How to Paginate Text within a TextView Control in Android?

Paginating Text in Android

Problem:

Paginating text within a TextView control in Android requires determining when and how to break the text into pages. This can be challenging as TextView's line-breaking and page-breaking algorithms are not readily accessible, making it difficult to identify where the text ends on the actual display.

Solution:

By monitoring the visible text range using the ViewTreeObserver, it is possible to track the last line that fully fits within the view's height. This allows for the creation of pages based on the cumulative height of the lines, ensuring that pages are broken when a line is encountered that exceeds the available vertical space.

Algorithm:

1. Iterate through the lines of text and check if the line's bottom exceeds the view's height.
2. If so, break a new page and calculate a new cumulative height value based on the top of the last line that did not fit on the previous page plus the view's height.

Implementation:

To implement this algorithm, use the following code:

// Setup code
ViewTreeObserver vto = txtViewEx.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
        ViewTreeObserver obs = txtViewEx.getViewTreeObserver();
        obs.removeOnGlobalLayoutListener(this);
        height = txtViewEx.getHeight();
        scrollY = txtViewEx.getScrollY();
        Layout layout = txtViewEx.getLayout();
        firstVisibleLineNumber = layout.getLineForVertical(scrollY);
        lastVisibleLineNumber = layout.getLineForVertical(height + scrollY);
    }
});

Note:

This solution efficiently paginates text while respecting line height and character spacing. It also handles special characters and dynamic text changes.

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