问题

Issue

I was able to clear my last issue after ignoring the errors and following the rest of the steps in the React Native Navigation installation. Those warnings went away.

However, when I run npm run android, it builds successfully but does not launch the app

Configure project :app
...
Configure project :react-native-navigation
...
Task :app:installDebug
...
BUILD SUCCESSFUL in 6s

The android emulator goes to its home screen and the app does not launch.

What I've Tried

I've tried running/building/clean&rebuilding from android studio. This led to Could not connect to development server when I refreshed from the white blank screen.

I've followed the steps in here by creating assets folder and running this code

react-native bundle --platform android --dev false --entry-file index.android.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res

build.gradle

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

buildscript {
    ext {
        buildToolsVersion = "28.0.3"
        minSdkVersion = 19
        compileSdkVersion = 28
        targetSdkVersion = 28
        supportLibVersion = "28.0.0"
    }
    repositories {
        google()
        mavenLocal()
        mavenCentral()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.3.0'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

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

app/build.gradle

apply plugin: "com.android.application"

import com.android.build.OutputFile

project.ext.react = [
    entryFile: "index.js"
]

apply from: "../../node_modules/react-native/react.gradle"

/**
 * Set this to true to create two separate APKs instead of one:
 *   - An APK that only works on ARM devices
 *   - An APK that only works on x86 devices
 * The advantage is the size of the APK is reduced by about 4MB.
 * Upload all the APKs to the Play Store and people will download
 * the correct one based on the CPU architecture of their device.
 */
def enableSeparateBuildPerCPUArchitecture = false

/**
 * Run Proguard to shrink the Java bytecode in release builds.
 */
def enableProguardInReleaseBuilds = false

android {
    compileSdkVersion rootProject.ext.compileSdkVersion

    defaultConfig {
        applicationId "com.appname"
        minSdkVersion rootProject.ext.minSdkVersion
        targetSdkVersion rootProject.ext.targetSdkVersion
        missingDimensionStrategy "RNN.reactNativeVersion", "reactNative57_5"
        versionCode 1
        versionName "1.0"
        ndk {
            abiFilters "armeabi-v7a", "x86"
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    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
            }
        }
    }
}

configurations.all {
    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
        def requested = details.requested
        if (requested.group == 'com.android.support' && requested.name != 'multidex') {
            details.useVersion "${rootProject.ext.supportLibVersion}"
        }
    }
}

dependencies {
    implementation fileTree(dir: "libs", include: ["*.jar"])
    implementation "com.android.support:design:28.0.0"
    implementation "com.android.support:appcompat-v7:${rootProject.ext.supportLibVersion}"
    implementation "com.facebook.react:react-native:+"  // From node_modules
    implementation project(':react-native-navigation')
}

// 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'
}

react-native: "0.57.8"
react-native-navigation: "^2.7.0"
Android 9.0 API 28

回答1:

I think you maybe have to run the metro bundler before running npm run android.

react-native start --reset-cache

This will start the bundler, so you will have to run

npm run android

in a different terminal window, but same project directory. This script is mentioned below! This is the way I'm doing it. It has been an issues since RN 57.2 that there were some problems with the metro bundler and this is the way to go. I have updated in the meantime to RN 57.8 and the latest RNN also, but I still run the project like that.

I also have to mention that I'm running this on a emulator with API 26 and Android Studio 3.3 and normally If I run it as I said above, it will start the app in the emulator.

BUILD SCRIPTS

"scripts": {
    "build-android": "cd ./android && ./gradlew app:assembleDebug && ./gradlew installDebug && cd ../",
    "android": "npm run build-android && (adb reverse tcp:8081 tcp:8081 || true) && react-native run-android"
}

EDIT

It is especially important that you follow the instructions given by RNN team under this link for running your app on Android: The instructions from RNN team for running your app on an Android emulator or device.

EDIT 2

As per request, API 26 is required as that is your compile SDK version(currently for RNN v2.7.1) as well as your target SDK version. This info you can find in the documentation for RNN at the same link as above.

来源：https://stackoverflow.com/questions/54245925/npm-run-android-does-not-launch-the-android-app

标签

android