將JSON數據解析為Android ListView

Question

我已經潛伏了這個網站很長一段時間了，幸運的是直到現在我所有的問題都得到了解答。 我希望你們中的一些人可以在這里闡明我的問題。 我可以成功地獲取ListView以顯示字符串數組 - 但是當我嘗試將JSON數據解析為數組時 - 我的程序只是強制關閉而LogCat對我沒什么幫助。 Anywho - 這是我正在使用的代碼。

String[] journals = {"Filler"};
String result;
JSONArray jArray[];
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    try{
  //http post
            HttpClient httpclient = new DefaultHttpClient();
            HttpPost httppost = new HttpPost("http://xxx.xxx.xxx.xxx/query.php");
            org.apache.http.HttpResponse response = httpclient.execute(httppost);
            HttpEntity entity = response.getEntity();
            InputStream is = entity.getContent();


  //convert response to string
            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();

   //I think the problem is somewhere here ....
            JSONArray jArray = new JSONArray(result);
            for(int i=0;i<jArray.length();i++){
                    JSONObject json_data = jArray.getJSONObject(i);
                    journals[i] = json_data.getString("JournalName");
                    Log.i("log_tag","JournalID: "+json_data.getInt("JournalID") +
                            ",JournalName: " + json_data.getString("JournalName"));
            }
    }
    catch (Exception e) {
    }

    //Or here -- I know this code should REALLY be separated and not in onCreate -- I feel like that's half my problem
    setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item, journals));
    ListView lv = getListView();

先謝謝你們！ 我很感激。

03-07 22:24:33.060: ERROR/AndroidRuntime(7986): FATAL EXCEPTION: main
03-07 22:24:33.060: ERROR/AndroidRuntime(7986): java.lang.RuntimeException: Unable to start activity ComponentInfo{Andrew.Badura.A4A.com/Andrew.Badura.A4A.com.SurvAcademia}: java.lang.RuntimeException: Unable to start activity ComponentInfo{Andrew.Badura.A4A.com/Andrew.Badura.A4A.com.JournalActivity}: java.lang.NullPointerException
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.os.Looper.loop(Looper.java:123)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.main(ActivityThread.java:4627)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at java.lang.reflect.Method.invokeNative(Native Method)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at java.lang.reflect.Method.invoke(Method.java:521)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at dalvik.system.NativeStart.main(Native Method)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986): Caused by: java.lang.RuntimeException: Unable to start activity ComponentInfo{Andrew.Badura.A4A.com/Andrew.Badura.A4A.com.JournalActivity}: java.lang.NullPointerException
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.startActivityNow(ActivityThread.java:2503)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:127)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:654)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.widget.TabHost.setCurrentTab(TabHost.java:326)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.widget.TabHost.addTab(TabHost.java:216)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at Andrew.Badura.A4A.com.SurvAcademia.onCreate(SurvAcademia.java:25)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     ... 11 more
03-07 22:24:33.060: ERROR/AndroidRuntime(7986): Caused by: java.lang.NullPointerException
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at java.util.Arrays$ArrayList.<init>(Arrays.java:49)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at java.util.Arrays.asList(Arrays.java:171)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:125)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at Andrew.Badura.A4A.com.JournalActivity.onCreate(JournalActivity.java:69)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
03-07 22:24:33.060: ERROR/AndroidRuntime(7986):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)

Answer 1

這個代碼在如此多的級別上是錯誤的，從忽略Java約定開始，完全吞噬了異常處理。

我強烈建議您在應用程序的主線程中執行任何類型的遠程調用。 您需要將其至少包裝到AsyncTask （或可能是Service）中，並使用回調填充ListView以確保您返回到主UI線程

Answer 2

你可以使用一個開放的API Gson.jar從Json獲取數據。它以標准化的方式獲取數據...試試它...例如http://blog.foos-bar.com/2010/08/parsing -facebook-json.html