Question

我正在尝试从JSON 获取数据 ListView ，但每次我都会收到空白页面，既没有获取类别列表也没有错误。

我是Android新手，尝试使用JSON 制作多级ListView ，

就我而言，我只想使用 JSON 来实现这一目标：类别＆gt;项目＆gt;细节

但我在第一个屏幕上遇到问题，即使无法获取类别

JSON：

{ "categoryId": "1", "categoryTitle": { "SmartPhones": [ { "itemId": "1", "itemTitle": "Galaxy Mega 5.8" }, { "itemId": "2", "itemTitle": "Galaxy Mega 6.3" } ] }, "categoryId": "2", "categoryTitle": { "Tablets": [ { "itemId": "1", "itemTitle": "Galaxy Note 510" }, { "itemId": "2", "itemTitle": "Galaxy Note 800" } ]} }

感谢@Segi给我正确的JSON格式

活动代码：

public class CategoriesActivity extends ListActivity { // Connection detector ConnectionDetector cd; // Alert dialog manager AlertDialogManager alert = new AlertDialogManager(); // Progress Dialog private ProgressDialog pDialog; // Creating JSON Parser object JSONParser jsonParser = new JSONParser(); ArrayList<HashMap<String, String>> categoriesList; // albums JSONArray JSONArray categories = null; // albums JSON url private static final String URL_CATEGORIES = "my.json"; // providing proper URL // ALL JSON node names private static final String TAG_ID = "categoryId"; private static final String TAG_TITLE = "categoryTitle"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_albums); cd = new ConnectionDetector(getApplicationContext()); // Check for internet connection if (!cd.isConnectingToInternet()) { // Internet Connection is not present alert.showAlertDialog(CategoriesActivity.this, "Internet Connection Error", "Please connect to working Internet connection", false); // stop executing code by return return; } // Hashmap for ListView categoriesList = new ArrayList<HashMap<String, String>>(); // Loading Categories JSON in Background Thread new LoadCategories().execute(); // get listview ListView lv = getListView(); /** * Listview item click listener * ProductListActivity will be lauched by passing category id * */ lv.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> arg0, View view, int arg2, long arg3) { // on selecting a single category // ProductListActivity will be launched to show products inside the category Intent i = new Intent(getApplicationContext(), TrackListActivity.class); // send category id to productlist activity to get list of products under that category String category_id = ((TextView) view.findViewById(R.id.album_id)).getText().toString(); i.putExtra("category_id", category_id); startActivity(i); } }); } /** * Background Async Task to Load all Categories by making http request * */ class LoadCategories extends AsyncTask<String, String, String> { /** * Before starting background thread Show Progress Dialog * */ @Override protected void onPreExecute() { super.onPreExecute(); pDialog = new ProgressDialog(CategoriesActivity.this); pDialog.setMessage("Listing Categories ..."); pDialog.setIndeterminate(false); pDialog.setCancelable(false); pDialog.show(); } /** * getting Categories JSON * */ protected String doInBackground(String... args) { // Building Parameters List<NameValuePair> params = new ArrayList<NameValuePair>(); // getting JSON string from URL String json = jsonParser.makeHttpRequest(URL_CATEGORIES, "GET", params); // Check your log cat for JSON reponse Log.d("Categories JSON: ", "> " + json); try { categories = new JSONArray(json); if (categories != null) { // looping through all categories for (int i = 0; i < categories.length(); i++) { JSONObject c = categories.getJSONObject(i); // Storing each json item values in variable String id = c.getString(TAG_ID); String title = c.getString(TAG_TITLE); // creating new HashMap HashMap<String, String> map = new HashMap<String, String>(); // adding each child node to HashMap key => value map.put(TAG_ID, id); map.put(TAG_TITLE, title); // adding HashList to ArrayList categoriesList.add(map); } }else{ Log.d("Categories: ", "null"); } } catch (JSONException e) { e.printStackTrace(); } return null; } /** * After completing background task Dismiss the progress dialog * **/ protected void onPostExecute(String file_url) { // dismiss the dialog after getting all categories pDialog.dismiss(); // updating UI from Background Thread runOnUiThread(new Runnable() { public void run() { /** * Updating parsed JSON data into ListView * */ ListAdapter adapter = new SimpleAdapter( CategoriesActivity.this, categoriesList, R.layout.list_item_albums, new String[] { TAG_ID, TAG_TITLE }, new int[] { R.id.category_id, R.id.category_title }); // updating listview setListAdapter(adapter); } }); } } }

logcat的：

06-15 12:21:27.124: D/dalvikvm(786): GC_FOR_ALLOC freed 68K, 8% free 2488K/2680K, paused 173ms, total 213ms 06-15 12:21:27.174: I/dalvikvm-heap(786): Grow heap (frag case) to 3.152MB for 635812-byte allocation 06-15 12:21:27.264: D/dalvikvm(786): GC_FOR_ALLOC freed 1K, 6% free 3108K/3304K, paused 89ms, total 89ms 06-15 12:21:27.354: D/dalvikvm(786): GC_CONCURRENT freed <1K, 6% free 3111K/3304K, paused 5ms+3ms, total 95ms 06-15 12:21:28.274: I/Choreographer(786): Skipped 41 frames! The application may be doing too much work on its main thread. 06-15 12:21:28.874: I/Choreographer(786): Skipped 123 frames! The application may be doing too much work on its main thread. 06-15 12:21:29.044: D/gralloc_goldfish(786): Emulator without GPU emulation detected. 06-15 12:21:29.134: D/dalvikvm(786): GC_CONCURRENT freed 19K, 4% free 3478K/3620K, paused 8ms+38ms, total 268ms 06-15 12:21:30.894: I/Choreographer(786): Skipped 51 frames! The application may be doing too much work on its main thread. 06-15 12:20:36.624: D/Categories JSON:(786): > { 06-15 12:20:36.624: D/Categories JSON:(786): "categoryId": "1", 06-15 12:20:36.624: D/Categories JSON:(786): "categoryTitle": { 06-15 12:20:36.624: D/Categories JSON:(786): "SmartPhones": [ 06-15 12:20:36.624: D/Categories JSON:(786): { 06-15 12:20:36.624: D/Categories JSON:(786): "itemId": "1", 06-15 12:20:36.624: D/Categories JSON:(786): "itemTitle": "Galaxy Mega 5.8" 06-15 12:20:36.624: D/Categories JSON:(786): }, 06-15 12:20:36.624: D/Categories JSON:(786): { 06-15 12:20:36.624: D/Categories JSON:(786): "itemId": "2", 06-15 12:20:36.624: D/Categories JSON:(786): "itemTitle": "Galaxy Mega 6.3" 06-15 12:20:36.624: D/Categories JSON:(786): } 06-15 12:20:36.624: D/Categories JSON:(786): ] 06-15 12:20:36.624: D/Categories JSON:(786): }, 06-15 12:20:36.624: D/Categories JSON:(786): "categoryId": "2", 06-15 12:20:36.624: D/Categories JSON:(786): "categoryTitle": {"Tablets": [ 06-15 12:20:36.624: D/Categories JSON:(786): { 06-15 12:20:36.624: D/Categories JSON:(786): "itemId": "1", 06-15 12:20:36.624: D/Categories JSON:(786): "itemTitle": "Galaxy Note 510" 06-15 12:20:36.624: D/Categories JSON:(786): }, 06-15 12:20:36.624: D/Categories JSON:(786): { 06-15 12:20:36.624: D/Categories JSON:(786): "itemId": "2", 06-15 12:20:36.624: D/Categories JSON:(786): "itemTitle": "Galaxy Note 800" 06-15 12:20:36.624: D/Categories JSON:(786): } 06-15 12:20:36.624: D/Categories JSON:(786): ]} 06-15 12:20:36.624: D/Categories JSON:(786): } 06-15 12:20:36.814: W/System.err(786): org.json.JSONException: Value {"categoryTitle":{"SmartPhones":[{"itemId":"1","itemTitle":"Galaxy Mega 5.8"},{"itemId":"2","itemTitle":"Galaxy Mega 6.3"}]},"categoryId":"2"} of type org.json.JSONObject cannot be converted to JSONArray 06-15 12:20:36.824: W/System.err(786): at org.json.JSON.typeMismatch(JSON.java:111) 06-15 12:20:36.836: W/System.err(786): at org.json.JSONArray.<init>(JSONArray.java:91) 06-15 12:20:36.836: W/System.err(786): at org.json.JSONArray.<init>(JSONArray.java:103) 06-15 12:20:36.904: W/System.err(786): at com.my.json.CategoriesActivity$LoadCategories.doInBackground(CategoriesActivity.java:135) 06-15 12:20:36.904: W/System.err(786): at com.my.json.CategoriesActivity$LoadCategories.doInBackground(CategoriesActivity.java:1) 06-15 12:20:36.914: W/System.err(786): at android.os.AsyncTask$2.call(AsyncTask.java:287) 06-15 12:20:36.914: W/System.err(786): at java.util.concurrent.FutureTask.run(FutureTask.java:234) 06-15 12:20:36.925: W/System.err(786): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 06-15 12:20:36.925: W/System.err(786): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 06-15 12:20:36.934: W/System.err(786): at java.lang.Thread.run(Thread.java:856) 06-15 12:20:45.984: D/InputEventConsistencyVerifier(786): KeyEvent: ACTION_UP but key was not down. 06-15 12:20:45.984: D/InputEventConsistencyVerifier(786): in android.view.ViewRootImpl@40de89c8 06-15 12:20:45.984: D/InputEventConsistencyVerifier(786): 0: sent at 106936000000, KeyEvent { action=ACTION_UP, keyCode=KEYCODE_MENU, scanCode=229, metaState=0, flags=0x8, repeatCount=0, eventTime=106936, downTime=106820, deviceId=0, source=0x101 }

注意：获取空白活动，不将数据导入ListView，不会出现任何错误

Answer 1

JSON是有效的，但不合逻辑，应该是这样的

[
{
"categoryId": "1",
"categoryTitle": "SmartPhones", "SmartPhones": [
        {
            "itemId": "1",
            "itemTitle": "Galaxy Mega 5.8"
        },
        {
            "itemId": "2",
            "itemTitle": "Galaxy Mega 6.3"
        }
    ]
},
{
"categoryId": "1",
"categoryTitle": "Tablets", "Tablets": [
        {
            "itemId": "1",
            "itemTitle": "Galaxy Mega 5.8"
        },
        {
            "itemId": "2",
            "itemTitle": "Galaxy Mega 6.3"
        }
    ]
}
]

然后代码将是：

            if (categories != null) {
                // looping through All albums
                for (int i = 0; i < categories.length(); i++) {

                    JSONObject oneCategory = categories.getJSONObject(i);
                    String categoryName = oneCategory.getString(TAG_ID);

                    String catTitle = oneCategory.getString( TAG_TITLE );

                    JSONArray categoryTitle = oneCategory.getJSONArray(catTitle);

                    for( int i = 0 ; i < categoryTitle.length() ; i++ )
                    {
                         JSONObject item = categoryTitle.getJSONObject(i);
                         String id = item.getString("itemId");
                         String name = item.getString("itemTitle");

                         // creating new HashMap
                         HashMap<String, String> map = new HashMap<String, String>();

                         // adding each child node to HashMap key => value
                         map.put(TAG_ID, id);
                         map.put(TAG_TITLE, name);
                    }

                    // adding HashList to ArrayList
                    categoriesList.add(map);
                }
            }else{
                Log.d("Categories: ", "null");
            }

Answer 2

是的，从Logcat可以看出JSON存在问题。

试试以下JSON .-＆gt;

[{“categoryId”：“1”，{“categoryTitle”：“平板电脑”，“平板电脑”：[{“itemId”：“1”，“itemTitle”：“Galaxy Mega 5.8”}，{“itemId “：”2“，”itemTitle“：”Galaxy Mega 6.3“}}}，{”categoryId“：”2“，”categoryTitle“：{”Tablets“：[{”itemId“：”1“，”itemTitle“ ：“Galaxy Note 510”}，{“itemId”：“2”，“itemTitle”：“Galaxy Note 800”}]}}]

我没有做任何特别的事情，但添加了一些括号以使其成为JSON格式。如果您从php获取此信息，请在那里进行必要的更改以对其进行格式化。

注意：在这里，JSON具有复杂的结构，因此在解析时要小心。

Answer 3

"categoryTitle" : "Appetizers" : [

和

"categoryTitle" : "Mixed Platter" : [

这是不正确的。你想做什么？

Answer 4

尝试以下Json：

{
    "categoryId": "1",
    "categoryTitle": {
        "Appetizers": [
            {
                "itemId": "1",
                "itemTitle": "Samosa"
            },
            {
                "itemId": "2",
                "itemTitle": "Vegetable Pakora"
            }
        ]
    },
    "categoryId": "2",
    "categoryTitle": {"Mixed Platter": [
        {
            "itemId": "1",
            "itemTitle": "Veggie"
        },
        {
            "itemId": "2",
            "itemTitle": "Non Veggie"
        }
    ]}
}

Answer 5

String json = "{'categoryId': '1', 'categoryTitle': {'Appetizers': [{'itemId': '1','itemTitle': 'Samosa'},{'itemId': '2','itemTitle': 'Vegetable Pakora'}]}},{'categoryId': '2', 'categoryTitle': {'Appetizers': [{'itemId': '1','itemTitle': 'Samosa'},{'itemId': '2','itemTitle': 'Vegetable Pakora'}]}}";
        try {
            json = "[" + json + "]";
            JSONArray mArray = new JSONArray(json);
            for (int i = 0; i < mArray.length(); i++) {
                JSONObject mJsonObject = new JSONObject(mArray.get(0)
                        .toString());
                String categoryId = mJsonObject.getString("categoryId");
                String categoryTitle = mJsonObject.getString("categoryTitle");
                mJsonObject = new JSONObject(categoryTitle);
                String mVal = mJsonObject.toString().split(":")[0].replace(
                        "\"", "").replace("{", "");
                String Resutlt = mJsonObject.getString(mVal);
                JSONArray mArray1 = new JSONArray(Resutlt);
                for (int j = 0; j < mArray1.length(); j++) {
                    mJsonObject = mArray1.getJSONObject(j);
                    String itemId = mJsonObject.getString("itemId");
                    String itemTitle = mJsonObject.getString("itemTitle");
                }
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

Answer 6

尝试在退出循环后立即将适配器设置为listview（JSON循环）

将数据从JSON获取到列表视图中

6 个答案: