我正在开发一个 android 应用程序，它向 php 文件发出 HTTP 请求，然后给我一个字符串。该代码在 android 2.x 及更低版本中运行良好，但是当我在更高版本的 android 操作系统中运行它时，它会崩溃。我在清单文件中拥有所有必要的权限。
这是我的代码：
getData data;
String result;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
data = new getData("http://alexanderpadin.uphero.com/copyDataBase.php");
result = data.getResult();
Log.i("Data", result);
}
还有我的 getData 类：
package com.application.uprm_map;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import android.util.Log;
public class getData {
private String result;
private InputStream is;
private StringBuilder sb;
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
public getData(String url){
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(url);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
String line="0";
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
}
public String getResult(){
return result;
}
}
日志猫：
04-17 01:29:43.593: E/Trace(13235): error opening trace file: No such file or directory (2)
04-17 01:29:44.118: E/log_tag(13235): Error in http connection android.os.NetworkOnMainThreadException
04-17 01:29:44.118: E/log_tag(13235): Error converting result java.lang.NullPointerException: lock == null
04-17 01:29:44.133: E/AndroidRuntime(13235): FATAL EXCEPTION: main
04-17 01:29:44.133: E/AndroidRuntime(13235): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.application.uprm_map/com.application.uprm_map.MainActivity}: java.lang.NullPointerException: println needs a message
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2357)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread.access$600(ActivityThread.java:153)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.os.Handler.dispatchMessage(Handler.java:99)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.os.Looper.loop(Looper.java:137)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread.main(ActivityThread.java:5226)
04-17 01:29:44.133: E/AndroidRuntime(13235): at java.lang.reflect.Method.invokeNative(Native Method)
04-17 01:29:44.133: E/AndroidRuntime(13235): at java.lang.reflect.Method.invoke(Method.java:511)
04-17 01:29:44.133: E/AndroidRuntime(13235): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
04-17 01:29:44.133: E/AndroidRuntime(13235): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
04-17 01:29:44.133: E/AndroidRuntime(13235): at dalvik.system.NativeStart.main(Native Method)
04-17 01:29:44.133: E/AndroidRuntime(13235): Caused by: java.lang.NullPointerException: println needs a message
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.util.Log.println_native(Native Method)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.util.Log.i(Log.java:159)
04-17 01:29:44.133: E/AndroidRuntime(13235): at com.application.uprm_map.MainActivity.onCreate(MainActivity.java:64)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.Activity.performCreate(Activity.java:5104)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-17 01:29:44.133: E/AndroidRuntime(13235): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)
04-17 01:29:44.133: E/AndroidRuntime(13235): ... 11 more
我也尝试使用这个包： http: //loopj.com/android-async-http/：
这是代码：
String result;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
AsyncHttpClient client = new AsyncHttpClient();
client.get("http://alexanderpadin.uphero.com/copyDataBase", new AsyncHttpResponseHandler() {
@Override
public void onSuccess(String response) {
result = response;
}
});
log.i("Data", result);
}
当我尝试在函数 onSuccess 中打印响应变量时，它可以工作，但是当我尝试让该变量做其他事情时，它就不起作用了。
日志猫：
04-17 01:22:11.358: E/Trace(12475): error opening trace file: No such file or directory (2)
04-17 01:22:26.103: E/Trace(12710): error opening trace file: No such file or directory (2)
04-17 01:22:26.618: E/AndroidRuntime(12710): FATAL EXCEPTION: main
04-17 01:22:26.618: E/AndroidRuntime(12710): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.application.uprm_map/com.application.uprm_map.MainActivity}: java.lang.NullPointerException: println needs a message
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2357)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread.access$600(ActivityThread.java:153)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.os.Handler.dispatchMessage(Handler.java:99)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.os.Looper.loop(Looper.java:137)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread.main(ActivityThread.java:5226)
04-17 01:22:26.618: E/AndroidRuntime(12710): at java.lang.reflect.Method.invokeNative(Native Method)
04-17 01:22:26.618: E/AndroidRuntime(12710): at java.lang.reflect.Method.invoke(Method.java:511)
04-17 01:22:26.618: E/AndroidRuntime(12710): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
04-17 01:22:26.618: E/AndroidRuntime(12710): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
04-17 01:22:26.618: E/AndroidRuntime(12710): at dalvik.system.NativeStart.main(Native Method)
04-17 01:22:26.618: E/AndroidRuntime(12710): Caused by: java.lang.NullPointerException: println needs a message
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.util.Log.println_native(Native Method)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.util.Log.i(Log.java:159)
04-17 01:22:26.618: E/AndroidRuntime(12710): at com.application.uprm_map.MainActivity.onCreate(MainActivity.java:69)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.Activity.performCreate(Activity.java:5104)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-17 01:22:26.618: E/AndroidRuntime(12710): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)
04-17 01:22:26.618: E/AndroidRuntime(12710): ... 11 more
我的代码中是否缺少某些内容？有人可以帮我实现这一目标吗？我将不胜感激任何帮助。谢谢你。