尝试/捕获不起作用答案

【问题标题】：Try/catch doesn't work尝试/捕获不起作用
【发布时间】：2018-05-31 19:50:52
【问题描述】：

我有一个类来显示 HTTP 的错误消息。

根据 throwable 它显示一条消息。

但有时我得到空指针异常

public static void showGeneralErrors(Throwable throwable) {
    String message = "";
    AppInitialization appInitialization = AppInitialization.getInstance();

    if (appInitialization == null) {
        return;
    }

    try {
        if (throwable instanceof HttpException) {
            if (((HttpException) throwable).code() == 500) {
                message = appInitialization.getString(R.string.server_error);
            } else {
                message = appInitialization.getString(R.string.parsing_problem);
            }
        } else if (throwable instanceof IOException) {
            message = appInitialization.getString(R.string.internet_error);
        }else if(throwable instanceof SSLHandshakeException){
            message = appInitialization.getString(R.string.internet_error);
        }
        if (!TextUtils.isEmpty(message)) {
            Toast.makeText(appInitialization, message, Toast.LENGTH_SHORT).show();
        }
    } catch (Exception e) {
        Log.e(">>>>>", "Exception network error handler " + e.getMessage());
    } catch (IllegalStateException e) {
        Log.e(">>>>>", "IllegalStateException network error handler " + e.getMessage());
    } catch (NullPointerException e) {
        Log.e(">>>>>", "NullPointerException network error handler " + e.getMessage());
    }
}

错误信息是：

原因：java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法 'android.content.res.Resources android.content.Context.getResources()' 在 android.widget.Toast.makeText(Toast.java:298)

而公共 AppInitialization 是：

public class AppInitialization extends Application {
private static AppInitialization mInstance;

public static synchronized AppInitialization getInstance() {
    return mInstance;
}

public void onCreate() {
    super.onCreate();

    mInstance = this;
}

它来自于改造Onfailure方法：

GeneralRepo.getCountryFromIp(getContext())
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(countryFromIPResponse -> {
        //do something
    }, throwable -> {
        // Where i got error
        NetworkErrorHandler.showGeneralErrors(throwable);
    });

为什么会出现这个错误以及为什么 try/catch 不起作用？

【问题讨论】：

因为您的错误不会在该代码块上触发，请在您的答案中添加更多 logcat 以查看原始错误。
同意@diegoveloper，同时检查可抛出对象是否为空
@diegoveloper 更新
你能把这个代码： AppInitialization.getInstance() ，你的appinitialization类
你确定问题出在这段代码上吗？

标签： java android android-resources android-context

【解决方案1】：

将你的 try catch 块放在 else 部分，因为会发生 NullPointerException

应用初始化

即将为空所以..

写：

public static void showGeneralErrors(Throwable throwable) { 字符串消息 = ""; AppInitialization appInitialization = AppInitialization.getInstance();
if (appInitialization == null) {
    return;
}else{

  try {           if (throwable instanceof HttpException) {
          if (((HttpException) throwable).code() == 500) {
              message = appInitialization.getString(R.string.server_error);
          } else {
              message = appInitialization.getString(R.string.parsing_problem);
          }           } else if (throwable instanceof IOException) {
          message = appInitialization.getString(R.string.internet_error);             }else if(throwable instanceof SSLHandshakeException){
          message = appInitialization.getString(R.string.internet_error);             }           if (!TextUtils.isEmpty(message)) {
          Toast.makeText(appInitialization, message, Toast.LENGTH_SHORT).show();          }       } catch (Exception e) {
      Log.e(">>>>>", "Exception network error handler " +
e.getMessage()); } 捕捉（IllegalStateException e）{ Log.e(">>>>>", "IllegalStateException 网络错误处理程序" + e.getMessage()); } 捕捉（NullPointerException e）{ Log.e(">>>>>", "NullPointerException 网络错误处理程序" + e.getMessage()); } } }

【讨论】：