JAVAAndroid中的lang.NullPointerException错误

Question

我是安卓新手，我正在尝试从mysql数据库检索数据到安卓文本字段。当我在java文件中添加以下行时

JSONObject json = jsonParser.makeHttpRequest(
                url_product_detials, "GET", params);

它显示了错误。如果我删除上面的（jsonParser.makeHttpRequest）行，它就可以正常工作。我在日志文件中得到的错误是

01-02 11:16:50.418: W/System.err(968):  ... 17 more
01-02 11:16:50.418: E/Buffer Error(968): Error converting result java.lang.NullPointerException
01-02 11:16:50.418: E/JSON Parser(968): Error parsing data org.json.JSONException: End of input at character 0 of 
01-02 11:16:50.428: D/AndroidRuntime(968): Shutting down VM
01-02 11:16:50.428: W/dalvikvm(968): threadid=1: thread exiting with uncaught exception (group=0x40015560)
01-02 11:16:50.428: E/AndroidRuntime(968): FATAL EXCEPTION: main
01-02 11:16:50.428: E/AndroidRuntime(968): java.lang.NullPointerException
01-02 11:16:50.428: E/AndroidRuntime(968):  at com.example.matrixarc.Syl$GetProductDetails$1.run(Syl.java:153)
01-02 11:16:50.428: E/AndroidRuntime(968):  at 安卓.os.Handler.handleCallback(Handler.java:587)
01-02 11:16:50.428: E/AndroidRuntime(968):  at 安卓.os.Handler.dispatchMessage(Handler.java:92)
01-02 11:16:50.428: E/AndroidRuntime(968):  at 安卓.os.Looper.loop(Looper.java:130)
01-02 11:16:50.428: E/AndroidRuntime(968):  at 安卓.app.ActivityThread.main(ActivityThread.java:3683)
01-02 11:16:50.428: E/AndroidRuntime(968):  at java.lang.reflect.Method.invokeNative(Native Method)
01-02 11:16:50.428: E/AndroidRuntime(968):  at java.lang.reflect.Method.invoke(Method.java:507)
01-02 11:16:50.428: E/AndroidRuntime(968):  at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-02 11:16:50.428: E/AndroidRuntime(968):  at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-02 11:16:50.428: E/AndroidRuntime(968):  at dalvik.system.NativeStart.main(Native Method)
01-02 11:16:52.808: I/Process(968): Sending signal. PID: 968 SIG: 9

我已将url\u产品详细信息初始化为

private static final String url_product_detials = "http://localhost/connection/ggg.php";

Answer 1

在android中，{}代表设备/模拟器。如果要连接到计算机/本地计算机，请使用IP 10.0.2.2

更改private static final String url_product_detials = "http://localhost/connection/ggg.php";

到private static final String url_product_detials = "http://10.0.2.2/connection/ggg.php";