ChartDirectorvk如何测试文本的长度跟宽度

在使用charDirector画图时, 要确定setPlotArea的位置. setPlotArea方法的参数如下.

public PlotArea setPlotArea(int x, int y, int width, int height [, int bgColor [, int altBgColor [, int edgeColor [, int hGridColor [, int vGridColor ]]]]])

其中参数解释如下:

x	The x coordinate of the left of the plot area.
y	The y coordinate of the top of the plot area.
width	The width of the plot area in pixels.
height	The height of the plot area in pixels.

因为画图的时候, y轴的值有大有小, 所以我们不能固定一个值. 应该要根据y轴值的最长宽度的计算出点的位置.

找了一下, 在chartDirtect中, 可以使用以下代码计算文本的宽度和高度:

//这里得到一个TTFText文本对象
TTFText testTTF = c.getDrawArea().text3(ylabelStr[0], 字体名称, 字体大小);
int plotLeft = testTTF.getWidth() + 5; //计算出最宽的
int plotWith = picWith - plotLeft - plotRight; //画图的宽度
int plotTop = testTTF.getHeight();
plotHeight = picHeiht - plotTop - plotBottom; //画图的高度

其实, 它的原理跟java.awt.FontMetrics很类似的.
关于java.awt.FontMetrics请参考:

androd之绘制文本
JAVA:图形之利用FontMetrics类居中

附上个关于java里font的图解

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

该图片将如下

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);