How to page a long text?

Question

I have a long text and fixed size textView. How can show the text page by page? Users will interactive with the program in this way: He swipe left or right to turn to next or previous page.

Currently, I create a PageManager to do this job. But it's very limited. The core code to process the text is:

while (true) {
        newLineIndex = TextUtils.indexOf(content, '\n', processIndex);
        if (newLineIndex == -1) {// till the end of content
            charCount = paint.breakText(content, processIndex, content.length(), false, leftLines * lineWidth, width);
        } else {
            charCount = paint.breakText(content, processIndex, ++newLineIndex, false, leftLines * lineWidth, width);
        }

        leftLines = (int) ((leftLines * lineWidth - width[0]) / lineWidth);
        processIndex += charCount;

        if (leftLines < 1 || processIndex >= content.length()) {
            page = new Page();
            page.endIndex = processIndex;
            page.startIndex = pageBaseLine;
            page.content = content.subSequence(page.startIndex, page.endIndex);
            result.add(page);
            pageBaseLine = processIndex;

            leftLines = lineNumber;
        }

        if (processIndex >= content.length()) {
            break;
        }
    }

The limitation is the page may truncate the text like

|A lon|
|g wor|
|d man|

// a long word man

or incorrec lines due to word wrapping:

//Page Manager calculates this(2 lines):

|a sentence with loooooooo|

|ooong word abcdefghijklmn|

//But actually in text view(3 lines):

|a sentence with           |

|looooooooooong word      |

|abcdefghijklmn           |

So the final line count is more than calculation. So my page manager is stupid. Would any one help me? thanks!

Answer 1

It might be too late for answer, but I'll post how I solved problem like this.

I made similar project, but for android tablet. In my application, I have system bottom bar, my navigation bar and header. These parts of Activity don't take part in text preview, so I want to exclude them in calculations. For screen 750px these parts takes 24% of screen, it's about 180px. So I use the following algorithm to view text in text view:

1. Calculate actual height to view text, it's height of my textview: ScreenHeight - ScreenHeight*0.24
2. Set text size, for example 14.0
3. Calculate number of lines in text file
4. Calculate number of lines per page: Actual height/ text size
5. Calculate number of pages and load them in HashMap

---

Display display = getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight() — 0.24*display.getHeight();
mLinesInPage = (int) (Math.floor(height / mTextSize));
mPages = (int) (Math.ceil(mLinesInText / mLinesInPage));

---

Formatting and other transformations executes "on the fly". Nothing difficult, but works for me. There are examples

Before using algorithm:

After using algorithm: