java - Justifying text in Android

Question

I need to justify some text (RTL), which is a string (S1) from the server. But a TextView can't justify text, so I have to use a WebView, now I have to create a HTML file in which will display S1. And then I store the address of that html file in the database and then I display that html file. I've seen this question asked before on SO and many have recommended to use a 3rd party library, I've tried all of those approaches to no avail (they work in 90% of scenarios but are no fully reliable).

I feel that this approach seems convoluted, I was wondering if there is a better approach?

Answer 1

I use the following code that answer with very people that need this subject and i create formula that support in every display.

    public class TextJustify {

final static String SYSTEM_NEWLINE = "
";
final static float COMPLEXITY = 5.12f; // Reducing this will increase
                                        // efficiency but will decrease
                                        // effectiveness
final static Paint p = new Paint();

/* @author Mathew Kurian */

public static void run(final TextView tv, float origWidth, int paddingLeft, int paddingRight, int marginLeft, int marginRight) {


    origWidth-= paddingRight+marginRight+paddingLeft+marginLeft;
    String s = tv.getText().toString();
    p.setTypeface(tv.getTypeface());
    String[] splits = s.split(SYSTEM_NEWLINE);
    float width = origWidth - 5;
    for (int x = 0; x < splits.length; x++)
        if (p.measureText(splits[x]) > width) {
            splits[x] = wrap(splits[x], width, p);
            String[] microSplits = splits[x].split(SYSTEM_NEWLINE);
            for (int y = 0; y < microSplits.length - 1; y++)
                microSplits[y] = justify(removeLast(microSplits[y], " "),
                        width, p);
            StringBuilder smb_internal = new StringBuilder();
            for (int z = 0; z < microSplits.length; z++)
                smb_internal.append(microSplits[z]
                        + ((z + 1 < microSplits.length) ? SYSTEM_NEWLINE
                                : ""));
            splits[x] = smb_internal.toString();
        }
    final StringBuilder smb = new StringBuilder();
    for (String cleaned : splits)
        smb.append(cleaned + SYSTEM_NEWLINE);
    tv.setGravity(Gravity.RIGHT);
    tv.setText(smb);
}

private static String wrap(String s, float width, Paint p) {
    String[] str = s.split("\s"); // regex
    StringBuilder smb = new StringBuilder(); // save memory
    smb.append(SYSTEM_NEWLINE);
    for (int x = 0; x < str.length; x++) {
        float length = p.measureText(str[x]);
        String[] pieces = smb.toString().split(SYSTEM_NEWLINE);
        try {
            if (p.measureText(pieces[pieces.length - 1]) + length > width)
                smb.append(SYSTEM_NEWLINE);
        } catch (Exception e) {
        }
        smb.append(str[x] + " ");
    }
    return smb.toString().replaceFirst(SYSTEM_NEWLINE, "");
}

private static String removeLast(String s, String g) {
    if (s.contains(g)) {
        int index = s.lastIndexOf(g);
        int indexEnd = index + g.length();
        if (index == 0)
            return s.substring(1);
        else if (index == s.length() - 1)
            return s.substring(0, index);
        else
            return s.substring(0, index) + s.substring(indexEnd);
    }
    return s;
}

private static String justifyOperation(String s, float width, Paint p) {
    float holder = (float) (COMPLEXITY * Math.random());
    while (s.contains(Float.toString(holder)))
        holder = (float) (COMPLEXITY * Math.random());
    String holder_string = Float.toString(holder);
    float lessThan = width;
    int timeOut = 100;
    int current = 0;
    while (p.measureText(s) < lessThan && current < timeOut) {
        s = s.replaceFirst(" ([^" + holder_string + "])", " "
                + holder_string + "$1");
        lessThan = p.measureText(holder_string) + lessThan
                - p.measureText(" ");
        current++;
    }
    String cleaned = s.replaceAll(holder_string, " ");
    return cleaned;
}

private static String justify(String s, float width, Paint p) {
    while (p.measureText(s) < width) {
        s = justifyOperation(s, width, p);
    }
    return s;
}
  }

and for calling this you mus use following code, I tested for Persian language and in every display and device worked fine.

     public static final int FinallwidthDp  = 320 ;
     public static final int widthJustify  = 223 ;

     DisplayMetrics metrics = new DisplayMetrics();
     getWindowManager().getDefaultDisplay().getMetrics(metrics);
     int widthPixels = metrics.widthPixels;

     float scaleFactor = metrics.density;
     float widthDp = widthPixels / scaleFactor;

     TextView tv = (TextView) findViewById(R.id.textView1);
     ViewGroup.MarginLayoutParams lp1 = (ViewGroup.MarginLayoutParams) tv.getLayoutParams();

     tv.setText(text);
     TextJustify.run(tv,widthDp / FinallwidthDp * widthJustify , tv.getPaddingLeft(),tv.getPaddingRight() , lp1.leftMargin, lp1.rightMargin);

this algorithm tested on various device and worked fine in normal activity (not dialog) and wrap-content width for TextView, and worked with every padding and margin.if not good for you, you can change widthJustify until look good to you, I hope this useful. for newly update see This