takepicture()给出Nullpointer异常

Question

我正在构建一个同时使用前置和后置摄像头的摄像头应用程序，但在该语句中出现了空指针错误。

public void onClick（查看视图）｛

  //camera.takePicture(shutter, raw, postview, jpeg)
  //camera.takePicture(null, null, new PhotoHandler(getApplicationContext()));
camera.takePicture(null, null,
    new PhotoHandler(MakePhotoActivity.this));

}

请帮帮我，因为我不知道问题在哪里。

提前谢谢。

02-07 23:06:12.445: E/AndroidRuntime(30045): FATAL EXCEPTION: main
02-07 23:06:12.445: E/AndroidRuntime(30045): java.lang.IllegalStateException: Could not execute method of the activity
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.view.View$1.onClick(View.java:2144)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.view.View.performClick(View.java:2485)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.view.View$PerformClick.run(View.java:9080)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.os.Handler.handleCallback(Handler.java:587)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.os.Looper.loop(Looper.java:130)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.app.ActivityThread.main(ActivityThread.java:3687)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at java.lang.reflect.Method.invoke(Method.java:507)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at dalvik.system.NativeStart.main(Native Method)
02-07 23:06:12.445: E/AndroidRuntime(30045): Caused by: java.lang.reflect.InvocationTargetException
02-07 23:06:12.445: E/AndroidRuntime(30045):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at java.lang.reflect.Method.invoke(Method.java:507)
02-07 23:06:12.445: E/AndroidRuntime(30045):    at android.view.View$1.onClick(View.java:2139)
02-07 23:06:12.445: E/AndroidRuntime(30045):    ... 11 more
02-07 23:06:12.445: E/AndroidRuntime(30045): Caused by: java.lang.NullPointerException
02-07 23:06:12.445: E/AndroidRuntime(30045):    at com.example.cameraapp.MakePhotoActivity.onClick(MakePhotoActivity.java:41)

Answer 1

将"getApplicationContext（）"更改为"ActivityClassName.this"

Answer 2

我在我的应用程序中使用了与您类似的代码，我的应用也曾在以下行中抛出空指针异常：

camera.takePicture(null, null,new PhotoHandler(getApplicationContext()));

我认为这是由于相机得到一个空值造成的。为了避免这个异常，我在这行代码的顶部进行了检查。因此onClick功能看起来像：

public void onClick(View view) {
  if (camera != null) {
    Log.d("camera state","camera is NOT null");  
  }else{
    Log.d("camera state","camera is null");
    camera = android.hardware.Camera.open(cameraId);
  }
  camera.takePicture(null, null,new PhotoHandler(getApplicationContext()));
}

ps：我的代码是为只使用前置摄像头而编写的。希望它能有所帮助！