【移動(dòng)應(yīng)用開(kāi)發(fā)技術(shù)】JetPack中的LiveData+ViewModel使用

/upload/information/20200214/43/8940.svg先闡述一下JetPack：這四個(gè)部分都十分優(yōu)秀，這里我選擇LiveData和ViewModel來(lái)給大家做案例分析，能夠達(dá)到屏幕旋轉(zhuǎn)自動(dòng)記住旋轉(zhuǎn)前的數(shù)據(jù)狀態(tài)實(shí)時(shí)自動(dòng)同步LiveData在底層數(shù)據(jù)庫(kù)更改時(shí)通知視圖ViewModel以注重生命周期的方式管理界面相關(guān)的數(shù)據(jù)以上為viewmodel的生命周期，它會(huì)自動(dòng)監(jiān)聽(tīng)activity的生命周期。它只有在activcity完全被摧毀的時(shí)候才會(huì)調(diào)用onCleared（）,你可以在這邊釋放你需要釋放的問(wèn)題。classSeekBarModel:ViewModel(){

//繼承ViewModel

val_sBar=MutableLiveData<BarI>()

valsBar:MutableLiveData<BarI>

get()=_sBar

varprogress:Int?=null

get()=_sBar?.value?.progress

varobservable:Subscription?=null

get()=_sBar?.value?.observable

overridefunonCleared(){

super.onCleared()

Log.d("SeekBarModel","ViewModel-->正在摧毀")

observable?.unsubscribe()

}

}

classBarI(progress:Int,observable:Subscription?){

varprogress:Int?=null

varobservable:Subscription?=null

init{

gress=progress

this.observable=observable

}

}

classOriginLiveDataActivity:AppCompatActivity(){

privatelateinitvarsekBarModel:SeekBarModel

varobservable:Subscription?=null

overridefunonCreate(savedInstanceState:Bundle?){

super.onCreate(savedInstanceState)

setContentView(R.layout.activity_origin_live_data)

sekBarModel=ViewModelProviders.of(this).get(SeekBarModel::class.java)

sekBarModel.sBar.observe(this,Observer{data->

bar_gress=if(data==null)0elsegress!!

btn_life.text="當(dāng)前進(jìn)度"+bar_gress

})

start()

btn_start.setOnClickListener{view->

finish()

}

}

//一秒加1，在bar上顯示進(jìn)度條

privatefunstart(){

if(sekBarModel.observable==null)

observable=Observable

.interval(1000,TimeUnit.MILLISECONDS)

.observeOn(AndroidSchedulers.mainThread())

.subscribe{

bar_gress+=1

sekBarModel.sBar.postValue(BarI(bar_gress,observable!!))

if(bar_gr