写本文章的目的在于记录在实践过程中遇到的问题，因为我发现很多文章都是一样的，当我照着其他文章的教程实践时，出现了一些问题。因此在这里记录一下：
1.在原项目中以module的方式集成flutter，在setting.gradle中添加
setBinding(new Binding([gradle: this]))
evaluate(new File(
settingsDir.parentFile,
'my_flutter/.android/include_flutter.groovy'
))
出现问题
* What went wrong:
A problem occurred evaluating settings 'xxx'.
> /Users/gindoc/Desktop/my_flutter/.android/include_flutter.groovy
(/Users/gindoc/Desktop/my_flutter/.android/include_flutter.groovy)
你会发现你的flutter 模块名前面不是项目根目录
解决办法：
如果你创建的flutter moduel是作为原应用的子mudule，则为不需要在settingsDir后面加.parentFile，即
setBinding(new Binding([gradle: this]))
evaluate(new File(
settingsDir,
'my_flutter/.android/include_flutter.groovy'
))
2.在编写完Flutter代码后，运行报错，可以通过命令行flutter analyze查看错误信息。
3.由于我是在AndroidX的项目下集成flutter的，而用flutter create -t module <module name>方式创建的module里面的Android项目是依赖support包的，所以需要做一些修改。
方案来自https://github.com/flutter/flutter/issues/23586：
具体步骤如下
1、打开flutter module里面的.android目录下的gradle.properties，添加
android.enableJetifier=true
android.useAndroidX=true
2、将.android目录下的build.gradle的build tool版本改为3.3.1，即
buildscript {
...
dependencies {
classpath "com.android.tools.build:gradle:3.3.1"
...
}
...
}
3、将.android目录下app里面的build.gradle的targetSdkVersion修改为28
android {
defaultConfig {
...
targetSdkVersion 28
}
...
}
4、MissingPluginException(No implementation found for method getBatteryLevel on channel samples.flutter.io/battery)
在尝试在flutter中与原生交互（比如获取手机电量，跳转原生页面）时，出现MissingPluginException。
出现这种情况的原因是因为plugin没有注册成功。
这里需要注意的是: 1、每个flutterView所在的Activity都要注册plugin，否则就可能出现这种情况。 2、给activity添加flutterView的操作要在注册plugin之前
示例：
// 这里定义一个基类BaseActivity，因为
// 1、我们注册plugin需要PluginRegistry，
// 2、添加flutterView需要lifecycle或者supportFragmentManager，
// 而 FlutterActivity 和 FragmentActivity 都不能同时满足以上两个条件
abstract class BaseActivity :AppCompatActivity(), FlutterView.Provider, PluginRegistry, FlutterActivityDelegate.ViewFactory{
private val delegate = FlutterActivityDelegate(this, this)
private val eventDelegate: FlutterActivityEvents
private val viewProvider: FlutterView.Provider
private val pluginRegistry: PluginRegistry
init {
this.eventDelegate = this.delegate
this.viewProvider = this.delegate
this.pluginRegistry = this.delegate
}
override fun getFlutterView(): FlutterView {
return this.viewProvider.flutterView
}
override fun createFlutterView(context: Context): FlutterView? {
return null
}
override fun createFlutterNativeView(): FlutterNativeView? {
return null
}
override fun retainFlutterNativeView(): Boolean {
return false
}
override fun hasPlugin(key: String): Boolean {
return this.pluginRegistry.hasPlugin(key)
}
override fun <T> valuePublishedByPlugin(pluginKey: String): T {
return this.pluginRegistry.valuePublishedByPlugin(pluginKey)
}
override fun registrarFor(pluginKey: String): PluginRegistry.Registrar {
return this.pluginRegistry.registrarFor(pluginKey)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
this.eventDelegate.onCreate(savedInstanceState)
}
override fun onStart() {
super.onStart()
this.eventDelegate.onStart()
}
override fun onResume() {
super.onResume()
this.eventDelegate.onResume()
}
override fun onDestroy() {
this.eventDelegate.onDestroy()
super.onDestroy()
}
override fun onBackPressed() {
if (!this.eventDelegate.onBackPressed()) {
super.onBackPressed()
}
}
override fun onStop() {
this.eventDelegate.onStop()
super.onStop()
}
override fun onPause() {
super.onPause()
this.eventDelegate.onPause()
}
override fun onPostResume() {
super.onPostResume()
this.eventDelegate.onPostResume()
}
override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<String>, grantResults: IntArray) {
this.eventDelegate.onRequestPermissionsResult(requestCode, permissions, grantResults)
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
if (!this.eventDelegate.onActivityResult(requestCode, resultCode, data)) {
super.onActivityResult(requestCode, resultCode, data)
}
}
override fun onNewIntent(intent: Intent) {
this.eventDelegate.onNewIntent(intent)
}
public override fun onUserLeaveHint() {
this.eventDelegate.onUserLeaveHint()
}
override fun onTrimMemory(level: Int) {
this.eventDelegate.onTrimMemory(level)
}
override fun onLowMemory() {
this.eventDelegate.onLowMemory()
}
override fun onConfigurationChanged(newConfig: Configuration) {
super.onConfigurationChanged(newConfig)
this.eventDelegate.onConfigurationChanged(newConfig)
}
}
// FlutterView所在的Activity
class FlutterPageActivity : BaseActivity() {
private val CHANNEL = "samples.flutter.io/battery"
override fun onCreate(savedInstanceState: Bundle?) {
FlutterMain.startInitialization(applicationContext)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// 1、创建flutterView
val flutterView = Flutter.createView(this, lifecycle, "route1")
val layout =
FrameLayout.LayoutParams(FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT)
addContentView(flutterView, layout)
// 2、注册plugin
GeneratedPluginRegistrant.registerWith(this)
MethodChannel(flutterView, CHANNEL).setMethodCallHandler { call, result ->
// 在这里和原生交互
if (call.method == "getBatteryLevel") {
val batteryLevel = getBatteryLevel()
if (batteryLevel != -1) {
result.success(batteryLevel)
} else {
result.error("UNAVAILABLE", "Battery level not available.", null)
}
startActivity(Intent(this@FlutterPageActivity, NativeActivity::class.java)) // 跳转原生界面
} else {
result.notImplemented()
}
}
}
// 获取电量
private fun getBatteryLevel(): Int {
var batteryLevel = -1
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
val batteryManager = getSystemService(Context.BATTERY_SERVICE) as BatteryManager
batteryLevel = batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)
} else {
val intent =
ContextWrapper(applicationContext).registerReceiver(null, IntentFilter(Intent.ACTION_BATTERY_CHANGED))
batteryLevel =
intent!!.getIntExtra(
BatteryManager.EXTRA_LEVEL,
-1
) * 100 / intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1)
}
return batteryLevel
}
}
另外这里推荐以https://www.cnblogs.com/fuyaozhishang/p/9617234.html该博客的方式集成Android和Flutter，进行混合开发，达到原生开发和Flutter开发互不干扰。
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