本文主要是介绍Jetpack 之Glance+Compose实现一个小组件，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
Glance，官方对其解释是使用 Jetpack Compose 样式的 API 构建远程 Surface 的布局，通俗的讲就是使用Compose风格的API来搭建小插件布局，其最新版本是2022年2月23日更新的1.0.0-alpha03。众所周知，Compose样式的API与原生差别不小，至于widget这块改动如何，接下来让我们来一探究竟。
声明依赖项
第一步肯定要添加对应依赖，相应的都是在build.gradle中添加，如果你的工程还没支持Compose，要先添加：
android {buildFeatures {compose = true}composeOptions {kotlinCompilerExtensionVersion = "1.1.0-beta03"}kotlinOptions {jvmTarget = "1.8"}
}
如果已经支持，上述依赖可以省略，但下述依赖不能省略，继续添加：
dependencies {implementation("androidx.glance:glance-appwidget:1.0.0-alpha03")implementation("androidx.glance:glance-wear-tiles:1.0.0-alpha03")
}
以上是官方的标准依赖方式，同样以下面这种方式依赖也可以：
implementation 'androidx.glance:glance-appwidget:+'
implementation 'androidx.glance:glance:+'
implementation "androidx.glance:glance-appwidget:1.0.0-alpha03"
创建对应 widget
首先编写对应布局，放在对应/layout/xml目录下：
widget_info.xml
<?xml version="1.0" encoding="utf-8"?>
<appwidget-providerxmlns:android="http://schemas.android.com/apk/res/android"android:description="@string/app_name"android:minWidth="150dp"android:minHeight="66dp"android:resizeMode="horizontal|vertical"android:targetCellWidth="3"android:targetCellHeight="2"android:widgetCategory="home_screen"/>
我在上一篇介绍widget的文章中说过，widget其实就是个广播，广播属于四大组件，而四大组件都要在AndroidManifest清单文件中注册：
<receiverandroid:name=".CounterWidgetReceiver"android:enabled="@bool/glance_appwidget_available"android:exported="false"><intent-filter><action android:name="android.appwidget.action.APPWIDGET_UPDATE" /></intent-filter><meta-dataandroid:name="android.appwidget.provider"android:resource="@xml/widget_info" />
</receiver>
对应CounterWidgetReceiver代码为：
import androidx.glance.appwidget.GlanceAppWidget
import androidx.glance.appwidget.GlanceAppWidgetReceiver
import com.ktfly.comapp.ui.theme.CounterWidgetclass CounterWidgetReceiver : GlanceAppWidgetReceiver(){override val glanceAppWidget: GlanceAppWidget = CounterWidget()
}
可能看到这里你就迷惑了，widget对应广播类不是要继承AppWidgetProvider然后实现相应方法的吗，其实Glance提供的GlanceAppWidgetReceiver类就已经继承了AppWidgetProvider，我们使用Glance需要GlanceAppWidgetReceiver：
abstract class GlanceAppWidgetReceiver : AppWidgetProvider() {private companion object {private const val TAG = "GlanceAppWidgetReceiver"}/*** Instance of the [GlanceAppWidget] to use to generate the App Widget and send it to the* [AppWidgetManager]*/abstract val glanceAppWidget: GlanceAppWidget@CallSuperoverride fun onUpdate(context: Context,appWidgetManager: AppWidgetManager,appWidgetIds: IntArray) {if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {Log.w(TAG,"Using Glance in devices with API<23 is untested and might behave unexpectedly.")}goAsync {updateManager(context)appWidgetIds.map { async { glanceAppWidget.update(context, appWidgetManager, it) } }.awaitAll()}}@CallSuperoverride fun onAppWidgetOptionsChanged(context: Context,appWidgetManager: AppWidgetManager,appWidgetId: Int,newOptions: Bundle) {goAsync {updateManager(context)glanceAppWidget.resize(context, appWidgetManager, appWidgetId, newOptions)}}@CallSuperoverride fun onDeleted(context: Context, appWidgetIds: IntArray) {goAsync {updateManager(context)appWidgetIds.forEach { glanceAppWidget.deleted(context, it) }}}private fun CoroutineScope.updateManager(context: Context) {launch {runAndLogExceptions {GlanceAppWidgetManager(context).updateReceiver(this@GlanceAppWidgetReceiver, glanceAppWidget)}}}override fun onReceive(context: Context, intent: Intent) {runAndLogExceptions {if (intent.action == Intent.ACTION_LOCALE_CHANGED) {val appWidgetManager = AppWidgetManager.getInstance(context)val componentName =ComponentName(context.packageName, checkNotNull(javaClass.canonicalName))onUpdate(context,appWidgetManager,appWidgetManager.getAppWidgetIds(componentName))return}super.onReceive(context, intent)}}
}private inline fun runAndLogExceptions(block: () -> Unit) {try {block()} catch (ex: CancellationException) {// Nothing to do} catch (throwable: Throwable) {logException(throwable)}
}
基本流程方法跟原生widget的差别不大，其含义也无差别，如果对原生Widget不太了解的同学可以翻阅我上一篇文章，这里还有官方注释：“Using Glance in devices with API<23 is untested and might behave unexpectedly.”。在6.0版本以下的Android系统上使用Glance的情况未经测试可能有出乎意料的情况发生。在开始编写widget代码之前，我们先来了解下其使用组件与Compose中的对应组件的些许差别。
差别
根据官方提示，可使用的Compose组合项如下：Box、Row、Column、Text、Button、LazyColumn、Image、Spacer。原生widget是不支持自定义View的，但Compose能通过自定义组件的方式来“自定义”出我们想要的视图，这一点来看相对更加灵活。
Compose中使用的修饰符是Modifier，这里修饰可组合项的修饰符是GlanceModifier，使用方式并无二致，其余组件也有些许差异，这个我们放到后面来说，
Action
以前使用widget跳转页面啥的，都离不开PendingIntent，但是Glance中则采取另一套方式：
actionStartActivity
看函数命名就得知，通过Action启动Activity。共有三种使用方式：
// 通过包名启动Activity
public fun actionStartActivity(componentName: ComponentName,parameters: ActionParameters = actionParametersOf()
): Action = StartActivityComponentAction(componentName, parameters)// 直接启动Activity
public fun <T : Activity> actionStartActivity(activity: Class<T>,parameters: ActionParameters = actionParametersOf()
): Action = StartActivityClassAction(activity, parameters)//调用actionStartActivity启动Activity，内联函数
public inline fun <reified T : Activity> actionStartActivity(parameters: ActionParameters = actionParametersOf()
): Action = actionStartActivity(T::class.java, parameters)\
其对应的使用方式也简单：
Button(text = "Jump", onClick = actionStartActivity(ComponentName("com.ktfly.comapp","com.ktfly.comapp.page.ShowActivity")))
Button(text = "Jump", onClick = actionStartActivity<ShowActivity>())
Button(text = "Jump", onClick = actionStartActivity(ShowActivity::class.java))
actionRunCallback
顾名思义，此函数是通过Action执行Callback，以下是官方提供的使用说明：\
fun <T : ActionCallback> actionRunCallback(callbackClass: Class<T>, parameters: ActionParameters = actionParametersOf()
): Actioninline fun <reified T : ActionCallback> actionRunCallback(parameters: ActionParameters = actionParametersOf()): Action
使用方式：
先创建一个继承actionRunCallback的回调类：
class ActionDemoCallBack : ActionCallback {override suspend fun onRun(context: Context, glanceId: GlanceId, parameters: ActionParameters) {TODO("Not yet implemented")}
}
然后在控件中调用：
Button(text = "CallBack", onClick = actionRunCallback<ActionDemoCallBack>())Button(text = "CallBack", onClick = actionRunCallback(ActionDemoCallBack::class.java))\
actionStartService
此函数是通过Action启动Service，有以下四个使用方式：
fun actionStartService(intent: Intent, isForegroundService: Boolean = false
): Actionfun actionStartService(componentName: ComponentName, isForegroundService: Boolean = false
): Actionfun <T : Service> actionStartService(service: Class<T>, isForegroundService: Boolean = false
): Actioninline fun <reified T : Service> actionStartService(isForegroundService: Boolean = false): Action
这里的isForegroundService参数含义是此服务是前台服务。在调用之前也需要先创建对应Service：
class ActionDemoService : Service() {override fun onBind(intent: Intent?): IBinder? {TODO("Not yet implemented")}
}
其在控件中使用方式如下：
Button(text = "start", onClick = actionStartService<ActionDemoService>())Button(text = "start", onClick = actionStartService(ActionDemoService::class.java))
actionStartBroadcastReceiver
此函数是通过Action启动BroadcastReceiver，有以下使用方式：
fun actionSendBroadcast(action: String, componentName: ComponentName? = null
): Actionfun actionSendBroadcast(intent: Intent): Actionfun actionSendBroadcast(componentName: ComponentName): Actionfun <T : BroadcastReceiver> actionSendBroadcast(receiver: Class<T>): Actioninline fun <reified T : BroadcastReceiver> actionSendBroadcast(): Actionfun actionStartActivity(intent: Intent, parameters: ActionParameters = actionParametersOf()
): Action
其各函数用法跟actionStartActivity函数差不多，这里不做赘述。你会发现以上函数中经常出现ActionParameters。其实ActionParameters就是给Action提供参数，这里不做赘述。
创建widget
创建对应的widget类，通过GlanceStateDefinition来保留GlanceAppWidget的状态，通过点击事件回调自定义的ActionCallBack达到更改widget中数字的目的：
import android.content.Context
import androidx.compose.runtime.Composable
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.datastore.preferences.core.Preferences
import androidx.datastore.preferences.core.intPreferencesKey
import androidx.glance.*
import androidx.glance.action.ActionParameters
import androidx.glance.action.actionParametersOf
import androidx.glance.appwidget.GlanceAppWidget
import androidx.glance.appwidget.action.ActionCallback
import androidx.glance.appwidget.action.actionRunCallback
import androidx.glance.appwidget.state.updateAppWidgetState
import androidx.glance.layout.*
import androidx.glance.state.GlanceStateDefinition
import androidx.glance.state.PreferencesGlanceStateDefinition
import androidx.glance.text.Text
import androidx.glance.text.TextAlign
import androidx.glance.text.TextStyle
import androidx.glance.unit.ColorProviderprivate val countPreferenceKey = intPreferencesKey("widget-key")
private val countParamKey = ActionParameters.Key<Int>("widget-key")class CounterWidget : GlanceAppWidget(){override val stateDefinition: GlanceStateDefinition<*> =PreferencesGlanceStateDefinition@Composableoverride fun Content(){val prefs = currentState<Preferences>()val count = prefs[countPreferenceKey] ?: 1Column(horizontalAlignment = Alignment.CenterHorizontally,verticalAlignment = Alignment.CenterVertically,modifier = GlanceModifier.background(Color.Yellow).fillMaxSize()) {Text(text = count.toString(),modifier = GlanceModifier.fillMaxWidth(),style = TextStyle(textAlign = TextAlign.Center,color = ColorProvider(Color.Blue),fontSize = 50.sp))Spacer(modifier = GlanceModifier.padding(8.dp))Button(text = "变两倍",modifier = GlanceModifier.background(Color(0xFFB6C0C9)).size(100.dp,50.dp),onClick = actionRunCallback<UpdateActionCallback>(parameters = actionParametersOf(countParamKey to (count + count))))}}
}class UpdateActionCallback : ActionCallback{override suspend fun onRun(context: Context, glanceId: GlanceId,parameters: ActionParameters) {val count = requireNotNull(parameters[countParamKey])updateAppWidgetState(context = context,definition = PreferencesGlanceStateDefinition,glanceId = glanceId){ preferences ->preferences.toMutablePreferences().apply {this[countPreferenceKey] = count}}CounterWidget().update(context,glanceId)}
}
运行后效果如下：
也许你会发现上述导包与平常Compose导包不一样：
控件导的包都是glance包下的，当然不仅是Column，还有Button、Image等参数都有变化，但变化不大，例如Image的差异：
原Compose中：
Image(modifier = modifier,painter = BitmapPainter(bitmap),contentDescription = "",contentScale = contentScale)Image(modifier = modifier,painter = painterResource(资源id),contentDescription = "",contentScale = contentScale)Glance中：
public fun Image(provider: ImageProvider,contentDescription: String?,modifier: GlanceModifier = GlanceModifier,contentScale: ContentScale = ContentScale.Fit
)
其余控件差异大同小异，这里不做赘述。
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