Question

将 Json 字符串( strWebserviceResult) 转换为我的对象时, 我使用以下代码 :

EntMyClass entMyClass = gson.fromJson(strWebserviceResult,EntMyClass.class);

当 < 坚固> strWebserviceResult 很大( 约2.5 MB) 时, 我得到这条线上的“ 坚固” 排除记忆

我怎样才能解决呢?

有人有什么建议吗?

05-26 15:52:49.607: E/dalvikvm-heap(2078): Out of memory on a 9200-byte allocation.
05-26 15:52:49.618: E/dalvikvm(2078): Out of memory: Heap Size=31879KB, Allocated=27693KB, Bitmap Size=936KB, Limit=32768KB
05-26 15:52:49.618: E/dalvikvm(2078): Extra info: Footprint=31879KB, Allowed Footprint=31879KB, Trimmed=7400KB
05-26 15:52:49.618: E/AndroidRuntime(2078): FATAL EXCEPTION: Thread-19
05-26 15:52:49.618: E/AndroidRuntime(2078): java.lang.OutOfMemoryError: (Heap Size=31879KB, Allocated=27693KB, Bitmap Size=936KB)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at java.util.ArrayList.add(ArrayList.java:123)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:664)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:624)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializerExceptionWrapper.deserialize(JsonDeserializerExceptionWrapper.java:51)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationVisitor.invokeCustomDeserializer(JsonDeserializationVisitor.java:92)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonObjectDeserializationVisitor.visitFieldUsingCustomHandler(JsonObjectDeserializationVisitor.java:117)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.ReflectingFieldNavigator.visitFieldsReflectively(ReflectingFieldNavigator.java:63)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:120)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationContextDefault.fromJsonObject(JsonDeserializationContextDefault.java:76)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationContextDefault.deserialize(JsonDeserializationContextDefault.java:54)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:663)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.DefaultTypeAdapters$CollectionTypeAdapter.deserialize(DefaultTypeAdapters.java:624)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializerExceptionWrapper.deserialize(JsonDeserializerExceptionWrapper.java:51)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationVisitor.invokeCustomDeserializer(JsonDeserializationVisitor.java:92)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationVisitor.visitUsingCustomHandler(JsonDeserializationVisitor.java:80)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.ObjectNavigator.accept(ObjectNavigator.java:101)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationContextDefault.fromJsonArray(JsonDeserializationContextDefault.java:67)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.JsonDeserializationContextDefault.deserialize(JsonDeserializationContextDefault.java:52)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.Gson.fromJson(Gson.java:551)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.Gson.fromJson(Gson.java:498)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.Gson.fromJson(Gson.java:467)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.Gson.fromJson(Gson.java:417)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at com.google.gson.Gson.fromJson(Gson.java:389)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at org.mabna.order.businessLayer.BoWebService.getDataForUpdate(BoWebService.java:188)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at org.mabna.order.ui.ActToolDataExchange.threadGetDataForFullUpdate(ActToolDataExchange.java:371)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at org.mabna.order.ui.ActToolDataExchange.access$9(ActToolDataExchange.java:362)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at org.mabna.order.ui.ActToolDataExchange$33.run(ActToolDataExchange.java:603)
05-26 15:52:49.618: E/AndroidRuntime(2078):     at org.mabna.order.utils.Utilities$5.run(Utilities.java:778)

Answer 1

尝试使用"http://google-gson.googlecode.com/svn/trunk/gson/docs/javadocs/com/google/gson/Gson.html#来自Json%28com.google.gson.strong.JsonReader,%20java.lang.refect.Type%29" rel=“norefererr” >来自Json 的方法,该方法取JsonReader作为输入。这应该允许您一次不需要整个输入字符串在记忆中。这里有一些样本代码 :

        final HttpURLConnection c = (HttpURLConnection) url.openConnection();
        final InputStreamReader isr = new InputStreamReader(c.getInputStream());
        final JsonReader reader = new JsonReader(isr);
        final EntMyClass entMyClass = GSON.fromJson(reader, EntMyClass.class);
        reader.close();
        c.disconnect();

Answer 2

与其它文章一样, 我将询问是否有办法可以避免您的应用程序使用大型内存。如果您可以这样做, 这将是最理想的解决方案。如果您的应用程序真的需要这么多内存, 您可以尝试设置 < code> and mid: largeHeap=“ true” 用于您在列表中的应用程序。以下是引用 :

< a href="http:// developmenter.android.com/ reference/android/R.stingable.html#android Manifest Application_ largeHeap" rel="noreferr" >http:// developinger.android.com/ reference/android/R. styleable.html#android Manifest Application_ largeheap

详情请见此影片:

http://www.youtube.com/watch?vCruQY55Hok" rel=“noreferrer>>http://www.youtube.com/watch?vCruQY55Hok

Answer 3

First of all. Do you really need to load 2.5MB data into memory?
At first there is created a big string, then it s parsed (another objects in memory), and then there is created a huge instance of EntMyClass. This approach is really inefficient.

我猜您在此对象中有列表。只有您已经提供的信息, 我建议将数据输入数据库。然后您可以创建适应器, 在 ListView 中显示数据。

有许多方法可以做到这一点。我使用杰克逊图书馆,因为图书馆是最快的,GSON应该有类似的功能。

假设您在下面的此对象中有列表,请举例说明如何在数据库中存储 json 阵列:

    //create parser
    final JsonParser jsonParser = objectMapper.getJsonFactory().createJsonParser(inputStream);

    JsonToken jsonToken = jsonParser.nextToken();
    while ((jsonToken = jsonParser.nextToken()) != null && jsonToken != JsonToken.END_ARRAY) {
        //map json object to ItemClass
        final ItemClass item = jsonParser.readValueAs(ItemClass.class);
        //store in database
        itemDAO.insert(item);
    }

围绕着数据库交易, 不仅数据在出错时会回落, 而且效率也会提高。

Answer 4

请读读Gson-的作者的回答“https://stackoverflow.com/a/9460267/394678>这里。

还有我的5美分:

        JsonReader r = null;
        try {
            Reader reader = new BufferedReader(new InputStreamReader(is));
            r = new JsonReader(reader);
            result = gson.fromJson(r, clazz);
        } finally {
            if (null != r) {
                r.close();
            }
        }

友情链接