在Android的TextView
中,是否有一种方法可以调整字符之间的间距?我相信这通常被称为“字距调整(kerning)”。
我知道android:textScaleX
属性,但它会压缩字符和间距。
我建立了一个自定义类,继承了TextView并添加了一个方法"setSpacing"。解决方法类似于@Noah所说的。该方法在字符串每个字母之间添加空格,并使用SpannedString更改空格的TextScaleX,从而允许正负间距。
/**
* Text view that allows changing the letter spacing of the text.
*
* @author Pedro Barros (pedrobarros.dev at gmail.com)
* @since May 7, 2013
*/
import android.content.Context;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.style.ScaleXSpan;
import android.util.AttributeSet;
import android.widget.TextView;
public class LetterSpacingTextView extends TextView {
private float spacing = Spacing.NORMAL;
private CharSequence originalText = "";
public LetterSpacingTextView(Context context) {
super(context);
}
public LetterSpacingTextView(Context context, AttributeSet attrs){
super(context, attrs);
}
public LetterSpacingTextView(Context context, AttributeSet attrs, int defStyle){
super(context, attrs, defStyle);
}
public float getSpacing() {
return this.spacing;
}
public void setSpacing(float spacing) {
this.spacing = spacing;
applySpacing();
}
@Override
public void setText(CharSequence text, BufferType type) {
originalText = text;
applySpacing();
}
@Override
public CharSequence getText() {
return originalText;
}
private void applySpacing() {
if (this == null || this.originalText == null) return;
StringBuilder builder = new StringBuilder();
for(int i = 0; i < originalText.length(); i++) {
builder.append(originalText.charAt(i));
if(i+1 < originalText.length()) {
builder.append("\u00A0");
}
}
SpannableString finalText = new SpannableString(builder.toString());
if(builder.toString().length() > 1) {
for(int i = 1; i < builder.toString().length(); i+=2) {
finalText.setSpan(new ScaleXSpan((spacing+1)/10), i, i+1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}
super.setText(finalText, BufferType.SPANNABLE);
}
public class Spacing {
public final static float NORMAL = 0;
}
}
使用它:
LetterSpacingTextView textView = new LetterSpacingTextView(context);
textView.setSpacing(10); //Or any float. To reset to normal, use 0 or LetterSpacingTextView.Spacing.NORMAL
textView.setText("My text");
//Add the textView in a layout, for instance:
((LinearLayout) findViewById(R.id.myLinearLayout)).addView(textView);
如果有人想要以简单的方式对任何字符串(在技术上是CharSequence
)应用调整字距(kerning),而不使用TextView
:
public static Spannable applyKerning(CharSequence src, float kerning)
{
if (src == null) return null;
final int srcLength = src.length();
if (srcLength < 2) return src instanceof Spannable
? (Spannable)src
: new SpannableString(src);
final String nonBreakingSpace = "\u00A0";
final SpannableStringBuilder builder = src instanceof SpannableStringBuilder
? (SpannableStringBuilder)src
: new SpannableStringBuilder(src);
for (int i = src.length() - 1; i >= 1; i--)
{
builder.insert(i, nonBreakingSpace);
builder.setSpan(new ScaleXSpan(kerning), i, i + 1,
Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
}
return builder;
}
据我所知,在 TextView
中无法调整字距。但如果你使用 2D 图形 API 自己在 Canvas
上绘制文本,则可能可以调整字距。
android:letterSpacing
https://developer.android.com/reference/android/widget/TextView#attr_android:letterSpacing - joerickletterSpacing
属性来设置字母间距。<TextView
android:width="..."
android:height="..."
android:letterSpacing="1.3"/>
SpannableStringBuilder builder = new SpannableStringBuilder("WIDE normal");
builder.setSpan(new TrackingSpan(20), 0, 4, Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
...
private static class TrackingSpan extends ReplacementSpan {
private float mTrackingPx;
public TrackingSpan(float tracking) {
mTrackingPx = tracking;
}
@Override
public int getSize(Paint paint, CharSequence text,
int start, int end, Paint.FontMetricsInt fm) {
return (int) (paint.measureText(text, start, end)
+ mTrackingPx * (end - start - 1));
}
@Override
public void draw(Canvas canvas, CharSequence text,
int start, int end, float x, int top, int y,
int bottom, Paint paint) {
float dx = x;
for (int i = start; i < end; i++) {
canvas.drawText(text, i, i + 1, dx, y, paint);
dx += paint.measureText(text, i, i + 1) + mTrackingPx;
}
}
}
当你使用TextView时,调整字符间距是很困难的。但是如果你能够自己处理绘图,应该有一些方法可以实现。
对于这个问题,我的答案是:使用自定义Span。
我的代码:
public class LetterSpacingSpan extends ReplacementSpan {
private int letterSpacing = 0;
public LetterSpacingSpan spacing(int space) {
letterSpacing = space;
return this;
}
@Override
public int getSize(@NonNull Paint paint, CharSequence text, int start, int end, @Nullable Paint.FontMetricsInt fm) {
return (int) paint.measureText(text, start, end) + (text.length() - 1) * letterSpacing;
}
@Override
public void draw(@NonNull Canvas canvas, CharSequence text, int start, int end, float x, int top, int y, int bottom, @NonNull Paint paint) {
int length = text.length();
float currentX = x;
for (int i = 1; i < length; i++) {
canvas.drawText(text, i, i + 1, currentX, y, paint);
currentX += paint.measureText(text, i, i + 1) + letterSpacing;
}
}
}
解释:
构建自己的Span
可以帮助您实现许多惊人的效果,比如使模糊的TextView、更改TextView的背景或前景,甚至制作一些动画。我从这篇文章Span a powerful concept中学到了很多。
因为您正在为每个字符添加间距,所以我们应该使用基于字符级别的Span,在这种情况下,ReplacementSpan是最好的选择。我添加了一个spacing
方法,因此在使用它时,您可以简单地将每个字符所需的空格作为参数传递。
构建自定义span时,您需要覆盖至少两个方法:getSize
和draw
。 getSize
方法应返回添加整个charsequence的间距后的最终宽度,而在draw
方法块内,您可以控制Canvas
进行所需的绘制。
那么我们如何使用这个LetterSpacingSpan呢?很简单:
用法:
TextView textView;
Spannable content = new SpannableString("This is the content");
textView.setSpan(new LetterSpacingSpan(), 0, 4, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
textView.setText(content);
就是这样。
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
paint.setLetterSpacing(-0.04f); // setLetterSpacing is only available from LOLLIPOP and on
canvas.drawText(text, xOffset, yOffset, paint);
} else {
float spacePercentage = 0.05f;
drawKernedText(canvas, text, xOffset, yOffset, paint, spacePercentage);
}
/**
* Programatically drawn kerned text by drawing the text string character by character with a space in between.
* Return the width of the text.
* If canvas is null, the text won't be drawn, but the width will still be returned
* kernPercentage determines the space between each letter. If it's 0, there will be no space between letters.
* Otherwise, there will be space between each letter. The value is a fraction of the width of a blank space.
*/
private int drawKernedText(Canvas canvas, String text, float xOffset, float yOffset, Paint paint, float kernPercentage) {
Rect textRect = new Rect();
int width = 0;
int space = Math.round(paint.measureText(" ") * kernPercentage);
for (int i = 0; i < text.length(); i++) {
if (canvas != null) {
canvas.drawText(String.valueOf(text.charAt(i)), xOffset, yOffset, paint);
}
int charWidth;
if (text.charAt(i) == ' ') {
charWidth = Math.round(paint.measureText(String.valueOf(text.charAt(i)))) + space;
} else {
paint.getTextBounds(text, i, i + 1, textRect);
charWidth = textRect.width() + space;
}
xOffset += charWidth;
width += charWidth;
}
return width;
}
private void applySpacing() {
if (this == null || this.originalText == null) return;
Paint testPaint = new Paint();
testPaint.set(this.getPaint());
float spaceOriginalSize = testPaint.measureText("\u00A0");
float spaceScaleXFactor = ( spaceOriginalSize > 0 ? spacing/spaceOriginalSize : 1);
StringBuilder builder = new StringBuilder();
for(int i = 0; i < originalText.length(); i++) {
builder.append(originalText.charAt(i));
if(i+1 < originalText.length()) {
builder.append("\u00A0");
}
}
SpannableString finalText = new SpannableString(builder.toString());
if(builder.toString().length() > 1) {
for(int i = 1; i < builder.toString().length(); i+=2) {
finalText.setSpan(new ScaleXSpan(spaceScaleXFactor), i, i+1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}
super.setText(finalText, BufferType.SPANNABLE);
}
我是一名Android开发的初学者,请随时告诉我如果有不好的地方!
SpannedStringBuilder
在同一个循环中插入空格并设置跨度! - Takhion