android - 为什么在android中调用相机时，活动中的所有变量都会重新初始化？

Question

我是android的新手，我在android中遇到了相机问题。
在我的课堂上，我有一些实例变量（保存一些值）和一个按钮和图像视图。
当我单击该按钮时，应用程序会打开相机并存储在 sd 卡中，之后我将对实例变量进行一些操作。
但问题是变量被重新初始化为默认值。
我在另一个类中使用共享首选项或存储（变量数据）作为静态变量，然后它工作正常。
我的问题是为什么所有实例变量都被重新初始化。
以及如何克服这个问题？

SharedPreference，将（变量数据）作为静态变量存储在另一个类中是唯一的解决方案吗？

相机代码

 public void openCamera() {
    if (Helper.checkCameraHardware(this)) {
        try {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            String dateFileName = sdf.format(new Date()); // generating
                                                            // todays date
                                                            // for folder

            SimpleDateFormat sdf1 = new SimpleDateFormat("yyyyMMddHHmmss");
            String curentDateandTime = sdf1.format(new Date()); // generating
                                                                // todays
                                                                // date with
                                                                // min,seconds
                                                                // for image

            // creating an folder in sd card : ed ==> sdCard path/IMG_Folder
            // in helper class / folder with todays date
            File sdImageMainDirectory = new File(Environment
                    .getExternalStorageDirectory().getPath()
                    + "/"
                    + Helper.IMG_FOLDER + "/" + dateFileName);
            if (!sdImageMainDirectory.exists()) { // if folder not exists it
                                                    // created
                sdImageMainDirectory.mkdirs();
            }

            // setting image path to sd card/Img_folder in helper
            // class/todays date folder
            image_PATH = Environment.getExternalStorageDirectory()
                    .getPath()
                    + "/"
                    + Helper.IMG_FOLDER
                    + "/"
                    + dateFileName + "/";
            // creating a new file(jpg) at above image path
            File file = new File(image_PATH, curentDateandTime + ".jpg");

            // re-initilization of image_PATH to new file(jpg)
            image_PATH = image_PATH + curentDateandTime + ".jpg";
            savePreferences();

            // creating an uri for file
            Uri outputFileUri = Uri.fromFile(file);

            Intent i = new Intent("android.media.action.IMAGE_CAPTURE");
            i.putExtra(MediaStore.EXTRA_OUTPUT, outputFileUri);
            startActivityForResult(i, 1234);

        } catch (Exception e) {

            Helper.AlertBox(this,
                    "Error No: 001\nPlease Contact us.\n"
                            + e.toString());
        }
    } else {
        Helper.AlertBox(this, "Camera Not Found.!");
    }
}




public void onActivityResult(int requestCode, int resultCode, Intent data) {
    // image_PATH = "";
    image_str = "";

    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == 1234) {
        if (resultCode == RESULT_OK) {

            restorePreferences();

            System.out.println("image_PATH :" + image_PATH);

            File file = new File(image_PATH);
            if (file.exists()) {

                Log.e("File exist :", "File exist at " + image_PATH);

                FileInputStream in;
                BufferedInputStream buf;
                try {
                     in = new FileInputStream(image_PATH);
                     buf = new BufferedInputStream(in);
                     bMap = BitmapFactory.decodeStream(buf);

                     iv_image.setVisibility(View.VISIBLE);
                     iv_image.setImageBitmap(bMap);
                     ConstantClass.image_PATH = image_PATH;

                     if (in != null) {
                     in.close();
                     }
                     if (buf != null) {
                     buf.close();
                     }

                    intent = new Intent(TakePhoto.this, PhotoPreview.class);
                    intent.putExtra("index", Helper.index);
                    Helper.bitMap[Helper.index] = image_PATH;
                    Log.e("test", "1");

                    Helper.btn[Helper.index] = false;
                    Log.e("test", "2");

                    startActivity(intent);
                    Log.e("test", "3");

                    // Helper.AlertBox(this, "Image Captured.");

                } catch (Exception e) {
                    Helper.AlertBox(this,
                            "Error No: 004\nPlease contact Bluefrog technical person.\n"
                                    + e.toString());
                    Log.e("Error reading file", e.toString());
                }

            } else {
                Helper.AlertBox(this,
                        "Error No: 005\nPlease contact Bluefrog technical person.");
            }
        } else {
            Toast.makeText(getApplicationContext(), "Cam Not Supported",
                    5000).show();
        }
    }
}

这里 Helper.index（我已将某个类存储为静态变量）

提前致谢。