我正在创建一个应用程序并使用共享首选项。前两个活动是登录屏幕和重置密码屏幕。 登录用户名和密码最初是＆＃34;用户＆＃34;。当用户登录时，他们被重定向到重置密码活动，他们必须通过输入密码更改密码，确认密码，并输入原始密码（用户）。 新密码将保存到共享首选项，从而覆盖原始密码。
我的问题是，当我在模拟器上运行应用程序时，无论我使用什么用户名和密码，它每次都会崩溃。到目前为止，这是代码：
登录活动
public class SignIn extends Activity {
static final String MY_PREFS = "Prefs";
static final String SAVED_PASSWORD = "Password";
// Object used for Shared Preferences
SharedPreferences appPrefs;
// First method called when the activity is opened
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sign_in);
// get Shared Preferences for this application
SharedPreferences appPrefs = getSharedPreferences(SAVED_PASSWORD, 0);
}
// Called when the "LOGIN" button is pressed
public void loginBtnClicked(View v){
// The username and password that is to be used on initial use of the application
String userName = "user";
String original_password = "user";
// Get the settings for the password string from the prefs and assign a name
String existingPassword = appPrefs.getString(SAVED_PASSWORD,null);
// Widgets used during the login phase
EditText usernameField = (EditText)findViewById(R.id.editText_username);
EditText passwordField = (EditText)findViewById(R.id.editText_password);
Button reset =(Button)findViewById(R.id.goToReset);
Button next =(Button)findViewById(R.id.next);
// Get the text from the editText fields,convert to a string, and assign a name
String name = usernameField.getText().toString();
String pass = passwordField.getText().toString();
// If either field is empty inform user and return to give them another go
if (name.equals(null)|| pass.equals(null)){
Toast.makeText(this,"ERROR!!, all fields must be filled",Toast.LENGTH_SHORT).show();
return;
}
//========================================
// VALIDATION OF LOGIN INFORMATION SUBMITTED
//========================================
// If there NOT information saved to preferences.
if (existingPassword.equals(null)){
// IF the username and password are "USER"
if(name.equals(userName) && pass.equals(original_password)){
// Create an intent to open the next window
Intent reset_intent = new Intent(this,ResetPassword.class);
// Start the new activity
startActivity(reset_intent);
}
}
//If there IS information saved to preferences.
else if (existingPassword!=null){
//IF the username is "USER"...
if(name.equals(userName) ){
// If the password is what is saved to preferences.
if(pass.equals(existingPassword)){
// Make buttons visible for user choice
reset.setVisibility(View.VISIBLE);
next.setVisibility(View.VISIBLE);
}
else{
// Display a toast pop-up to show the text from the intent
Toast.makeText(this,"ERROR!!,password incorrect",Toast.LENGTH_SHORT).show();
}
}
else{
// Display a toast pop-up to show the text from the intent
Toast.makeText(this,"ERROR!!,username incorrect",Toast.LENGTH_SHORT).show();
}
}
}
// Called when the "GO TO RESET" button is pressed
public void ResetBtnClicked(View v){
// Create an intent to open the next window
Intent reset_intent = new Intent(this,ResetPassword.class);
// Start the new activity
startActivity(reset_intent);
}
//Called when the "NEXT" button is pressed
public void onNextBtnClicked (){
// Create an intent to open the next window
Intent personal_intent = new Intent(this,PersonalDetails.class);
// Start the new activity
startActivity(personal_intent);
}
}
public class ResetPassword extends Activity {
public static final String MY_PREFS = "Prefs";
public static final String SAVED_PASSWORD = "Password";
// for shared preferences
SharedPreferences appPrefs;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_reset_password);
// get shared prefs for this application
SharedPreferences appPrefs = getSharedPreferences(SAVED_PASSWORD, 0);
}
//Save the new password
public void resetBtnClicked(View v){
// Widgets used during password reset.
EditText newPassword = (EditText)findViewById(R.id.editText_newPassword);
EditText confirmPassword = (EditText)findViewById(R.id.editText_retypePassword);
EditText currentPassword = (EditText)findViewById(R.id.editText_existingPassword);
// Get the text from the editText fields,convert to a string, and assign a name
String newPass = newPassword.getText().toString();
String confirmPass = confirmPassword.getText().toString();
String currentPass = currentPassword.getText().toString();
// get the settings for the password string from the prefs
String existingPassword = appPrefs.getString(SAVED_PASSWORD,null);
//========================================
// VALIDATION OF PASSWORD INFORMATION SUBMITTED
//========================================
// if the current password submitted is the same as the saved password
if(currentPass.equals(existingPassword)){
//if the new password is the same in both the new and re-enter fields
if(newPass.equals(confirmPass)){
//save the preferences
//get the editor for prefs
Editor prefsEditor = appPrefs.edit();
// update the prefs with the new settings
prefsEditor.putString(SAVED_PASSWORD,newPass);
prefsEditor.commit();
// Create an intent to open the next window
Intent personal_intent = new Intent(this,PersonalDetails.class);
// display a toast pop-up to show the text from the intent
Toast.makeText(this,"New password saved",Toast.LENGTH_SHORT).show();
// Start the new activity
startActivity(personal_intent);
}
// If the passwords do not match
else {
// display a toast pop-up to show the text from the intent
Toast.makeText(this,"Passwords do not match!!",Toast.LENGTH_SHORT).show();
}
}
// if the current password is incorrect
else{
// display a toast pop-up to show the text from the intent
Toast.makeText(this,"Incorrect password used!!",Toast.LENGTH_SHORT).show();
}
// If there is no password saved to prefs.
if (existingPassword.equals(null)){
if(newPass.equals(confirmPass)){
//save the preferences
//get the editor for prefs
Editor prefsEditor = appPrefs.edit();
// update the prefs with the new settings
prefsEditor.putString(SAVED_PASSWORD,newPass);
prefsEditor.commit();
// Create an intent to open the next window
Intent personal_intent = new Intent(this,PersonalDetails.class);
// display a toast pop-up to show the text from the intent
Toast.makeText(this,"New password saved",Toast.LENGTH_SHORT).show();
// Start the new activity
startActivity(personal_intent);
}
else{
// display a toast pop-up to show the text from the intent
Toast.makeText(this,"Passwords do not match!!",Toast.LENGTH_SHORT).show();
}
}
}
}
任何帮助都会非常感谢大家。
答案 0 :(得分：0)
通过查看您的代码应用程序崩溃在这些行bcz您正在创建/初始化local variable具有相同的实例变量名称即。 appPrefs和实例变量appPrefs仍为空（默认值）
1。 登录活动
String existingPassword = appPrefs.getString(SAVED_PASSWORD,null);
2。 ResetPassword 活动
String existingPassword = appPrefs.getString(SAVED_PASSWORD,null);
原因：
对于这两个活动，您没有初始化appPrefs对象，这是一个实例变量
解决方案：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_reset_password);
// get shared prefs for this application
//your code creates a new local variable with same instance variable name ie. appPrefs
//SharedPreferences appPrefs = getSharedPreferences(SAVED_PASSWORD, 0);
//changes : init instance variable
appPrefs = getSharedPreferences(SAVED_PASSWORD, 0);
}