android studio

 Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
 com.android.build.api.transform.TransformException:
com.android.ide.common.process.ProcessException: org.gradle.process.internal.ExecException: 
Process 'command 'C:\Program Files\Java\jdk1.8.0_31\bin\java.exe'' 
finished with non-zero exit value 2

在build.gradle里添加：

defaultConfig {
    multiDexEnabled true
}

ES6

export:

命名导出

export function gank(n){
    return 'hello gank';
}
const carry = 'carry';
export {carry}
//或者直接export const carry = 'carry'

默认导出

export default gank(io){
    return 'hello default';
}

每个文件的export default 只能有一个

import:

以下代码将myDefault，foo，bar导入文件中,myDefault是默认导出的项,foo,bar为命名

导出的项（即my-module.js中的代码为：…;export foo;export bar;export default myDefault;）

import myDefault, {foo, bar} from "my-module.js"

在react native 可能看见如下写法：

import React, {Component} from 'react';

react native 初始化项目指定version

react-native init projectname --version 0.29.2

react native realm

定义model

var Realm = require('realm');
const CarSchema = {
    name: 'Car',
    properties: {
    make:  'string',    
    model: 'string',
    miles: {type: 'int', default: 0},
    }
};
const PersonSchema = {
    name: 'Person',
    properties: {
    name:     'string',
    birthday: 'date',
    cars:     {type: 'list', objectType: 'Car'},
    picture:  {type: 'data', optional: true}, // optional property
    }
};

// Initialize a Realm with Car and Person models
let realm = new Realm({schema: [CarSchema, PersonSchema]});

创建model

let realm = new Realm({schema: [CarSchema]);

realm.write(() => {
realm.create('Car', {make: 'Honda', model: 'Accord', drive: 'awd'});
});

通过主键创建更新对象

realm.write(() => {
// Create a book object
realm.create('Book', {id: 1, title: 'Recipes', price: 35});

// Update book with new price keyed off the id
realm.create('Book', {id: 1, price: 55}, true);
});

查询

let hondas = realm.objects('Car').filtered('make = "Honda"');
let cars = realm.objects('Car');

// get first 5 Car objects
let firstCars = cars.slice(0, 5);

node 返回json数据

var http = require('http');

var data = {key: 'value', hello: 'world'};

var srv = http.createServer(function (req, res) {
  res.writeHead(200, {'Content-Type': 'application/json'});
  res.end(JSON.stringify(data));
});

srv.listen(8080, function() {
  console.log('listening on localhost:8080');
});

iOS 真机调试

进入xcode，菜单栏选择xcode –> preferences （快捷键 command + ,）在Accounts选项卡添加自己的Apple ID,然后按步骤操作。

• react native TextInput 可以设置padding = 0,这样外部包裹view的的高度就等于TextInput的高度。

• 使用友盟推送的时候，点击通知跳转到相关的界面，原生android 里可以打开指定的Activity,react native里没有activity给我们

  用,这时候可以在原生监听通知消息，通过DeviceEventEmitter发送事件和参数给JS端,然后通过navigator跳转

  原生中发送事件会调用如下代码：

     private void sendEvent(ReactContext reactContext,
                 String eventName,
                 @Nullable WritableMap params) {
    reactContext
    .getJSModule(DeviceEventManagerModule.RCTDeviceEventEmitter.class)
    .emit(eventName, params);
  }
  

  如何在Activity/Application中获取ReactContext实例？

  reactContext = getReactNativeHost().getReactInstanceManager().getCurrentReactContext()
  

• 如何实现reactnative android 中按返回键不完全退出App?

     onBackAndroid = () => {
  const nav = this.navigator;
  const routers = nav.getCurrentRoutes();
  if (routers.length > 1) {
    nav.pop();
    return true;
  }
  ExitModule.exit();//调用原生的moveTaskToBack()方法
  return true;
    };
  

• react native 中 pageA->pageB 想在pageB返回时刷新pageA的内容

  方案一：

  props传递
  

  方案二：

  DeviceEventEmitter
  

• sina微博 授权未安装客户端登陆出错：

  android.content.ActivityNotFoundException: Unable to find explicit activity class {edu.gdut.myweibo/
  
  com.sina.weibo.sdk.component.WeiboSdkBrowser}; have you declared this 
  
  activity in your AndroidManifest.xml?
  

  在Manifest.xml中注入SDK的WebBrowser

  <activity
      android:name="com.sina.weibo.sdk.component.WeiboSdkBrowser"
      android:configChanges="keyboardHidden|orientation"
      android:exported="false"
      android:windowSoftInputMode="adjustResize" >
  </activity>
  

• react native 再次点击退出

  onBackAndroid() {
     let routers = this.nav.getCurrentRoutes();
   if (this.nav && routers.length > 1) {
         this.nav.pop();
        return true;
  }
  
  let current = new Date().getTime();
      if (current - last > 2000) {
    last = current;
    ToastAndroid.show('再次点击退出', 1000);
    return true;
      } else {
        return false;
          }
    }