两个小时精通Android开发之界面篇

1、笔者最近需要移植一个J2ME的项目到Android平台上，所以抽空研究了一下Android平台的接口规范。 Android平台除了在一些接口上采用了和J2ME不一样的名称之外，基本的接口内容还是一样的，那么移植J2ME到Android平台最方便的方法就是利用Android平台的接口重写J2ME的接口，本着这个思路笔者写了一个Wrap包，利用这个Wrap包，基本上J2ME程序不用修改，只需要重新导入一下重写后的Graphics、Image等类，就可以无缝的运行在Android平台上，所以笔者题目中所说的“两个小时精通Android”的前提是先精通J2ME。 既然要重写J2ME下的这些接口，那么就

2、要先了解Android和J2ME平台到底有哪些不同，然后重写这部分不同的接口即可。 Ø Font类Android平台里不再提供J2ME下面的Font类，而是以Typeface代替，这为读者提供了更多的选择空间，因为Typeface是可以自定义的，但是为了无缝移植J2ME程序到Android平台上，笔者封装了以个类似于J2ME平台下的Font类，如下： public class Font public static final int STYLE_PLAIN = 0; public static final int STYLE_BOLD = 1; public static final

3、 int STYLE_ITALIC = 2; public static final int STYLE_UNDERLINED = 4; public static final int SIZE_SMALL = 22; public static final int SIZE_MEDIUM = 31; public static final int SIZE_LARGE = 40; public static final int FACE_SYSTEM = 0; private int face; private int style; private int size; private int

4、 baseline; private int width; private int height; public void setWidth(int width) this.width = size; public void setHeight(int height) this.height = height; public int getWidth() return size; public int getHeight() return height; private Typeface iTypeface = Typeface.DEFAULT; public Typeface getType

5、face() return iTypeface; public void setSize(int fontSize) size = fontSize; public int getSize() return size; private static final Font DEFAULT_FONT = new Font(null,22); public Font(Typeface aTypeface,int aSize) if(iTypeface != null) iTypeface = aTypeface; size = aSize; public static Font getFont(in

6、t fontSepcifier) switch(fontSepcifier) case SIZE_SMALL: return new Font(null,22); case SIZE_MEDIUM: return new Font(null,31); case SIZE_LARGE: return new Font(null,40); return DEFAULT_FONT; public static Font getDefaultFont() return DEFAULT_FONT; public static Font getFont(int face,int style,int siz

7、e) switch(style) case STYLE_PLAIN: return new Font(Typeface.defaultFromStyle(Typeface.NORMAL),size); case STYLE_BOLD: return new Font(Typeface.defaultFromStyle(Typeface.BOLD),size); case STYLE_ITALIC: return new Font(Typeface.defaultFromStyle(Typeface.ITALIC),size); return DEFAULT_FONT; public int c

8、harWidth(char arg) return size; public int stringWidth(String arg) return size*(arg.length(); Ø Graphics类Android平台下不再提供Graphics类进行“视图上下文”的控制，而是以Canvas、Paint联合进行控制，笔者封装的Graphics类如下： public class Graphics public static final int HCENTER = 1; public static final int VCENTER = 2; public static fina

9、l int LEFT = 4; public static final int RIGHT = 8; public static final int TOP = 16; public static final int BOTTOM = 32; public static final int BASELINE = 64; public static final int SOLID = 0; public static final int DOTTED = 1; private Bitmap bitmap; private Canvas canvas; private Paint paint; p

10、rivate Rect clip; private Font font; public Graphics(Bitmap bitmap) this.bitmap = bitmap; this.canvas = new Canvas(bitmap); this.paint = new Paint(); this.clip = canvas.getClipBounds(); public void setAlign(int align) if(LEFT = align |(Graphics.LEFT | Graphics.TOP) = align |(Graphics.LEFT | Graphics

11、.BOTTOM) = align) paint.setTextAlign(Align.LEFT); else if(HCENTER = align |(Graphics.HCENTER|Graphics.TOP) = align) paint.setTextAlign(Align.CENTER); else if(RIGHT = align |(Graphics.RIGHT | Graphics.TOP) = align) paint.setTextAlign(Align.RIGHT); public void fillRoundRect(int x,int y,int width,int h

12、eight,int arcWidth,int arcHeight) paint.setStyle(Style.FILL); canvas.drawRoundRect(new RectF(x,y,x+width,y+height), arcWidth, arcHeight, paint); public void drawRoundRect(int x,int y,int width,int height,int arcWidth,int arcHeight) paint.setStyle(Style.STROKE); canvas.drawRoundRect(new RectF(x,y,x+w

13、idth,y+height), arcWidth, arcHeight, paint); public void fillTriangle(int x1,int y1,int x2,int y2,int x3,int y3) paint.setStyle(Style.FILL); canvas.drawLine(x1, y1, x2, y2, paint); canvas.drawLine(x2, y2, x3, y3, paint); canvas.drawLine(x3, y3, x1, y1, paint); public void setFont(Font font) paint.se

14、tTypeface(font.getTypeface(); paint.setTextSize(font.getSize(); FontMetrics fontMetrics = paint.getFontMetrics(); float height = fontMetrics.bottom-fontMetrics.top; font.setHeight(int)height); public void fillArc(int x,int y,int width,int height,int startAngle,int arcAngle) paint.setStyle(Style.FILL

15、); canvas.drawArc(new RectF(x,y,width,height), startAngle, arcAngle, true, paint); public void drawArc(int x,int y,int width,int height,int startAngle,int arcAngle) paint.setStyle(Style.STROKE); canvas.drawArc(new RectF(x,y,width,height), startAngle, arcAngle, true, paint); public Font getFont() ret

16、urn font; public void setAntiAlias(boolean flag) paint.setAntiAlias(flag); public void setAlphaValue(int alpha) paint.setAlpha(alpha); public void setAlpha(float alpha) setAlphaValue(int) (255 * alpha); public void translate(int x,int y) canvas.translate(x,y); public void setColor(int rgb) paint.set

17、Color(rgb); public void setColor(int r,int g,int b) int argb = (0xff000000)+(r<<16)+(g<<8)+b; paint.setColor(argb); public void drawImage(Image img, int x, int y) canvas.drawBitmap(img.getBitmap(), x, y, paint); public void drawImage(Image img, int x, int y,int align) setAlign(align); dr

18、awImage(img, x, y); public void drawLine(int x1, int y1, int x2, int y2) if (x1 > x2) x1+; else x2+; if (y1 > y2) y1+; else y2+; canvas.drawLine(x1, y1, x2, y2, paint); public void drawRect(int x, int y, int width, int height) canvas.drawRect(x, y, x + width, y + height, paint); public void dr

19、awString(String str, int x, int y) canvas.drawText(str, x, y, paint); public void drawString(String str, int x, int y,int align) setAlign(align); canvas.drawText(str, x, y, paint); public void drawClear() paint.setColor(Color.BLACK); canvas.drawColor(Color.BLACK); public void fillRect(int x, int y,

20、int width, int height) canvas.drawRect(x, y, x + width, y + height, paint); public int getClipHeight() return clip.bottom - clip.top; public int getClipWidth() return clip.right - clip.left; public int getClipX() return clip.left; public int getClipY() return clip.top; public int getColor() return p

21、aint.getColor(); public void dispose() paint = null; canvas = null; public void clearRect(int x, int y, int width, int height) canvas.clipRect(x, y, x + width, y + height); canvas.drawARGB(0xff, 0xff, 0xff, 0xff); public void copyArea(int x, int y, int width, int height, int dx, int dy) if (x < 0

22、) width += x; x = 0; if (y < 0) height += y; y = 0; if (x + width > bitmap.getWidth() width = bitmap.getWidth() - x; if (y + height > bitmap.getHeight() height = bitmap.getHeight() - y; Bitmap copy = Bitmap.createBitmap(bitmap, x, y, width, height); canvas.drawBitmap(copy, x + dx, y + dy, n

23、ull); public void clipRect(int x, int y, int width, int height) canvas.clipRect(x, y, x + width, y + height); clip = canvas.getClipBounds(); public void setClip(int x, int y, int width, int height) if (x = clip.left && x + width = clip.right && y = clip.top && y + height = cl

24、ip.bottom) return; if (x < clip.left | x + width > clip.right | y < clip.top | y + height > clip.bottom) canvas.restore(); canvas.save(Canvas.CLIP_SAVE_FLAG); clip.left = x; clip.top = y; clip.right = x + width; clip.bottom = y + height; canvas.clipRect(clip); public void drawOval(int x, int y, int width, int height) canvas.drawOval(new RectF(x, y, x + width, y + height), paint); public void drawPolygon(int xpoints, int ypoints, int npoints) canvas.drawLine(xpointsnpoints - 1, ypointsnpoints - 1, xpoints0, ypoints0, paint); for (int i = 0; i < npoints