日知其所亡,月勿忘其所能，可谓学也已矣。

很久前测试过。但是今天又温故下，发现好多细节有所遗忘，（忘性还真大）还是记录下吧。

调用原生Toast模块。

1.创建ToastModule Java类。

    import android.widget.Toast;

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

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


    public class ToastModule extends ReactContextBaseJavaModule {

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

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

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

        @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();
        }

    }

2.注册模块

     class ToastPackage implements ReactPackage {

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

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

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

        modules.add(new ToastModule(reactContext));

        return modules;
      }

3.在MainApplication.java中添加你自己定义的

new ToastPackage()

4.为了方便调用，可以在创建ToastAndroid.js 作为专门的模块，

    import { NativeModules } from 'react-native';


    export default NativeModules.MyToastAndroid;

5.index.android.js

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


    import ToastAndroid from './ToastAndroid';

    class MyDemo extends Component {
        render() {
            return (
                <View >
                    <TouchableWithoutFeedback
                        onPress={() =>
               ToastAndroid.show('show toast', ToastAndroid.SHORT)}>
                        <Text style={styles.text}>Click me.</Text>
                    </TouchableWithoutFeedback>
                </View>
            );
        }
    }

    const styles = StyleSheet.create({

        text: {
            color: 'black',
        },
    });

    AppRegistry.registerComponent('MyDemo', () => MyDemo);</span>