typeError: null 在访问 Native Module 时不是对象

Question

我正在开发一个 React Native 应用程序并尝试从 android 访问本机模块。我正在关注这个官方文档 在此处输入链接描述

创建本机模块后，当我尝试在 javaScript 类中访问它时，它显示错误“typeError: null is not an object (Evaluating _ToastExample.default.show)”

ToastModule.java

package com.awesomeproject;

import android.widget.Toast;

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 ToastModule extends ReactContextBaseJavaModule {
  private static ReactApplicationContext reactContext;

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

  ToastModule(ReactApplicationContext context) {
    super(context);
    reactContext = context;
  }

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

  @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();
  }
}

自定义ToastPackage.java

package com.awesomeproject;

import com.facebook.react.ReactPackage;
import com.facebook.react.bridge.NativeModule;
import com.facebook.react.bridge.ReactApplicationContext;
import com.facebook.react.uimanager.ViewManager;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class CustomToastPackage implements ReactPackage {

  @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;
  }

}

在 MainApplication.java 中插入了这个片段

 protected List<ReactPackage> getPackages() {
    @SuppressWarnings("UnnecessaryLocalVariable")
    List<ReactPackage> packages = new PackageList(this).getPackages();
    // Packages that cannot be autolinked yet can be added manually here, for example:
    // packages.add(new MyReactNativePackage());
    packages.add(new CustomToastPackage()); // <-- Add this line with your package name.
    return packages;
  }

ToastExample.js

import {NativeModules} from 'react-native';
module.exports = NativeModules.ToastExample;

App.js 在这里，我只是想从 Android 原生模块中调用那个简单的 Toast 函数。

import React, { Component } from 'react';
import EmojiDict from './components/EmojiDict';
import ToastExample from './ToastExample';

export default class App extends Component {

  componentDidMount(){
    ToastExample.show('Awesome', ToastExample.SHORT);
  }

  render() {
        return <
            EmojiDict />;
    }
}

还附上错误截图。

我是 ReactNative 的新手，所以请帮助我解决这个问题。提前致谢。

Answer 1

在 MainApplication 中，您可以看到 getPackages() 方法已经在 ReactNativeHost 中可用

您需要将该包添加到

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

    @Override
    protected List<ReactPackage> getPackages() {
        List<ReactPackage> packages = new PackageList(this).getPackages();
        packages.add(new ModuleRegistryAdapter(mModuleRegistryProvider));
        //here you need to add
        packages.add(new CustomToastPackage());
        return packages;
    }

    @Override
    protected String getJSMainModuleName() {
        return "index";
    }

    @Override
    protected @Nullable
    String getJSBundleFile() {
        if (BuildConfig.DEBUG) {
            return super.getJSBundleFile();
        } else {
            return UpdatesController.getInstance().getLaunchAssetFile();
        }
    }

    @Override
    protected @Nullable
    String getBundleAssetName() {
        if (BuildConfig.DEBUG) {
            return super.getBundleAssetName();
        } else {
            return UpdatesController.getInstance().getBundleAssetName();
        }
    }
};