我想在我的应用中实现一个登录表单，所以我尝试使用Android Studio向导生成的代码来创建一个新的Login类型的Activity。我认为Eclipse生成的代码几乎是一样的。
不幸的是，生成的代码没有提供预期的结果：我创建了一个很好的简单登录表单，但密码正确或错误，它不会从登录表单移动。
此外，我注意到没有创建“注册”表单。
看了一下，然后分析代码，我终于得到了它的工作：）
请参阅下面的回复。
答案 0 :(得分：43)
要在使用错误的用户/密码时使登录活动失败，并在成功时转到主要活动，您需要对生成的代码进行以下更正：
AndroidManifest.xml：
将以下代码从主活动移至LoginActivity部分：
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
然后编辑LoginActivity.java并执行以下更改：
在doInBackground方法内，最后将返回的值从true替换为false
@Override
protected Boolean doInBackground(Void... params) {
for (String credential : DUMMY_CREDENTIALS) {
String[] pieces = credential.split(":");
if (pieces[0].equals(mEmail)) {
// Account exists, return true if the password matches.
return pieces[1].equals(mPassword);
}
}
// TODO: register the new account here.
return false;
}
然后在onPostExecute方法上，在finish();：
@Override
protected void onPostExecute(final Boolean success) {
mAuthTask = null;
showProgress(false);
if (success) {
finish();
Intent myIntent = new Intent(LoginActivity.this,MyMainActivity.class);
LoginActivity.this.startActivity(myIntent);
} else {
mPasswordView.setError(getString(R.string.error_incorrect_password));
mPasswordView.requestFocus();
}
}
现在，使用以下user:password凭据之一登录成功：
其他user:password尝试应说明密码错误并留在登录页面。
我们现在将从数据库（SQLite）而不是静态变量获取登录信息。这将允许我们在设备上注册多个用户。
首先，创建一个新的User.java类：
package com.clinsis.onlineresults.utils;
/**
* Created by csimon on 5/03/14.
*/
public class User {
public long userId;
public String username;
public String password;
public User(long userId, String username, String password){
this.userId=userId;
this.username=username;
this.password=password;
}
}
然后创建或更新您的SQLite帮助程序（在我的案例中为DBTools.java）类：
package com.clinsis.onlineresults.utils;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* Created by csimon on 12/11/13.
*/
public class DBTools extends SQLiteOpenHelper {
private final static int DB_VERSION = 10;
public DBTools(Context context) {
super(context, "myApp.db", null,DB_VERSION);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String query = "create table logins (userId Integer primary key autoincrement, "+
" username text, password text)";
sqLiteDatabase.execSQL(query);
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
try{
System.out.println("UPGRADE DB oldVersion="+oldVersion+" - newVersion="+newVersion);
onCreate(sqLiteDatabase);
if (oldVersion<10){
String query = "create table logins (userId Integer primary key autoincrement, "+
" username text, password text)";
sqLiteDatabase.execSQL(query);
}
}
catch (Exception e){e.printStackTrace();}
}
@Override
public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// super.onDowngrade(db, oldVersion, newVersion);
System.out.println("DOWNGRADE DB oldVersion="+oldVersion+" - newVersion="+newVersion);
}
public User insertUser (User queryValues){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("username", queryValues.username);
values.put("password", queryValues.password);
queryValues.userId=database.insert("logins", null, values);
database.close();
return queryValues;
}
public int updateUserPassword (User queryValues){
SQLiteDatabase database = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("username", queryValues.username);
values.put("password", queryValues.password);
queryValues.userId=database.insert("logins", null, values);
database.close();
return database.update("logins", values, "userId = ?", new String[] {String.valueOf(queryValues.userId)});
}
public User getUser (String username){
String query = "Select userId, password from logins where username ='"+username+"'";
User myUser = new User(0,username,"");
SQLiteDatabase database = this.getReadableDatabase();
Cursor cursor = database.rawQuery(query, null);
if (cursor.moveToFirst()){
do {
myUser.userId=cursor.getLong(0);
myUser.password=cursor.getString(1);
} while (cursor.moveToNext());
}
return myUser;
}
}
注意：DB_VERSION用于检测数据库架构的升级/降级;）
然后修改LoginActivity.java，如下所示：
添加以下导入：
import android.widget.Toast;
import com.clinsis.onlineresults.utils.DBTools;
import com.clinsis.onlineresults.utils.User;
添加一个新变量：
private User myUser;
删除DUMMY_CREDENTIALS变量声明。
在attemptLogin方法中，在调用UserLoginTask时添加上下文：
mAuthTask = new UserLoginTask(email, password, this);
使用以下代码替换内部UserLoginTask类：
/**
* Represents an asynchronous login/registration task used to authenticate
* the user.
*/
public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {
private final String mEmail;
private final String mPassword;
private final Context mContext;
UserLoginTask(String email, String password, Context context) {
mEmail = email;
mPassword = password;
mContext= context;
}
@Override
protected Boolean doInBackground(Void... params) {
DBTools dbTools=null;
try{
dbTools = new DBTools(mContext);
myUser = dbTools.getUser(mEmail);
if (myUser.userId>0) {
// Account exists, check password.
if (myUser.password.equals(mPassword))
return true;
else
return false;
} else {
myUser.password=mPassword;
return true;
}
} finally{
if (dbTools!=null)
dbTools.close();
}
// return false if no previous checks are true
return false;
}
@Override
protected void onPostExecute(final Boolean success) {
mAuthTask = null;
showProgress(false);
if (success) {
if (myUser.userId>0){
finish();
Intent myIntent = new Intent(LoginActivity.this,ReportListActivity.class);
LoginActivity.this.startActivity(myIntent);
} else {
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
switch (which){
case DialogInterface.BUTTON_POSITIVE:
DBTools dbTools=null;
try{
finish();
dbTools = new DBTools(mContext);
myUser=dbTools.insertUser(myUser);
Toast myToast = Toast.makeText(mContext,R.string.updatingReport, Toast.LENGTH_SHORT);
myToast.show();
Intent myIntent = new Intent(LoginActivity.this,ReportListActivity.class);
LoginActivity.this.startActivity(myIntent);
} finally{
if (dbTools!=null)
dbTools.close();
}
break;
case DialogInterface.BUTTON_NEGATIVE:
mPasswordView.setError(getString(R.string.error_incorrect_password));
mPasswordView.requestFocus();
break;
}
}
};
AlertDialog.Builder builder = new AlertDialog.Builder(this.mContext);
builder.setMessage(R.string.confirm_registry).setPositiveButton(R.string.yes, dialogClickListener)
.setNegativeButton(R.string.no, dialogClickListener).show();
}
} else {
mPasswordView.setError(getString(R.string.error_incorrect_password));
mPasswordView.requestFocus();
}
}
@Override
protected void onCancelled() {
mAuthTask = null;
showProgress(false);
}
}
在strings.xml中，添加：
<string name="confirm_registry">Email not found. You want to create a new user with that email and password?</string>
<string name="yes">Yes</string>
<string name="no">No</string>
我希望我没有忘记任何事情......它对我来说很好：D
如果数据库中没有电子邮件，则会建议注册，否则将检查电子邮件与密码。
玩得开心：D