Android UI开发专题之界面设计

　　主要涉及以下四个包的相关内容:

　　Android.content.res 资源类

　　android.graphics 底层图形类

　　android.view 显示类

　　android.widget 控件类

一、android.content.res.Resources

对于Android平台的资源类android.content.res.Resources可能很多网友比较陌生，一起来看看SDK上是怎么介绍的吧，Containsclasses for accessing application resources, such as raw asset files, colors,drawables, media or other other files in the package, plus important deviceconfiguration details (orientation, input types, etc.) that affect how theapplication may behave.平时用到的二进制源文件raw、颜色colors、图形drawables和多媒体文件media的相关资源均通过该类来管理。

相关阅读：

int getColor(int id) 对应res/values/colors.xml

Drawable getDrawable(int id) 对应res/drawable/

XmlResourceParser getLayout(intid) 对应res/layout/

String getString(int id) 和CharSequencegetText(int id) 对应res/values/strings.xml

InputStreamopenRawResource(int id) 对应res/raw/

void parseBundleExtra (StringtagName, AttributeSet attrs, Bundle outBundle) 对应res/xml/

String[] getStringArray(intid) res/values/arrays.xml

float getDimension(int id)res/values/dimens.xml

二、android.graphics.Bitmap

作为位图操作类，Bitmap提供了很多实用的方法，常用的我们总结如下:

booleancompress(Bitmap.CompressFormat format, int quality, OutputStream stream) 压缩一个Bitmap对象根据相关的编码、画质保存到一个OutputStream中。其中第一个压缩格式目前有JPG和PNG

voidcopyPixelsFromBuffer(Buffer src) 从一个Buffer缓冲区复制位图像素

void copyPixelsToBuffer(Bufferdst) 将当前位图像素内容复制到一个Buffer缓冲区

我们看到创建位图对象createBitmap包含了6种方法在目前的Android2.1 SDK中，当然他们使用的是APILevel均为1，所以说从Android1.0 SDK开始就支持了，所以大家可以放心使用。

static BitmapcreateBitmap(Bitmap src)

static BitmapcreateBitmap(int[] colors, int width, int height, Bitmap.Config config)

static BitmapcreateBitmap(int[] colors, int offset, int stride, int width, int height,Bitmap.Config config)

static BitmapcreateBitmap(Bitmap source, int x, int y, int width, int height, Matrix m,boolean filter)

static Bitmap createBitmap(intwidth, int height, Bitmap.Config config)

static BitmapcreateBitmap(Bitmap source, int x, int y, int width, int height)

static BitmapcreateScaledBitmap(Bitmap src, int dstWidth, int dstHeight, boolean filter) //创建一个可以缩放的位图对象

final int getHeight() 获取高度

final int getWidth() 获取宽度

final boolean hasAlpha() 是否有透明通道

void setPixel(int x, int y,int color) 设置某像素的颜色

int getPixel(int x, int y) 获取某像素的颜色，android开发网提示这里返回的int型是color的定义

三、android.graphics.BitmapFactory

作为Bitmap对象的I/O类，BitmapFactory类提供了丰富的构造Bitmap对象的方法，比如从一个字节数组、文件系统、资源ID、以及输入流中来创建一个Bitmap对象，下面本类的全部成员，除了decodeFileDescriptor外其他的重载方法都很常用。

static BitmapdecodeByteArray(byte[] data, int offset, int length) //从字节数组创建

static BitmapdecodeByteArray(byte[] data, int offset, int length, BitmapFactory.Optionsopts)

static BitmapdecodeFile(String pathName, BitmapFactory.Options opts) //从文件创建，路径要写全

static BitmapdecodeFile(String pathName)

static BitmapdecodeFileDescriptor(FileDescriptor fd, Rect outPadding, BitmapFactory.Optionsopts) //从输入流句柄创建

static BitmapdecodeFileDescriptor(FileDescriptor fd)

static BitmapdecodeResource(Resources res, int id) //从Android的APK文件资源中创建，android123提示是从/res/的drawable中

static BitmapdecodeResource(Resources res, int id, BitmapFactory.Options opts)

static BitmapdecodeResourceStream(Resources res, TypedValue value, InputStream is, Rect pad,BitmapFactory.Options opts)

static BitmapdecodeStream(InputStream is) //从一个输入流中创建

static BitmapdecodeStream(InputStream is, Rect outPadding, BitmapFactory.Options opts)

四、android.graphics.Canvas

从J2ME MIDLET时我们就知道Java提供了Canvas类，而目前在Android平台中，它主要任务为管理绘制过程，TheCanvas class holds the "draw" calls. To draw something, you need 4basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls(writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap),and a paint (to describe the colors and styles for the drawing).

该类主要提供了三种构造方法，分别为构造一个空的Canvas、从Bitmap中构造和从GL对象中创建，如下

Canvas()

Canvas(Bitmap bitmap)

Canvas(GL gl)

同时Canvas类的一些字段保存着重要的绘制方法定义，比如Canvas.HAS_ALPHA_LAYER_SAVE_FLAG保存时需要alpha层，对于Canvas类提供的方法很多，每个都很重要，下面我们一一作介绍

boolean clipPath(Path path)

boolean clipPath(Path path,Region.Op op)

boolean clipRect(float left,float top, float right, float bottom)

boolean clipRect(Rect rect)

boolean clipRect(float left,float top, float right, float bottom, Region.Op op)

boolean clipRect(Rect rect,Region.Op op)

boolean clipRect(RectF rect)

boolean clipRect(RectF rect,Region.Op op)

boolean clipRect(int left, inttop, int right, int bottom)

boolean clipRegion(Regionregion, Region.Op op)

boolean clipRegion(Regionregion)

void concat(Matrix matrix)

void drawARGB(int a, int r,int g, int b)

void drawArc(RectF oval, floatstartAngle, float sweepAngle, boolean useCenter, Paint paint)

void drawBitmap(Bitmap bitmap,Matrix matrix, Paint paint)

void drawBitmap(int[] colors,int offset, int stride, float x, float y, int width, int height, booleanhasAlpha, Paint paint)

void drawBitmap(Bitmap bitmap,Rect src, Rect dst, Paint paint)

void drawBitmap(Bitmap bitmap,float left, float top, Paint paint)

void drawBitmap(int[] colors,int offset, int stride, int x, int y, int width, int height, boolean hasAlpha,Paint paint)

void drawBitmap(Bitmap bitmap,Rect src, RectF dst, Paint paint)

void drawBitmapMesh(Bitmapbitmap, int meshWidth, int meshHeight, float[] verts, int vertOffset, int[]colors, int colorOffset, Paint paint)

void drawCircle(float cx,float cy, float radius, Paint paint)

void drawColor(int color)

void drawColor(int color,PorterDuff.Mode mode)

void drawLine(float startX,float startY, float stopX, float stopY, Paint paint)

void drawLines(float[] pts,Paint paint)

void drawLines(float[] pts,int offset, int count, Paint paint)

void drawOval(RectF oval,Paint paint)

void drawPaint(Paint paint)

void drawPath(Path path, Paintpaint)

void drawPicture(Picturepicture, RectF dst)

void drawPicture(Picturepicture, Rect dst)

void drawPicture(Picturepicture)

void drawPoint(float x, floaty, Paint paint)

void drawPoints(float[] pts,int offset, int count, Paint paint)

void drawPoints(float[] pts,Paint paint)

void drawPosText(char[] text,int index, int count, float[] pos, Paint paint)

void drawPosText(String text,float[] pos, Paint paint)

void drawRGB(int r, int g, intb)

void drawRect(RectF rect,Paint paint)

void drawRect(float left,float top, float right, float bottom, Paint paint)

void drawRect(Rect r, Paintpaint)

void drawRoundRect(RectF rect,float rx, float ry, Paint paint)

void drawText(String text, intstart, int end, float x, float y, Paint paint)

void drawText(char[] text, intindex, int count, float x, float y, Paint paint)

void drawText(String text,float x, float y, Paint paint)

void drawText(CharSequencetext, int start, int end, float x, float y, Paint paint)

void drawTextOnPath(Stringtext, Path path, float hOffset, float vOffset, Paint paint)

void drawTextOnPath(char[]text, int index, int count, Path path, float hOffset, float vOffset, Paintpaint)

voiddrawVertices(Canvas.VertexMode mode, int vertexCount, float[] verts, intvertOffset, float[] texs, int texOffset, int[] colors, int colorOffset, short[]indices, int indexOffset, int indexCount, Paint paint)

static void freeGlCaches()

boolean getClipBounds(Rectbounds)

final Rect getClipBounds()

int getDensity()

DrawFilter getDrawFilter()

GL getGL()

int getHeight()

void getMatrix(Matrix ctm)

final Matrix getMatrix()

int getSaveCount()

int getWidth()

boolean isOpaque()

boolean quickReject(Path path,Canvas.EdgeType type)

boolean quickReject(floatleft, float top, float right, float bottom, Canvas.EdgeType type)

boolean quickReject(RectFrect, Canvas.EdgeType type)

void restore()

void restoreToCount(intsaveCount)

final void rotate(floatdegrees, float px, float py)

void rotate(float degrees)

int save()

int save(int saveFlags)

int saveLayer(float left,float top, float right, float bottom, Paint paint, int saveFlags)

int saveLayer(RectF bounds,Paint paint, int saveFlags)

int saveLayerAlpha(float left,float top, float right, float bottom, int alpha, int saveFlags)

int saveLayerAlpha(RectFbounds, int alpha, int saveFlags)

final void scale(float sx,float sy, float px, float py)

void scale(float sx, float sy)

void setBitmap(Bitmap bitmap)

void setDensity(int density)

void setDrawFilter(DrawFilterfilter)

void setMatrix(Matrix matrix)

void setViewport(int width,int height)

void skew(float sx, float sy)

void translate(float dx, floatdy)

五、android.graphics.Color

有关Android平台上表示颜色的方法有很多种，Color提供了常规主要颜色的定义比如Color.BLACK和Color.GREEN等等，我们平时创建时主要使用以下静态方法

static int argb(int alpha, intred, int green, int blue) 构造一个包含透明对象的颜色

static int rgb(int red, intgreen, int blue) 构造一个标准的颜色对象

static int parseColor(StringcolorString) 解析一种颜色字符串的值，比如传入Color.BLACK

本类返回的均为一个整形类似 绿色为0xff00ff00，红色为0xffff0000。我们将这个DWORD型看做AARRGGBB，AA代表Aphla透明色，后面的就不难理解，每个分成WORD整好为0-255。