问题
I make a chat room with AsyncTask for receive messages, so it always checking the coming messages and show it to client, but the code seems not works what i hope.
in client only show all old datas, for the new datas not show up.
because when I try to send messages from server, the new data didn't show in client.
I got confused with this problem, and really need help. anyone please help me, thank you.
AsyncTask for receive
public class ReceivedTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
}
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
try{
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(SERVER_URL);
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
//add parameter
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpRespose = httpClient.execute(httpPost);
HttpEntity httpEntity = httpRespose.getEntity();
//read content
InputStream in = httpEntity.getContent();
BufferedReader read = new BufferedReader(new InputStreamReader(in));
String content = "";
String line = "";
while((line = read.readLine())!=null){
content += line;
}
Log.d("ADBUG", "content: "+content);
//json
if(!content.equals("null")){
try{
JSONArray jArr = new JSONArray(content);
//String messages="";
for(int i=0; i < jArr.length() ; i++){
JSONObject jObj = jArr.getJSONObject(i);
String message = jObj.getString("message");
showMessage(message, false);
}
}catch(JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
else{
Toast.makeText(ChatRoom.this, "Error", Toast.LENGTH_LONG).show();
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}
the whole code
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.chatpage);
messagesContainer = (ViewGroup) findViewById(R.id.messagesContainer);
scrollContainer = (ScrollView) findViewById(R.id.scrollContainer);
Button sendMessageButton = (Button) findViewById(R.id.sendButton);
Bundle bundle = this.getIntent().getExtras();
/*final String paramnama = bundle.getString("nama");*/
messageText = (EditText) findViewById(R.id.messageEdit);
meLabel = (TextView) findViewById(R.id.meLabel);
friendLabel = (TextView) findViewById(R.id.friendLabel);
meLabel.setText("me");
final String param1 = bundle.getString("keyCourseId");
final String param2 = bundle.getString("keyUserId");
final String param3 = bundle.getString("keyChatsId");
String param4 = bundle.getString("keyMessagesId");
sendMessageButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//for send part already works fine
});
HttpURLConnection connection;
URL url = null;
try{
linkurl = new Koneksi(this);
SERVER_URL = linkurl.getUrl();
SERVER_URL += "/mobile/ChatRoom.php?idu="+param2+"&idch="+param3;
url = new URL(SERVER_URL);
connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
connection.setRequestMethod("POST");
new ReceivedTask().execute();
}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public class ReceivedTask extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
}
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
try{
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(SERVER_URL);
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
//add parameter
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpRespose = httpClient.execute(httpPost);
HttpEntity httpEntity = httpRespose.getEntity();
//read content
InputStream in = httpEntity.getContent();
BufferedReader read = new BufferedReader(new InputStreamReader(in));
String content = "";
String line = "";
while((line = read.readLine())!=null){
content += line;
}
Log.d("ADBUG", "content: "+content);
//json
if(!content.equals("null")){
try{
JSONArray jArr = new JSONArray(content);
// String messages="";
for(int i=0; i < jArr.length() ; i++){
JSONObject jObj = jArr.getJSONObject(i);
String message = jObj.getString("message");
showMessage(message, false);
}
}catch(JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
else{
Toast.makeText(ChatRoom.this, "Error", Toast.LENGTH_LONG).show();
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();}
catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}
public void showMessage(String message, boolean leftSide) {
final TextView textView = new TextView(ChatRoom.this);
textView.setTextColor(Color.BLACK);
textView.setText(message);
int bgRes = R.drawable.left_message_bg;
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
if (!leftSide) {
bgRes = R.drawable.right_message_bg;
params.gravity = Gravity.RIGHT;
}
textView.setLayoutParams(params);
textView.setBackgroundResource(bgRes);
runOnUiThread(new Runnable() {
@Override
public void run() {
messagesContainer.addView(textView);
// Scroll to bottom
if (scrollContainer.getChildAt(0) != null) {
scrollContainer.scrollTo(scrollContainer.getScrollX(), scrollContainer.getChildAt(0).getHeight());
}
scrollContainer.fullScroll(View.FOCUS_DOWN);
}
});
}
回答1:
You should be using onPostExcecute, this would automatically be placed back on the ui thread (if not started from inside another thread).
Refactor to something like this and it should get you closer if it wasn't the exact issue.
private static final String TAG = "CHAT";
public static class ReceivedTask extends AsyncTask<String, String, List<String>> {
@Override
protected void onPreExecute() {
}
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
try {
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(SERVER_URL);
ArrayList<NameValuePair> param = new ArrayList<NameValuePair>();
// add parameter
httpPost.setEntity(new UrlEncodedFormEntity(param));
HttpResponse httpRespose = httpClient.execute(httpPost);
HttpEntity httpEntity = httpRespose.getEntity();
// read content
InputStream in = httpEntity.getContent();
BufferedReader read = new BufferedReader(
new InputStreamReader(in));
String content = "";
String line = "";
while ((line = read.readLine()) != null) {
content += line;
}
Log.d(TAG, "content: " + content);
// json
List<String> messages = new ArrayList<String>();
if (!content.equals("null")) {
try {
JSONArray jArr = new JSONArray(content);
// String messages="";
for (int i = 0; i < jArr.length(); i++) {
JSONObject jObj = jArr.getJSONObject(i);
messages.add(jObj.getString("message"));
}
} catch (JSONException e) {
Log.e(TAG, e.getMessage(), e);
}
return messages;
} else {
Log.e(TAG, "content was null!");
}
} catch (ClientProtocolException e) {
Log.e(TAG, e.getMessage(), e);
} catch (IOException e) {
Log.e(TAG, e.getMessage(), e);
}
return null;
}
@Override
protected void onPostExecute(List<String> messages) {
if (result == null) {
Log.e(TAG, "Something failed!");
} else {
for (String message : messages) {
showMessage(result, true);
}
}
}
}
public void showMessage(String message, boolean leftSide) {
final TextView textView = new TextView(ChatRoom.this);
textView.setTextColor(Color.BLACK);
textView.setText(message);
int bgRes = R.drawable.left_message_bg;
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
if (!leftSide) {
bgRes = R.drawable.right_message_bg;
params.gravity = Gravity.RIGHT;
}
textView.setLayoutParams(params);
textView.setBackgroundResource(bgRes);
messagesContainer.addView(textView);
// Scroll to bottom
if (scrollContainer.getChildAt(0) != null) {
scrollContainer.scrollTo(scrollContainer.getScrollX(),
scrollContainer.getChildAt(0).getHeight());
}
scrollContainer.fullScroll(View.FOCUS_DOWN);
}
回答2:
AsyncTask will performed once , you have to use timer to perform it in period time ,You should use Handler's postDelayed function for this purpose. It will run your code with specified delay on the main UI thread, so you will be able to update UI controls. see repeat a task with a time delay
来源：https://stackoverflow.com/questions/17247010/already-use-asynctask-doinbackground-but-the-new-data-not-show-up