我正在开发一个需要用户登录的应用程序。登录通过网址正常工作。 但是，当我添加AsyncTask来添加进度对话框时，应用程序不会改变intent。我已经尝试了所有可能的方法，我都知道是徒劳的。 下面是代码：
package com.epolicing;
import java.util.ArrayList;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class LoginActivity extends Activity implements OnClickListener{
Button loginButton;
EditText usernme,passwrd;
TextView error;
String username,password;
static final int Dialog_logging_in=1;
boolean userverified=false;
// Session Manager Class
SessionManager session;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
session = new SessionManager(getApplicationContext());
loginButton = (Button) findViewById(R.id.loginButton);
usernme = (EditText) findViewById(R.id.UserName);
passwrd=(EditText) findViewById(R.id.password);
username=usernme.getText().toString().trim();
password=passwrd.getText().toString().trim();
error=(TextView)findViewById(R.id.errorTextView);
loginButton.setOnClickListener(this);
}
protected Dialog onCreateDialog(int id){
Dialog dialog = null;
switch(id){
case Dialog_logging_in:
ProgressDialog.show(LoginActivity.this,"","Authenticating user...");
break;
default:
dialog=null;
}
return dialog;
}
public void onClick(View v) {
switch(v.getId()){
case R.id.loginButton:
String user,pass;
user=usernme.getText().toString();
pass=passwrd.getText().toString();
if(user.equals("")||pass.equals("")){
message();
}
else {
new log_in().execute(this);
}
break;
}
}
//login method
public void login() {
ArrayList<NameValuePair>postParameters=new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("username",usernme.getText().toString()));
postParameters.add(new BasicNameValuePair("password",passwrd.getText().toString().trim()));
//String valid="1";
String response=null;
try{
response=CustomHttpClient.executeHttpPost("http://10.0.2.2/epolicing/tologin.php",postParameters);
String res=response.toString();
res=res.replaceAll("\\s+","");
if(res.equals("0")) {
error.setText("Wrong password or username combination");
}
else {
String usern=usernme.getText().toString().trim();
session.createLoginSession(usern,res);
userverified=true;
//Intent intent=new Intent(LoginActivity.this,menu.class);
//startActivity(intent);
}
}
catch(Exception e){
error.setText(e.toString());
}
}
public void message(){
Context context=getApplicationContext();
CharSequence text="username and/or password cannot be blank";
int duration=Toast.LENGTH_LONG;
Toast toast=Toast.makeText(context, text, duration);
toast.show();
}
private class log_in extends AsyncTask<LoginActivity,Void,LoginActivity>{
@Override
protected void onPreExecute(){
showDialog(Dialog_logging_in);
}
@Override
protected LoginActivity doInBackground(LoginActivity... Params) {
login();
return null;
}
protected void onPostExecute(LoginActivity params){
super.onPostExecute(params);
//dismissDialog(Dialog_logging_in);
if(userverified==true){
Intent intent=new Intent(LoginActivity.this,menu.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
LoginActivity.this.startActivity(intent);
}
}
}
}
这是日志：
01-20 19:36:53.685: E/WindowManager(1191): Activity com.epolicing.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@40555c68 that was originally added here
01-20 19:36:53.685: E/WindowManager(1191): android.view.WindowLeaked: Activity com.epolicing.LoginActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@40555c68 that was originally added here
01-20 19:36:53.685: E/WindowManager(1191): at android.view.ViewRoot.<init>(ViewRoot.java:258)
01-20 19:36:53.685: E/WindowManager(1191): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:148)
01-20 19:36:53.685: E/WindowManager(1191): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
01-20 19:36:53.685: E/WindowManager(1191): at android.view.Window$LocalWindowManager.addView(Window.java:424)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.Dialog.show(Dialog.java:241)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.ProgressDialog.show(ProgressDialog.java:107)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.ProgressDialog.show(ProgressDialog.java:90)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.ProgressDialog.show(ProgressDialog.java:85)
01-20 19:36:53.685: E/WindowManager(1191): at com.epolicing.LoginActivity.onCreateDialog(LoginActivity.java:50)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.Activity.onCreateDialog(Activity.java:2482)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.Activity.createDialog(Activity.java:882)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.Activity.showDialog(Activity.java:2557)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.Activity.showDialog(Activity.java:2524)
01-20 19:36:53.685: E/WindowManager(1191): at com.epolicing.LoginActivity$log_in.onPreExecute(LoginActivity.java:120)
01-20 19:36:53.685: E/WindowManager(1191): at android.os.AsyncTask.execute(AsyncTask.java:391)
01-20 19:36:53.685: E/WindowManager(1191): at com.epolicing.LoginActivity.onClick(LoginActivity.java:71)
01-20 19:36:53.685: E/WindowManager(1191): at android.view.View.performClick(View.java:2485)
01-20 19:36:53.685: E/WindowManager(1191): at android.view.View$PerformClick.run(View.java:9080)
01-20 19:36:53.685: E/WindowManager(1191): at android.os.Handler.handleCallback(Handler.java:587)
01-20 19:36:53.685: E/WindowManager(1191): at android.os.Handler.dispatchMessage(Handler.java:92)
01-20 19:36:53.685: E/WindowManager(1191): at android.os.Looper.loop(Looper.java:123)
01-20 19:36:53.685: E/WindowManager(1191): at android.app.ActivityThread.main(ActivityThread.java:3683)
01-20 19:36:53.685: E/WindowManager(1191): at java.lang.reflect.Method.invokeNative(Native Method)
01-20 19:36:53.685: E/WindowManager(1191): at java.lang.reflect.Method.invoke(Method.java:507)
01-20 19:36:53.685: E/WindowManager(1191): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-20 19:36:53.685: E/WindowManager(1191): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-20 19:36:53.685: E/WindowManager(1191): at dalvik.system.NativeStart.main(Native Method)
帮助将受到高度赞赏。谢谢。
答案 0 :(得分：14)
无需从doInBackground返回当前的Activity实例，因为AsyncTask是Activity的内部类，因此您只需使用LoginActivity.this启动下一个Activity，将AsyncTask类更改为：
private class log_in extends AsyncTask<String,Void,String>{
ProgressDialog pDialog;
@Override
protected void onPreExecute(){
pDialog = new ProgressDialog(LoginActivity.this);
pDialog.setMessage("Authenticating user...");
pDialog.show();
}
@Override
protected String doInBackground(String... params) {
login();
return null;
}
protected void onPostExecute(String params){
super.onPostExecute(params);
pDialog.dismiss();
if(userverified==true){
Intent intent=new Intent(LoginActivity.this,menu.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
LoginActivity.this.startActivity(intent);
}
else{
error.setText("Wrong password or username combination");
}
}
}
因为无法从doInBackground更新UI元素，而您尝试在login()方法中设置textview文本而不是更改Textview文本，只需创建userverified==false