Develop Reference

Error:Failed to resolve: Crosswalk

I'm trying to make a SDK using Crosswalk. So first I started to make a sample app using
compile 'org.xwalk:xwalk_core_library:23.53.589.4'. And it works. Then I tried to make a SDK using this. But it didn't work as I expected.
gradle file
apply plugin: 'com.android.library'
repositories {
maven {
url 'https://download.01.org/crosswalk/releases/crosswalk/android/maven2'
}
}
android {
compileSdkVersion 26
buildToolsVersion "26.0.2"
defaultConfig {
minSdkVersion 16
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:26.0.0-alpha1'
compile 'org.xwalk:xwalk_core_library:23.53.589.4'
testCompile 'junit:junit:4.12'
}
Here is the screenshot of error message

execution failed for tasks: multiple dex files define for appcompat version

android {
compileSdkVersion 27
buildToolsVersion "27.0.3"
defaultConfig {
applicationId "com.example.ceinfo.firebaseproject"
minSdkVersion 15
targetSdkVersion 19
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:27.0.0'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
testCompile 'junit:junit:4.12'
}
apply plugin: 'com.google.gms.google-services'
When I want to execute espresso test run, it shows me an error of multiple dex files define, I have set my appcompat version to 27.0.0, please suggest me solution to this error.

APK version code is 3 but still i get error " You need to use a different version code for your APK because you already have one with version code 1."

I have uploaded apk with versionCode 3,versionName "1.0.3" but PlayStore gives me error with
Upload failed You need to use a different version code for your APK
because you already have one with version code 1.
Here is my GradleFile:
apply plugin: 'com.android.application'
android {
compileSdkVersion 25
buildToolsVersion '26.0.2'
defaultConfig {
applicationId "netsol.xxxx.xxx"
minSdkVersion 16
targetSdkVersion 25
versionCode 3
versionName "1.0.3"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
multiDexEnabled true
vectorDrawables.useSupportLibrary = true
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
lintOptions {
abortOnError false
}
dexOptions {
preDexLibraries false
javaMaxHeapSize "4g"
incremental true
dexInProcess = true
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:multidex:1.0.1'
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support:design:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile 'com.android.support:cardview-v7:25.3.1'
compile 'com.android.support:recyclerview-v7:25.3.1'
compile 'com.android.support:support-vector-drawable:25.3.1'
compile 'com.squareup.okhttp3:logging-interceptor:3.6.0'
compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
testCompile 'junit:junit:4.12'
}

Android : app running issue on Nougat OS

I am working on an android app. Everything is working fine on marshmallow OS. But when i try to install app on Nougat OS then it is not allow me to install my app.
These is how my gradle file looks like :
apply plugin: 'com.android.application'
android {
compileSdkVersion 25
buildToolsVersion "25.0.2"
defaultConfig {
applicationId "com.example.*****"
minSdkVersion 19
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.1'
testCompile 'junit:junit:4.12'
}

Failed to resolve javax

I created a new Application and I am getting these errors
This is my app level
apply plugin: 'com.android.application'
android {
compileSdkVersion 24
buildToolsVersion "24.0.2"
defaultConfig {
applicationId "com.vfirst.genie"
minSdkVersion 15
targetSdkVersion 24
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:24.2.1'
testCompile 'junit:junit:4.12'
}

Download the latest version of Android Support Repository, Android Support Library and Google Repository from your SDK Manager.
I think it should solve the issue.