Question

我从MySQL获取数据并使用php以json格式显示，现在我想在Android中显示此数据我获取数据并保存在＆＃34; myJSON＆＃34;变量并使用此代码显示数据

String myJSON;

private static final String TAG_NEWS="allnews";
private static final String TAG_ID = "id";
private static final String TAG_ONVAN = "Onvan";
private static final String TAG_TARIKH ="Tarikh";
private static final String TAG_CNID ="cnid";

JSONArray jnews = null;

ArrayList<HashMap<String, String>> newsList;

ListView list;

和

protected void SaveNewNews(){
        try {
            JSONObject jsonObj = new JSONObject(myJSON);
            jnews = jsonObj.getJSONArray(TAG_NEWS);

            Log.i(DBAdapter.TAG, "news " + jnews.length());

           for(int i=0;i<jnews.length();i++){
                    JSONObject c = jnews.getJSONObject(i);
                    String id = c.getString(TAG_ID);
                    String title = c.getString(TAG_ONVAN);
                    String data = c.getString(TAG_TARIKH);
                    String nid = c.getString(TAG_CNID);

                    Log.i(DBAdapter.TAG, id);

                    HashMap<String,String> nnews = new HashMap<String,String>();

                    nnews.put(TAG_ID,id);
                    nnews.put(TAG_ONVAN,title);
                    nnews.put(TAG_TARIKH,data);
                    nnews.put(TAG_CNID,nid);

                    newsList.add(nnews);

                    ListAdapter adapter = new SimpleAdapter(
                            SplashActivity.this, personList, R.layout.list_item,
                            new String[]{TAG_ID,TAG_ONVAN,TAG_TARIKH,TAG_CNID},
                            new int[]{R.id.id, R.id.title, R.id.data, R.id.nid}
                    );

                    list.setAdapter(adapter);

            }

        } catch (JSONException e) {
            e.printStackTrace();
        }
        gonext();

    }

在日志中，您可以看到它获取数据列表news 5并获得第一个ID 35，但应用停止并且不执行任何操作

07-08 09:36:43.456: I/Ekhtraat app(1333): news 5
07-08 09:36:43.456: I/Ekhtraat app(1333): 35
07-08 09:36:43.476: W/System.err(1333): java.lang.NullPointerException
07-08 09:36:43.486: W/System.err(1333):     at ir.sheikhoo.ekhteraat_app.GetActivity.SaveNewNews(GetActivity.java:315)
07-08 09:36:43.496: W/System.err(1333):     at ir.sheikhoo.ekhteraat_app.GetActivity$GetData.onPostExecute(GetActivity.java:256)
07-08 09:36:43.496: W/System.err(1333):     at ir.sheikhoo.ekhteraat_app.GetActivity$GetData.onPostExecute(GetActivity.java:1)
07-08 09:36:43.496: W/System.err(1333):     at android.os.AsyncTask.finish(AsyncTask.java:631)
07-08 09:36:43.507: W/System.err(1333):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
07-08 09:36:43.507: W/System.err(1333):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
07-08 09:36:43.507: W/System.err(1333):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-08 09:36:43.507: W/System.err(1333):     at android.os.Looper.loop(Looper.java:137)
07-08 09:36:43.516: W/System.err(1333):     at android.app.ActivityThread.main(ActivityThread.java:5103)
07-08 09:36:43.516: W/System.err(1333):     at java.lang.reflect.Method.invokeNative(Native Method)
07-08 09:36:43.516: W/System.err(1333):     at java.lang.reflect.Method.invoke(Method.java:525)
07-08 09:36:43.526: W/System.err(1333):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
07-08 09:36:43.526: W/System.err(1333):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
07-08 09:36:43.526: W/System.err(1333):     at dalvik.system.NativeStart.main(Native Method)
07-08 09:36:43.536: I/Choreographer(1333): Skipped 168 frames!  The application may be doing too much work on its main thread.

请你检查一下哪里出错了。

Answer 1

看起来你没有初始化newsList。

在newsList = new ArrayList<>();行中添加并查看它的位置。（在SaveNewNews()方法的开头尝试）。

或者将行ArrayList<HashMap<String, String>> newsList;更改为也初始化，即ArrayList<HashMap<String, String>> newsList = new ArrayList<>();

Android：使用json获取数据列表时停止

1 个答案: