如何解决android中的异常
我已经在 android 中编写了 HttpDelete 来调用 REST Web 服务。
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView txt = (TextView) findViewById(R.id.textView1);
txt.setText(getInputStreamFromUrl("http://192.168.37.241:8080/kyaw/k"));
}
public static String getInputStreamFromUrl(String url) {
InputStream content = null;
HttpResponse response = null;
try {
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpDelete delete=new HttpDelete(url);
put.setHeader("Content-Type","application/vnd.org.snia.cdmi.container");
response = httpclient.execute(delete);
content = response.getEntity().getContent();
}catch (Exception e) {
Log.e("[DELETE REQUEST]", "Network exception");
}
String result=response.getStatusLine().toString()+"\n"+response.getHeaders(url);
return result;
}
我得到了例外，
05-23 08:30:16.868: ERROR/[DELETE REQUEST](1197): Network exception
05-23 08:30:16.868: DEBUG/AndroidRuntime(1197): Shutting down VM
05-23 08:30:16.878: WARN/dalvikvm(1197): threadid=1: thread exiting with uncaught exception (group=0x40015560)
05-23 08:30:16.908: ERROR/AndroidRuntime(1197): FATAL EXCEPTION: main
05-23 08:30:16.908: ERROR/AndroidRuntime(1197): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test/com.test.putandroid}: java.lang.NullPointerException
有人知道为什么吗？
i have written HttpDelete in android to call REST web service.
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView txt = (TextView) findViewById(R.id.textView1);
txt.setText(getInputStreamFromUrl("http://192.168.37.241:8080/kyaw/k"));
}
public static String getInputStreamFromUrl(String url) {
InputStream content = null;
HttpResponse response = null;
try {
DefaultHttpClient httpclient = new DefaultHttpClient();
HttpDelete delete=new HttpDelete(url);
put.setHeader("Content-Type","application/vnd.org.snia.cdmi.container");
response = httpclient.execute(delete);
content = response.getEntity().getContent();
}catch (Exception e) {
Log.e("[DELETE REQUEST]", "Network exception");
}
String result=response.getStatusLine().toString()+"\n"+response.getHeaders(url);
return result;
}
And I get the exception which is
05-23 08:30:16.868: ERROR/[DELETE REQUEST](1197): Network exception
05-23 08:30:16.868: DEBUG/AndroidRuntime(1197): Shutting down VM
05-23 08:30:16.878: WARN/dalvikvm(1197): threadid=1: thread exiting with uncaught exception (group=0x40015560)
05-23 08:30:16.908: ERROR/AndroidRuntime(1197): FATAL EXCEPTION: main
05-23 08:30:16.908: ERROR/AndroidRuntime(1197): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test/com.test.putandroid}: java.lang.NullPointerException
Do anyone know why?
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评论（3）
您是否检查了清单文件的互联网权限？
did you check for the manifest file for Internet permission?
目前还不知道网络异常，但最后一个 NPE 很可能是因为前一个异常是在通过
httpclient.execute(delete)初始化response之前引发的。您应该重写您的
catch块，并将捕获的异常的名称和消息写入日志。No idea for the network exception (yet) but the last NPE is most likely because the previous exception is thrown before
responsehas been initialized throughhttpclient.execute(delete).You should rewrite your
catchblock and write the name of the catched exception and the message to the log.在第 4 行的 onCreate() 函数中，我们发现在初始化
TextView后，您尝试设置一个值。您必须使用
Handler对象，因为您无法在单独的线程中更新 UI 对象。这是一些帮助链接
https://web.archive.org/web/20200810154212/http://www.tutorialforandroid.com/2009/01/using-handler-in-android.html
https://web.archive.org/web/20130306131310 /http://thedevelopersinfo.com/?p=150
In the onCreate() function on line 4 we find that after initializing your
TextViewyou are trying to set a value.You must use a
Handlerobject because you cannot update an UI objects while in a separate thread.Here is some link for your help
https://web.archive.org/web/20200810154212/http://www.tutorialforandroid.com/2009/01/using-handler-in-android.html
https://web.archive.org/web/20130306131310/http://thedevelopersinfo.com/?p=150