在 AsyncTask 的 doInBackground() 中执行 GraphRequest.executeAndWait() 时获取'android.os.NetworkOnMainThread

Question

我正在使用Facebook GraphAPI，我正在尝试使用此处所示的GraphRequest.executeAndWait()从下一页加载结果，但该应用程序崩溃，导致android.os.NetworkOnMainThreadException。

这是我的代码：

class RetrieveF extends AsyncTask<Void, Integer, String> {
GraphRequest request;
protected String doInBackground(Void...args0) {
new GraphRequest(
AccessToken.getCurrentAccessToken(), "/me/friends", null, HttpMethod.GET,
new GraphRequest.Callback() {
public void onCompleted(GraphResponse response) {
JSONObject innerJson = response.getJSONObject();
try {
JSONArray data = innerJson.getJSONArray("data");
for (int i = 0; i<data.length(); i++){
String id = data.getJSONObject(i).getString("id");
request = new GraphRequest(AccessToken.getCurrentAccessToken(), id+"/feed", null, HttpMethod.GET,
new GraphRequest.Callback() {
@Override
public void onCompleted(GraphResponse response) {
JSONObject innerJson = response.getJSONObject();
try {
JSONArray data = innerJson.getJSONArray("data");
for (int i = 0; i<data.length(); i++) {
JSONObject obj = data.getJSONObject(i);}
} catch (JSONException e) {
Log.d("innerFacebookException", e.getMessage());
}
GraphRequest nextResultsRequests = response.getRequestForPagedResults(GraphResponse.PagingDirection.NEXT);
if (nextResultsRequests != null) {
nextResultsRequests.setCallback(request.getCallback());
// error on this line
response = nextResultsRequests.executeAndWait();
//
}
}
}
);
request.executeAsync();
}
} catch (JSONException e) {
Log.d("facebookException", e.getMessage());
}
}
}
).executeAsync();
return "success";
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
}
}

下面是堆栈跟踪：

android.os.NetworkOnMainThreadException
 at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1273)
 at com.android.org.conscrypt.OpenSSLSocketImpl.shutdownAndFreeSslNative(OpenSSLSocketImpl.java:1131)
 at com.android.org.conscrypt.OpenSSLSocketImpl.close(OpenSSLSocketImpl.java:1126)
 at com.android.okhttp.Connection.closeIfOwnedBy(Connection.java:132)
 at com.android.okhttp.OkHttpClient$1.closeIfOwnedBy(OkHttpClient.java:75)
 at com.android.okhttp.internal.http.HttpConnection.closeIfOwnedBy(HttpConnection.java:137)
 at com.android.okhttp.internal.http.HttpTransport.disconnect(HttpTransport.java:135)
 at com.android.okhttp.internal.http.HttpEngine.disconnect(HttpEngine.java:578)
 at com.android.okhttp.internal.huc.HttpURLConnectionImpl.disconnect(HttpURLConnectionImpl.java:122)
 at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.disconnect(DelegatingHttpsURLConnection.java:93)
 at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.disconnect(HttpsURLConnectionImpl.java)
 at com.facebook.internal.Utility.disconnectQuietly(Utility.java:416)
 at com.facebook.GraphRequest.executeConnectionAndWait(GraphRequest.java:1272)
 at com.facebook.GraphRequest.executeBatchAndWait(GraphRequest.java:1168)
 at com.facebook.GraphRequest.executeBatchAndWait(GraphRequest.java:1134)
 at com.facebook.GraphRequest.executeBatchAndWait(GraphRequest.java:1118)
 at com.facebook.GraphRequest.executeAndWait(GraphRequest.java:1093)
 at com.facebook.GraphRequest.executeAndWait(GraphRequest.java:987)
 at com.qbc.xxx.MainActivity$RetrieveFacebookPosts$1$1.onCompleted(MainActivity.java:398)
 at com.facebook.GraphRequest$5.run(GraphRequest.java:1383)
 at android.os.Handler.handleCallback(Handler.java:739)
 at android.os.Handler.dispatchMessage(Handler.java:95)
 at android.os.Looper.loop(Looper.java:148)
 at android.app.ActivityThread.main(ActivityThread.java:5417)
 at java.lang.reflect.Method.invoke(Native Method)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)               

我无法弄清楚导致此错误的原因，因为此类错误通常是在未AsyncTask处理此类代码时引起的，但这里的情况并非如此。

请让我知道导致此错误的原因以及如何摆脱它。

Answer 1

无论哪个线程调用此请求，public void onCompleted()都在 UI 线程上运行。因此，如果您想在public void onCompleted()内执行另一个请求，则必须将其包装到另一个AsyncTask或其他异步机制中。

Answer 2

这不是正确的方法

Thread t = new Thread() {
@Override
public void run() {
GraphRequest nextResultsRequests = lastGraphResponse.getRequestForPagedResults(GraphResponse.PagingDirection.NEXT);
if (nextResultsRequests != null) {
nextResultsRequests.setCallback(request.getCallback());
lastGraphResponse = nextResultsRequests.executeAndWait();
}
}

}.start((;

您是通过创建新线程来执行此操作的。所有网络操作都应在已经存在的后台线程中完成，而不是通过创建新线程来完成。

执行此操作的方法是使用处理程序对象在主线程上运行代码。

Handler handler = new Handler();
handler.post(new Runnable() {
@Override
public void run() {
GraphRequest nextResultsRequests = lastGraphResponse.getRequestForPagedResults(GraphResponse.PagingDirection.NEXT);
if (nextResultsRequests != null) {
nextResultsRequests.setCallback(request.getCallback());
lastGraphResponse = nextResultsRequests.executeAndWait();
}
}
});

或者，您可以在一段时间延迟后使用postDelay进行操作

handler.postDelayed(new Runnable() {
@Override
public void run() {
GraphRequest nextResultsRequests = lastGraphResponse.getRequestForPagedResults(GraphResponse.PagingDirection.NEXT);
if (nextResultsRequests != null) {
nextResultsRequests.setCallback(request.getCallback());
lastGraphResponse = nextResultsRequests.executeAndWait();
}
}
}, DELAY_IN MILLISECONDS);

Answer 3

经过几次谷歌搜索，我得到了解决方案。

我只是将GraphRequest.executeAndWait()代码包装在这样的Thread中：

Thread t = new Thread() {
@Override
public void run() {
GraphRequest nextResultsRequests = lastGraphResponse.getRequestForPagedResults(GraphResponse.PagingDirection.NEXT);
if (nextResultsRequests != null) {
nextResultsRequests.setCallback(request.getCallback());
lastGraphResponse = nextResultsRequests.executeAndWait();
}
}
};
t.start();