【移动应用开发技术】怎么在Android中使用FontMetrics对象计算坐标

【移动应用开发技术】怎么在Android中使用FontMetrics对象计算坐标

这期内容当中在下将会给大家带来有关怎么在Android中使用FontMetrics对象计算坐标，文章内容丰富且以专业的角度为大家分析和叙述，阅读完这篇文章希望大家可以有所收获。Canvas绘制文本时，使用FontMetrics对象，计算位置的坐标。public

static

class

FontMetrics

{

/**

*

The

maximum

distance

above

the

baseline

for

the

tallest

glyph

in

*

the

font

at

a

given

text

size.

*/

public

float

top;

/**

*

The

recommended

distance

above

the

baseline

for

singled

spaced

text.

*/

public

float

ascent;

/**

*

The

recommended

distance

below

the

baseline

for

singled

spaced

text.

*/

public

float

descent;

/**

*

The

maximum

distance

below

the

baseline

for

the

lowest

glyph

in

*

the

font

at

a

given

text

size.

*/

public

float

bottom;

/**

*

The

recommended

additional

space

to

add

between

lines

of

text.

*/

public

float

leading;

}它的各基准线可以参考下图：上图其实是通过代码画出来的，具体代码如下：/**

绘制FontMetrics对象的各种线

*/

mPaint.reset();

mPaint.setColor(Color.WHITE);

mPaint.setTextSize(80);

//

FontMetrics对象

FontMetrics

fontMetrics

=

mPaint.getFontMetrics();

String

text

=

"abcdefg";

//

计算每一个坐标

float

textWidth

=

mPaint.measureText(text);

float

baseX

=

30;

float

baseY

=

700;

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,

mPaint);

//

BaseLine描画

mPaint.setColor(Color.RED);

canvas.drawLine(baseX,

baseY,

baseX

+

textWidth,

baseY,

mPaint);

mPaint.setTextSize(20);

canvas.drawText("base",

baseX

+

textWidth,

baseY,

mPaint);

//

Base描画

canvas.drawCircle(baseX,

baseY,

5,

mPaint);

//

TopLine描画

mPaint.setColor(Color.LTGRAY);

canvas.drawLine(baseX,

topY,

baseX

+

textWidth,

topY,

mPaint);

canvas.drawText("top",

baseX

+

textWidth,

topY,

mPaint);

//

AscentLine描画

mPaint.setColor(Color.GREEN);

canvas.drawLine(baseX,

ascentY,

baseX

+

textWidth,

ascentY,

mPaint);

canvas.drawText("ascent",

baseX

+

textWidth,

ascentY

+

10,

mPaint);

//

DescentLine描画

mPaint.setColor(Color.YELLOW);

canvas.drawLine(baseX,

descentY,

baseX

+

textWidth,

descentY,

mPaint);

canvas.drawText("descent",

baseX

+

textWidth,

descentY,

mPaint);

//

ButtomLine描画

mPaint.setColor(Color.MAGENTA);

canvas.drawLine(baseX,

bottomY,

baseX

+

textWidth,

bottomY,

mPaint);

canvas.drawText("buttom",

baseX

+

textWidth,

bottomY

+

10,

mPaint);相信通过以上程序，能够很好的理解topLine，buttomLine，baseLine，ascentLine，descentLine。另外：Paint类有两个方法/**

*

Return

the

distance

above

(negative)

the

baseline

(ascent)

based

on

the

*

current

typeface

and

text

size.

*

*

@return

the

distance

above

(negative)

the

baseline

(ascent)

based

on

the

*

current

typeface

and

text

size.

*/

public

native

float

ascent();

/**

*

Return

the

distance

below

(positive)

the

baseline

(descent)

based

on

the

*

current

typeface

and

text

size.

*

*

@return

the

distance

below

(positive)

the

baseline

(descent)

based

on

*

the

current

typeface

and

text

size.

*/

public

native

float

descent();ascent()：thedistanceabovethebaseline（baseline以上的height）descent()：thedistancebelowthebaseline（baseli