java - Android:如何捕获此异常

Question

我希望这将是一个简单的。

我重用了教程中的代码，该代码在 ListView 中解析和显示 RSS当从代理后面或没有互联网运行代码时，我获得以下崩溃报告:

12-12 09:48:57.372: W/RssApp(1494): Exception while retrieving the input stream
12-12 09:48:57.372: W/RssApp(1494): java.net.ConnectException: failed to connect to gigglepics.co.uk/188.121.41.139 (port 80): connect failed: ETIMEDOUT (Connection timed out)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.io.IoBridge.connect(IoBridge.java:114)
12-12 09:48:57.372: W/RssApp(1494):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
12-12 09:48:57.372: W/RssApp(1494):     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
12-12 09:48:57.372: W/RssApp(1494):     at java.net.Socket.connect(Socket.java:842)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:76)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177)
12-12 09:48:57.372: W/RssApp(1494):     at eu.MasterZangetsu.RssService.getInputStream(RssService.java:48)
12-12 09:48:57.372: W/RssApp(1494):     at eu.MasterZangetsu.RssService.onHandleIntent(RssService.java:33)
12-12 09:48:57.372: W/RssApp(1494):     at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
12-12 09:48:57.372: W/RssApp(1494):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-12 09:48:57.372: W/RssApp(1494):     at android.os.Looper.loop(Looper.java:137)
12-12 09:48:57.372: W/RssApp(1494):     at android.os.HandlerThread.run(HandlerThread.java:60)
12-12 09:48:57.372: W/RssApp(1494): Caused by: libcore.io.ErrnoException: connect failed: ETIMEDOUT (Connection timed out)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.io.Posix.connect(Native Method)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:85)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
12-12 09:48:57.372: W/RssApp(1494):     at libcore.io.IoBridge.connect(IoBridge.java:112)
12-12 09:48:57.372: W/RssApp(1494):     ... 20 more
12-12 09:48:57.382: W/dalvikvm(1494): threadid=11: thread exiting with uncaught exception (group=0x40a71930)
12-12 09:48:57.402: E/AndroidRuntime(1494): FATAL EXCEPTION: IntentService[RssService]
12-12 09:48:57.402: E/AndroidRuntime(1494): java.lang.NullPointerException
12-12 09:48:57.402: E/AndroidRuntime(1494):     at eu.MasterZangetsu.PcWorldRssParser.parse(PcWorldRssParser.java:33)
12-12 09:48:57.402: E/AndroidRuntime(1494):     at eu.MasterZangetsu.RssService.onHandleIntent(RssService.java:33)
12-12 09:48:57.402: E/AndroidRuntime(1494):     at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
12-12 09:48:57.402: E/AndroidRuntime(1494):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-12 09:48:57.402: E/AndroidRuntime(1494):     at android.os.Looper.loop(Looper.java:137)
12-12 09:48:57.402: E/AndroidRuntime(1494):     at android.os.HandlerThread.run(HandlerThread.java:60)

这发生在 inputStream.close();

    public List<RssItem> parse(InputStream inputStream)
        throws XmlPullParserException, IOException {
    try {
        XmlPullParser parser = Xml.newPullParser();
        parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
        parser.setInput(inputStream, null);
        parser.nextTag();
        return readFeed(parser);
    } finally {
        inputStream.close();

    }
}

我想做的就是捕捉这个异常，以确保应用程序不会崩溃，而是显示一条错误消息

我尝试的一切似乎仍然崩溃并给出一个完全不同的错误。我一定是遗漏了一些非常基本的东西

Answer 1

代码缺少实际的 catch 语句:

try {
    XmlPullParser parser = Xml.newPullParser();
    parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
    parser.setInput(inputStream, null);
    parser.nextTag();
    return readFeed(parser);
}catch(IllegalArgumentException e){ //Replace this with the more specific exception
  //do something
}catch(Excpetion e){ //You can have multiple catch blocks from specific to general
  //do something
}finally {
    inputStream.close();

}

添加此代码后，您仍然会收到错误，因为 inputStream 为 null 并在 finally block 中抛出 NullPointerException。有两种方法可以处理这个问题。

第一种是简单地在 finally block 中捕获 NullPointerException:

try {
    XmlPullParser parser = Xml.newPullParser();
    parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false);
    parser.setInput(inputStream, null);
    parser.nextTag();
    return readFeed(parser);
}catch(IllegalArgumentException e){ //Replace this with the more specific exception
  //do something
}catch(Excpetion e){ //You can have multiple catch blocks from specific to general
  //do something
}finally {
    try{
       inputStream.close();
    }catch(Exception e){
       //do something 
    }
}

第二种是在方法的开头添加一个保护条件，不接受空的InputStream。

public List<RssItem> parse(InputStream inputStream)
    throws IllegalArgumentException {

    if(inputStream == null){
        throw new IllegalArgumentException();
    }
}

可以这样称呼:

  try{
        someObject.parse(null);
  }catch(IllegalArgumentException e){
      //do something
  }