Android TextView两端对齐

Android中的TextView控件默认是做不到两端对齐的，都是左对齐。可能的原因是安卓默认数字、字母不能为第一行以后每行的开头字符，因为数字、字母为半角字符，还有就是文字中的英文字符占用1个字节，而一个汉字占用两个字节。下面我就介绍下实现两端对齐的原理：

1、测量一个中文汉字所占用的宽度

2、根据TextView的宽度和一个汉字所占用的宽度以及字符之间的间隔计算出总行数。

3、根据padding和margin以及行高计算出TextView的总高度。

4、绘制每一行的每一个字符

效果如下：



具体代码如下：

package com.wedroid.framework.module.ui;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.text.TextPaint;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.view.ViewGroup.MarginLayoutParams;
import android.view.ViewTreeObserver.OnPreDrawListener;
import android.widget.TextView;

public class WeDroidAlignTextView extends TextView {

private boolean first = true;

public WeDroidAlignTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
getViewTreeObserver().addOnPreDrawListener(new OnPreDrawListener() {
@Override
public boolean onPreDraw() {
initTextInfo();
return true;
}
});
}

public WeDroidAlignTextView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}

public WeDroidAlignTextView(Context context) {
this(context, null, 0);
}

private float textSize;
private float textLineHeight;
private int top;
private int y;
private int lines;
private int bottom;
private int right;
private int left;
private int lineDrawWords;
private char[] textCharArray;
private float singleWordWidth;

private float lineSpacingExtra;

public void initTextInfo() {
textSize = getTextSize();
textLineHeight = getLineHeight();
left = 0;
right = getRight();
y = getTop();
// 要画的宽度
int drawTotalWidth = right - left;
String text = getText().toString();
if (!TextUtils.isEmpty(text) && first) {
textCharArray = text.toCharArray();
TextPaint mTextPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
mTextPaint.density = getResources().getDisplayMetrics().density;
mTextPaint.setTextSize(textSize);
// 一个单词的的宽度
singleWordWidth = mTextPaint.measureText("一") + lineSpacingExtra;
// 一行可以放多少个字符
lineDrawWords = (int) (drawTotalWidth / singleWordWidth);
int length = textCharArray.length;
lines = length / lineDrawWords;
if ((length % lineDrawWords) > 0) {
lines = lines + 1;
}
first = false;
MarginLayoutParams layoutParams = (MarginLayoutParams) getLayoutParams();
int totalHeight = (int) (lines*textLineHeight+textLineHeight*2 + getPaddingBottom()+getPaddingTop()+layoutParams.bottomMargin+layoutParams.topMargin);
setHeight(totalHeight);
}
}

@Override
protected void onDraw(Canvas canvas) {
bottom = getBottom();
int drawTotalLine = lines;

if(maxLine!=0&&drawTotalLine>maxLine){
drawTotalLine = maxLine;
}

for (int i = 0; i < drawTotalLine; i++) {
try {
int length = textCharArray.length;
int mLeft = left;
// 第i+1行开始的字符index
int startIndex = (i * 1) * lineDrawWords;
// 第i+1行结束的字符index
int endTextIndex = startIndex + lineDrawWords;
if (endTextIndex > length) {
endTextIndex = length;
y += textLineHeight;
} else {
y += textLineHeight;
}
for (; startIndex < endTextIndex; startIndex++) {
char c = textCharArray[startIndex];
//                  if (c == ' ') {
//                      c = '\u3000';
//                  } else if (c < '\177') {
//                      c = (char) (c + 65248);
//                  }
canvas.drawText(String.valueOf(c), mLeft, y, getPaint());
mLeft += singleWordWidth;
}
} catch (Exception e) {
e.printStackTrace();
}
}
}

int maxLine;

public void setMaxLines(int max){
this.maxLine = max;
}

public void setLineSpacingExtra(int lineSpacingExtra){
this.lineSpacingExtra = lineSpacingExtra;
}

/**
* 判断是否为中文
* @return
*/
public static boolean containChinese(String string){
boolean flag = false;
for (int i = 0; i < string.length(); i++) {
char c = string.charAt(i);
if ((c >= 0x4e00) && (c <= 0x9FA5)) {
flag = true;
}
}
return flag;
}

public static String ToDBC(String input) {
// 导致TextView异常换行的原因：安卓默认数字、字母不能为第一行以后每行的开头字符，因为数字、字母为半角字符
// 所以我们只需要将半角字符转换为全角字符即可
char c[] = input.toCharArray();
for (int i = 0; i < c.length; i++) {
if (c[i] == ' ') {
c[i] = '\u3000';
} else if (c[i] < '\177') {
c[i] = (char) (c[i] + 65248);
}
}
return new String(c);
}

}