我在android 2.3.5上有这个异步任务
class InternetConnexionErrorAsync extends AsyncTask<String, String, String>
{
@Override
protected void onPreExecute() {
super.onPreExecute();
mdpiImageView.setClickable(false);
journalsImageView.setClickable(false);
accountImageView.setClickable(false);
Toast.makeText(getBaseContext(),errorMessage , Toast.LENGTH_LONG).show();
}
@Override
protected String doInBackground(String... aurl) {
try {
Thread.sleep(3450);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String unused)
{
finish();
}
}
一切都运作良好。
当我在Android 4.0中尝试这个时，我是onPostExecute的新访问。
你能帮我吗？没有错误消息，只是更新了onPostExecute。答案 0 :(得分：1)
无论您需要在UI上进行更新，都需要在onPostExecute中进行更新。
下面的代码，看看onPostExecute - 特别是activity.xx（）方法将更新发送到在UI上执行操作的主活动。
例如：
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import library.DatabaseHandler;
import library.JSONParser;
import library.UserFunctions;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import com.actionbarsherlock.R;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.support.v4.app.FragmentActivity;
import android.util.Log;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class LoginTask extends AsyncTask<String, Void, Integer> {
private ProgressDialog progressDialog;
private Polling activity;
private int id = -1;
private JSONParser jsonParser;
private static String loginURL = "http://davidjkelley.net/android_api/";
private static String registerURL = "http://davidjkelley.net/android_api/";
private static String KEY_SUCCESS = "success";
private static String KEY_ERROR = "error";
private static String KEY_ERROR_MSG = "error_msg";
private static String KEY_UID = "uid";
private static String KEY_NAME = "name";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";
private int responseCode = 0;
public LoginTask(Polling activity, ProgressDialog progressDialog)
{
this.activity = activity;
this.progressDialog = progressDialog;
}
@Override
protected void onPreExecute()
{
progressDialog.show();
}
protected Integer doInBackground(String... arg0) {
EditText userName = (EditText)activity.findViewById(R.id.emailEditText);
EditText passwordEdit = (EditText)activity.findViewById(R.id.passEditText);
String email = userName.getText().toString();
String password = passwordEdit.getText().toString();
UserFunctions userFunction = new UserFunctions();
JSONObject json = userFunction.loginUser(email, password);
// check for login response
try {
if (json.getString(KEY_SUCCESS) != null) {
String res = json.getString(KEY_SUCCESS);
if(Integer.parseInt(res) == 1){
//user successfully logged in
// Store user details in SQLite Database
DatabaseHandler db = new DatabaseHandler(activity.getApplicationContext());
JSONObject json_user = json.getJSONObject("user");
//Log.v("name", json_user.getString(KEY_NAME));
// Clear all previous data in database
userFunction.logoutUser(activity.getApplicationContext());
db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL),
json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));
responseCode = 1;
// Close Login Screen
//finish();
}else{
responseCode = 0;
// Error in login
}
}
} catch (NullPointerException e) {
e.printStackTrace();
}
catch (JSONException e) {
e.printStackTrace();
}
return responseCode;
}
@Override
protected void onPostExecute(Integer responseCode)
{
EditText userName = (EditText)activity.findViewById(R.id.emailEditText);
EditText passwordEdit = (EditText)activity.findViewById(R.id.passEditText);
if (responseCode == 1) {
progressDialog.dismiss();
activity.loginReport(responseCode);
userName.setText("");
passwordEdit.setText("");
//shared prefences, store name
}
if (responseCode == 0) {
progressDialog.dismiss();
activity.loginReport(responseCode);
}
//if(responseCode == 202)
//activity.login(id);
//else
//activity.showLoginError("");
}
}
这是主要活动，您可以看到loginReport的作用：
public class Polling extends SherlockFragmentActivity {
private ViewPager mViewPager;
private TabsAdapter mTabsAdapter;
private final static String TAG = "21st Polling:";
private Button loginButton;
private Button registerButton;
private CheckBox remember;
SharedPreferences sharedPreferences;
Toast toast;
ActionBar bar;
//DatabaseHandler ;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v(TAG, "onCreate");
mViewPager = new ViewPager(this);
mViewPager.setId(R.id.pager);
setContentView(mViewPager);
bar = getSupportActionBar();
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
bar.setDisplayShowTitleEnabled(false);
bar.setDisplayShowHomeEnabled(false);
mTabsAdapter = new TabsAdapter(this, mViewPager);
mTabsAdapter.addTab(bar.newTab().setText(R.string.login),
LoginFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.economics),
EconFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.elections),
ElectionsFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.politics),
PoliticsFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.science),
ScienceFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.finance),
FinanceFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.religion),
ReligionFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.military),
MilitaryFragment.class, null);
mTabsAdapter.addTab(bar.newTab().setText(R.string.international),
InternationalFragment.class, null);
}
public void loginReport(int responseCode) {
DatabaseHandler db = new DatabaseHandler(getApplicationContext());
UserFunctions userFunctions = new UserFunctions();
Context context = getApplicationContext();
//login succeeded, sent when LoginTask doInBg sends a 1 to onPostExecute
if (responseCode == 1) {
loginButton = (Button)findViewById(R.id.loginButton);
loginButton.setText("Log Out");
int duration = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, "Logged in.", duration);
toast.show();
bar.getTabAt(0).setText(db.getUserDetails().get(db.KEY_EMAIL));
//Log.v(TAG, db.getUserDetails().toString());
}
//login failed, sent when LoginTask doInBg sends a 0 to onPostExecute
if (responseCode == 0) {
int duration = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, "Incorrect username/password", duration);
toast.show();
}
if (responseCode == 2) {
//logout button clicked, listened from within LoginFragment
//remove user from active sql db here rather than LoginFragment?!
bar.getTabAt(0).setText(R.string.login);
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, "Logged out", duration);
toast.show();
userFunctions.logoutUser(context);
}
}
答案 1 :(得分：1)
在@ Davek804的建议之后我采用的解决方案是我用这样的延迟可运行替换AsyncTask：
private Runnable mMyRunnable = new Runnable()
{
public void run()
{
finish();
}
};
Toast.makeText(getBaseContext(),errorMessage , Toast.LENGTH_LONG).show();
Handler myHandler = new Handler();
myHandler.postDelayed(mMyRunnable, 3450);
所以效果会一样。
答案 2 :(得分：0)
我找到了解决方案here
而不是使用：
task.execute();
使用：
task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, null);