Question

我有一个导航抽屉和一些异步任务，它将在后台执行。我想要做的是当从导航抽屉中选择某个项目时，我然后执行在异步任务中在后台执行的方法。以下是从导航抽屉中选择内容的代码：

private void selectItem(int position) {
    selectedPosition = position;
    mDrawerLayout.closeDrawer(navDrawerView);

    switch (selectedPosition) {
    case 0:
        try {
            ViewEventsOnMap();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        Toast.makeText(ENeighbourhoodActivity.this, "Press and hold at the area where you wish to create an event!",
                Toast.LENGTH_LONG).show();
        break;
    case 1:
        Toast.makeText(ENeighbourhoodActivity.this, "Analyze Event",
                Toast.LENGTH_LONG).show();
        break;
    }

    setTitle(mEventSelection[selectedPosition]);

}

我的异步任务类：

private class MyAsyncTask extends AsyncTask<Void, Integer, Double> {
    @Override
    protected Double doInBackground(Void... params) {
        try {
            ViewEventsOnMap();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }

    protected void onPostExecute(Double result) {
    }

    protected void onProgressUpdate(Integer... progress) {
    }
}

我在onCreate时调用了这个异步任务类，因此它不依赖于从导航抽屉中选择的项目。

public void ViewEventsOnMap() throws JSONException {
    String page;
    JSONArray jsonArray;

    try {
        HttpClient client = new DefaultHttpClient();
        HttpGet request = new HttpGet(URL);
        HttpResponse response = client.execute(request);
        HttpEntity entity = response.getEntity();
        try {
            // Codes to retrieve data from servlet and plot marker onto the map
            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

但是使用这些代码，我收到以下错误消息：

11-04 20:54:45.642: W/dalvikvm(25527): threadid=1: thread exiting with uncaught exception (group=0x40c3f1f8)
11-04 20:54:45.673: E/AndroidRuntime(25527): FATAL EXCEPTION: main
11-04 20:54:45.673: E/AndroidRuntime(25527): android.os.NetworkOnMainThreadException
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at libcore.io.IoBridge.connect(IoBridge.java:112)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at java.net.Socket.connect(Socket.java:842)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at nyp.edu.eneighbourhood.ENeighbourhoodActivity.ViewEventsOnMap(ENeighbourhoodActivity.java:204)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at nyp.edu.eneighbourhood.ENeighbourhoodActivity.selectItem(ENeighbourhoodActivity.java:385)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at nyp.edu.eneighbourhood.ENeighbourhoodActivity.access$4(ENeighbourhoodActivity.java:378)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at nyp.edu.eneighbourhood.ENeighbourhoodActivity$5.onChildClick(ENeighbourhoodActivity.java:341)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.widget.ExpandableListView.handleItemClick(ExpandableListView.java:584)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.widget.ExpandableListView.performItemClick(ExpandableListView.java:521)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:2713)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.widget.AbsListView$1.run(AbsListView.java:3468)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.os.Handler.handleCallback(Handler.java:605)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.os.Handler.dispatchMessage(Handler.java:92)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.os.Looper.loop(Looper.java:137)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at android.app.ActivityThread.main(ActivityThread.java:4512)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at java.lang.reflect.Method.invokeNative(Native Method)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at java.lang.reflect.Method.invoke(Method.java:511)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:982)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:749)
11-04 20:54:45.673: E/AndroidRuntime(25527):    at dalvik.system.NativeStart.main(Native Method)

任何指南？提前谢谢。

Answer 1

你写了一个AsyncTask课程，但你没有使用它。您的堆栈跟踪显示您在主应用程序线程上从ViewEventsOnMap()调用了selectItem()，并且您没有在任何地方使用MyAsyncTask。

Answer 2

您没有使用AsyncTask进行网络通话。您已撰写AsyncTask但未完全使用它。

在导航抽屉中选择项目时，您将直接调用在UI线程上运行的方法ViewEventsOnMap()。

而不是这样做，你应该调用你的AsycnTask

Android异步任务NetworkOnMainThreadException

2 个答案: