我在我的真实 android 设备上运行我现有的 React Native 项目。然后以某种方式弹出这个错误。错误总是关于“找不到符号”。我有 JDK 和 SDK 并添加到我的系统变量中。但我仍然不知道为什么它会给我这样的错误。我记得，我只是降级了 react-native 的版本。

:app:compileDebugJavaWithJavac - 不是增量的（例如，输出已经改变，之前没有执行，等等）。D:\rnprojects\firstproject\android\app\src\main\java\com\emptyprojecttemplate\MainApplication.java:5: 错误：找不到符号 import com.facebook.react.ReactApplication; ^ 符号：类 ReactApplication 位置：包 com.facebook.react D:\rnprojects\firstproject\android\app\src\main\java\com\emptyprojecttemplate\MainApplication.java:6: 错误：找不到符号导入 com.facebook。 react.ReactNativeHost; ^ 符号：类 ReactNativeHost 位置：包 com.facebook.react D:\rnprojects\firstproject\android\app\src\main\java\com\emptyprojecttemplate\MainApplication.java:14: 错误：

FAILURE：构建失败，出现异常。

• 出了什么问题：任务“:app:compileDebugJavaWithJavac”的执行失败。编译失败；有关详细信息，请参阅编译器错误输出。

构建.gradle：

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
        repositories {
           jcenter()
        }
     dependencies {
         classpath 'com.android.tools.build:gradle:2.2.3'

         // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
     }
}

allprojects {
    repositories {
        mavenLocal()
        jcenter()
        maven {
             // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
             url "$rootDir/../node_modules/react-native/android"
        }
    }
}

Build.gradle/应用程序：

android {
compileSdkVersion 23
buildToolsVersion "23.0.1"

defaultConfig {
    applicationId "com.emptyprojecttemplate"
    minSdkVersion 16
    targetSdkVersion 22
    versionCode 1
    versionName "1.0"
    ndk {
        abiFilters "armeabi-v7a", "x86"
    }
}
splits {
    abi {
        reset()
        enable enableSeparateBuildPerCPUArchitecture
        universalApk false  // If true, also generate a universal APK
        include "armeabi-v7a", "x86"
    }
}
buildTypes {
    release {
        minifyEnabled enableProguardInReleaseBuilds
        proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard-rules.pro"
    }
}
// applicationVariants are e.g. debug, release
applicationVariants.all { variant ->
    variant.outputs.each { output ->
        // For each separate APK per architecture, set a unique version code as described here:
        // http://tools.android.com/tech-docs/new-build-system/user-guide/apk-splits
        def versionCodes = ["armeabi-v7a":1, "x86":2]
        def abi = output.getFilter(OutputFile.ABI)
        if (abi != null) {  // null for the universal-debug, universal-release variants
            output.versionCodeOverride =
                    versionCodes.get(abi) * 1048576 + defaultConfig.versionCode
        }
    }
}
}

dependencies {
    compile fileTree(dir: "libs", include: ["*.jar"])
    compile "com.android.support:appcompat-v7:23.0.1"
    compile "com.facebook.react:react-native:+"  // From node_modules
}

 // Run this once to be able to run the application with BUCK
 // puts all compile dependencies into folder libs for BUCK to use
 task copyDownloadableDepsToLibs(type: Copy) {
     from configurations.compile
     into 'libs'
 }