1+ package org.ninetripods.mq.study.jetpack.compose
2+
3+ import android.content.res.Resources
4+ import android.graphics.BitmapShader
5+ import android.graphics.Shader
6+ import android.os.Parcelable
7+ import androidx.activity.compose.setContent
8+ import androidx.activity.viewModels
9+ import androidx.annotation.DrawableRes
10+ import androidx.compose.foundation.background
11+ import androidx.compose.foundation.layout.Column
12+ import androidx.compose.foundation.layout.fillMaxWidth
13+ import androidx.compose.material.Button
14+ import androidx.compose.material.Text
15+ import androidx.compose.runtime.Composable
16+ import androidx.compose.runtime.getValue
17+ import androidx.compose.runtime.livedata.observeAsState
18+ import androidx.compose.runtime.mutableStateOf
19+ import androidx.compose.runtime.produceState
20+ import androidx.compose.runtime.remember
21+ import androidx.compose.runtime.saveable.listSaver
22+ import androidx.compose.runtime.saveable.mapSaver
23+ import androidx.compose.runtime.saveable.rememberSaveable
24+ import androidx.compose.runtime.setValue
25+ import androidx.compose.ui.Modifier
26+ import androidx.compose.ui.graphics.Color
27+ import androidx.compose.ui.graphics.ImageBitmap
28+ import androidx.compose.ui.graphics.ShaderBrush
29+ import androidx.compose.ui.graphics.asAndroidBitmap
30+ import androidx.compose.ui.platform.LocalContext
31+ import androidx.compose.ui.res.imageResource
32+ import androidx.lifecycle.compose.ExperimentalLifecycleComposeApi
33+ import androidx.lifecycle.compose.collectAsStateWithLifecycle
34+ import kotlinx.coroutines.flow.map
35+ import kotlinx.parcelize.Parcelize
36+ import org.ninetripods.mq.study.R
37+ import org.ninetripods.mq.study.jetpack.mvvm.base.BaseMvvmActivity
38+ import org.ninetripods.mq.study.jetpack.mvvm.base.BaseViewModel
39+ import org.ninetripods.mq.study.jetpack.mvvm.model.WanModel
40+ import org.ninetripods.mq.study.kotlin.ktx.log
41+
42+ /* *
43+ * Created by mq on 2023/10/23
44+ */
45+ class ComposeExampleActivity : BaseMvvmActivity () {
46+
47+ private val mVModel: ComposeVModel by viewModels()
48+
49+ override fun getViewModel (): BaseViewModel = mVModel
50+
51+ override fun init () {}
52+
53+ override fun setContentView () {
54+ setContent { GreetingScreen () }
55+ }
56+
57+ @Composable
58+ fun GreetingScreen () {
59+ var resId = remember { mutableStateOf(R .drawable.icon_flower) }
60+ log(" resId: ${resId.value} "
61+
62+ Greeting (resId = resId.value,
63+ onClickAction = {
64+ resId.value = R .drawable.icon_qrcode_we_chat
65+ mVModel.getWanInfo()
66+ })
67+ }
68+
69+ @OptIn(ExperimentalLifecycleComposeApi ::class )
70+ @Composable
71+ fun Greeting (
72+ res : Resources = LocalContext .current.resources,
73+ @DrawableRes resId : Int ,
74+ onClickAction : () -> Unit ,
75+ ) {
76+ // 1、remember的三种用法 ，remember会存储值，直到退出组合。
77+ val mutableState = remember { mutableStateOf(" init0" // 返回MutableState<T>类型
78+ var value1 by remember { mutableStateOf(" init1" // 返回T类型
79+ val (value2, setValue) = remember { mutableStateOf(" init" // 返回两个值分别为：T,Function1<T, kotlin.Unit>
80+
81+ // 2、remember还可以接受key参数，当key发生变化，缓存值会失效并再次对 lambda 块进行计算。这种机制可控制组合中对象的生命周期。在key发生变化之前（而不是在记住的值退出组合之前），计算会一直有效。
82+ // 示例：下面这个代码段会创建一个 ShaderBrush 并将其用作 Box 可组合项的背景绘制。remember 则会存储 ShaderBrush 实例，因为其重建成本高昂（如前所述）。此外，remember 也会接受 avatarRes 作为 key1 参数，即选定的背景图片。如果 avatarRes 发生变化，笔刷会根据新图片进行重组，然后重新应用于 Box。当用户从选择器中选择另一张图片作为背景时，可能就会发生这种情况。
83+ val bitmap = remember(key1 = resId) {
84+ ShaderBrush (
85+ BitmapShader (
86+ ImageBitmap .imageResource(res, resId).asAndroidBitmap(),
87+ Shader .TileMode .REPEAT ,
88+ Shader .TileMode .REPEAT
89+ )
90+ )
91+ }
92+
93+ // 1、如果涉及到配置更改后的状态恢复，直接使用rememberSaveable，会将值存储到Bundle中
94+ // 2、如果存储的值不支持Bundle，可以将Model声明为@Parcelable 或者使用MapSaver、ListSaver自定义存储规则
95+ var parcelCity by rememberSaveable {
96+ mutableStateOf(CityParcel (" Beijing" " China"
97+ }
98+
99+ var mapSaverCity by rememberSaveable(stateSaver = CityMapSaver ) {
100+ mutableStateOf(City (" Beijing" " China"
101+ }
102+
103+ var listSaverCity by rememberSaveable(stateSaver = CityListSaver ) {
104+ mutableStateOf(City (" Beijing" " China"
105+ }
106+ log(" parcelCity: $parcelCity "
107+ log(" mapSaverCity: $mapSaverCity "
108+ log(" listSaverCity: $listSaverCity "
109+
110+ // Flow转State
111+ val state by mVModel.mWanFlow.collectAsStateWithLifecycle()
112+ // LiveData转State
113+ val liveDataState by mVModel.mWanLiveData.observeAsState()
114+ log(" state:${state} "
115+
116+ val uiState by produceState<WanUiState >(WanUiState .Loading , mVModel) {
117+ // 在协程中
118+ mVModel.mWanFlow
119+ .map { WanUiState .SUC (it) }
120+ .collect { value = it }
121+ }
122+ when (val finalUiState = uiState) {
123+ is WanUiState .Loading -> Text (" Loading..."
124+ is WanUiState .SUC -> Column {
125+ for (model in finalUiState.models) {
126+ Text (" Hello, ${model.desc} "
127+ }
128+ }
129+ }
130+
131+ Column (modifier = Modifier .background(bitmap)) {
132+ Text (
133+ text = " $state "
134+ color = Color .Red ,
135+ modifier = Modifier .fillMaxWidth()
136+ )
137+ Text (
138+ text = " $liveDataState "
139+ color = Color .Red ,
140+ modifier = Modifier .fillMaxWidth()
141+ )
142+ Button (onClick = onClickAction) {
143+ Text (text = " 点击更改文本"
144+ }
145+ }
146+ }
147+ }
148+
149+ sealed class WanUiState {
150+ object Loading : WanUiState()
151+ data class SUC (val models : List <WanModel >) : WanUiState()
152+ }
153+
154+ @Parcelize
155+ data class CityParcel (val name : String , val country : String ) : Parcelable
156+
157+ data class City (val name : String , val country : String )
158+
159+ // MapSaver自定义存储规则，将对象转换为系统可保存到 Bundle 的一组值。
160+ val CityMapSaver = run {
161+ val nameKey = " Beijing"
162+ val countryKey = " China"
163+ mapSaver(
164+ save = { mapOf (nameKey to it.name, countryKey to it.country) },
165+ restore = { City (it[nameKey] as String , it[countryKey] as String ) }
166+ )
167+ }
168+
169+ // ListSaver
170+ val CityListSaver = listSaver<City , Any >(
171+ save = { listOf (it.name, it.country) },
172+ restore = { City (it[0 ] as String , it[1 ] as String ) }
173+ )
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