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：
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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);
}
}
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希望本文所述对大家学习android程序设计有所帮助。