android - onCreateView() 中 getWidth() 返回 0

Question

我开始从图库中选择图像，然后缩放图像并将 ImageView 动态添加到布局中。

我希望在方向改变时重新加载该图像。我在onCreate中设置了setRetainInstance(true)。但是，在方向更改之后，当我尝试通过在应该是其容器的 FrameLayout 上调用 getWidth() 来缩放位图的适当宽度时，我得到 0。

public class NewWallpaper extends Fragment {
    private static final int PICK_BACKGROUND = 1;

    private BitmapFactory.Options bitmapFactoryOptions;

    // Data
    private Uri backgroundURI = null;
    private WeakReference<Bitmap> backgroundBitmap = null;

    // Views
    FrameLayout backgroundContainer;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.layout_new_wallpaper, container, false);

        // BitmapFactory options
        bitmapFactoryOptions = new BitmapFactory.Options();
        bitmapFactoryOptions.inPurgeable = true;

        Button pickBackground = (Button) view.findViewById(R.id.buttonPickBackground);
        pickBackground.setOnClickListener(pickBackgroundListener);

        backgroundContainer = (FrameLayout) view.findViewById(R.id.frameLayoutbackgroundContainer);

        if (backgroundURI != null)
            setBackgroundPreview();

        return view;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setRetainInstance(true);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
    }


    private Button.OnClickListener pickBackgroundListener = new Button.OnClickListener() {

        @Override
        public void onClick(View view) {
            Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
            intent.addCategory(Intent.CATEGORY_OPENABLE);
            intent.setType("image/*");

            startActivityForResult(intent, PICK_BACKGROUND);
        }
    };

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode == PICK_BACKGROUND && resultCode == getActivity().RESULT_OK && data != null && data.getData() != null) {
            backgroundURI = data.getData();
            setBackgroundPreview();
        }

        super.onActivityResult(requestCode, resultCode, data);
    }

    private void setBackgroundPreview() {
        try {
            backgroundContainer.removeAllViews();

            Bitmap background = BitmapHelper.loadScaledBitmap(getActivity(), backgroundURI, backgroundContainer.getWidth());

            backgroundBitmap = new WeakReference<Bitmap>(background);

            // returns 0
            int containerWidth = backgroundContainer.getWidth();

            ImageView backgroundView = new ImageView(getActivity());
            backgroundView.setLayoutParams(new LinearLayout.LayoutParams(
                    backgroundContainer.getWidth(),
                    BitmapHelper.calculateHeight(
                            background.getWidth(),
                            background.getHeight(),
                            backgroundContainer.getWidth())
            ));
            backgroundView.setAdjustViewBounds(true);
            backgroundView.setScaleType(ImageView.ScaleType.FIT_XY);
            backgroundView.setImageBitmap(background);

            backgroundContainer.addView(backgroundView);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

我似乎找不到在方向更改后重新填充 View 的方法。有人可以告诉我我做错了什么吗？

Answer 1

不要从 onCreateView 调用 setBackgroundPreview()。如果 View 尚未创建完成，则无法测量该 View 。

改为在 onActivityCreated 中调用 setBackgroundPreview()。