Question

我正在尝试从网址http://api.geonames.org/earthquakesJSON?north=44.1&south=-9.9&east=-22.4&west=55.2&username=demo

上的json格式中提取数据

这是我的代码：

package com.pxr.tutorial.json;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class TestConnectionActivity {

    public static JSONObject getJSONfromURL(String url){
        InputStream is = null;
        String result = "";
        JSONObject jArray = null;

        //http post
        try{
                HttpClient httpclient = new DefaultHttpClient();
                HttpGet httppost = new HttpGet(url);
                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());
        }

      //convert response to string
        try{
                BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
                StringBuilder sb = new StringBuilder();
                String line = null;
                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());
        }

        try{

            jArray = new JSONObject(result);            
        }catch(JSONException e){
                Log.e("log_tag", "Error parsing data "+e.toString());
        }

        return jArray;
    }

这是logcat：

10-20 17:44:20.149: ERROR/AndroidRuntime(449): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.pxr.tutorial.json/com.pxr.tutorial.json.TestConnectionActivity}: java.lang.ClassCastException: com.pxr.tutorial.json.TestConnectionActivity
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.os.Looper.loop(Looper.java:123)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.main(ActivityThread.java:3683)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at java.lang.reflect.Method.invokeNative(Native Method)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at java.lang.reflect.Method.invoke(Method.java:507)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at dalvik.system.NativeStart.main(Native Method)
10-20 17:44:20.149: ERROR/AndroidRuntime(449): Caused by: java.lang.ClassCastException: com.pxr.tutorial.json.TestConnectionActivity
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
10-20 17:44:20.149: ERROR/AndroidRuntime(449):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)

它说它是一个类强制转换异常：s ..请帮助！这是android.manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.pxr.tutorial.json"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="10" />
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".TestConnectionActivity"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
</manifest>

Answer 1

您的TestConnectionActivity课程需要延长Activity：

public class TestConnectionActivity extends Activity {
.
.
.
}

从网站中提取json

1 个答案: