运行我的 android 应用程序时出现错误。有时它可以顺利运行，但有时它会显示如下错误：
java.net.SocketException: Connection timed out
at org.apache.harmony.luni.platform.OSNetworkSystem.read(Native Method)
at dalvik.system.BlockGuard$WrappedNetworkSystem.read(BlockGuard.java:273)
at org.apache.harmony.luni.net.PlainSocketImpl.read(PlainSocketImpl.java:458)
at org.apache.harmony.luni.net.SocketInputStream.read(SocketInputStream.java:85)
at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103)
at org.apache.http.impl.io.AbstractSessionInputBuffer.readLine(AbstractSessionInputBuffer.java:191)
at org.apache.http.impl.conn.DefaultResponseParser.parseHead(DefaultResponseParser.java:82)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:174)
at org.apache.http.impl.AbstractHttpClientConnection.receiveResponseHeader(AbstractHttpClientConnection.java:179)
at org.apache.http.impl.conn.DefaultClientConnection.receiveResponseHeader(DefaultClientConnection.java:235)
at org.apache.http.impl.conn.AbstractClientConnAdapter.receiveResponseHeader(AbstractClientConnAdapter.java:259)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:279)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:121)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:421)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
错误转换结果 java.lang.NullPointerException 解析数据时出错 org.json.JSONException: End of input at character 0 of
有人可以告诉我这个问题的主要原因是什么吗？谢谢。