AndroidStudio实现简易android登录注册修改密码页面。

利用sqlite实现简易登录注册以及修改密码功能。

页面设计
登录页面activity_login.xml

界面截图

注册界面
activity_register.xml

界面截图

修改密码界面
activity_forget_password.xml

界面截图

这几个界面的按钮都进行的圆角的设计，可参考
button_shape.xml

这些背景颜色什么的可以根据自己需要进行设计哈，然后将其放在drawable文件夹下，需要用到的时候直接调用就可以了。尽量规范命名哈。
功能实现
登录功能实现，Login.java

/**
 * 账号密码登录
 */

public class Login extends AppCompatActivity {
    private EditText edt_Username, edt_PassWord;
    private Button btn_Login, btn_Forget, btn_Register;
    boolean isFlag = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        edt_Username = this.findViewById(R.id.edt_UserName);
        edt_PassWord = this.findViewById(R.id.edt_Password);
        btn_Login = this.findViewById(R.id.btn_Login);
        btn_Forget = this.findViewById(R.id.btn_Forget);
        btn_Register = this.findViewById(R.id.btn_Register);
        //用户名
        edt_Username.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {
                    //当点击用户名输入框时，清空密码框
                    edt_PassWord.setText("");
                } else {
                    String username = edt_Username.getText().toString();
                    if (username.length() < 4) {
                        Toast.makeText(Login.this, "用户名长度必须大于4,请重新输入", Toast.LENGTH_SHORT).show();
                        edt_Username.setText("");

                    }
                }
            }
        });
        //密码框
        edt_PassWord.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {

                } else {
                    String password = edt_PassWord.getText().toString();
                    if (password.length() < 6 || password.length() > 12) {
                        Toast.makeText(Login.this, "密码长度必须为6-12位,请重新输入", Toast.LENGTH_LONG).show();
                        edt_PassWord.setText("");

                    }
                }
            }
        });
        //打开数据库
        SQLiteDatabase database = openOrCreateDatabase("user.db", MODE_PRIVATE, null);
        //若不存在user表，则创建user表
        String createSQL = "create table IF NOT EXISTS user(username text,password text,password2 text,phone text)";
        database.execSQL(createSQL);//执行创表语句
        //登录事件监听
        btn_Login.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                isFlag = false;
                String username = edt_Username.getText().toString();
                String password = edt_PassWord.getText().toString();
                //判断输入是否为空，若为空，给出提示
                if (username.equals("") || password.equals("")) {
                    Toast.makeText(Login.this, "请输入账号或密码！", Toast.LENGTH_SHORT).show();
                    isFlag = true;
                }
                //查询账号密码，若数据库表为空，提示用户注册

                Cursor cursor = database.query("user", new String[]{"username,password"}, null, null, null, null, null);
                if (cursor.getCount() == 0) {
                    Toast.makeText(Login.this, "请先注册账号！", Toast.LENGTH_SHORT).show();
                isFlag=true;
                }
                //若数据库表不为空，查看用户输入的账号密码是否与数据库表中的相匹配，若匹配，登录成功，跳转到主界面
                // 否则无法登录，给出账号密码错误提示
                else {
                    while (cursor.moveToNext()) {

                        if (username.equals(cursor.getString(cursor.getColumnIndex("username"))) && password.equals(cursor.getString(cursor.getColumnIndex("password")))) {
                            Toast.makeText(Login.this, "登录成功", Toast.LENGTH_SHORT).show();
                            Intent intent = new Intent(Login.this, MainActivity.class);
                            startActivity(intent);
                            isFlag = true;
                            break;

                        }
                    }
                    if (isFlag == false) {
                        Toast.makeText(Login.this, "账号或密码错误，请重新输入", Toast.LENGTH_SHORT).show();
                    }
                }


            }


        });
        //修改密码监听事件，点击忘记密码，跳转到修改密码界面
        btn_Forget.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Login.this, Forget_Password.class);
                startActivity(intent);

            }
        });
        //注册监听事件，点击新用户，跳转到注册界面
        btn_Register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Login.this, Register.class);
                startActivity(intent);
            }
        });
    }
}

利用数据库查询账号是都存在，以及账号密码是否匹配验证，否则是登录不成功的，若没有账号就先注册账号。
注册账号功能
Register.java

/**
 * 用户注册
 */
public class Register extends AppCompatActivity {

    private Spinner sp_Provinces;
    private Spinner sp_Cities;
    private RadioGroup rdg_Sex;
    private RadioButton rb_Man, rb_Woman;
    private Button btn_Register;
    private EditText edt_UserName, edt_Password, edt_Password2, edt_Phone;
    private boolean isFlag = true;

    @Override

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_register);

        //用户名及密码
        edt_UserName = this.findViewById(R.id.edt_UserName);
        edt_Password = this.findViewById(R.id.edt_Password);
        edt_Password2 = this.findViewById(R.id.edt_Password2);

        //手机号
        edt_Phone = this.findViewById(R.id.edt_Phone);

        //出生地
        sp_Provinces = this.findViewById(R.id.sp_Provinces);
        sp_Cities = this.findViewById(R.id.sp_Cities);

        //性别选择
        rdg_Sex = this.findViewById(R.id.rdg_Sex);
        rb_Man = this.findViewById(R.id.rb_Man);
        rb_Woman = this.findViewById(R.id.rb_Woman);

        //确认注册按钮
        btn_Register = this.findViewById(R.id.btn_Register);

        //用户名输入框失焦处理
        edt_UserName.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {
                    isFlag = true;
                } else {
                    isFlag = true;
                    String username = edt_UserName.getText().toString();
                    if (username.length() < 4) {
                        Toast.makeText(Register.this, "用户名长度必须大于4,请重新输入", Toast.LENGTH_SHORT).show();
                        edt_UserName.setText("");
                    }
                }
            }
        });
        //密码输入框失焦处理
        edt_Password.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {
                    isFlag=true;
                } else {
                    isFlag = true;
                    String password = edt_Password.getText().toString();
                    if (password.length() < 6 || password.length() > 12) {
                        Toast.makeText(Register.this, "密码长度必须为6-12位,请重新输入", Toast.LENGTH_LONG).show();
                        edt_Password.setText("");
                    }
                }
            }
        });
        //确认密码输入框失焦处理
        edt_Password2.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {
                    isFlag=true;
                } else {
                    isFlag = true;
                    String password = edt_Password.getText().toString();
                    String password2 = edt_Password2.getText().toString();

                    if (!(password.equals(password2))) {
                        Toast.makeText(Register.this, "两次密码不一致,请重新输入", Toast.LENGTH_SHORT).show();
                        edt_Password2.setText("");

                    } else if (password2.length() < 6 || password2.length() > 12) {
                        Toast.makeText(Register.this, "密码长度必须为6-12位", Toast.LENGTH_LONG).show();
                        edt_Password2.setText("");
                    }

                }
            }

        });
        //手机号
        edt_Phone.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {
                    isFlag=true;
                } else {
                    isFlag = true;
                    String phone = edt_Phone.getText().toString();
                    if (!(phone.length() == 11)) {
                        Toast.makeText(Register.this, "请输入11位手机号", Toast.LENGTH_SHORT).show();
                        edt_Phone.setText("");
                    }
                }
            }
        });
        //性别处理
        rdg_Sex.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId) {
                switch (checkedId) {
                    case R.id.rb_Man:
                        Toast.makeText(Register.this, "男", Toast.LENGTH_LONG).show();
                        break;
                    case R.id.rb_Woman:
                        Toast.makeText(Register.this, "女", Toast.LENGTH_LONG).show();
                        break;
                }
            }
        });
        //出生地处理
        ArrayAdapter adapter = ArrayAdapter.createFromResource(Register.this, R.array.provinces, android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_item);
        sp_Provinces.setAdapter(adapter);
        sp_Provinces.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override//省市联动
            public void onItemSelected(AdapterView parent, View view, int position, long id) {

                if (position == 0) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.yunnan, android.R.layout.simple_spinner_item);
                    sp_Cities.setAdapter(cityAdapter);
                } else if (position == 1) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.shanxi, android.R.layout.simple_spinner_item);
                    sp_Cities.setAdapter(cityAdapter);
                } else if (position == 2) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.fj, android.R.layout.simple_spinner_item);

                    sp_Cities.setAdapter(cityAdapter);
                } else if (position == 3) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.guangxi, android.R.layout.simple_spinner_item);

                    sp_Cities.setAdapter(cityAdapter);
                } else if (position == 4) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.guangdong, android.R.layout.simple_spinner_item);

                    sp_Cities.setAdapter(cityAdapter);
                } else if (position == 5) {
                    ArrayAdapter cityAdapter = ArrayAdapter.createFromResource(Register.this, R.array.guizhou, android.R.layout.simple_spinner_item);
                    sp_Cities.setAdapter(cityAdapter);
                }

            }

            @Override
            public void onNothingSelected(AdapterView parent) {

            }
        });
        //打开数据库或创建数据库
        SQLiteDatabase database = openOrCreateDatabase("user.db", MODE_PRIVATE, null);
        String createSQL = "create table IF NOT EXISTS user(username text,password text,password2 text,phone text)";
        database.execSQL(createSQL);
        //确认注册处理
        btn_Register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //获取用户输入信息
                String username = edt_UserName.getText().toString();
                String password = edt_Password.getText().toString();
                String password2 = edt_Password2.getText().toString();
                String phone = edt_Phone.getText().toString();
                //判断用户输入是否为空，若有一个输入框为空，则给出提示信息

                if (username.equals("") || password.equals("") || password2.equals("") || phone.equals("")) {
                    Toast.makeText(Register.this, "请输入完整信息", Toast.LENGTH_SHORT).show();
                    isFlag = false;


                }
                //判断用户是否存在，若已有此账号，则不允许重复注册，否则允许注册
                Cursor cursor = database.query("user", new String[]{"username"}, null, null, null, null, null);
                while (cursor.moveToNext()) {
                    if (username.equals(cursor.getString(cursor.getColumnIndex("username")))) {
                        Toast.makeText(Register.this, "该账户已存在", Toast.LENGTH_SHORT).show();
                        isFlag = false;//
                    }
                }

                 if(!password.equals(password2)) {

                    Toast.makeText(Register.this, "两次密码不一致", Toast.LENGTH_SHORT).show();

                    //若允许注册，则将用户输入的信息，插入到数据库表（user）中,插入成功跳转到登录界面
                 }else if (!(phone.length() == 11)){
                     Toast.makeText(Register.this, "请输入11位手机号！", Toast.LENGTH_SHORT).show();
                 }
                 else if (isFlag ) {
                    ContentValues values = new ContentValues();
                    //将数据放入values中
                    values.put("username", username);
                    values.put("password", password);
                    values.put("password2", password2);
                    values.put("phone", phone);
                    //用insert()方法将values中的数据插入到user表中
                    database.insert("user", null, values);
                    Toast.makeText(Register.this, "注册成功,请登录！", Toast.LENGTH_SHORT).show();
                    Intent intent = new Intent(Register.this, Login.class);
                    startActivity(intent);
                    database.close();
                }


            }
        });
    }


}

用户注册的账号密码保存在数据库中，手机号用作验证功能，不过选择出生地的时候还没有加入数据库的哈，数据库中没有出生地属性，大家可以自行加入。

最后为忘记密码功能
Forget_Password.java

/**
 * 修改密码
 */
public class Forget_Password extends AppCompatActivity {
    private EditText edt_UserName, edt_Phone, edt_NewPassWord, edt_NewPassWord2;
    private Button btn_Confirm;
    private boolean isFlag = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_forget_password);
        //获取实例对象
        edt_UserName = this.findViewById(R.id.edt_UserName);
        edt_Phone = this.findViewById(R.id.edt_Phone);
        edt_NewPassWord = this.findViewById(R.id.edt_NewPassWord);
        edt_NewPassWord2 = this.findViewById(R.id.edt_NewPassWord2);
        btn_Confirm = this.findViewById(R.id.btn_Confirm);

        //用户名
        edt_UserName.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {

                } else {
                    String username = edt_UserName.getText().toString();
                    if (username.length() < 4) {
                        Toast.makeText(Forget_Password.this, "用户名长度必须大于4,请重新输入", Toast.LENGTH_SHORT).show();
                        edt_UserName.setText("");
                    }
                }
            }
        });

        //手机号，用作用户修改密码验证条件
        edt_Phone.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {


                } else {
                    String phone = edt_Phone.getText().toString();
                    if (!(phone.length() == 11)) {
                        Toast.makeText(Forget_Password.this, "请输入11位手机号", Toast.LENGTH_SHORT).show();
                        edt_Phone.setText("");
                    }


                }
            }
        });

        //新密码
        edt_NewPassWord.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {

                } else {
                    String newPassword = edt_NewPassWord.getText().toString();
                    if (newPassword.length() < 6 || newPassword.length() > 12) {
                        Toast.makeText(Forget_Password.this, "密码长度必须为6-12位,请重新输入", Toast.LENGTH_LONG).show();
                        edt_NewPassWord.setText("");
                    }
                }
            }
        });
        //确认新密码
        edt_NewPassWord2.setOnFocusChangeListener(new View.OnFocusChangeListener() {
            @Override
            public void onFocusChange(View v, boolean hasFocus) {
                if (hasFocus) {

                } else {
                    String newPassword = edt_NewPassWord.getText().toString();
                    String newPassword2 = edt_NewPassWord2.getText().toString();

                    if (!(newPassword.equals(newPassword2))) {
                        Toast.makeText(Forget_Password.this, "两次密码不一致,请重新输入", Toast.LENGTH_SHORT).show();
                        edt_NewPassWord2.setText("");

                    } else if (newPassword2.length() < 6 || newPassword2.length() > 12) {
                        Toast.makeText(Forget_Password.this, "密码长度必须为6-12位", Toast.LENGTH_LONG).show();
                        edt_NewPassWord2.setText("");
                    }

                }
            }
        });
        //确认修改密码，若用户名与此手机号匹配，则可以修改密码，否则不允许修改密码
        SQLiteDatabase database = openOrCreateDatabase("user.db", MODE_PRIVATE, null);
        btn_Confirm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String username = edt_UserName.getText().toString();
                String password = edt_NewPassWord.getText().toString();
                String password2 = edt_NewPassWord2.getText().toString();
                String phone = edt_Phone.getText().toString();
                //判断用户输入是否为空，若有一个输入框为空，则给出提示信息
                if (username.equals("") || password.equals("") || password2.equals("") || phone.equals("")) {
                    Toast.makeText(Forget_Password.this, "请输入完整信息", Toast.LENGTH_SHORT).show();

                }else if (!(password.equals(password2))){
                    Toast.makeText(Forget_Password.this, "两次密码不一致", Toast.LENGTH_SHORT).show();

                }else {

                Cursor cursor = database.query("user", new String[]{"username,phone"}, null, null, null, null, null);
                while (cursor.moveToNext()) {
                    //判断用户名和手机号是否匹配
                    //首先利用查询语句，查询username和phone，若手机号和用户名匹配，则允许修改密码。
                    if ((username.equals(cursor.getString(cursor.getColumnIndex("username")))
                            && phone.equals(cursor.getString(cursor.getColumnIndex("phone"))))) {
                        ContentValues values = new ContentValues();
                        //将数据放入values中
                        String Username = edt_UserName.getText().toString();
                        values.put("password", password);
                        values.put("password2", password2);
                        //用update()方法将values中的数据更新对应的用户名密码
                        database.update("user", values, "username=?", new String[]{username});
                        Toast.makeText(Forget_Password.this, "修改密码成功,请登录！", Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(Forget_Password.this, Login.class);
                        isFlag = true;
                        startActivity(intent);
                        database.close();
                        break;

                    }
                    isFlag = false;
                }
                }
                if (isFlag == false) {
                    Toast.makeText(Forget_Password.this, "用户名与手机号不匹配，修改失败", Toast.LENGTH_SHORT).show();
                }


            }
        });
    }
}

手机号为用户注册时的手机号，暂时用手机号作为验证功能，用户的账号和手机号与数据库的匹配就允许修改密码。
地名资源文件
放在res文件夹的values的string.xml文件

    Words
    
        云南省
        山西省
        福建省
        广西壮族自治区
        广东省
        贵州省
    

    


        昆明市
        曲靖市
        玉溪市
        昭通市
        保山市
        丽江市

    

    

        南宁市
        桂林市
        柳州市
        北海市
        钦州市
        玉林市
        百色市
        河池市
        防城港市
    
    

        大同市
        临汾市
        太原市
        阳泉市
        长治市
        晋城市
        朔州市
        晋中市
        运城市
    
    
        福州市
        厦门市
        泉州市
        漳州市
        福清市
        莆田市
        宁德市
    
    
        广州市
        深圳市
        中山市
        佛山市
        惠州市
        珠海市
        汕头市
    
    
        贵阳市
        遵义市
        安顺市
        毕节市
        铜仁市
        六盘水市
    

大家有什么问题以及建议欢迎讨论留言。