Android的绘制文本对象FontMetrics的介绍及绘制文本

一。Android绘制文本对象FontMetrics介绍

FontMetrics对象
它以四个基本坐标为基准，分别为：

・FontMetrics.top
・FontMetrics.ascent
・FontMetrics.descent
・FontMetrics.bottom

实例JAVA代码如下：
Paint textPaint = new Paint( Paint.ANTI_ALIAS_FLAG);
textPaint.setTextSize( 35);
textPaint.setColor( Color.WHITE);

// FontMetrics对象
FontMetrics fontMetrics = textPaint.getFontMetrics();
String text = "abcdefghijklmnopqrstu";

// 计算每一个坐标
float baseX = 0;
float baseY = 100;
float topY = baseY + fontMetrics.top;
float ascentY = baseY + fontMetrics.ascent;
float descentY = baseY + fontMetrics.descent;
float bottomY = baseY + fontMetrics.bottom;

// 绘制文本
canvas.drawText( text, baseX, baseY, textPaint);

// BaseLine描画
Paint baseLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
baseLinePaint.setColor( Color.RED);
canvas.drawLine(0, baseY, getWidth(), baseY, baseLinePaint);

// Base描画
canvas.drawCircle( baseX, baseY, 5, baseLinePaint);

// TopLine描画
Paint topLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
topLinePaint.setColor( Color.LTGRAY);
canvas.drawLine(0, topY, getWidth(), topY, topLinePaint);

// AscentLine描画
Paint ascentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
ascentLinePaint.setColor( Color.GREEN);
canvas.drawLine(0, ascentY, getWidth(), ascentY, ascentLinePaint);

// DescentLine描画
Paint descentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
descentLinePaint.setColor( Color.YELLOW);
canvas.drawLine(0, descentY, getWidth(), descentY, descentLinePaint);

// ButtomLine描画
Paint bottomLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
bottomLinePaint.setColor( Color.MAGENTA);
canvas.drawLine(0, bottomY, getWidth(), bottomY, bottomLinePaint);

二。繪製文本。

1.TextUtil 類

package com.wistron.test.DrawText;import java.util.Vector;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Paint.FontMetrics;import android.view.KeyEvent;public class TextUtil { private int mTextPosx = 0;// x坐标 private int mTextPosy = 0;// y坐标 private int mTextWidth = 0;// 绘制宽度 private int mTextHeight = 0;// 绘制高度 private int mFontHeight = 0;// 绘制字体高度 private int mPageLineNum = 0;// 每一页显示的行数 private int mCanvasBGColor = 0;// 背景颜色 private int mFontColor = 0;// 字体颜色 private int mAlpha = 0;// Alpha值 private int mRealLine = 0;// 字符串真实的行数 private int mCurrentLine = 0;// 当前行 private int mTextSize = 0;// 字体大小 private String mStrText = ""; private Vector mString = null; private Paint mPaint = null; public TextUtil(String StrText, int x, int y, int w, int h, int bgcolor,   int textcolor, int alpha, int textsize) {  mPaint = new Paint();  mString = new Vector();  this.mStrText = StrText;  this.mTextPosx = x;  this.mTextPosy = y;  this.mTextWidth = w;  this.mTextHeight = h;  this.mCanvasBGColor = bgcolor;  this.mFontColor = textcolor;  this.mAlpha = alpha;  this.mTextSize = textsize; } public void InitText() {  mString.clear();// 清空Vector  // 对画笔属性的设置  // mPaint.setARGB(this.mAlpha, Color.red(this.mFontColor), Color  // .green(this.mFontColor), Color.blue(this.mFontColor));  mPaint.setTextSize(this.mTextSize);  mPaint.setColor(Color.BLUE);  this.GetTextIfon(); } /**  * 得到字符串信息包括行数，页数等信息  */ public void GetTextIfon() {  char ch;  int w = 0;  int istart = 0;  FontMetrics fm = mPaint.getFontMetrics();// 得到系统默认字体属性  mFontHeight = (int) (Math.ceil(fm.descent - fm.top) + 2);// 获得字体高度  mPageLineNum = mTextHeight / mFontHeight;// 获得行数  int count = this.mStrText.length();  for (int i = 0; i < count; i++) {   ch = this.mStrText.charAt(i);   float[] widths = new float[1];   String str = String.valueOf(ch);   mPaint.getTextWidths(str, widths);   if (ch == '\n') {    mRealLine++;// 真实的行数加一    mString.addElement(this.mStrText.substring(istart, i));    istart = i + 1;    w = 0;   } else {    w += (int) Math.ceil(widths[0]);    if (w > this.mTextWidth) {     mRealLine++;// 真实的行数加一     mString.addElement(this.mStrText.substring(istart, i));     istart = i;     i--;     w = 0;    } else {     if (i == count - 1) {      mRealLine++;// 真实的行数加一      mString.addElement(this.mStrText.substring(istart,        count));     }    }   }  } } /**  * 绘制字符串  *   * @param canvas  */ public void DrawText(Canvas canvas) {  for (int i = this.mCurrentLine, j = 0; i < this.mRealLine; i++, j++) {   if (j > this.mPageLineNum) {    break;   }   canvas.drawText((String) (mString.elementAt(i)), this.mTextPosx,     this.mTextPosy + this.mFontHeight * j, mPaint);  } } /**  * 翻页等按键处理  *   * @param keyCode  * @param event  * @return  */ public boolean KeyDown(int keyCode, KeyEvent event) {  if (keyCode == KeyEvent.KEYCODE_DPAD_UP) {   if (this.mCurrentLine > 0) {    this.mCurrentLine--;   }  } else if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN) {   if ((this.mCurrentLine + this.mPageLineNum) < (this.mRealLine - 1)) {    this.mCurrentLine++;   }  }  return false; }}

2. MyView 類

package com.wistron.test.DrawText;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.view.KeyEvent;import android.view.View;public class MyView extends View implements Runnable { private final Paint mPaint; private int mICount = 0; private final TextUtil mTextUtil; public MyView(Context context) {  super(context);  mPaint = new Paint();  String string = "测试自动换行(第1行)\n\n测试自动换行(第2行)\n测试自动换行(第3行)\n测试自动换行(第4行)\n测试自动换行(第5行)\n测试自动换行(第6行)\n测试自动换行(第7行)"    + "生活教會了我們什麼，自己的感覺現在已經徹底的隕滅，生命中彷彿是蒸發了為自己幸福而爭的念頭，一切就這樣的循規蹈矩！";  mTextUtil = new TextUtil(string, 15, 150, 300, 80, Color.LTGRAY,    0xff00ff, 255, 16);  mTextUtil.InitText();  new Thread(this).start(); } @Override protected void onDraw(Canvas canvas) {  super.onDraw(canvas);  canvas.drawColor(Color.LTGRAY);  mPaint.setAntiAlias(true);  if (mICount < 100) {   mICount++;  }  mPaint.setColor(Color.RED);  canvas.drawText("裝載進度：" + mICount + "%......", 10, 20, mPaint);  mTextUtil.DrawText(canvas); } @Override public void run() {  Thread.currentThread();  while (!Thread.interrupted()) {   try {    Thread.sleep(10);   } catch (Exception ex) {    ex.printStackTrace();    Thread.currentThread().interrupt();   }   this.postInvalidate();  } } @Override public boolean onKeyDown(int keyCode, KeyEvent event) {  return mTextUtil.KeyDown(keyCode, event); }}

3. DrawText Activity.

package com.wistron.test.DrawText;import android.app.Activity;import android.os.Bundle;import android.view.KeyEvent;public class DrawText extends Activity {    /** Called when the activity is first created. */ private MyView mv; @Override public void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  mv = new MyView(this);  setContentView(mv); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) {  mv.onKeyDown(keyCode, event);  return super.onKeyDown(keyCode, event); }}

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