在Android上从URL简单解析JSON并显示在列表视图中

问题描述：

我正在尝试解析从我的Android应用中的URL提取的JSON结果...

I'm trying to parse a JSON result fetched from a URL in my Android app...

我在Internet上尝试了一些示例，但无法使其正常工作. JSON数据如下所示:

I have tried a few examples on the Internet, but can't get it to work. The JSON data looks like this:

[
    {
        "city_id": "1",
        "city_name": "Noida"
    },
    {
        "city_id": "2",
        "city_name": "Delhi"
    },
    {
        "city_id": "3",
        "city_name": "Gaziyabad"
    },
    {
        "city_id": "4",
        "city_name": "Gurgaon"
    },
    {
        "city_id": "5",
        "city_name": "Gr. Noida"
    }
]

获取URL并解析JSON数据的最简单方法是在列表视图中显示

What's the simplest way to fetch the URL and parse the JSON data show it in the listview

答

您可以使用AsyncTask，您必须进行自定义以满足您的需求，但是类似以下内容

You could use AsyncTask, you'll have to customize to fit your needs, but something like the following

异步任务具有三种主要方法:

Async task has three primary methods:

onPreExecute()-最常用来设置和启动进度对话框

onPreExecute() - most commonly used for setting up and starting a progress dialog

doInBackground()-建立连接并从服务器接收响应(请勿尝试将响应值分配给GUI元素，这是一个常见错误，无法在后台线程中完成).

doInBackground() - Makes connections and receives responses from the server (Do NOT try to assign response values to GUI elements, this is a common mistake, that cannot be done in a background thread).

首先，我们将启动类，初始化String以将结果保存在方法外部但在类内部，然后运行onPreExecute()方法以设置简单的进度对话框.

First we will start the class, initialize a String to hold the results outside of the methods but inside the class, then run the onPreExecute() method setting up a simple progress dialog.

class MyAsyncTask extends AsyncTask<String, String, Void> {

    private ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
    InputStream inputStream = null;
    String result = ""; 

    protected void onPreExecute() {
        progressDialog.setMessage("Downloading your data...");
        progressDialog.show();
        progressDialog.setOnCancelListener(new OnCancelListener() {
            public void onCancel(DialogInterface arg0) {
                MyAsyncTask.this.cancel(true);
            }
        });
    }

然后，我们需要建立连接以及我们如何处理响应:

Then we need to set up the connection and how we want to handle the response:

    @Override
    protected Void doInBackground(String... params) {

        String url_select = "http://yoururlhere.com";

        ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();

        try {
            // Set up HTTP post

            // HttpClient is more then less deprecated. Need to change to URLConnection
            HttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost(url_select);
            httpPost.setEntity(new UrlEncodedFormEntity(param));
            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();

            // Read content & Log
            inputStream = httpEntity.getContent();
        } catch (UnsupportedEncodingException e1) {
            Log.e("UnsupportedEncodingException", e1.toString());
            e1.printStackTrace();
        } catch (ClientProtocolException e2) {
            Log.e("ClientProtocolException", e2.toString());
            e2.printStackTrace();
        } catch (IllegalStateException e3) {
            Log.e("IllegalStateException", e3.toString());
            e3.printStackTrace();
        } catch (IOException e4) {
            Log.e("IOException", e4.toString());
            e4.printStackTrace();
        }
        // Convert response to string using String Builder
        try {
            BufferedReader bReader = new BufferedReader(new InputStreamReader(inputStream, "utf-8"), 8);
            StringBuilder sBuilder = new StringBuilder();

            String line = null;
            while ((line = bReader.readLine()) != null) {
                sBuilder.append(line + "\n");
            }

            inputStream.close();
            result = sBuilder.toString();

        } catch (Exception e) {
            Log.e("StringBuilding & BufferedReader", "Error converting result " + e.toString());
        }
    } // protected Void doInBackground(String... params)

最后，这里我们将分析返回值，在此示例中，它是一个JSON数组，然后关闭该对话框:

Lastly, here we will parse the return, in this example it was a JSON Array and then dismiss the dialog:

    protected void onPostExecute(Void v) {
        //parse JSON data
        try {
            JSONArray jArray = new JSONArray(result);    
            for(i=0; i < jArray.length(); i++) {

                JSONObject jObject = jArray.getJSONObject(i);

                String name = jObject.getString("name");
                String tab1_text = jObject.getString("tab1_text");
                int active = jObject.getInt("active");

            } // End Loop
            this.progressDialog.dismiss();
        } catch (JSONException e) {
            Log.e("JSONException", "Error: " + e.toString());
        } // catch (JSONException e)
    } // protected void onPostExecute(Void v)
} //class MyAsyncTask extends AsyncTask<String, String, Void>

在Android上从URL简单解析JSON并显示在列表视图中

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