# rnDemo

**Repository Path**: tzjin/rnDemo

## Basic Information

- **Project Name**: rnDemo
- **Description**: rndemo
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2018-03-27
- **Last Updated**: 2020-12-19

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

 rn demo
 
# 已有
 1.http 请求
 
 2.realm 数据库
 
 3.js 与 native 的互调
 
 
# todo
 1.尺寸的适配问题
 
 3.如何自定义组件 
 >http://www.lrdcq.com/me/read.php/61.htm
 
 4.各种现有组件学习
 
 5.热更新问题
 
 6.报错收集问题
 
 7.二维码
 
 android 权限问题
 
 多图选择
>https://github.com/syanbo/react-native-syan-image-picker
 

# npm 发现个网址
https://registry.npmjs.org/+xxx
 
 
## android
### Reload崩溃
    
    E/AndroidRuntime: FATAL EXCEPTION: mqt_native_modules
          Process: com.rndemo, PID: 29465
          java.lang.NullPointerException
              at java.lang.AbstractStringBuilder.<init>(AbstractStringBuilder.java:87)
              at java.lang.StringBuilder.<init>(StringBuilder.java:95)
              at com.facebook.react.devsupport.DevSupportManagerImpl$JSExceptionLogger.log(DevSupportManagerImpl.java:303)
              at com.facebook.react.devsupport.DevSupportManagerImpl.handleException(DevSupportManagerImpl.java:287)
              at com.facebook.react.bridge.CatalystInstanceImpl.onNativeException(CatalystInstanceImpl.java:501)
              at com.facebook.react.bridge.CatalystInstanceImpl.access$900(CatalystInstanceImpl.java:40)
              at com.facebook.react.bridge.CatalystInstanceImpl$NativeExceptionHandler.handleException(CatalystInstanceImpl.java:517)
              at com.facebook.react.bridge.queue.MessageQueueThreadHandler.dispatchMessage(MessageQueueThreadHandler.java:33)
              at android.os.Looper.loop(Looper.java:229)
              at com.facebook.react.bridge.queue.MessageQueueThreadImpl$3.run(MessageQueueThreadImpl.java:194)
              at java.lang.Thread.run(Thread.java:848)
    
然后跟踪到这里，涉及到handler无法跟踪

    MessageQueueThreadHandler extends Handler{
          public void dispatchMessage(Message msg) {
            try {
              super.dispatchMessage(msg);
            } catch (Exception e) {
              mExceptionHandler.handleException(e);
            }
          }
    }
接着我打印了第一次启动与Reload比较

    D/ReactNative: ReactInstanceManager.ctor()
    D/ReactNative: ReactInstanceManager.createReactContextInBackground()
    D/ReactNative: ReactInstanceManager.recreateReactContextInBackgroundInner()
    D/ReactNative: ReactInstanceManager.onJSBundleLoadedFromServer()
    D/ReactNative: ReactInstanceManager.recreateReactContextInBackground()
    D/ReactNative: ReactInstanceManager.runCreateReactContextOnNewThread()
    W/unknown:ReactNative: Packager connection already open, nooping.
    D/ReactNative: ReactInstanceManager.createReactContext()
    D/ReactNative: Initializing React Xplat Bridge.
    D/ReactNative: Initializing React Xplat Bridge before initializeBridge
    D/ReactNative: Initializing React Xplat Bridge after initializeBridge
    D/ReactNative: CatalystInstanceImpl.runJSBundle()
    D/ReactNative: ReactInstanceManager.setupReactContext()
    D/ReactNative: CatalystInstanceImpl.initialize()
    W/unknown:ReactNative: Packager connection already open, nooping.
    D/ReactNative: ReactInstanceManager.attachRootViewToInstance()
    I/ReactNativeJS: Running application "Zxing" with appParams: {"rootTag":1}. __DEV__ === true, development-level warning are ON, performance optimizations are OFF
Reload
    
    D/ReactNative: ReactInstanceManager.onJSBundleLoadedFromServer()
    D/ReactNative: ReactInstanceManager.recreateReactContextInBackground()
    D/ReactNative: ReactInstanceManager.runCreateReactContextOnNewThread()
    D/ReactNative: ReactInstanceManager.tearDownReactContext()
    D/ReactNative: CatalystInstanceImpl.destroy() start
    W/unknown:ReactNative: Packager connection already open, nooping.
    D/ReactNative: ReactInstanceManager.createReactContext()
    D/ReactNative: Initializing React Xplat Bridge.
    D/ReactNative: Initializing React Xplat Bridge before initializeBridge
    D/ReactNative: Initializing React Xplat Bridge after initializeBridge
    D/ReactNative: CatalystInstanceImpl.runJSBundle()
    D/ReactNative: ReactInstanceManager.setupReactContext()
    D/ReactNative: CatalystInstanceImpl.initialize()
    D/ReactNative: ReactInstanceManager.attachRootViewToInstance()
    W/unknown:ReactNative: Packager connection already open, nooping.
与init新工程对比发现
    
    有：D/ReactNative: CatalystInstanceImpl.destroy() start
    少了：D/ReactNative: CatalystInstanceImpl.destroy() end

然后跟还是没跟到原因,最后打断点查看e的内容 找到了
    
    ReactInstanceManager reactInstanceManager = ((ReactApplication) getReactApplicationContext().getApplicationContext()).getReactNativeHost().getReactInstanceManager();
    reactInstanceManager.getCurrentReactContext().removeActivityEventListener(listener);