如何在Horizo​​ntalScrollView中使用自定义视图？

Question

I've got a custom view (called CustomStrechView ) which extends an ImageView . The point of this view is so that I can get an image to fill the view without losing the aspect ratio.

Now the CustomStrechView works fine when I use it in most applications, but when I try to apply it within my HorizontalScrollView , the images all seem to disappear. I'm not sure why this happens. I've tried removing the <HorizontalScrollView /> and when I do the images show back up, so I feel there is some property that needs to be set, but I can't seem to find it.

Can anyone point out what I'm doing wrong or a better way to get a custom view to work in a HorizontalScrollView ?

---

Edit :

After playing around with this for a bit, I've determined that I can get the custom view to show the image only if I hardcode the width dimension, ie:

<com.example.dragdropshapes.CustomStrechView
    android:layout_width="200dp"

Leaving the height as fill_parent is fine...

---

Code :

Here's how my custom view is being used in the xml file:

<!-- Removing this makes the images show up -->
<HorizontalScrollView       
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:fillViewport="true"
    android:layout_marginTop="50dp">

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:showDividers="middle"
        android:orientation="horizontal">

        <!-- Changing this to a normal ImageView makes the image show up -->
        <com.example.dragdropshapes.CustomStrechView
            android:id="@+id/pickshapes"
            android:layout_height="fill_parent"
            android:layout_width="fill_parent"
            android:clickable="true"
            android:onClick="pickShapes"
            android:background="@drawable/border"
            android:src="@drawable/ic_launcher"
            />
        <!-- There are 5 other custom ImageViews here -->
    </LinearLayout>
</HorizontalScrollView>

Here's the major part of the custom view code:

public class CustomStrechView extends ImageView{

  private final Drawable srcPic;
  private final String TAG = "strechyTag";
  private boolean changeSize = false;
  private int Xpx;
  private int Ypx;

    public CustomStrechView(Context context) {
        super(context);
        srcPic = this.getDrawable();
    }

     //... other constructors, not really important...

     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
         Log.d(TAG, "in the onMeasure!!\n");
         int width, height;

        width = MeasureSpec.getSize(widthMeasureSpec);
        height = width * srcPic.getIntrinsicHeight() / srcPic.getIntrinsicWidth();
        setMeasuredDimension(width, height);
    }
}

Answer 1

Through some debugging I was able to at least partially solve this myself. Turns out that the width acquired from the MeasureSpec.getSize(widthMeasureSpec); call was 0. Thus the calculation ended in width and height being 0 and the setMeasuredDimension call would then make the image invisible.

Now I'm saying I have this partially solved, because I still don't understand why I was getting that value of 0. I think it's because in a HorizontalScrollView the width isn't determined (it depends on the content within) thus whatever MeasureSpec.getSize(widthMeasureSpec); is actually doing is talking to the parent, and the parent in a normal Linear or RelativeLayout has a defined width where as in a HorizontalScrollView it does not... but that's just speculation at this point.

So I made a fix for it, if the width is 0 we run the calculation via the height instead. The height needed two cases to cover it to avoid divide by 0 errors (the else if and the else collectively).

Here's my current solution with the same xml file I noted in the Question.

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);

    if(width > 0)
        height = width * srcPic.getIntrinsicHeight() / srcPic.getIntrinsicWidth();
    else if(srcPic.getIntrinsicWidth() < srcPic.getIntrinsicHeight())
     width = height / (srcPic.getIntrinsicHeight() / srcPic.getIntrinsicWidth());
    else
     width = height / (srcPic.getIntrinsicWidth() / srcPic.getIntrinsicHeight());

    setMeasuredDimension(width, height);
}