[React Naitve] Native module for android

CustomToastModule.java

package com.your.package.name;

import android.widget.Toast;
import android.app.Activity;

import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.bridge.ReactContext;
import com.facebook.react.bridge.ReactContextBaseJavaModule;
import com.facebook.react.bridge.ReactMethod;

import java.util.Map;
import java.util.HashMap;

public class CustomToastModule extends ReactContextBaseJavaModule {

    private static final String DURATION_SHORT_KEY = "SHORT";
    private static final String DURATION_LONG_KEY = "LONG";

    public CustomToastModule(ReactApplicationContext reactContext) {
        super(reactContext);
    }

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

    @Override
    public Map<String, Object> getConstants() {
        final Map<String, Object> constants = new HashMap<>();
        constants.put(DURATION_SHORT_KEY, Toast.LENGTH_SHORT);
        constants.put(DURATION_LONG_KEY, Toast.LENGTH_LONG);
        return constants;
    }

    @ReactMethod
    public void show(String message, int duration) {
        Toast.makeText(getReactApplicationContext(), message, duration).show();
    }
}

CustomToastModulePackage.java

package com.your.package.name;

import android.app.Activity;
import java.util.*;

import com.facebook.react.ReactPackage;
import com.facebook.react.bridge.JavaScriptModule;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.modules.toast.ToastModule;
import com.facebook.react.uimanager.ViewManager;

public class CustomToastPackage implements ReactPackage {

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

    return modules;
  }

  @Override
  public List<Class<? extends JavaScriptModule>> createJSModules() {
    return Collections.emptyList();
  }

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

index.android.js

import React, { Component } from 'react';
import {
  AppRegistry,
  StyleSheet,
  Text,
  View
} from 'react-native';

import { NativeModules } from 'react-native';
var CustomToastModule = NativeModules.CustomToastModule;

class StreamingSample extends Component {
  componentDidMount() {
    CustomToastModule.show('Toast testing', CustomToastModule.SHORT);
  }

  render() {
    return (
      <View style={styles.container}>
        <Text style={styles.welcome}>
          Welcome to React Native!
        </Text>
      </View>
    );
  }
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
    backgroundColor: '#F5FCFF',
  },
  welcome: {
    fontSize: 20,
    textAlign: 'center',
    margin: 10,
  },
});

AppRegistry.registerComponent('StreamingSample', () => StreamingSample);

MainApplication.java

package com.your.package.name;

import android.app.Application;
import android.util.Log;

import com.facebook.react.ReactApplication;
import com.facebook.react.ReactInstanceManager;
import com.facebook.react.ReactNativeHost;
import com.facebook.react.ReactPackage;
import com.facebook.react.modules.toast.ToastModule;
import com.facebook.react.shell.MainReactPackage;

import com.your.package.name.CustomToastPackage; // Add this line

import java.util.Arrays;
import java.util.List;

public class MainApplication extends Application implements ReactApplication {

  private final ReactNativeHost mReactNativeHost = new ReactNativeHost(this) {
    @Override
    protected boolean getUseDeveloperSupport() {
      return BuildConfig.DEBUG;
    }

    @Override
    protected List<ReactPackage> getPackages() {
      return Arrays.<ReactPackage>asList(
          new MainReactPackage(),
          new CustomToastPackage()  // Add this line
      );
    }
  };

  @Override
  public ReactNativeHost getReactNativeHost() {
      return mReactNativeHost;
  }
}