CoordinatorLayout和ImageView在滚动时会调整宽度的问题

您可以通过跟踪AppBarLayout的垂直偏移量来实现所需的功能.它具有漂亮的方法addOnOffsetChangedListener，因此您可以根据AppBarLayout的偏移量缩放图像.

You can achieve what you want by tracking vertical offset of AppBarLayout. It has beautiful method addOnOffsetChangedListener, so you can scale your image depending on offset of AppBarLayout.

因此，要使其正常运行，您需要执行三件事:

So, there are three things that you have to do to get it working:

1. 您需要将图片放置在drawable-nodpi文件夹中，以防止Android将其缩放为不同的屏幕尺寸.
2. 将您的ImageView的属性scaleType更改为matrix-这是必需的，因为我们将自己更改此ImageView的矩阵.

3. 通过以下方式为您AppBarLayout实施addOnOffsetChangedListener:

1. You need to place your image into drawable-nodpi folder, to prevent Android from scaling it for different screen sizes.
2. Change your ImageView's property scaleType to matrix - it's needed as we will change matrix of this ImageView by ourselves.

3. Implement addOnOffsetChangedListener for you AppBarLayout by next way:

final ImageView imageView = (ImageView) findViewById(R.id.img_hero);
AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
    @Override
    public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
        Matrix matrix = new Matrix(imageView.getImageMatrix());

        //get image's width and height
        final int dwidth = imageView.getDrawable().getIntrinsicWidth();
        final int dheight = imageView.getDrawable().getIntrinsicHeight();

        //get view's width and height
        final int vwidth = imageView.getWidth() - imageView.getPaddingLeft() - imageView.getPaddingRight();
        int vheight = imageView.getHeight() - imageView.getPaddingTop() - imageView.getPaddingBottom();

        float scale;
        float dx = 0, dy = 0;
        float parallaxMultiplier = ((CollapsingToolbarLayout.LayoutParams) imageView.getLayoutParams()).getParallaxMultiplier();

        //maintain the image's aspect ratio depending on offset
        if (dwidth * vheight > vwidth * dheight) {
            vheight += (verticalOffset); //calculate view height depending on offset
            scale = (float) vheight / (float) dheight; //calculate scale
            dx = (vwidth - dwidth * scale) * 0.5f; //calculate x value of the center point of scaled drawable
            dy = -verticalOffset * (1 - parallaxMultiplier); //calculate y value by compensating parallaxMultiplier
        } else {
            scale = (float) vwidth / (float) dwidth;
            dy = (vheight - dheight * scale) * 0.5f;
        }

        int currentWidth = Math.round(scale * dwidth); //calculate current intrinsic width of the drawable

        if (vwidth <= currentWidth) { //compare view width and drawable width to decide, should we scale more or not
            matrix.setScale(scale, scale);
            matrix.postTranslate(Math.round(dx), Math.round(dy));
            imageView.setImageMatrix(matrix);
        }
    }
});

我在这里所做的只是获取ImageView的源代码，以确定其具有centerCrop比例类型时的范围，然后仅根据verticalOffset计算比例和矩阵平移.如果比例值小于1.0f，那么我们就达到了视图的纵横比等于可绘制对象的纵横比的程度，并且不需要缩放更多.

What I did here is just get ImageView's source code to determine bounds when it has centerCrop scale type and then just calculate the scale and translation of matrix depending on verticalOffset. If scale value is less than 1.0f then we've just reached the point where our view's aspect ratio is equal to the drawable's aspect ratio, and we don't need to scale more.

注意 :

Note:

1. 它将仅按宽度>高度的图像工作，否则其行为将与centerCrop
相同
2. 仅当您的parallaxMultiplier介于0和1之间时，它才有效.

1. It would work as you wish, only with the image whose width > height, otherwise its behavior would be the same as centerCrop
2. It would work only if your parallaxMultiplier is in between 0 and 1.

对我的感觉如何