Question

我在Facebook的代码中使用了一个arraylist的问题。公共类Facebook {

//this are global variable
HashMap<String,String> postsMap = new HashMap<>();
ArrayList<HashMap<String, String>> list = new ArrayList<>();
...
private void retrievePosts() {
GraphRequest postsRequest = new GraphRequest(
            AccessToken.getCurrentAccessToken(),
            "/{page-id}/",
            null,
            HttpMethod.GET,
            new GraphRequest.Callback() {
                public void onCompleted(GraphResponse response) {
                    Log.d("Facebook: ", response.toString());

                    try {
                        JSONObject jobj = response.getJSONObject().getJSONObject(TAG_POST);
                        JSONArray posts = jobj.getJSONArray(TAG_DATA);

                        for (int i = 0; i < posts.length(); i++) {
                            JSONObject c = posts.getJSONObject(i);

                            String message = c.getString(TAG_MESSAGE);
                            String createdTime = c.getString(TAG_CREATION);

                            map.put(TAG_MESSAGE, message);
                            map.put(TAG_CREATION, createdTime);


                            list.add(postsMap);

                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            });
    Bundle parameters = new Bundle();
    parameters.putString("fields", "posts.limit(20)");
    postsRequest.setParameters(parameters);
    postsRequest.executeAsync();
}

当我尝试查看Facebook方法调用内的列表内部时，我可以看到正确的元素，但是当方法结束时，我的arraylist变空。如何解决此问题？

Answer 1

如果我没有弄错的话，您的HashMap应该用

初始化

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

然后，您应该在调用postsMap

时使用put()变量

postsMap.put(TAG_MESSAGE, message);
postsMap.put(TAG_CREATION, createdTime);

Answer 2

我找到了解决问题的方法。问题是我在主线程中执行asyncTask。我以这种方式解决了：

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.list_view);

    new RetrievePosts().execute();

}
class RetrievePosts extends AsyncTask<String, String, String> {

    @Override
    protected String doInBackground(String... params) {
         GraphRequest postsRequest = new GraphRequest(
        AccessToken.getCurrentAccessToken(),
        "/{page-id}/",
        null,
        HttpMethod.GET,
        new GraphRequest.Callback() {
            public void onCompleted(GraphResponse response) {
                Log.d("Facebook: ", response.toString());
                //my stuff
            }
        });
Bundle parameters = new Bundle();
parameters.putString("fields", "posts.limit(20)");
postsRequest.setParameters(parameters);
postsRequest.executeAndWait();
}

我用方法.executeAndWait（）更改了.executeAsynk（）因为我已经在asyncTask中了。

全局变量在Facebook的GraphRequest之后失去价值 - 安卓

2 个答案: