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我想将 Json 解析为字符串，以将其显示在 listView 上。我搜索并阅读了很多文章和问题，但我找不到解决方案

我试过这个解析器 JSON 来自：Android JSON Parsing Tutorial

    public class JSONParser {

    static InputStream is = null;
    static JSONObject jObj = null;
    static String json = "";

    // constructor
    public JSONParser() {

    }

    public JSONObject getJSONFromUrl(String url) {

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();           

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        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();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }
}

另一个来自How to parse JSON in Android：

    DefaultHttpClient   httpclient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httppost = new HttpPost("http://someJSONUrl.com/jsonWebService");
// Depends on your web service
httppost.setHeader("Content-type", "application/json");

InputStream inputStream = null;
String result = null;
try {
HttpResponse response = httpclient.execute(httppost);           
HttpEntity entity = response.getEntity();

inputStream = entity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();

String line = null;
while ((line = reader.readLine()) != null)
{
    sb.append(line + "\n");
}
result = sb.toString();
} catch (Exception e) { 
    // Oops
}
finally {
    try{if(inputStream != null)inputStream.close();}catch(Exception squish){}
}

但是在他们两个中，当我使用字符串 Json 时，一切正常，但是当我想从 Web API（例如：http ://api.androidhive.info/contacts/ ）读取 Json 时，我会遇到这个错误：

09-27 23:47:11.015: E/AndroidRuntime(28635): FATAL EXCEPTION: main
09-27 23:47:11.015: E/AndroidRuntime(28635): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mas.forcheksulotion/com.mas.forcheksulotion.MainActivity}: java.lang.NullPointerException
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1666)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1682)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:943)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.os.Handler.dispatchMessage(Handler.java:99)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.os.Looper.loop(Looper.java:130)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread.main(ActivityThread.java:3744)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at java.lang.reflect.Method.invokeNative(Native Method)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at java.lang.reflect.Method.invoke(Method.java:507)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at dalvik.system.NativeStart.main(Native Method)
09-27 23:47:11.015: E/AndroidRuntime(28635): Caused by: java.lang.NullPointerException
09-27 23:47:11.015: E/AndroidRuntime(28635):    at java.io.StringReader.<init>(StringReader.java:46)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at org.json.simple.JSONValue.parse(JSONValue.java:33)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at com.mas.forcheksulotion.MainActivity.onCreate(MainActivity.java:57)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-27 23:47:11.015: E/AndroidRuntime(28635):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1630)
09-27 23:47:11.015: E/AndroidRuntime(28635):    ... 11 more

而且我仍然不知道在 android 上使用 Json 我应该使用 JSONArray 或 JSONObject 还是将 Json 解析为 String ？

4

2 回答 2

1

这样做..这是我在许多应用程序中使用从 url 获取 json 响应的工作代码。

 /**
 * This method used to get json from url.
 * 
 * @param url
 *            represented url
 * @return represented {@link JSONObject}
 */
public JSONObject getJSONFromUrl(String url) {

    InputStream is = null;
    JSONObject jObj = null;
    try {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);
        HttpResponse httpResponse = httpClient.execute(httpGet);

        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();
    } catch (Exception e) {
        e.printStackTrace();
    }
    try {
        jObj = new JSONObject(getResponseBody(is));

    } catch (Exception e) {
        e.printStackTrace();
    }
    return jObj;
}

/**
 * This method used to get response body.
 * 
 * @param instream
 *            represented input stream
 * @return represented {@link String}
 * @throws IOException
 *             represented {@link IOException}
 * @throws ParseException
 *             represented {@link ParseException}
 */
public String getResponseBody(final InputStream instream) throws IOException, ParseException {

    if (instream == null) {
        return "";
    }

    StringBuilder buffer = new StringBuilder();

    BufferedReader reader = new BufferedReader(new InputStreamReader(instream, "utf-8"));

    String line = null;
    try {
        while ((line = reader.readLine()) != null) {
            buffer.append(line);
        }

    } finally {
        instream.close();
        reader.close();
    }
    System.out.println(buffer.toString());
    return buffer.toString();

}
于 2013-09-28T07:17:18.390 回答
-1

我发现了问题

两个解决方案很棒而且很有用，但我的错误是关于使用许可。

我应该将此添加到 AndroidManifest ：

<uses-permission android:name="android.permission.INTERNET"></uses-permission>
于 2013-09-28T18:55:04.053 回答