我有一项活动，我必须填写列表视图。活动发布到网址并接收JSON作为响应。我已经解析了JSON以在列表视图中显示，但列表视图没有被填充。
活动的完整代码：
public class RegisterFirstActivity extends ListActivity {
private static final String TAG_CODE = "Code";
private static final String TAG_ID = "Id";
private static final String TAG_LAT = "Lat";
private static final String TAG_LON = "Lon";
private static final String TAG_NAME = "Name";
static String response_str=null;
static String response_code=null;
String ac_code;
String ac_id;
String ac_lat;
String ac_lon;
String ac_name;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register_first);
sendPostRequest();
}
//sending async post request---------------------------------------------------------------------------------------
private void sendPostRequest() {
class SendPostReqAsyncTask extends AsyncTask<String, Void, String>{
@Override
protected String doInBackground(String... params) {
String result = "";
HttpClient hc = new DefaultHttpClient();
String message;
//HttpPost p = new HttpPost("http://192.168.1.60/tr/MobileService/GetAC");
HttpPost p = new HttpPost("http://bumba27.byethost16.com/xxxxxxx/");
JSONObject object = new JSONObject();
try {
//object.put("Id",deviceid);
//object.put("StringValue",value);
// object.put("last_name", lastname);
// object.put("first_name", firstname);
// object.put("email", email);
} catch (Exception ex) {
}
try {
message = object.toString();
p.setEntity(new StringEntity(message, "UTF8"));
p.setHeader("Content-type", "application/json");
HttpResponse resp = hc.execute(p);
response_code=""+ resp.getStatusLine().getStatusCode();
Log.d("Response Code: ", "" + response_code);
InputStream inputStream = resp.getEntity().getContent();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
StringBuilder stringBuilder = new StringBuilder();
String bufferedStrChunk = null;
while((bufferedStrChunk = bufferedReader.readLine()) != null){
stringBuilder.append(bufferedStrChunk);
}
response_str= stringBuilder.toString();
parse_json_str(response_str);
if (resp != null) {
if (resp.getStatusLine().getStatusCode() == 204)
result = "true";
makeAToast("Response: "+resp.toString());
}
Log.d("Status line", "" + resp.getStatusLine().getStatusCode());
} catch (Exception e) {
e.printStackTrace();
Log.i("Error in response: ",e.getMessage());
}
return result;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
//Toast.makeText(getApplicationContext(), result, Toast.LENGTH_LONG).show();
//writeToFile(result, "record.txt");
Log.i("RESPONSE",result);
}
}
SendPostReqAsyncTask sendPostReqAsyncTask = new SendPostReqAsyncTask();
sendPostReqAsyncTask.execute();
}
//-----------------------------------------------------------------------------------------------
public void parse_json_str(String json_str)
{
// Hashmap for ListView
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
JSONArray lJSONArray;
String jString = json_str;
try
{
lJSONArray = new JSONArray( jString );
JSONObject lJSONObject;
for ( int i = 0; i < lJSONArray.length(); i++ )
{
lJSONObject = lJSONArray.getJSONObject( i );
// PARSE FIELD HERE
ac_code = lJSONObject.getString( TAG_CODE );
Log.i("Code: ",ac_code);
ac_id=lJSONObject.getString( TAG_ID );
Log.i("Id: ",ac_id);
ac_lat=lJSONObject.getString( TAG_LAT );
Log.i("Lat: ",ac_lat);
ac_lon=lJSONObject.getString( TAG_LON );
Log.i("Lon: ",ac_lon);
ac_name=lJSONObject.getString( TAG_NAME );
Log.i("Name: ",ac_name);
// ETC
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_CODE, ac_code);
map.put(TAG_ID, ac_id);
map.put(TAG_LAT, ac_lat);
map.put(TAG_LON, ac_lon);
map.put(TAG_NAME, ac_name);
Log.d("map","haeflloter putting");
Log.d("map",map+"");
// adding HashList to ArrayList
contactList.add(map);
//Log.d("tag name", contactList+"");
}
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(this, contactList,R.layout.list_item,new String[] { TAG_NAME }, new int[] {R.id.name});
Log.d("tag name", contactList+"");
setListAdapter(adapter);
}
catch( Exception e )
{
Log.d("catch", e+"");
}
}
public void makeAToast(String str) {
//yet to implement
Toast toast = Toast.makeText(this,str, Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER, 0, 0);
toast.show();
}
}
布局文件activity_register_first：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
list_item.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<!-- Name Label -->
<TextView
android:id="@+id/name"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#43bd00"
android:textSize="16sp"
android:textStyle="bold"
android:paddingTop="6dip"
android:paddingBottom="2dip" />
<!-- Description label -->
</LinearLayout>
</LinearLayout>
我得到的错误是：
02-15 19:26:46.154: D/catch(1429): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
我已经按照this教程查看了列表视图。
我哪里错了？如何解决这个问题？
答案 0 :(得分：3)
在AsyncTask中，只有onPreExecute()，onProgressUpdate()和onPostExecute()在UI线程中执行。
doInBackground()在后台线程中执行。
您应该存储来自doInBackground()的数据，然后在onPostExecute()更新您的用户界面。
修改
使您的contactList成为您的AsyncTask的成员，并添加此代码（未经测试）：
protected void onPostExecute(String result) {
super.onPostExecute(result);
if(mContactList != null) {
ListAdapter adapter = new SimpleAdapter(this, contactList,R.layout.list_item,new String[] { TAG_NAME }, new int[] {R.id.name});
Log.d("tag name", contactList+"");
setListAdapter(adapter);
}
Log.i("RESPONSE",result);
}
答案 1 :(得分：1)
UI更改必须在UI线程中完成。这就是onPostExecute()的用途，它在UI线程中运行。