kotlin android extensions 插件实现示例详解

import kotlinx.android.synthetic.main.activity_main.*
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        viewToShowText.text = "Hello"
    }
}

public final class MainActivity extends AppCompatActivity {
   private HashMap _$_findViewCache;
   protected void onCreate(@Nullable Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      this.setContentView(1300023);
      TextView var10000 = (TextView)this._$_findCachedViewById(id.textView);
      var10000.setText((CharSequence)"Hello");
   }
   public View _$_findCachedViewById(int var1) {
      if (this._$_findViewCache == null) {
         this._$_findViewCache = new HashMap();
      }
      View var2 = (View)this._$_findViewCache.get(var1);
      if (var2 == null) {
         var2 = this.findViewById(var1);
         this._$_findViewCache.put(var1, var2);
      }
      return var2;
   }
   public void _$_clearFindViewByIdCache() {
      if (this._$_findViewCache != null) {
         this._$_findViewCache.clear();
      }
   }   
}

implementation-class=org.jetbrains.kotlin.gradle.internal.AndroidExtensionsSubpluginIndicator

class AndroidExtensionsSubpluginIndicator @Inject internal constructor(private val registry: ToolingModelBuilderRegistry) :
    Plugin<Project> {
    override fun apply(project: Project) {
        project.extensions.create("androidExtensions", AndroidExtensionsExtension::class.java)
        addAndroidExtensionsRuntime(project)
        project.plugins.apply(AndroidSubplugin::class.java)
    }
    private fun addAndroidExtensionsRuntime(project: Project) {
        project.configurations.all { configuration ->
            val name = configuration.name
            if (name != "implementation") return@all
            configuration.dependencies.add(
                project.dependencies.create(
                    "org.jetbrains.kotlin:kotlin-android-extensions-runtime:$kotlinPluginVersion"
                )
            )
        }
    }
}
open class AndroidExtensionsExtension {
    open var isExperimental: Boolean = false
    open var features: Set<String> = AndroidExtensionsFeature.values().mapTo(mutableSetOf()) { it.featureName }
    open var defaultCacheImplementation: CacheImplementation = CacheImplementation.HASH_MAP
}

class AndroidSubplugin : KotlinCompilerPluginSupportPlugin {
    // 1. 是否开启编译器插件
    override fun isApplicable(kotlinCompilation: KotlinCompilation<*>): Boolean {
        if (kotlinCompilation !is KotlinJvmAndroidCompilation)
            return false
        // ...    
        return true
    }
    // 2. 传递给编译器插件的参数
    override fun applyToCompilation(
        kotlinCompilation: KotlinCompilation<*>
    ): Provider<List<SubpluginOption>> {
        //...
        val pluginOptions = arrayListOf<SubpluginOption>()
        pluginOptions  = SubpluginOption("features",
                                         AndroidExtensionsFeature.parseFeatures(androidExtensionsExtension.features).joinToString(",") { it.featureName })
        fun addVariant(sourceSet: AndroidSourceSet) {
            val optionValue = lazy {
                sourceSet.name   ';'   sourceSet.res.srcDirs.joinToString(";") { it.absolutePath }
            }
            pluginOptions  = CompositeSubpluginOption(
                "variant", optionValue, listOf(
                    SubpluginOption("sourceSetName", sourceSet.name),
                    //use the INTERNAL option kind since the resources are tracked as sources (see below)
                    FilesSubpluginOption("resDirs", project.files(Callable { sourceSet.res.srcDirs }))
                )
            )
            kotlinCompilation.compileKotlinTaskProvider.configure {
                it.androidLayoutResourceFiles.from(
                    sourceSet.res.sourceDirectoryTrees.layoutDirectories
                )
            }
        }
        addVariant(mainSourceSet)
        androidExtension.productFlavors.configureEach { flavor ->
            androidExtension.sourceSets.findByName(flavor.name)?.let {
                addVariant(it)
            }
        }
        return project.provider { wrapPluginOptions(pluginOptions, "configuration") }
    }
    // 3. 定义编译器插件的唯一 id，需要与后面编译器插件中定义的 pluginId 保持一致
    override fun getCompilerPluginId() = "org.jetbrains.kotlin.android"
    // 4. 定义编译器插件的 `Maven` 坐标信息，便于编译器下载它
    override fun getPluginArtifact(): SubpluginArtifact =
        JetBrainsSubpluginArtifact(artifactId = "kotlin-android-extensions")
}

import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.debug.activity_debug.*
import kotlinx.android.synthetic.demo.activity_demo.*

class AndroidCommandLineProcessor : CommandLineProcessor {
    override val pluginId: String = ANDROID_COMPILER_PLUGIN_ID
    override val pluginOptions: Collection<AbstractCliOption>
            = listOf(VARIANT_OPTION, PACKAGE_OPTION, EXPERIMENTAL_OPTION, DEFAULT_CACHE_IMPL_OPTION, CONFIGURATION, FEATURES_OPTION)
    override fun processOption(option: AbstractCliOption, value: String, configuration: CompilerConfiguration) {
        when (option) {
            VARIANT_OPTION -> configuration.appendList(AndroidConfigurationKeys.VARIANT, value)
            PACKAGE_OPTION -> configuration.put(AndroidConfigurationKeys.PACKAGE, value)
            EXPERIMENTAL_OPTION -> configuration.put(AndroidConfigurationKeys.EXPERIMENTAL, value)
            DEFAULT_CACHE_IMPL_OPTION -> configuration.put(AndroidConfigurationKeys.DEFAULT_CACHE_IMPL, value)           
            else -> throw CliOptionProcessingException("Unknown option: ${option.optionName}")
        }
    }
}

class AndroidComponentRegistrar : ComponentRegistrar {
    companion object {
        fun registerViewExtensions(configuration: CompilerConfiguration, isExperimental: Boolean, project: MockProject) {
            ExpressionCodegenExtension.registerExtension(project,
                    CliAndroidExtensionsExpressionCodegenExtension(isExperimental, globalCacheImpl))
            IrGenerationExtension.registerExtension(project,
                    CliAndroidIrExtension(isExperimental, globalCacheImpl))
            StorageComponentContainerContributor.registerExtension(project,
                    AndroidExtensionPropertiesComponentContainerContributor())
            ClassBuilderInterceptorExtension.registerExtension(project,
                    CliAndroidOnDestroyClassBuilderInterceptorExtension(globalCacheImpl))
            PackageFragmentProviderExtension.registerExtension(project,
                    CliAndroidPackageFragmentProviderExtension(isExperimental))
        }
    }
    override fun registerProjectComponents(project: MockProject, configuration: CompilerConfiguration) {
        if (AndroidExtensionsFeature.VIEWS in features) {
            registerViewExtensions(configuration, isExperimental, project)
        }
    }
}

private class AndroidIrTransformer(val extension: AndroidIrExtension, val pluginContext: IrPluginContext) :
    IrElementTransformerVoidWithContext() {
    override fun visitClassNew(declaration: IrClass): IrStatement {
        if ((containerOptions.cache ?: extension.getGlobalCacheImpl(declaration)).hasCache) {
            val cacheField = declaration.getCacheField() 
            declaration.declarations  = cacheField // 添加_$_findViewCache属性
            declaration.declarations  = declaration.getClearCacheFun() // 添加_$_clearFindViewByIdCache方法
            declaration.declarations  = declaration.getCachedFindViewByIdFun() // 添加_$_findCachedViewById方法
        }
        return super.visitClassNew(declaration)
    }
    override fun visitCall(expression: IrCall): IrExpression {
        val result = if (expression.type.classifierOrNull?.isFragment == true) {
            // this.get[Support]FragmentManager().findFragmentById(R$id.<name>)
            createMethod(fragmentManager.child("findFragmentById"), createClass(fragment).defaultType.makeNullable()) {
                addValueParameter("id", pluginContext.irBuiltIns.intType)
            }.callWithRanges(expression).apply {
                // ...
            }
        } else if (containerHasCache) {
            // this._$_findCachedViewById(R$id.<name>)
            receiverClass.owner.getCachedFindViewByIdFun().callWithRanges(expression).apply {
                dispatchReceiver = receiver
                putValueArgument(0, resourceId)
            }
        } else {
        	// this.findViewById(R$id.<name>)
            irBuilder(currentScope!!.scope.scopeOwnerSymbol, expression).irFindViewById(receiver, resourceId, containerType)
        }
        return with(expression) { IrTypeOperatorCallImpl(startOffset, endOffset, type, IrTypeOperator.CAST, type, result) }
    }
}

class AndroidExtensionPropertiesCallChecker : CallChecker {
    override fun check(resolvedCall: ResolvedCall<*>, reportOn: PsiElement, context: CallCheckerContext) {
        // ...
        with(context.trace) {
            checkUnresolvedWidgetType(reportOn, androidSyntheticProperty)
            checkDeprecated(reportOn, containingPackage)
            checkPartiallyDefinedResource(resolvedCall, androidSyntheticProperty, context)
        }
    }
}    

private class AndroidOnDestroyCollectorClassBuilder(
    private val delegate: ClassBuilder,
    private val hasCache: Boolean
) : DelegatingClassBuilder() {      
    override fun newMethod(
        origin: JvmDeclarationOrigin,
        access: Int,
        name: String,
        desc: String,
        signature: String?,
        exceptions: Array<out String>?
    ): MethodVisitor {
        val mv = super.newMethod(origin, access, name, desc, signature, exceptions)
        if (!hasCache || name != ON_DESTROY_METHOD_NAME || desc != "()V") return mv
        hasOnDestroy = true
        return object : MethodVisitor(Opcodes.API_VERSION, mv) {
            override fun visitInsn(opcode: Int) {
                if (opcode == Opcodes.RETURN) {
                    visitVarInsn(Opcodes.ALOAD, 0)
                    visitMethodInsn(Opcodes.INVOKEVIRTUAL, currentClassName, CLEAR_CACHE_METHOD_NAME, "()V", false)
                }
                super.visitInsn(opcode)
            }
        }
    }
}

import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.android.synthetic.debug.activity_debug.*
import kotlinx.android.synthetic.demo.activity_demo.*