How to detect scrollend of webview in android?

In Android, to detect the scroll position of WebView, we can implement it by listening to the onScrollChanged method of WebView. This method is invoked when WebView scrolls, and we can use it to obtain the current scroll position and determine if it has reached the top or bottom.

Here is a specific implementation example:

First, we need to create a custom WebView class that extends the native WebView class and override its onScrollChanged method:

java
public class ObservableWebView extends WebView {
    public interface OnScrollChangeListener {
        void onScrollChanged(ObservableWebView webView, int x, int y, int oldx, int oldy);
        void onScrollEnd(ObservableWebView webView, int x, int y);
    }

    private OnScrollChangeListener onScrollChangeListener;

    public ObservableWebView(Context context) {
        super(context);
    }

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

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

    public void setOnScrollChangeListener(OnScrollChangeListener listener) {
        this.onScrollChangeListener = listener;
    }

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

        // Check if scrolled to the bottom
        int height = (int) Math.floor(this.getContentHeight() * this.getScale());
        int webViewHeight = this.getMeasuredHeight();
        if (t + webViewHeight >= height) {
            if (onScrollChangeListener != null) {
                onScrollChangeListener.onScrollEnd(this, l, t);
            }
        }
    }
}

In this custom WebView, we add an interface OnScrollChangeListener which includes two methods: onScrollChanged and onScrollEnd. The onScrollChanged method is called when WebView scrolls, while onScrollEnd is invoked when scrolling reaches the bottom.

Next, in your Activity or Fragment, you can use this custom WebView as follows:

java
ObservableWebView webView = new ObservableWebView(context);
webView.setOnScrollChangeListener(new ObservableWebView.OnScrollChangeListener() {
    @Override
    public void onScrollChanged(ObservableWebView webView, int x, int y, int oldx, int oldy) {
        // Handle scroll events, such as updating UI
    }

    @Override
    public void onScrollEnd(ObservableWebView webView, int x, int y) {
        // Handle when scrolled to the bottom, such as loading more content
        Toast.makeText(context, "Reached the bottom of the WebView!", Toast.LENGTH_SHORT).show();
    }
});

Thus, whenever the user scrolls to the bottom of the WebView, a Toast message is displayed. Additionally, you can handle other scroll events as needed. By this approach, we can effectively monitor and respond to WebView scroll events.