如何在绘制到UI之前在片段中每次获取ImageView的高度和宽度

如何解决如何在绘制到UI之前在片段中每次获取ImageView的高度和宽度

我想将外部存储中的照片设置为（Circular）ImageView。因此，我有一个函数，要求ImageView的“高”和“宽”来裁剪图片，然后将其设置为“位图”。

我的问题是，在加载UI之前会调用此函数。我遇到的解决方案是，我第一次在onViewCreated中调用此函数，在其中我向addOnWindowFocusChangeListener添加了一个侦听器。这是第一次。

该片段位于ViewPager内，如果我转到左侧的片段，然后转到右侧的中间，则片段又消失了。

我是StackOverflow的新手。我感谢每一个提示，我可以做得更好。

//This works for the First Time

    @Override
    public void onViewCreated(@NonNull View view,@Nullable Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);

        View m = getView();
        ViewTreeObserver n = m.getViewTreeObserver();
        n.addOnWindowFocusChangeListener(new ViewTreeObserver.OnWindowFocusChangeListener() {
            @Override
            public void onWindowFocusChanged(final boolean hasFocus) {
                // do your stuff here
                ImageUtil.setPic(binding.photoRoundProfile,mCurrentPhotoPath);

            }
        });
    }

//The function where I set the Picture into the ImageView

static public void setPic(ImageView mImageView,String pPath) {
        try {
            if (pPath == null) return;
            File f = new File(pPath);
            if (!f.exists() || f.isDirectory()) return;

            // Get the dimensions of the View
            int targetW = mImageView.getWidth();
            if (targetW == 0) targetW = mImageView.getMeasuredWidth();
            int targetH = mImageView.getHeight();
            if (targetH == 0) targetH = mImageView.getMeasuredHeight();

            // Get the dimensions of the bitmap
            BitmapFactory.Options bmOptions = new BitmapFactory.Options();
            bmOptions.inJustDecodeBounds = true;
            BitmapFactory.decodeFile(pPath,bmOptions);
            int photoW = bmOptions.outWidth;
            int photoH = bmOptions.outHeight;

            // Determine how much to scale down the image
            int scaleFactor = photoW / targetW; //Math.min(photoW/targetW,photoH/targetH);

            // Decode the image file into a Bitmap sized to fill the View
            bmOptions.inJustDecodeBounds = false;
            bmOptions.inSampleSize = scaleFactor;
            bmOptions.inPurgeable = true;

            Bitmap bitmap = BitmapFactory.decodeFile(pPath,bmOptions);
            Bitmap orientedBitmap = ExifUtil.rotateBitmap(pPath,bitmap);
            mImageView.setImageBitmap(orientedBitmap);

            //mImageView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.WRAP_CONTENT));
            mImageView.setAdjustViewBounds(true);
            mImageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

有一个视频，供您更好地理解：https://www.loom.com/share/05c4174562d74c9bba8ff02c9072c866

解决方法

我找到了解决问题的方法。我在onPreDraw中找到了方法OnPreDrawListener。每当ImageView更新时，此侦听器就会运行。因此，我添加了一个if语句来节省性能，而不是每次都重新绘制。

@Override
    public void onViewCreated(@NonNull View view,@Nullable Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);

        ImageView iv= binding.photoRoundProfile;
        ViewTreeObserver vto = iv.getViewTreeObserver();
        vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {

            private int mFinalWidth = 0;
            private int mFinalHeight = 0;

            public boolean onPreDraw() {

                if(mFinalHeight != 0 || mFinalWidth != 0)
                    return true;

                mFinalHeight = iv.getHeight();
                mFinalWidth = iv.getWidth();
                Log.d("hilength","Height: " + mFinalHeight + " Width: " + mFinalWidth);

                ImageUtil.setPic(binding.photoRoundProfile,mCurrentPhotoPath);
                return true;
            }
        });
    }