op 的值是 0 ~ 47，其中0代表粗略定位許可權，1代表精確定位許可權，24代表懸浮窗許可權。（具體可以看看android原始碼在android.app下就有個AppOpsManager類）

    private static int checkOp(Context context, int op){
        final int version = Build.VERSION.SDK_INT;
        if (version >= 19){
            Object object = context.getSystemService("appops");
            Class c = object.getClass();
            try {          
                Class[] cArg = new Class[3];
                cArg[0] = int.class;
                cArg[1] = int.class;
                cArg[2] = String.class;
                Method lMethod = c.getDeclaredMethod("checkOp", cArg);
                return (Integer) lMethod.invoke(object, op, Binder.getCallingUid(), context.getPackageName());
            } catch(NoSuchMethodException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }        
        }
        return -1;
    }
 

呼叫上面的函式，返回 0 就代表有許可權，1代表沒有許可權，-1函數出錯啦