JAVA教程之J2ME MIDP Currency Converter Tutoria...

到时我们不用学struts，不用学spring，不用学Hibernate，只要能把jsf学会了，完全可以替代所有的框架，包括AJAX，都知道AJAX并不是新技术，虽说我没深入学习jsf但我认为jsf应该已经能通过其它技术替代AJAX，实现无缝刷新。j2meMIDPCurrencyConverterTutorialforNetBeansIDE4.0
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TheCurrencyConverterapplicationyouwillbuildinthistutorialshowsyouhowto:

startaj2meMIDPproject
codeaworkingj2meMIDPapplication,orMIDlet,usingtheIDE
createprojectconfigurationstotesttheapplicationsperformanceontwodifferentdeviceemulators
TheCurrencyConverterapplicationconvertsamountsfromonecurrencytotwoothers.Youcanchoosetodisplaythreedifferentcurrencies:euros,yen,ordollars.Youcanalsoenteravalueinonecurrencytobeconvertedintotheotherselectedcurrencies.

TherearethreeJavasourcecodefilesforthesampleapplication:

ConverterMIDlet.java.ThecodefortheMIDletclass.
Converter.java.AMIDPformthatdefinesthemainscreenoftheapplicationasitappearsonamobiledevice.
CurrenciesSelector.java.AMIDPlistthatmaintainsthecurrenciesandrates.
Thefirstpartofthistutorialwillshowyouhowtoquicklyinstall,run,andtesttheCurrencyConverterapplication,whichisavailableasasampleprojectincludedintheIDE.Inthesecondpartofthetutorial,youwillcreateanewprojectandaddcodetocreateandtesttheapplicationyourself.

Thistutorialshouldtakeapproximatelyanhourtocomplete.

Requirements
YoumusthaveNetBeansIDE4.0andtheNetBeansMobilityPack4.0installedbeforeyoucanstartj2meMIDPdevelopment.Seethej2meMIDPDevelopmentDownloadpageforinstructionsondownloadingandinstallingthecompleteenvironment.

InstallingandTestingtheSampleCurrencyConverterProject
Inthisfirstsection,youwillseehowquicklyyoucaninstallandrunasampleprojectontwodifferentemulatordevices.

CreatingtheProjectChooseFile>NewProject.UnderCategories,selectSamples>Mobile.UnderProjects,selectCurrencyConverter.ClickNext.
TheProjectNameandLocationpagesetsthenameandlocationoftheprojectfolder,andgivesyoutheoptionofsettingtheprojectasthemainproject.ClickNexttoacceptthedefaults.
ThePlatformselectionpagesetsthedefaultexecutionenvironment,theemulatorplatform,fortheproject.Notethatthedefaultemulatorplatformisthej2meWirelessToolkit,andthedefaultdeviceistheDefaultColorPhone,agenericmobiledevice.ClickFinishtocompletethewizard.
TheCurrencyConverterdisplaysintheProjectswindow.

RunningtheProjectChooseRun>RunMainProject.
TheCurrencyConverterdisplaysintheDefaultColorPhonedeviceemulator.
Nowyourereadytotesttheapplicationinthedeviceemulator.

TestingtheApplicationIntheDefaultColorPhonescreen,clickthebuttonundertheword"Launch."
Selectthecurrencyyouwanttoconvertbyclickingtheupanddownarrowkeys
ontheSelectbutton.YoucanselectDollars,Euros,orYen.
Enterthecurrencyamounttoconvertbyclickingtheemulator’snumerickeys.
Theapplicationmakestheconversioncalculationsanddisplaystheresults.
Clickthebuttonunderneaththeword“Exit”toexittheapplication.
Clicktheredbuttonintheupperrightcornertoclosetheemulator.

ChangingtheDefaultEmulatorDeviceYoucancreatedifferentprojectconfigurationstotestyourMIDletondifferentemulatorplatforms,orsimplychangethedeviceforthedefaultconfiguration.

ChooseFile>"CurrencyConverter"PropertiesfromtheMainmenu.InthePropertiesdialog,choosethePlatformnode.Youcanchangethedeviceforthedefaultconfiguration.
ClicktheDevicedropdownmenuandchooseQwertyDevice.ClickOK.
ChooseRun>RunMainProjectRuntheapplicationagain,andtheapplicationrunsintheQwertyDeviceemulator.


Inthenextpartofthistutorial,youwillstartover,creatinganewproject.ThiswillgiveyouanopportunitytolearnmoreaboutthecodebehindtheapplicationandhowyoucanusetheIDEtocodeandtestyourownapplications.

CreatingtheCurrencyConverterApplication
CreatingtheProjectChooseFile>NewProject.UnderCategories,selectMobile.UnderProjects,selectMobileApplication.ClickNext.
IntheProjectNameandLocationpage,nametheprojectNewCurrencyConverter,andacceptthedefaultforProjectHome.LeavetheSetasMainProjectcheckboxchecked,asyoullwantthisprojecttobeyourmainprojectClickNext.
AcceptthedefaultsonthePlatformpagebyclickingFinish.
TheNewCurrencyConverterapplicationdisplaysintheProjectswindow.

CreatingtheconverterMIDlet.javaMIDlet
ChooseFile>NewFile.UnderCategories,chooseMIDP.UnderFileTypes,chooseMIDlet.ClickNext.
IntheNameandLocationpage,EnterCurrencyConverterfortheMIDletname,ConverterMIDletfortheMIDPClassName,andmyconverterforthepackagename.


CodingtheMIDlet
YoucanwritethecodeforaMIDletinoneoftwoways:eitherbydirectlyenteringcodeintheSourceEditororbyusingtheIDEtoaddmethods,fields,constructors,initializers,classes,andinterfaces.Typically,youusetheIDEtoaddnewfieldsandmethodstoaclass,ormodifyexistingfieldsandmethods,andthenlaterfine-tunethecodedirectlyintheSourceEditor.
ThefollowingprocedureshowsyouhowtousethetoolandtheSourceEditortoenterorchangecode.However,tosavetimeandeffort,youcanalsocopytheconvertercodefromtheexampleyouinstalled.

CodingtheConverterMIDlet.javaMIDletIntheSourceEditor,addthefollowingimportstatementstoConverterMIDlet.java:

importjava.io.*;importjavax.microedition.rms.*;
IntheProjectsTab,expandtheConverterMIDletnode,right-clicktheConverterMIDletclassandchooseAdd>Field.
ThisnextstepwillusetheAddNewFielddialogboxtoaddthefieldstoredDataStrtotheMIDlet.ThestoredDataStrstringcontainsthenameoftheRMSstoredrecord.
CompletetheAddNewFielddialogbox:
Enterthenameofthenewfield,storedDataStr,intheNameboxandselect
itstype,String,fromtheTypecombobox.
IntheModifiersbox,selectthetypeofaccessforthefield,private,fromthe
Accesscombobox.
Checktheothermodifiersforthefield,whichinthiscaseisstatic.
SettheinitialvalueforstoredDataStrto"ConverterData".
ClickOKtoclosethedialogbox.
ThefieldisaddedtothecodeintheSourceEditorwindow.

AddthefollowingfieldstotheConverterMIDlet.javaclassusingtheSourceEditor.
YoucanusetheAddFielddialogbox,copythetextfromthispage,orfromtheinstalledCurrencyConverterapplication,andpasteitintheSourceEditor.Becareful,however,nottochangethepackagenamefrommyconverter.

publicclassConverterMIDletextendsjavax.microedition.midlet.MIDlet{privatestaticStringstoredDataStr="ConverterData";
publicString[]currencies=newString[]{"US$","Yenu00a5","Eurou20ac"};publicboolean[]selected=newboolean[]{true,true,true,true};publiclong[][]rates={{1000000,117580000,911079},{8504,1000000,7749},
{1097600,129056000,1000000}};privateRecordStorestoredData;
AddthefollowingcodetothemethodstartApp().Thismethodiscalledwhentheapplicationisstarted.Itloadsallthedata(currencies,selectedcurrencies,andexchangerates)frompersistentstorageandinitiallydisplaystheConverterform.Themethodshouldlooklikethis:

publicvoidstartApp(){try{
storedData=RecordStore.openRecordStore(storedDataStr,true);
if(storedData.getNumRecords()>0){
DataInputStreamin=newDataInputStream(newByteArrayInputStream(storedData.getRecord(1)));try{intsize=in.readInt();currencies=newString[size];selected=newboolean[size];rates=newlong[size][];for(inti=0;i<size;i++){currencies[i]=in.readUTF();selected[i]=in.readBoolean();rates[i]=newlong[size];for(intj=0;j<size;j++){rates[i][j]=in.readLong();
}}
in.close();}catch(IOExceptionioe){}}}catch(RecordStoreExceptione){}notifySettingsChanged();}
Thedestroyapp()methodiscalledwhentheapplicationisfinished,ordestroyed.AddthefollowingcodetocompletethedestroyApp()method:

publicvoiddestroyApp(booleanunconditional){try{ByteArrayOutputStreambytes=newByteArrayOutputStream();DataOutputStreamout=newDataOutputStream(bytes);try{out.writeInt(currencies.length);for(inti=0;i<currencies.length;i++){out.writeUTF(currencies[i]);out.writeBoolean(selected[i]);for(intj=0;j<currencies.length;j++){out.writeLong(rates[i][j]);}}out.close();if(storedData.getNumRecords()>0)storedData.setRecord(1,bytes.toByteArray(),0,bytes.size());elsestoredData.addRecord(bytes.toByteArray(),0,bytes.size());}catch(IOExceptionioe){ioe.printStackTrace();}}catch(RecordStoreExceptione){e.printStackTrace();}notifyDestroyed();}
Addthefollowingthreenewmethods:
showSettings()
ThismethodcreatesanddisplaystheCurrenciesSelectorlist.

publicvoidshowSettings(){
Display.getDisplay(this).setCurrent(newCurrenciesSelector(this));
}
notifySettingsChanged()
ThismethoddisplaysanewConverterformafterthesettingsarechanged.

publicvoidnotifySettingsChanged(){Display.getDisplay(this).setCurrent(newConverter(this));}
longconvert()
Thismethodperformsthecurrencyconversion.Theinputvalue,frval,ismultipliedbytheexchangeratestoredintheratestableanddividedby1,000,000.Thefridxandtoidxvaluesaretheindexesofthesourceandtargetcurrencies.

publiclongconvert(longfrval,intfridx,inttoidx){return(frval*rates[fridx][toidx])/1000000;
8.SavetheConverterMIDletbychoosingFile>Save.


CreatingaMIDPForm
NowthatyouhavecompletedthecodefortheMIDlet,youwillcreatetheapplication’sgraphicalinterface.AformisaJavaclassthatcancontainanarbitrarymixtureofitems,includingimages,read-onlyandeditabletextfields,editabledatefields,gauges,choicegroups,andcustomitems.TheformyoucreateherewillspecifyatextboxforeachselectedcurrencyandspecifytheItemStateListener()methodtomonitorandreflecttypedvaluesandperformconversions.

CodingtheConverter.javaMIDPForm
IntheProjectswindow,right-clickthemyconverterpackage.ChooseFile>NewFile/Folder.
TheNewFilewizardopens.
UnderCategories,expandMIDP,thenexpandMIDPForms.UnderFileTypeschooseMIDPForm.ClickNext.
IntheNameandLocationpage,enterConverterfortheclassname.ClickFinish.
AMIDPformiscreatedandaddedtothemyconverterpackage.
IntheSourceEditor,addthefollowingfieldstothecodebelowthepublicclassConverterdeclaration:

privateConverterMIDletmidlet;privateint[]translate;
Addthefollowingcodetocompletetheconstructor,soitlookslikethesamplebelow:

publicConverter(ConverterMIDletmidlet){super("CurrencyConverter");
this.midlet=midlet;this.translate=newint[midlet.currencies.length];intcurrent=0;for(inti=0;i<translate.length;i++){if(midlet.selected[i]){translate[current++]=i;append(newTextField(midlet.currencies[i],"",12,TextField.NUMERIC));}}try{//SetupthisformtolistentocommandeventssetCommandListener(this);//SetupthisformtolistentochangesintheinternalstateofitsinteractiveitemssetItemStateListener(this);//AddtheCurrenciescommandaddCommand(newCommand("Currencies",Command.OK,1));//AddtheExitcommandaddCommand(newCommand("Exit",Command.EXIT,1));
}catch(Exceptione){e.printStackTrace();}
}

AddthefollowingcodetocompletethemethodcommandAction(),soitlookslikethesamplebelow:
publicvoidcommandAction(Commandcommand,Displayabledisplayable){if(command.getCommandType()==Command.EXIT){midlet.destroyApp(true);}elseif(command.getCommandType()==Command.OK){midlet.showSettings();}
}
AddthefollowingcodetocompletetheitemStateChanged()method,soitlookslikethesamplebelow:
publicvoiditemStateChanged(Itemitem){try{longvalue=Long.parseLong(((TextField)item).getString());intfrom=0;while(get(from)!=item)from++;from=translate[from];for(inti=0;i<size();i++){intto=translate[i];if(from!=to){((TextField)get(i)).setString(String.valueOf(midlet.convert(value,from,to)));}}}catch(NumberFormatExceptionnfe){for(inti=0;i<size();i++){((TextField)get(i)).setString("");}}}

ThiscompletestheConverter.javaformfile.


CreatingaMIDPList
ThefinalpieceoftheCurrencyConverterapplicationistheCurrenciesSelector.javalistfile,whichdefinesthecurrenciesthatcanbe
selectedfordisplay.

CodingtheCurrenciesSelector.javaMIDPList
IntheProjectswindow,right-clickthemyconverterpackage.ChooseFile>NewFile/Folder.
TheNewFilewizardopens.
UnderCategories,expandMIDP,thenexpandMIDPForms.UnderFileTypeschooseMIDPList.ClickNext.
IntheNameandLocationpage,enterCurrenciesSelectorfortheclassname.ClickFinish.
AMIDPlistfileiscreatedandaddedtothemyconverterpackage.
AfterthelinepublicclassCurrenciesSelectorextendsListimplementsCommandListener{,declareafield:

privateConverterMIDletmidlet;
Addthefollowingcodetocompletetheconstructor,soitlookslikethesamplebelow:

publicCurrenciesSelector(ConverterMIDletmidlet){super("SelectCurrencies",List.MULTIPLE,midlet.currencies,null);this.midlet=midlet;setSelectedFlags(midlet.selected);try{//SetupthislisttolistentocommandeventssetCommandListener(this);//AddtheSavecommandaddCommand(newCommand("Save",Command.OK,1));}catch(Exceptione){e.printStackTrace();}}
AddthefollowingcodetocompletethemethodcommandAction(),soitlookslikethesamplebelow:
publicvoidcommandAction(Commandcommand,Displayabledisplayable){if(command.getCommandType()==Command.OK){getSelectedFlags(midlet.selected);midlet.notifySettingsChanged();}}
ThiscompletestheCurrenciesSelector.javalistfile.


TestingYourApplication
Nowthatyouhavecreatedyourapplication,youcantestitwithdifferentemulatordevices,asyoudidwiththesampleCurrencyConverterprojectyoufirstinstalled.However,insteadofswitchingtheemulatordeviceinthedefaultconfiguration,thistimeyouwillcreateasecondprojectconfigurationfortheQwertyDevicedeviceemulator.

CreatingaNewProjectConfiguration
ChooseFile>"NewCurrencyConverter"Properties.
ClicktheManageConfigurationsbutton.
TheProjectConfigurationManageropens.
ClicktheAddButton.
TheAddConfigurationbuttondisplays.
NamethenewconfigurationQwertyDevice.ClickOk.
ClickClosetoclosetheProjectConfigurationManager.
Younowhaveasecondconfiguration,QwertyDevice,thathasthesamepropertiesastheDefaultConfiguration.

ChangingtheDevicePropertyWhilestillintheProjectProperties,choosePlatformfromthetreemenuintheleftpaneofthewindow.
IfitQwertyDeviceisnotshownastheactiveprojectconfiguration,chooseitfromtheProjectConfigurationdropdownmenu.
Sothatyoucanchoosenewvaluesforthisconfiguration,Uncheckthe"UseValuesfromDefaultConfiguration"checkbox.
ChooseQwertyDevicefromtheDevicedropdownmenu.ClickOK.

RunningtheApplicationonBothConfigurationsMakesurethattheConfigurationdropdownmenuonthetoolbarlistsDefaultConfigurationastheactiveprojectconfiguration.
ChooseRun>RunMainProject.
TheCurrencyConverteropensintheDefaultColorPhoneDeviceemulatorscreen.
ChooseQwertyDevicefromtheConfigurationdropdownmenuinthetoolbar.
ChooseRun>RunMainProject.
TheCurrencyConverteropensintheQwertyDeviceDeviceemulatorscreen.
Nowyoucantestandcomparetheapplicationsperformanceondifferentdevicesatthesametime.



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