android - 为什么在 startActivityForResult 之后调用 oncreate 方法？

Question

在我的应用程序中，我想从 Gallery 中选择图像并在 ListView 中设置图像。在我的 ListView 中，我有 16 行。因此，当项目单击ListView时，打开图库并将图像设置为ListView。但我的问题有时出现在调用 startActivityForResult(),oncreate()` 方法之后。这是点击代码

Intent intent = new Intent(
                            Intent.ACTION_PICK,
                            android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
                    intent.setType("image/*");
                    startActivityForResult(
                            Intent.createChooser(intent, "Select File"),
                            SELECT_PICTURE);

这是onactivityresult

public void onActivityResult(int requestcode, int resultcode, Intent data) {
    Log.e("result", "result");
    displayMetrics = this.getResources().getDisplayMetrics();
    Ew = displayMetrics.widthPixels;
    Eh = displayMetrics.heightPixels;

    switch (requestcode) {
    case SELECT_PICTURE:
        if (resultcode == RESULT_OK) {

            lelListLayout.setVisibility(View.GONE);
            relImageLayout.setVisibility(View.VISIBLE);


            Uri selectedImageUri = data.getData();
            selectedImagePath = getPath(selectedImageUri);

            ExifInterface exif = null;
            // Bitmap bmRotated = null;

            try {
                exif = new ExifInterface(selectedImagePath);
            } catch (IOException e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
            int orientation = exif.getAttributeInt(
                    ExifInterface.TAG_ORIENTATION,
                    ExifInterface.ORIENTATION_UNDEFINED);
            Log.e("Orientation==>", "" + orientation);

            try {

                bmRotated = null;
                bmGallayImage = null;
                trimCache();
                bmGallayImage = convertBitmap(selectedImagePath);
                bmRotated = InventorySubmitImagesActivity.rotateBitmap(
                        bmGallayImage, orientation);

                // if(bmRotated.getWidth()>bmRotated.getHeight()){
                if (bmRotated.getWidth() > 1024) {
                    float x = 0;
                    x = 1024 / (float) bmRotated.getWidth();
                    // Log.e("x====","value "+x);

                    bmRotated = Bitmap.createScaledBitmap(bmRotated, 1024,
                            (int) (bmRotated.getHeight() * x), true);
                }
                /*
                 * }else{ if(bmRotated.getHeight() > 1024){ float x=0;
                 * x=1024/(float)bmRotated.getHeight();
                 * Log.e("x====","value "+x);
                 * 
                 * bmRotated = Bitmap.createScaledBitmap(bmRotated,
                 * (int)(bmRotated.getWidth()*x), 1024, true); } }
                 */


                Eh = Eh - ll_buttonlayout.getHeight();


                float iw = bmRotated.getWidth();
                float ih = bmRotated.getHeight();



                float diff = Ew / iw;

                float layoutwidth = Ew;
                float layoutheight = diff * ih;

                if (layoutheight > Eh) {

                    diff = Eh / ih;
                    layoutwidth = Ew * diff;
                    layoutheight = Eh;
                }

                bmGallayImage = bmRotated;
                if (bmRotated != null) {

                    RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
                            (int) layoutwidth, (int) layoutheight);
                    relImage.setLayoutParams(layoutParams);


                    Drawable dr = new BitmapDrawable(bmRotated);
                    old_width = bmRotated.getWidth();
                    old_height = bmRotated.getHeight();

                    relImage.setBackgroundDrawable(dr);

                }
                left = (int) layoutwidth / 2 - 34;
                top = (int) layoutheight / 2 - 8;

            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            // drag_check=true;
            relImage.removeAllViews();

            imgMarker = new ImageView(this);
            final RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
                    RelativeLayout.LayoutParams.MATCH_PARENT,
                    RelativeLayout.LayoutParams.MATCH_PARENT);
            relImage.addView(imgMarker, layoutParams);
            imgMarker.setScaleType(ImageView.ScaleType.MATRIX);
            bmdragImage = BitmapFactory.decodeResource(getResources(),
                    R.drawable.image_marker);
            imgMarker.setImageBitmap(bmdragImage);

            matrix = new Matrix();
            savedMatrix = new Matrix();
            oldDist = 0f;
            start = new PointF();
            mid = new PointF();

            matrix.postTranslate(left, top);
            imgMarker.setImageMatrix(matrix);

            imgMarker.setOnTouchListener(RefurbishmentImageActivity.this);
            imgMarker.setVisibility(View.VISIBLE);

            // end..
            // }

        }
        break;

}

在这个 ListView 中，在选择 6 或 7 个图像之后调用 oncreate 方法，在 onactivityresult() 之前。但是在 oncreate() 方法之后又调用了 startactivity 结果。请指导我是什么问题。提前感谢大家..

Answer 1

before the onactivityresult(). But after oncreate() method again startactivity result called

当 Activity 被发送到后台时(当其他 Activity 成为它的顶部时，或者当它被主页按钮发送到后台时)只要系统没有内存压力，它的实例就会保持 Activity 状态。当系统没有足够的内存来执行当前在前台执行的任何操作时，它通常会通过停止和释放内存后台 Activity 来回收内存。

在这种情况下 - 系统会为您提供 Activity.onSaveInstanceState将从将要被杀死的 Activity 中调用的回调，让您有机会在被杀死之前保存任何需要保存的状态。

当您的 Activity 返回前台时 - 它会被重新创建(这就是 onCreate() 再次调用的原因)，savedInstanceState 参数不会为空。

savedInstanceState 将包含您在 onSavedInstanceState() 回调中提供的所有额外内容。

理解这一点非常重要。

为了更好的理解，我建议你认真阅读- http://developer.android.com/training/basics/activity-lifecycle/recreating.html