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 中选择图像并将图像设置在ListView 中。在我的 ListViewI have 16 rows. So when ever item click inListViewopen the gallery and set the image toListView. But my problem is some times afterstartActivityForResult(),oncreate()` 方法中调用。这是onclick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 选择6 或7 个图像后调用oncreate 方法，在onactivityresult() 之前。但是在oncreate() 方法之后再次调用了startactivity 结果。请指导我是什么问题。感谢 InAdvance 所有人..

Answer 1

在 onactivityresult() 之前。但是在 oncreate() 方法之后再次调用 startactivity 结果

当 Activity 被发送到后台时（当其他 Activity 位于它之上时，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，它的实例就会保持活动状态。当系统没有足够的内存来做它当前在前台做的任何事情时，它通常会通过停止和释放内存后台活动来重新声明内存。

在这种情况下 - 系统会为您提供 Activity.onSaveInstanceState 回调，该回调将从将要被终止的活动中调用，以便您有机会在它被终止之前保存任何需要保存的状态。

当您的活动返回前台时 - 它将被重新创建（这就是再次调用 onCreate() 的原因），且 savedInstanceState 参数不会为空。

savedInstanceState 将包含您在 onSavedInstanceState() 回调中提供的所有附加功能。

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

Answer 2

可能是带有选择器的对话框对系统来说太大了，它会通过缓存您的应用程序来减少内存。检查是在onCreate 之前调用的方法onSaveInstanceState。如果是，那么您可以将所需的数据保存在 bundle 中并在onCreate 方法中加载