Android实现TextView两端对齐的方法

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);
  }

}

希望本文所述对大家学习android程序设计有所帮助。