview = new CameraPreview(this, mCamera);
layout.addView(mPreview);
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
}
return c; // returns null if activity_hologram is unavailable
}
}
我的舱单上有:
<uses-feature android:name="android.hardware.camera" />
<uses-permission android:name="android.permission.CAMERA" />
有什么办法可以在Android 6上解决这个问题吗
谢谢您的时间,干杯。我在评论中标出了有问题的地方:
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open(); // attempt to get a Camera instance
}
catch (Exception e){
// Camera is not available (in use or does not exist)
// >>> HERE is your problem! Do not swallow exceptions silently!
}
return c; // returns null if activity_hologram is unavailable
}
看起来getCameraInstance返回null。这可能有两个原因:
Camera.Open返回空值
有一个例外,你不会意识到,因为你只是默默地吞下它,继续前进。
另一点:
该类在API级别21中被弃用。
我们建议在新应用程序中使用新的android.hardware.camera2 API
从建立在@Fildor的答案之上,该答案为我指明了正确的方向。摄影机对象为空。在API 23及更高版本中,进入app info->permissions并启用camera权限以成功获取camera对象 此api仍然适用于Android的较新版本,在6.0.1上进行了测试。唯一的问题是添加摄像头权限并要求用户明确授予它。解决此问题 转到应用程序管理器。 选择你的应用并转到“权限”选项卡,然后打开所需的权限。 该应用程序将在这之后完美运行 要在运行时修复此问题,请执行以下操作:- 检查链接
感谢您的回答,getCameraInstance代码可以工作,当我在以下位置添加视图时,它崩溃:layout.addViewmPreview@mmsergi异常消息的含义不同。我从那里读到的是,您试图调用setPreviewDisplay in surfaceCreated on a reference为null。那是麦卡梅拉。如果getCameraInstance返回null,mCamera只能为null,不是吗?在getCameraInstance中记录异常-如果只是为了证明我错了。我会马上承认,但在那之前,我的赌注是这个方法。你能在CameraPreview.java中标出哪一行是第31行吗?mCamera.setPreviewDisplayholder;好吧,那么我很确定,我的回答会引导你找到问题的根源。