React Native : Error: Duplicate resources - Android

I was trying to create a release apk file from Android but when I create a release apk with PNG image I'm getting Duplicate Resource error. Initially I thought this is happening because I made a mistake in the existing project but when I created a new project with a single Image component itself I'm getting the Duplicate Resource error. Here are the steps I followed

1. Create a app - react-native init demo

2. Create a assets folder in the project root folder.

3. Add a PNG image inside the assets folder.

4. Now implement the Image component with the above PNG image.

5. Now bundle it using the cmd

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

6. Then generate release apk using Generate Signed APK from Android Studio.

This will throw the following error:

[drawable-mdpi-v4/assets_mario] /Users/jeffreyrajan/Tutorials/RN/errorCheck/android/app/src/main/res/drawable-mdpi/assets_mario.png	[drawable-mdpi-v4/assets_mario] /Users/jeffreyrajan/Tutorials/RN/errorCheck/android/app/build/generated/res/react/release/drawable-mdpi-v4/assets_mario.png: Error: Duplicate resources
:app:mergeReleaseResources FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':app:mergeReleaseResources'.
> [drawable-mdpi-v4/assets_mario] /Users/jeffreyrajan/Tutorials/RN/errorCheck/android/app/src/main/res/drawable-mdpi/assets_mario.png	[drawable-mdpi-v4/assets_mario] /Users/jeffreyrajan/Tutorials/RN/errorCheck/android/app/build/generated/res/react/release/drawable-mdpi-v4/assets_mario.png: Error: Duplicate resources

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 22s

Note: When you generate a release apk without any PNG image you will not get any error, it will create you the release apk.

Here are the other files code.

App.js

import React, {Component} from 'react';
import {Platform, StyleSheet, Image, View} from 'react-native';

export default class App extends Component {
  render() {
    return (
      <View style={styles.container}>
        <Image source={require('./assets/mario.png')} />
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
  instructions: {
    textAlign: 'center',
    color: '#333333',
    marginBottom: 5,
  },
});

package.json

{
  "name": "errorCheck",
  "version": "0.0.1",
  "private": true,
  "scripts": {
    "start": "node node_modules/react-native/local-cli/cli.js start",
    "test": "jest"
  },
  "dependencies": {
    "react": "16.6.0-alpha.8af6728",
    "react-native": "0.57.4"
  },
  "devDependencies": {
    "babel-jest": "23.6.0",
    "jest": "23.6.0",
    "metro-react-native-babel-preset": "0.49.0",
    "react-test-renderer": "16.6.0-alpha.8af6728"
  },
  "jest": {
    "preset": "react-native"
  }
}

Any solution for this?

Update:

Here are the other details

classpath 'com.android.tools.build:gradle:3.1.4'

ext {
        buildToolsVersion = "27.0.3"
        minSdkVersion = 16
        compileSdkVersion = 27
        targetSdkVersion = 26
        supportLibVersion = "27.1.1"
    }

distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip

Tried with Android Studio 3.0, 3.0.1, 3.1, 3.1.4 & 3.2

(UPDATED)

This solution works for me

rm -rf ./android/app/src/main/res/drawable-*

rm -rf ./android/app/src/main/res/raw

In my case, the build failed because there are duplicated resources in my Android project (in Android folder), these two lines are necessary to remove duplicated resources, that's all.

After trying a lot of solutions I found only Three solution is working. Here they are

Solution 1:

Clean the drawable folder from the terminal using Gradle. cd into the android folder, then run cmd ./gradlew clean

Solution 2:

After bundling delete the drawable folder from Android Studio. You could find this in android/app/src/main/res/drawable

Solution 3:

> PLEASE DO NOT USE SOLUTION #2, AS PROPOSED BY THE ORIGINAL AUTHOR! All packages under node_modules are generated, and any changes you make will be lost when the react-native package is reinstalled / upgraded.

In this solution you no need to delete any drawable folder. Just add the following code in the react.gradle file which you could find under node_modules/react-native/react.gradle path

doLast {
    def moveFunc = { resSuffix ->
        File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
        if (originalDir.exists()) {
            File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
            ant.move(file: originalDir, tofile: destDir);
        }
    }
    moveFunc.curry("ldpi").call()
    moveFunc.curry("mdpi").call()
    moveFunc.curry("hdpi").call()
    moveFunc.curry("xhdpi").call()
    moveFunc.curry("xxhdpi").call()
    moveFunc.curry("xxxhdpi").call()
}

For reference I will add the full react.gradle file code here

import org.apache.tools.ant.taskdefs.condition.Os

def config = project.hasProperty("react") ? project.react : [];

def cliPath = config.cliPath ?: "node_modules/react-native/local-cli/cli.js"
def bundleAssetName = config.bundleAssetName ?: "index.android.bundle"
def entryFile = config.entryFile ?: "index.android.js"
def bundleCommand = config.bundleCommand ?: "bundle"
def reactRoot = file(config.root ?: "../../")
def inputExcludes = config.inputExcludes ?: ["android/**", "ios/**"]
def bundleConfig = config.bundleConfig ? "${reactRoot}/${config.bundleConfig}" : null ;


afterEvaluate {
    android.applicationVariants.all { def variant ->
        // Create variant and target names
        def targetName = variant.name.capitalize()
        def targetPath = variant.dirName

        // React js bundle directories
        def jsBundleDir = file("$buildDir/generated/assets/react/${targetPath}")
        def resourcesDir = file("$buildDir/generated/res/react/${targetPath}")

        def jsBundleFile = file("$jsBundleDir/$bundleAssetName")

        // Additional node and packager commandline arguments
        def nodeExecutableAndArgs = config.nodeExecutableAndArgs ?: ["node"]
        def extraPackagerArgs = config.extraPackagerArgs ?: []

        def currentBundleTask = tasks.create(
            name: "bundle${targetName}JsAndAssets",
            type: Exec) {
            group = "react"
            description = "bundle JS and assets for ${targetName}."

            // Create dirs if they are not there (e.g. the "clean" task just ran)
            doFirst {
                jsBundleDir.deleteDir()
                jsBundleDir.mkdirs()
                resourcesDir.deleteDir()
                resourcesDir.mkdirs()
            }

            doLast {
                def moveFunc = { resSuffix ->
                    File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
                    if (originalDir.exists()) {
                        File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
                        ant.move(file: originalDir, tofile: destDir);
                    }
                }
                moveFunc.curry("ldpi").call()
                moveFunc.curry("mdpi").call()
                moveFunc.curry("hdpi").call()
                moveFunc.curry("xhdpi").call()
                moveFunc.curry("xxhdpi").call()
                moveFunc.curry("xxxhdpi").call()
            }

            // Set up inputs and outputs so gradle can cache the result
            inputs.files fileTree(dir: reactRoot, excludes: inputExcludes)
            outputs.dir jsBundleDir
            outputs.dir resourcesDir

            // Set up the call to the react-native cli
            workingDir reactRoot

            // Set up dev mode
            def devEnabled = !(config."devDisabledIn${targetName}"
                || targetName.toLowerCase().contains("release"))

            def extraArgs = extraPackagerArgs;

            if (bundleConfig) {
                extraArgs = extraArgs.clone()
                extraArgs.add("--config");
                extraArgs.add(bundleConfig);
            }

            if (Os.isFamily(Os.FAMILY_WINDOWS)) {
                commandLine("cmd", "/c", *nodeExecutableAndArgs, cliPath, bundleCommand, "--platform", "android", "--dev", "${devEnabled}",
                    "--reset-cache", "--entry-file", entryFile, "--bundle-output", jsBundleFile, "--assets-dest", resourcesDir, *extraArgs)
            } else {
                commandLine(*nodeExecutableAndArgs, cliPath, bundleCommand, "--platform", "android", "--dev", "${devEnabled}",
                    "--reset-cache", "--entry-file", entryFile, "--bundle-output", jsBundleFile, "--assets-dest", resourcesDir, *extraArgs)
            }

            enabled config."bundleIn${targetName}" ||
                config."bundleIn${variant.buildType.name.capitalize()}" ?:
                targetName.toLowerCase().contains("release")
        }

        // Expose a minimal interface on the application variant and the task itself:
        variant.ext.bundleJsAndAssets = currentBundleTask
        currentBundleTask.ext.generatedResFolders = files(resourcesDir).builtBy(currentBundleTask)
        currentBundleTask.ext.generatedAssetsFolders = files(jsBundleDir).builtBy(currentBundleTask)

        // registerGeneratedResFolders for Android plugin 3.x
        if (variant.respondsTo("registerGeneratedResFolders")) {
            variant.registerGeneratedResFolders(currentBundleTask.generatedResFolders)
        } else {
            variant.registerResGeneratingTask(currentBundleTask)
        }
        variant.mergeResources.dependsOn(currentBundleTask)

        // packageApplication for Android plugin 3.x
        def packageTask = variant.hasProperty("packageApplication")
            ? variant.packageApplication
            : tasks.findByName("package${targetName}")

        def resourcesDirConfigValue = config."resourcesDir${targetName}"
        if (resourcesDirConfigValue) {
            def currentCopyResTask = tasks.create(
                name: "copy${targetName}BundledResources",
                type: Copy) {
                group = "react"
                description = "copy bundled resources into custom location for ${targetName}."

                from resourcesDir
                into file(resourcesDirConfigValue)

                dependsOn(currentBundleTask)

                enabled currentBundleTask.enabled


            }

            packageTask.dependsOn(currentCopyResTask)
        }

        def currentAssetsCopyTask = tasks.create(
            name: "copy${targetName}BundledJs",
            type: Copy) {
            group = "react"
            description = "copy bundled JS into ${targetName}."

            if (config."jsBundleDir${targetName}") {
                from jsBundleDir
                into file(config."jsBundleDir${targetName}")
            } else {
                into ("$buildDir/intermediates")
                into ("assets/${targetPath}") {
                    from jsBundleDir
                }

                // Workaround for Android Gradle Plugin 3.2+ new asset directory
                into ("merged_assets/${targetPath}/merge${targetName}Assets/out") {
                    from jsBundleDir
                }
            }

            // mergeAssets must run first, as it clears the intermediates directory
            dependsOn(variant.mergeAssets)

            enabled currentBundleTask.enabled
        }

        packageTask.dependsOn(currentAssetsCopyTask)
    }
}

Credit: ZeroCool00 mkchx

For generating debug apk

"debug-build": "react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/src/main/res/ && cd android && ./gradlew assembleDebug && cd .."

For generating release apk

"release-build": "react-native bundle --platform android --dev false --entry-file index.js --bundle-output android/app/src/main/assets/index.android.bundle --assets-dest android/app/build/intermediates/res/merged/release/ && rm -rf android/app/src/main/res/drawable-* && rm -rf android/app/src/main/res/raw/* && cd android && ./gradlew assembleRelease && cd .."

Works fine for my react-native >= 0.61.2 project by using the above code on my scripts section of package.json file.

The accepted answer will work, however it does not take into account that modifying a node package means that if you update your change will be lost (as well as being against best-practices, you should extend the module somehow).

This is originally from React-native android release error: duplicate resource

1. Create folder "fixAndroid" in the "android" folder of your project ({project-root}/android/fixAndroid).

2. Create file android-gradle-fix in the "fixAndroid" folder of your project ({project-root}/android/fixAndroid/android-gradle-fix).

    		doLast {
    	def moveFunc = { resSuffix ->
    		File originalDir = file("${resourcesDir}/drawable-${resSuffix}")
    		if (originalDir.exists()) {
    			File destDir = file("${resourcesDir}/drawable-${resSuffix}-v4")
    			ant.move(file: originalDir, tofile: destDir)
    		}
    	}
    	moveFunc.curry("ldpi").call()
    	moveFunc.curry("mdpi").call()
    	moveFunc.curry("hdpi").call()
    	moveFunc.curry("xhdpi").call()
    	moveFunc.curry("xxhdpi").call()
    	moveFunc.curry("xxxhdpi").call()
    }
   
    // Set up inputs and outputs so gradle can cache the result
   

3. Create file android-release-fix.js in the "fixAndroid" folder you created:

    		const fs = require('fs')
   
    	try {
    			var curDir = __dirname
    			var rootDir = process.cwd()
   
    			var file = `${rootDir}/node_modules/react-native/react.gradle`
    			var dataFix = fs.readFileSync(`${curDir}/android-gradle-fix`, 'utf8')
    			var data = fs.readFileSync(file, 'utf8')
   
    			var doLast = "doLast \{"
    			if (data.indexOf(doLast) !== -1) {
    				throw "Already fixed."
    			}
   
    			var result = data.replace(/\/\/ Set up inputs and outputs so gradle can cache the result/g, dataFix);
    			fs.writeFileSync(file, result, 'utf8')
    			console.log('Android Gradle Fixed!')
    		} catch (error) {
    			console.error(error)
    		}
   

4. Add script to package.json scripts section:

    "postinstall": "node ./android/fixAndroid/android-release-fix.js"
   

This will find and insert content of “android-gradle-fix” file into node_modules/react-native/react.gradle.

5. Run npm install from the root of your project.
6. Run rm -rf android/app/src/main/res/drawable-* from the root of your project.

Now you can bundle the release with either React Native at the console or Android Studio:

React Native command line

1. cd {project-root}/android
2. ./gradlew/bundleRelease

Android Studio

1. Open folder android in Android Studio and build project.
2. Select Build/Generate signed APK to build release.

1. Delete drawable-xxx folders
2. Delete raw

inside src -> main -> res folder then

3. run this command in terminal:

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

4. then generate signed apk using keystore, alias and passwords using terminal or android studio

who are facing the same issue in RN! I think it's absolutely awful that this issue stands here for so long time already, but I want to share the way to solve it after investigation of different solutions.

Jeffrey Rajan is absolutely right about the possible solutions here https://stackoverflow.com/a/53260522/1611414

I think it's super bad to change react.gradle file in node_modules and it leads to many many different issues with the maintenance of this RN project. So I would recommend to chose the first option - to use bash command to remove that folder before running build.

I want to share what I've done in my project and maybe you can reuse the same approach:

// ./package.json

...
scripts: {
   "build": "react-native bundle --platform android 
             --dev false
             --entry-file index.js
             --bundle-output android/app/src/main/assets/index.android.bundle
             --assets-dest android/app/src/main/res/
          && rm -rf ./android/app/src/main/res/drawable-mdpi/
          && rm -rf ./android/app/src/main/res/raw/",

   "release": "yarn build && cd ./android && ./gradlew bundleRelease"
}
...

and the release is running by doing yarn release.

Very important those lines:

...
&& rm -rf ./android/app/src/main/res/drawable-mdpi/
&& rm -rf ./android/app/src/main/res/raw/
...

they remove duplicated resources from the build step before bundleRelease is running. The solution is tested with RN 0.57, 0.58, 0.59 and 0.60

Enjoy!

tolotrasmile's answer worked for me.

I included it in my little bash script that I run whenever I want to build & install Android

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

        rm -rf $PROJECT_DIRECTORY/android/app/src/main/res/drawable-*
        rm -rf $PROJECT_DIRECTORY/android/app/src/main/res/raw

        cd $PROJECT_DIRECTORY/android/
        ./gradlew clean
        ./gradlew assembleRelease

        adb install -r $PROJECT_DIRECTORY/android/app/build/outputs/apk/release/app-release.apk

for latest version of React-Native and gradle, you don't need to bundle your assets. Once you are done with the code, just cd into the android folder and run:

./gradlew assembleRelease

The assets are automatically bundled while the above command is been executed. The duplicate resources error shows up because you have explicitly bundled before and running the above command bundles again hence the error.

Try to use another directory for assets destination (for example res_temp).

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

I am also adding res_temp in gitignore. Tested in Gradle 6.0.1 and RN 0.62.2

In my case, it worked after adding a few lines to Jaffrey's Answer

doLast {
            def moveFunc = { resSuffix ->
                File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
                if (originalDir.exists()) {
                    File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
                    ant.move(file: originalDir, tofile: destDir);
                }
            }
            moveFunc.curry("ldpi").call()
            moveFunc.curry("mdpi").call()
            moveFunc.curry("hdpi").call()
            moveFunc.curry("xhdpi").call()
            moveFunc.curry("xxhdpi").call()
            moveFunc.curry("xxxhdpi").call()

            File originalDir = file("$buildDir/generated/res/react/release/raw");
            if (originalDir.exists()) {
                File destDir = file("$buildDir/../src/main/res/raw");
                ant.move(file: originalDir, tofile: destDir);
            }
        }

was error with release build /android/app/src/main/res/raw/app.json [raw/app] /android/app/build/generated/res/react/release/raw/app.json: Error: Duplicate resources

deleted /android/app/src/main/res/raw/app.json then ./gradlew clean in android folder and then ./gradlew bundleRelease

For me it was a cache issue. The following command worked for me

cd into android folder

Run ./gradlew clean

Solution.
I just clean gradlew and starts working no need to change anything in.
/node_modules/react-native/react.gradle

Steps

1. cd android && ./gradlew clean && cd ..

2. react-native run-android

   "dependencies": { "react": "16.11.0", "react-native": "0.62.2", }

Spent ages on this! None of the proposed solutions were an immediate fix for me.

So I moved out all the dirs that were getting mentioned in the "duplicate resource" error message:

mv ./android/app/src/main/res/drawabl* /tmp

mv ./android/app/src/main/res/raw /tmp

then I ran a

./gradlew clean

then I ran a build:

/gradlew bundleRelease

the build was giving me a couple of errors along the lines of 'could not find a specific file in a specific place', so for each of these files I found them in the tmp/drawable folders and copied them to the exact path that the error message said it expected them to be e.g (you'll have to customise this according to the error message you get):

cp /tmp/drawable-mdpi/launch_screen.png app/src/main/res/drawable/

then:

./gradlew clean

/gradlew bundleRelease

And it finally buily successfully

Use com.android.tools.build:gradle:3.1.4 It should work. RN 0.57 has problem with building in 3.2

This question is a possible duplicate of:

https://stackoverflow.com/questions/52668524/react-native-assets-coming-in-some-screens-and-not-coming-in-others-in-android-r/52767101#52767101

If it still doesn't work try to use RN 0.57.2, I am using it and creating releases works very well with these deps:

   "dependencies": {
    "react": "16.5.0",
    "react-native": "0.57.2",
    .......
  }

  "devDependencies": {
    "@babel/core": "^7.0.0",
    "@babel/plugin-proposal-class-properties": "^7.0.0",
    "@babel/plugin-proposal-decorators": "^7.0.0",
    "@babel/plugin-proposal-do-expressions": "^7.0.0",
    "@babel/plugin-proposal-export-default-from": "^7.0.0",
    "@babel/plugin-proposal-export-namespace-from": "^7.0.0",
    "@babel/plugin-proposal-function-bind": "^7.0.0",
    "@babel/plugin-proposal-function-sent": "^7.0.0",
    "@babel/plugin-proposal-json-strings": "^7.0.0",
    "@babel/plugin-proposal-logical-assignment-operators": "^7.0.0",
    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.0.0",
    "@babel/plugin-proposal-numeric-separator": "^7.0.0",
    "@babel/plugin-proposal-object-rest-spread": "^7.0.0",
    "@babel/plugin-proposal-optional-chaining": "^7.0.0",
    "@babel/plugin-proposal-pipeline-operator": "^7.0.0",
    "@babel/plugin-proposal-throw-expressions": "^7.0.0",
    "@babel/plugin-syntax-dynamic-import": "^7.0.0",
    "@babel/plugin-syntax-import-meta": "^7.0.0",
    "@babel/plugin-syntax-object-rest-spread": "^7.0.0",
    "@babel/plugin-transform-runtime": "^7.0.0",
    "@babel/preset-env": "^7.0.0",
    "@babel/preset-flow": "^7.0.0",
    "@babel/register": "^7.0.0",
    "babel-core": "^7.0.0-bridge.0",
    "babel-preset-react-native-stage-0": "^1.0.1",
    .....
}

Gradle deps:

classpath 'com.android.tools.build:gradle:3.1.4'
classpath "io.realm:realm-gradle-plugin:4.0.0"

App gradle

compileSdkVersion 27
    buildToolsVersion "27.0.3"

    defaultConfig {
        applicationId "de.burda.buntede"
        minSdkVersion 17
        targetSdkVersion 27

Gradle wrapper props:

distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip

Remove the files you might have on:

android/app/src/main/res/drawable-mdpi/ android/app/src/main/res/drawable-xhdpi/ android/app/src/main/res/drawable-xxhdpi/ Run Build again, This fixed the issue for me.

So basically edit the /node_modules/react-native/react.gradle file and add the doLast right after the doFirst block, manually.

doFirst { ... }
doLast {
    def moveFunc = { resSuffix ->
        File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
        if (originalDir.exists()) {
            File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
            ant.move(file: originalDir, tofile: destDir);
        }
    }
    moveFunc.curry("ldpi").call()
    moveFunc.curry("mdpi").call()
    moveFunc.curry("hdpi").call()
    moveFunc.curry("xhdpi").call()
    moveFunc.curry("xxhdpi").call()
    moveFunc.curry("xxxhdpi").call()
}

I am using react-native 0.63.2. I also faced this issue and tried editing react.gradle, deleted resources/drawable and all. But at last cleaning gradle and running the command gradlew assembleRelease worked.

I didn't run the react-native bundle command separately. gradlew assembleRelease is running the react-native bundle and building apk itself.

The solutions like patching the react.gradle file may work but they are just workarounds. The real solution lies in figuring out the problem.

1. If its only happening while creating release build then chances are you're bundling separately. If you're upgrading from older versions of react native which didn't have a react.gradle file you'd have to bundle separately and then do 'cd android && ./gradlew assembleRelease' but with the introduction of react.gradle the bundling process has now been taken care by the react.gradle file, so don't bundle separately just run 'cd android && ./gradlew clean && ./gradlew assembleRelease' to build the release apk.

2. If this happens in debug also then chances are some generated assets or all of the generated assets have been pushed and currently reside in your directory. So i would suggest just delete all of them from the respective directory and if they are tracked by git try adding them back one by one. We had some assets starting with src_assets_blahblah which we had to delete since they were already getting generated during the build process.

None of the suggested solutions works for me

In my case it was related to .gradle folder. Before getting this error i have moved the folder to another disk, but some files failed to copy to the destination folder.

I just cut the old folder and merge it with the destination folder.

In my case, raw directory was containing some duplicates. So, I have to add a different function for that as well, name of added function is moveFuncRaw below worked perfectly for me.

        doLast {

            // Address issue #22234 by moving generated resources into build dir so they are in one spot, not duplicated
                def moveFuncRaw = { dirName ->
                    File originalDir = file("$buildDir/generated/res/react/release/${dirName}");
                    if (originalDir.exists()) {
                        File destDir = file("$buildDir/../src/main/res/${dirName}");
                        ant.move(file: originalDir, tofile: destDir);
                    }
                }
                
                // Address issue #22234 by moving generated resources into build dir so they are in one spot, not duplicated
                def moveFunc = { resSuffix ->
                    File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
                    if (originalDir.exists()) {
                        File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
                        ant.move(file: originalDir, tofile: destDir);
                    }
                }
                moveFunc.curry("ldpi").call()
                moveFunc.curry("mdpi").call()
                moveFunc.curry("hdpi").call()
                moveFunc.curry("xhdpi").call()
                moveFunc.curry("xxhdpi").call()
                moveFunc.curry("xxxhdpi").call()
                moveFuncRaw.curry("raw").call()
        }

One more thing to realize that doLast do not gets called every time as there could be some conditions on it like in my case there were, so you have to call separately to get it executed.

for me go to dir: android/app/src/main/assets/fonts

check .ttf files you expect, delete .ttf of vector icons

I had also this problem and to solve it, I have deleted resource folders and used gradlew clean.

I ended up with this Windows cmd script for compiling my app:

@echo off

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

rmdir android\app\src\main\res\drawable-hdpi /s/q
rmdir android\app\src\main\res\drawable-mdpi /s/q
rmdir android\app\src\main\res\drawable-xhdpi /s/q
rmdir android\app\src\main\res\drawable-xxhdpi /s/q
rmdir android\app\src\main\res\drawable-xxxhdpi /s/q
rmdir android\app\src\main\res\raw /s/q

cd android
call gradlew clean
REM call gradlew assembleRelease
call gradlew bundle
cd ..

dir /o:d android\app\build\outputs\apk\release
dir /o:d android\app\build\outputs\bundle

My version react native is: 0.66.3 , I had fix trought commands:

rm -rf ./android/app/src/main/res/drawable-*

rm -rf ./android/app/src/main/res/raw

Then run :

./gradlew clean

Finally: Generate Signed Bundle from Android Studio and works.

If the above answers are not working and if the issue is similar to the below error

> Task :app:mergeReleaseResources FAILED
ERROR: [drawable-mdpi-v4/node_modules_reactnative_libraries_newappscreen_components_logofgdsfsdfsdfds] 
/Users/emmsdan/Repo/untitledApp/android/app/src/main/res/drawable-mdpi/node_modules_reactnative_libraries_newappscreen_components_logofgdsfsdfsdfds.png 
[drawable-mdpi-v4/node_modules_reactnative_libraries_newappscreen_components_logofgdsfsdfsdfds]
/Users/emmsdan/Repo/untitledApp/android/app/build/generated/res/react/release/drawable-mdpi/
node_modules_reactnative_libraries_newappscreen_components_logofgdsfsdfsdfds.png: Resource and asset merger: Duplicate resources

Not the most elegant solution but this worked for me.

Delete this

> rm -rf rmnode_modules/react-native/Libraries/NewAppScreen

I had similar issues, even on a newly created react-native app. Deleting NewAppScreen and everywhere it was called fixed it for me.

By adding this is in /node_modules/react-native/react.gradle

After DoFirst Paste This Code

doLast {
def moveFunc = { resSuffix ->
    File originalDir = file("$buildDir/generated/res/react/release/drawable-${resSuffix}");
    if (originalDir.exists()) {
        File destDir = file("$buildDir/../src/main/res/drawable-${resSuffix}");
        ant.move(file: originalDir, tofile: destDir);
    }
}
moveFunc.curry("ldpi").call()
moveFunc.curry("mdpi").call()
moveFunc.curry("hdpi").call()
moveFunc.curry("xhdpi").call()
moveFunc.curry("xxhdpi").call()
moveFunc.curry("xxxhdpi").call()

}

I encountered the same problem after using 0.57.7, Look at the node_modules/react-native/react.gradle file, The resource output directory is $buildDir/generated/res/react/${targetPath} . Look at the address from the log as app/build/generated/res/react/release,

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

The resource output directory is android/app/src/main/res/

The problem is here.

I solved this:

1. Delete duplicate files in android/app/res (If your resources are imported from React Native, you can directly delete the directory under res).

2. Delete the App/build folder.

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

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

No longer specify --assets-dest Run command

4. Use Android Studio's Generate Signed APK to package properly.

the above