自定义相机定位问题

Question

我已经建立了一个自定义相机应用程序。面对屏幕方向的问题，我不希望当方向发生变化时，活动被重新创建。请帮我解决这个问题。

在预览类中的surfaceChanged方法中获取空指针异常。

  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

        if (mCamera != null) {
            Camera.Parameters parameters = mCamera.getParameters();
            Log.d("SurfaceChanged", "getting parameters" + parameters);

在下面的行中获取空指针异常：

        Display display =                               ((WindowManager)context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
        Log.d("SurfaceChanged", "Getting the system services");
        if(display.getRotation() == Surface.ROTATION_0){
            Log.d("SurfaceChanged", "Inside the if condition 1");
            parameters.setPreviewSize(height,width);
            Log.d("SurfaceChanged", "setting preview size");
            mCamera.setDisplayOrientation(90);
            Log.d("SurfaceChanged", "setting display orientation as 90");
        }

        if(display.getRotation() == Surface.ROTATION_90){
            Log.d("SurfaceChanged", "Inside the if condition 2");
            parameters.setPreviewSize(width,height);
            Log.d("SurfaceChanged", "setting the preview size 2 ");
        }

        if(display.getRotation() == Surface.ROTATION_180){
            Log.d("SurfaceChanged", "Inside the if condition 3");
            parameters.setPreviewSize(height,width);
            Log.d("SurfaceChanged", "setting the preview size 3");
        }

        if(display.getRotation() == Surface.ROTATION_270){
            Log.d("SurfaceChanged", "Inside the if condition 4");
            parameters.setPreviewSize(width,height);
            Log.d("SurfaceChanged", "setting preview size 4");
            mCamera.setDisplayOrientation(180);
            Log.d("SurfaceChanged", "setting display orientation as 180");
        }

        mCamera.setParameters(parameters);
        Log.d("SurfaceChanged", "setting the parameters");
       try {
            mCamera.setPreviewDisplay(mHolder);
            Log.d("SurfaceChanged", "setting preview display to mHolder");
            mCamera.startPreview();
            Log.d("SurfaceChanged", "preview as started");
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

任何帮助都将不胜感激。

以下是错误日志：

12-23 16:07:34.962 8845-8845/com.clarity.camera E/AndroidRuntime:致命异常:主进程: com.clarity.camera，PID: 8845 java.lang.NullPointerException:尝试在com.clarity.camera.CameraPreview.surfaceChanged(CameraPreview.java:230) at android.view.SurfaceView.updateWindow(SurfaceView.java:583) at android.view.SurfaceView.access$000(SurfaceView.java:86) at android.view.SurfaceView.access$000(SurfaceView.java:86)上调用空对象引用上的虚拟方法'java.lang.Object java.lang.NullPointerException.view.SurfaceView$3.onPreDraw(SurfaceView.java:175) at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:847) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1897) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1019) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5725) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)在android.view.Choreographer.doCallbacks(Choreographer.java:574) at android.view.Choreographer.doFrame(Choreographer.java:544) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) at android.os.Handler.handleCallback(Handler.java:733) at android.os.Handler.dispatchMessage(Handler.java:95)在android.app.ActivityThread.main(ActivityThread.java:5086) at android.os.Looper.loop(Looper.java:136) at java.lang.reflect.Method.invoke(原生方法) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)

Answer 1

如果你不想你的Activity被破坏，你可以把它放在你的活动标签中，你的manifest file

android:configChanges="orientation|screenSize|keyboardHidden"

这将告诉Android，您将自己处理orientationChanges。如果您是在Android 13或更高版本上开发，screenSize是很重要的。如果您正在为Android 12或更低版本开发，您可以不使用screenSize！

这意味着onDestroy将不再被调用。相反，将调用onConfigurationChanged，当设备发生旋转时，您可以在此方法中处理任何您想要做的事情。

见此处：http://developer.android.com/guide/topics/resources/runtime-changes.html

为了帮助您完成NullPointerException，您需要发布LogCat输出，并告诉我们哪一行会抛出NPE！