牛面對(duì)面android gui培訓(xùn)

Android啟動(dòng)過程及GUI系統(tǒng)基本原理GUI系統(tǒng)功能基本圖元繪制點(diǎn)，線，面高級(jí)圖形操作遮擋，裁剪用戶輸入響應(yīng)鍵盤，鼠標(biāo)，觸屏控件系統(tǒng)View，buttonGUI系統(tǒng)的一般流程開始獲取用戶輸入是否退出變更數(shù)據(jù)更新顯示結(jié)束從開機(jī)加電開始Zygote啟動(dòng)SystemService執(zhí)行Android應(yīng)用加載系統(tǒng)資源資源共享加載應(yīng)用程序代碼預(yù)加載程序資源創(chuàng)建子線程執(zhí)行子程序

Android

UI的架構(gòu)組成View繪制流程Measure過程Layout過程Draw過程高級(jí)繪圖功能應(yīng)用Android圖形系統(tǒng)基本組成兩個(gè)部分應(yīng)用側(cè)繪制系統(tǒng)側(cè)渲染兩個(gè)機(jī)制進(jìn)程間通訊機(jī)制顯示刷新機(jī)制應(yīng)用側(cè)繪制確定繪圖區(qū)域位置/大小View測(cè)量遞歸（深度優(yōu)先）確定所有視圖的大?。ǜ?、寬）布局遞歸（深度優(yōu)先）確定所有視圖的位置（左上角坐標(biāo)）實(shí)際繪制Canvas基于軟件的繪制硬件加速系統(tǒng)側(cè)渲染進(jìn)程間通訊匿名共享內(nèi)存顯示刷新機(jī)制雙緩存FrontBufferBackBufferVSYNC三緩存Canvas&PaintCanvasTheCanvasclassholdsthe"draw"callsPaintholdsthestyleandcolorinformationabouthowtodrawgeometries,textandbitmaps圖片高級(jí)處理屏幕基本屬性尺寸分辨率尺寸vs分辨率=密度（density）一英寸有多少個(gè)點(diǎn)兒?jiǎn)挝唬篸pi(DotsPerInch)ldpi 120dpi low 0.75mdpi 160dpi medium 1.0hdpi 240dpi high 1.5xhdpi 320dpi extrahigh 2.0圖片映射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按需加載10801920Mem:1080X607X4=2560K=2.5MBitmapFactory.Optionspublicint

inSampleSizerequeststhedecodertosubsampletheoriginalimage,returningasmallerimagetosavememoryThesamplesizeisthenumberofpixelsineitherdimensionthatcorrespondtoasinglepixelinthedecodedbitmapinSampleSize==4->?->1/16thedecoderusesafinalvaluebasedonpowersof2Drawable相關(guān)DrawableBitmap:thesimplestDrawable,aPNGorJPEGimage.NinePatch:anextensiontothePNGformatallowsittospecifyinformationabouthowtostretchitandplacethingsinsideofit.Shape:containssimpledrawingcommandsinsteadofarawbitmap,allowingittoresizebetterinsomecases.Layers:acompounddrawable,whichdrawsmultipleunderlyingdrawablesontopofeachother.States:acompounddrawablethatselectsoneofasetofdrawablesbasedonitsstate.Levels:acompounddrawablethatselectsoneofasetofdrawablesbasedonitslevel.Scale:acompounddrawablewithasinglechilddrawable,whoseoverallsizeismodifiedbasedonthecurrentlevel.Nine-Patch以[.9.png]結(jié)尾可拉伸可PaddingStretch&PaddingStateListDrawableDrawable列表?yè)?jù)不同狀態(tài)，顯示不同的DrawableView的狀態(tài)Selected&Focused&Pressed都會(huì)高亮Selected一般與Adapter