牛面对面android gui培训

Android启动过程及GUI系统基本原理GUI系统功能基本图元绘制点，线，面高级图形操作遮挡，裁剪用户输入响应键盘，鼠标，触屏控件系统View，buttonGUI系统的一般流程开始获取用户输入是否退出变更数据更新显示结束从开机加电开始Zygote启动SystemService执行Android应用加载系统资源资源共享加载应用程序代码预加载程序资源创建子线程执行子程序

Android

UI的架构组成View绘制流程Measure过程Layout过程Draw过程高级绘图功能应用Android图形系统基本组成两个部分应用侧绘制系统侧渲染两个机制进程间通讯机制显示刷新机制应用侧绘制确定绘图区域位置/大小View测量递归（深度优先）确定所有视图的大小（高、宽）布局递归（深度优先）确定所有视图的位置（左上角坐标）实际绘制Canvas基于软件的绘制硬件加速系统侧渲染进程间通讯匿名共享内存显示刷新机制双缓存FrontBufferBackBufferVSYNC三缓存Canvas&PaintCanvasTheCanvasclassholdsthe"draw"callsPaintholdsthestyleandcolorinformationabouthowtodrawgeometries,textandbitmaps图片高级处理屏幕基本属性尺寸分辨率尺寸vs分辨率=密度（density）一英寸有多少个点儿单位：dpi(DotsPerInch)ldpi 120dpi low 0.75mdpi 160dpi medium 1.0hdpi 240dpi high 1.5xhdpi 320dpi extrahigh 2.0图片映射ldpimdpihdpidip(dp)deviceindependentpixelsdp之外px:pixelpt:pointin:inchmm:millimetersp:scale-independentpixeldp:deviceindependentpixels分辨率之外大胖子！1280X720Mem:1280X720X4=3600K=3.5MBitmap.ConfigALPHA_8Eachpixelisstoredasasingletranslucency(alpha)channel.

ARGB_4444

Eachpixelisstoredon2bytes

deprecatedinAPIlevel13ARGB_8888Eachpixelisstoredon4bytesRGB_565

Eachpixelisstoredon2bytesandonlytheRGBchannelsareencoded按需加载10801920Mem:1080X607X4=2560K=2.5MBitmapFactory.Optionspublicint

inSampleSizerequeststhedecodertosubsampletheoriginalimage,returningasmallerimagetosavememoryThesamplesizeisthenumberofpixelsineitherdimensionthatcorrespondtoasinglepixelinthedecodedbitmapinSampleSize==4->¼->1/16thedecoderusesafinalvaluebasedonpowersof2Drawable相关DrawableBitmap:thesimplestDrawable,aPNGorJPEGimage.NinePatch:anextensiontothePNGformatallowsittospecifyinformationabouthowtostretchitandplacethingsinsideofit.Shape:containssimpledrawingcommandsinsteadofarawbitmap,allowingittoresizebetterinsomecases.Layers:acompounddrawable,whichdrawsmultipleunderlyingdrawablesontopofeachother.States:acompounddrawablethatselectsoneofasetofdrawablesbasedonitsstate.Levels:acompounddrawablethatselectsoneofasetofdrawablesbasedonitslevel.Scale:acompounddrawablewithasinglechilddrawable,whoseoverallsizeismodifiedbasedonthecurrentlevel.Nine-Patch以[.9.png]结尾可拉伸可PaddingStretch&PaddingStateListDrawableDrawable列表据不同状态，显示不同的DrawableView的状态Selected&Focused&Pressed都会高亮Selected一般与Adapter