我已经为我的 android 应用程序编写了一个登录功能，我想让它在 API 17 上运行，现在它在主线程上给出一个网络异常，我知道你不能在主线程上进行网络操作，我试过尝试插入线程，但似乎没有成功。所以我现在正在尝试异步任务
任何帮助建议都会很棒
package khs.studentsupport;
import java.util.HashMap;
import khs.supportapp.library.DatabaseHandler;
import khs.supportapp.library.UserFunctions;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class New_Login extends Activity{
// Progress Dialog
private ProgressDialog pDialog;
public String storedEmail="";
public String stroedPW = "";
boolean GCMFlag=false;
// Shared Preferences
SharedPreferences pref;
// Editor for Shared preferences
Editor editor;
// Context
Context _context;
// Shared pref mode
int PRIVATE_MODE = 0;
// Sharedpref file name
private static final String PREF_NAME = "AndroidHivePref";
// All Shared Preferences Keys
private static final String IS_LOGIN = "IsLoggedIn";
// User name (make variable public to access from outside)
public static final String KEY_NAME = "name";
// Email address (make variable public to access from outside)
public static final String KEY_EMAIL = "email";
// Constructor
public void SessionManager(Context context){
this._context = context;
pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
editor = pref.edit();
}
/**
* Create login session
* */
public void createLoginSession(String name, String email){
// Storing login value as TRUE
editor.putBoolean(IS_LOGIN, true);
// Storing name in pref
editor.putString(KEY_NAME, name);
// Storing email in pref
editor.putString(KEY_EMAIL, email);
// commit changes
editor.commit();
}
// Internet detector
ConnectionDetector cd;
AlertDialogManager alert = new AlertDialogManager();
Button btnLogin;
Button btnLinkToRegister;
EditText inputEmail;
EditText inputPassword;
TextView loginErrorMsg;
// JSON Response node names
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_STUDENT_ID = "studentUser";
private static String KEY_CREATED_AT = "created_at";
public HashMap<String, String> getUserDetails(){
HashMap<String, String> user = new HashMap<String, String>();
// user name
user.put(KEY_NAME, pref.getString(KEY_NAME, null));
//ID of student
user.put(KEY_STUDENT_ID, pref.getString(KEY_STUDENT_ID, null));
// user email id
user.put(KEY_EMAIL, pref.getString(KEY_EMAIL, null));
// return user
return user;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
}
// Response from Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted product
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all product by making HTTP Request
* */
class LoadAlldetails extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(New_Login.this);
pDialog.setMessage("Logging you in. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
/**
* getting user details from url
* */
protected String doInBackground(String... args) {
cd = new ConnectionDetector(getApplicationContext());
String storedEmail = Appconfig.stored_user_name.toString();
String stroedPW = Appconfig.stored_password.toString();
// Check if Internet present
if (!cd.isConnectingToInternet())
{
if((inputEmail.toString()==storedEmail)&&(inputPassword.toString()==stroedPW))
{
// Launch Dashboard Screen
Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
// Close all views before launching Dashboard
dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(dashboard);
}
}
// Importing all assets like buttons, text fields
inputEmail = (EditText) findViewById(R.id.loginEmail);
inputPassword = (EditText) findViewById(R.id.loginPassword);
//Auto fill for login only if the user has logged in before
if((Appconfig.stored_user_name.length()>0)&&(Appconfig.stored_password.length()>0))
{
inputEmail.setText(Appconfig.stored_user_name.toString());
inputPassword.setText(Appconfig.stored_password.toString());
}
// Importing all assets like buttons, text fields
btnLogin = (Button) findViewById(R.id.btnLogin);
btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegisterScreen);
loginErrorMsg = (TextView) findViewById(R.id.login_error);
// Login button Click Event
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
new LoadAlldetails().execute();
String email = inputEmail.getText().toString();
String password = inputPassword.getText().toString();
UserFunctions userFunction = new UserFunctions();
Log.d("Button", "Login");
JSONObject json = userFunction.loginUser(email, password);
//Check to see if user has put in details
if ((email.matches("")||(password.matches(""))))
{
loginErrorMsg.setText("Please enter your details ");
}
else
{ //Checks to see if first time in the app
// launces gcm activity
if (Appconfig.GCMactivity == false) {
Intent intent = new Intent();
intent.setClass(getApplicationContext(),RegisterForGCMActivity.class);
startActivity(intent);
//set to true so GCm register wont show again
Appconfig.GCMactivity=true;
}
else{
// check for login response
try {
if (json.getString(KEY_SUCCESS) != null) {
loginErrorMsg.setText("");
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(getApplicationContext());
JSONObject json_user = json.getJSONObject("user");
Appconfig.stored_user_name=json_user.getString(KEY_EMAIL);
Appconfig.stored_password = password;
if(Appconfig.email_is_set==false)
{
Appconfig.student_ID = json_user.getString(KEY_STUDENT_ID);
}
Appconfig.email_is_set=true;
// Clear all previous data in database
userFunction.logoutUser(getApplicationContext());
db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));
// Launch Dashboard Screen
Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
// Close all views before launching Dashboard
dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(dashboard);
// Close Login Screen
finish();
}else{
// Error in login
loginErrorMsg.setText("Incorrect username/password");
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}}});
GCMFlag = true;
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Intent i = new Intent(getApplicationContext(),
RegisterActivity.class);
startActivity(i);
finish();
}
});
return null;
}
public boolean isLoggedIn(){
return pref.getBoolean(IS_LOGIN, false);
}
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting user details
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
}
});
}
}
最佳答案
到目前为止我看到了很多，所以我会让你知道这些，但我知道可能还有更多。
首先，您从后台Thread 调用startActivity，因此您需要向它添加一个Context。由于它是 Activity 的内部类，您可以使用
New_Login.this.startActivity(dashboard);
但是，您应该将数据返回到 onPostExecute() 并从那里启动 Activity。
我看到的另一件事是您正在尝试从后台 Thread 更新 Views，这是不行的。您不应尝试在 doInBackground() 中更新它们。
您正在尝试错误地比较 String
if((inputEmail.toString()==storedEmail)&&(inputPassword.toString()==stroedPW))
应该是
if((inputEmail.toString().equals(storedEmail))&&(inputPassword.toString().equals(stroedPW)))
看起来您是在 AsyncTask 中声明您的 View 但这应该在您的 Activity 中完成(最有可能在 onCreate() 或 onResume()。
除非绝对必要，否则不要使用 getApplicationContext()。在 onClick() 内部，您可以使用 v.getContext()，在 Activity 内部，但在监听器外部，您可以使用 ActivitiyName.this(那里有更多选项，但我现在会保持简单)。
我的建议是，去除您的 AsyncTask 并正确设置您的 Activity，然后实现您的 AsyncTask。并且一定要仔细阅读文档。
关于java - Android AsyncTask 无法运行，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/19127970/