Can not get by react-native

[echokk11]

1. doing all steps in README.
2. add 2 java class ChannelModule, ChannelPackage

public class ChannelModule extends ReactContextBaseJavaModule {

    private String channel;
    public ChannelModule(ReactApplicationContext reactContext) {
        super(reactContext);
        channel = ChannelReaderUtil.getChannel(reactContext);
    }

    @Override
    public String getName() {
        return "ChannelModule";
    }

    @ReactMethod
    public String getChannel() {
        return channel;
    }
}

public class ChannelPackage implements ReactPackage {

    @Override
    public List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
        List<NativeModule> modules = new ArrayList<>();
        modules.add(new ChannelModule(reactContext));
        return modules;
    }

    @Override
    public List<ViewManager> createViewManagers(ReactApplicationContext reactContext) {
        return Collections.emptyList();
    }
}

3. add new ChannelPackage() to MainApplication

   @Override
   protected List<ReactPackage> getPackages() {
   return Arrays.<ReactPackage>asList(
   new MainReactPackage(),
   ...
   new ChannelPackage()
   );
   }

4. in JavaScript.

   
   import { NativeModules } from "react-native";

const channel = NativeModules.ChannelModule.getChannel();

but i got `undefined`

### this is my release apk
<img width="318" alt="image" src="https://user-images.githubusercontent.com/8499152/60655806-f67e8500-9e80-11e9-9d64-92ade2eae8f0.png">

### this is parts of log

generateV2ChannelApk , channel = robot , apkChannelName = app-1.0-1-robot-release.apk addIdValueByteBufferMap , new IdValueMap = {-2012129793=java.nio.HeapByteBuffer[pos=0 lim=5 cap=5]} find V2 signature block Id : 1896449818 addIdValueByteBufferMap , existed IdValueMap = {1896449818=java.nio.HeapByteBuffer[pos=0 lim=1545 cap=1545], 1114793335=java.nio.HeapByteBuffer[pos=0 lim=2495 cap=2495]} addIdValueByteBufferMap , final IdValueMap = {1896449818=java.nio.HeapByteBuffer[pos=0 lim=1545 cap=1545], 1114793335=java.nio.HeapByteBuffer[pos=0 lim=2495 cap=2495], -2012129793=java.nio.HeapByteBuffer[pos=0 lim=5 cap=5]} generateApkSigningBlock , needPadding = true generateApkSigningBlock , final length = 4088 padding = 2490 bufferSize = 2478 addIdValueByteBufferMap , oldApkSigningBlock size = 4096 , newApkSigningBlock size = 4096 addIdValueByteBufferMap , after add channel , new apk is /Users/x/ideaprojects/y/android/app/build/channel/release/app-1.0-1-robot-release.apk , length = 12990563 try to read channel info from apk : /Users/x/ideaprojects/y/android/app/build/channel/release/app-1.0-1-robot-release.apk find V2 signature block Id : 1896449818 getByteBufferValueById , destApk /Users/x/ideaprojects/y/android/app/build/channel/release/app-1.0-1-robot-release.apk IdValueMap = {1896449818=java.nio.HeapByteBuffer[pos=0 lim=1545 cap=1545], -2012129793=java.nio.HeapByteBuffer[pos=0 lim=5 cap=5], 1114793335=java.nio.HeapByteBuffer[pos=0 lim=2478 cap=2478]} getByteValueById , id = -2012129793 , value = java.nio.HeapByteBuffer[pos=0 lim=5 cap=5] generateV2ChannelApk , /Users/x/ideaprojects/y/android/app/build/channel/release/app-1.0-1-robot-release.apk add channel success verified : true Verified using v1 scheme (JAR signing): true Verified using v2 scheme (APK Signature Scheme v2): true generateV2ChannelApk , after add channel , apk /Users/x/ideaprojects/y/android/app/build/channel/release/app-1.0-1-robot-release.apk v2 verify success

### success using VasDolly.jar CLI

java -jar VasDolly.jar get -c xxx.apk

could get the channel

Did I make some mistakes ?

[echokk11]

I reslove it myself.

React-native nativeModules can not return things. Only use Callback or Promise

@ReactMethod
public void getChannel(Promise promise) {
  promise.resolve(channel);
}

then in js

NativeModules.ChannelModule.getChannel().then(c => {
  // got c
})