AutoFitTextUtil

AutoFitTextUtil.java

package com.example;

import android.text.Editable;
import android.text.Layout;
import android.text.StaticLayout;
import android.text.TextPaint;
import android.text.TextWatcher;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.View;
import android.widget.TextView;

/**
 * @author Vince Mi
 *
 * Based on Grantland Chew's AutoFitTextView (https://github.com/grantland/android-autofittextview)
 * This allows us provide functionality to any TextView subclass without having to create another custom view
 */
public class AutoFitTextUtil implements TextWatcher, View.OnLayoutChangeListener {

  private final TextView view;
  private final DisplayMetrics displayMetrics;
  private final TextPaint mPaint = new TextPaint();
  private final float maxTextSize;
  private final float minTextSize = 0; // todo set in constructor or something
  private final int maxLines = 1; // todo
  private final float precision = 0.5f; // todo set in constructor

  /**
   * Use this method to attach to a view so we can update its text to fit
   */
  public static void attachListeners(TextView view) {
    AutoFitTextUtil autoFitUtil = new AutoFitTextUtil(view);
    view.addTextChangedListener(autoFitUtil);
    view.addOnLayoutChangeListener(autoFitUtil);
  }

  private AutoFitTextUtil(TextView view) {
    this.view = view;
    this.displayMetrics = view.getResources().getDisplayMetrics();
    this.maxTextSize = view.getTextSize();
  }

  public void refitText() {
    String text = view.getText().toString();
    int targetWidth = view.getWidth() - view.getPaddingLeft() - view.getPaddingRight();
    if (targetWidth > 0) {

      float size = maxTextSize;
      float high = size;
      float low = 0;

      mPaint.set(view.getPaint());
      mPaint.setTextSize(size);

      if ((maxLines == 1 && mPaint.measureText(text) > targetWidth)
          || getLineCount(text, mPaint, size, targetWidth, displayMetrics) > maxLines) {
        size = getTextSize(text, mPaint, targetWidth, maxLines, low, high, precision,
            displayMetrics);
      }

      if (size < minTextSize) {
        size = minTextSize;
      }

      view.setTextSize(TypedValue.COMPLEX_UNIT_PX, size);
    }
  }

  /**
   * Recursive binary search to find the best size for the text
   */
  private static float getTextSize(String text, TextPaint paint,
      float targetWidth, int maxLines,
      float low, float high, float precision,
      DisplayMetrics displayMetrics) {
    float mid = (low + high) / 2.0f;
    int lineCount = 1;
    StaticLayout layout = null;

    paint.setTextSize(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_PX, mid,
        displayMetrics));

    if (maxLines != 1) {
      layout = new StaticLayout(text, paint, (int) targetWidth, Layout.Alignment.ALIGN_NORMAL,
          1.0f, 0.0f, true);
      lineCount = layout.getLineCount();
    }

    //Timber.d("low=" + low + " high=" + high + " mid=" + mid
    //    + " target=" + targetWidth + " maxLines=" + maxLines + " lineCount=" + lineCount);

    if (lineCount > maxLines) {
      return getTextSize(text, paint, targetWidth, maxLines, low, mid, precision,
          displayMetrics);
    } else if (lineCount < maxLines) {
      return getTextSize(text, paint, targetWidth, maxLines, mid, high, precision,
          displayMetrics);
    } else {
      float maxLineWidth = 0;
      if (maxLines == 1) {
        maxLineWidth = paint.measureText(text);
      } else {
        for (int i = 0; i < lineCount; i++) {
          if (layout.getLineWidth(i) > maxLineWidth) {
            maxLineWidth = layout.getLineWidth(i);
          }
        }
      }

      if ((high - low) < precision) {
        return low;
      } else if (maxLineWidth > targetWidth) {
        return getTextSize(text, paint, targetWidth, maxLines, low, mid, precision,
            displayMetrics);
      } else if (maxLineWidth < targetWidth) {
        return getTextSize(text, paint, targetWidth, maxLines, mid, high, precision,
            displayMetrics);
      } else {
        return mid;
      }
    }
  }

  private static int getLineCount(String text, TextPaint paint, float size, float width,
      DisplayMetrics displayMetrics) {
    paint.setTextSize(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_PX, size,
        displayMetrics));
    StaticLayout layout = new StaticLayout(text, paint, (int) width,
        Layout.Alignment.ALIGN_NORMAL, 1.0f, 0.0f, true);
    return layout.getLineCount();
  }

  @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) {
  }

  @Override public void onTextChanged(CharSequence s, int start, int before, int count) {
    refitText();
  }

  @Override public void afterTextChanged(Editable s) {
  }

  @Override public void onLayoutChange(View v, int left, int top, int right, int bottom,
      int oldLeft, int oldTop, int oldRight, int oldBottom) {
    refitText();
  }
}