Detect end of ScrollView

Question

I have an app, that has an Activity that uses a `ScrollView`. I need to detect when user gets to the bottom of the `ScrollView`. I did some googleing and I found this page where is explained. But, in the example, that guys extends `ScrollView`. As I said, I need to extend Activity. So, I said "ok, let's try to make a custom class extending `ScrollView`, override the `onScrollChanged()` method, detect the end of the scroll, and act accordingly". I did, but in this line: ``` scroll = (ScrollViewExt) findViewById(R.id.scrollView1); ``` it throws a `java.lang.ClassCastException`. I changed the `<ScrollView>` tags in my XML but, obviously, it doesn't work. My questions are: Why, if `ScrollViewExt` extends `ScrollView`, throws to my face a `ClassCastException`? is there any way to detect end of scrolling without messing too much? Thank you people. EDIT: As promised, here is the piece of my XML that matters: ``` <ScrollView android:id="@+id/scrollView1" android:layout_width="match_parent" an…

Accepted Answer

Did it!

Aside of the fix Alexandre kindly provide me, I had to create an Interface:

```
public interface ScrollViewListener {
    void onScrollChanged(ScrollViewExt scrollView, 
                         int x, int y, int oldx, int oldy);
}
```

Then, i had to override the OnScrollChanged method from ScrollView in my ScrollViewExt:

```
public class ScrollViewExt extends ScrollView {
    private ScrollViewListener scrollViewListener = null;
    public ScrollViewExt(Context context) {
        super(context);
    }

public ScrollViewExt(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

public ScrollViewExt(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

public void setScrollViewListener(ScrollViewListener scrollViewListener) {
        this.scrollViewListener = scrollViewListener;
    }

@Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (scrollViewListener != null) {
            scrollViewListener.onScrollChanged(this, l, t, oldl, oldt);
        }
    }
}
```

Now, as Alexandre said, put the package name in the XML tag (my fault), make my Activity class implement the interface created before, and then, put it all together:

```
scroll = (ScrollViewExt) findViewById(R.id.scrollView1);
scroll.setScrollViewListener(this);
```

And in the method OnScrollChanged, from the interface...

```
@Override
public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {
    // We take the last son in the scrollview
    View view = (View) scrollView.getChildAt(scrollView.getChildCount() - 1);
    int diff = (view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY()));

// if diff is zero, then the bottom has been reached
    if (diff == 0) {
        // do stuff
    }
}
```

And it worked!

Thank you very much for your help, Alexandre!

Detect end of ScrollView

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