diff --git a/src/net/micode/notes/ui/Changepassword.java b/src/net/micode/notes/ui/Changepassword.java
new file mode 100644
index 0000000..3f344de
--- /dev/null
+++ b/src/net/micode/notes/ui/Changepassword.java
@@ -0,0 +1,78 @@
+package net.micode.notes.ui;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.view.View;
+import android.view.WindowManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import net.micode.notes.R;
+
+public class Changepassword extends Activity{
+    EditText OldPassword;
+    EditText NewPassword;
+    EditText AckPassword;
+    Button Acknowledged;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState){
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_change_password);
+        getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE
+                | WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
+        OldPassword=(EditText) findViewById(R.id.old_password);
+        NewPassword=(EditText) findViewById(R.id.new_password);
+        AckPassword=(EditText) findViewById(R.id.ack_password);
+        Acknowledged=(Button)findViewById(R.id.Acknowledged);
+        Acknowledged.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String old_password = OldPassword.getText().toString();
+                String new_password = NewPassword.getText().toString();
+                String ack_password = AckPassword.getText().toString();
+                SharedPreferences pref = getSharedPreferences("user
+                        management",MODE_PRIVATE);
+                        String login_password = pref.getString("password","");
+                if(old_password.equals("")==true || new_password.equals("")==true
+                        || ack_password.equals("")==true) {
+                    Toast.makeText(ChangingPassword.this, "密码不能为空",
+                            Toast.LENGTH_SHORT).show();
+                }
+                else if (new_password.equals(ack_password) == false) {
+                    Toast.makeText(ChangingPassword.this, "新建密码与重复密码不匹配，
+                            请重新输入密码", Toast.LENGTH_SHORT).show();
+                            AckPassword.setText("");
+                }
+                else if(old_password.equals(login_password) == false){
+                    Toast.makeText(ChangingPassword.this, "原有密码错误，请重新输入
+                            密码", Toast.LENGTH_SHORT).show();
+                            OldPassword.setText("");
+                }
+                else if (new_password.equals(ack_password) == true &&
+                        old_password.equals(login_password) == true){
+                    SharedPreferences.Editor editor=getSharedPreferences("user
+                            management", MODE_PRIVATE).edit();
+                            editor.putString("password",new_password);
+                    editor.apply();
+                    Toast.makeText(ChangingPassword.this, "修改密码成功",
+                            Toast.LENGTH_SHORT).show();
+                    Intent intent=new
+                            Intent(ChangingPassword.this,NotesListActivity.class);
+                    startActivity(intent);
+                    finish();
+                }
+            }
+        });
+    }
+    @Override
+    public void onBackPressed(){
+        Intent intent=new Intent(ChangingPassword.this,NotesListActivity.class);
+        startActivity(intent);
+        finish();
+    }
+}
+
diff --git a/src/net/micode/notes/ui/DeletingPassword.java b/src/net/micode/notes/ui/DeletingPassword.java
new file mode 100644
index 0000000..0058bba
--- /dev/null
+++ b/src/net/micode/notes/ui/DeletingPassword.java
@@ -0,0 +1,65 @@
+package net.micode.notes.ui;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.view.View;
+import android.view.WindowManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import net.micode.notes.R;
+
+public class DeletingPassword extends Activity {
+    EditText Dt_password;
+    Button Acknowledged;
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_delete_password);
+        getWindow().setSoftInputMode(
+                WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE
+                        | WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
+        Dt_password=(EditText) findViewById(R.id.thepassword);
+        Acknowledged=(Button)findViewById(R.id.Dt_Acknowledged);
+        Acknowledged.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String text02 = Dt_password.getText().toString();
+                if(text02.equals("")==true)
+                    Toast.makeText(DeletingPassword.this, "密码不能为空",
+                            Toast.LENGTH_SHORT).show();
+                SharedPreferences pref=getSharedPreferences("user
+                        management",MODE_PRIVATE);
+                        String password = pref.getString("password","");
+                if(password.equals("")==false&&password.equals(text02)==true){
+                    SharedPreferences.Editor editor=getSharedPreferences("user
+                            management",
+                            MODE_PRIVATE).edit();
+                    editor.putBoolean("user",false);//false 表示已经设置登录密码
+                    editor.putString("password","");
+                    editor.apply();
+                    Toast.makeText(DeletingPassword.this, "已经删除登录密码",
+                            Toast.LENGTH_SHORT).show();
+                    Intent intent=new
+                            Intent(DeletingPassword.this,NotesListActivity.class);
+                    startActivity(intent);
+                    finish();
+                }
+                else{
+                    Toast.makeText(DeletingPassword.this, "密码错误",
+                            Toast.LENGTH_SHORT).show();
+                    Dt_password.setText("");//把密码框内输入过的错误密码清空
+                }
+            }
+        });
+    }
+    @Override
+    public void onBackPressed() {
+        Intent intent=new Intent(DeletingPassword.this,NotesListActivity.class);
+        startActivity(intent);
+        finish();
+    }
+}
\ No newline at end of file
diff --git a/src/net/micode/notes/ui/LoginActivity.java b/src/net/micode/notes/ui/LoginActivity.java
new file mode 100644
index 0000000..98555f8
--- /dev/null
+++ b/src/net/micode/notes/ui/LoginActivity.java
@@ -0,0 +1,54 @@
+package net.micode.notes.ui;
+
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.view.View;
+import android.view.WindowManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import net.micode.notes.R;
+
+public class LoginActivity {
+
+    EditText lgn_password;
+    Button lgn_login;
+
+    @Override
+    protected void onCreate(Bundle saverInstanceState) {
+        super.onCreate(savedInstanceState);
+        SharedPreferences pref = getSharedPreferences("user managemet", MODE_PRIVATE);
+        boolean User_boolean = pref.getBoolean("user", false); //检查用户是否设置了密码
+        if (!User_boolean) {  //如果用户没有设置密码,则直接跳转到便签主界面
+            Intent intent = new Intent(LoginActivity.this, NotesListActivity.class);
+            startActivity(intent);
+            finish();
+        }
+
+        setContentView(R.layout.activity_login);
+        getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE | WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE);
+        lgn_password = (EditTExt) findViewById(R.id.lgn_password);
+        lgn_login = (Button) findViewById(R.id.login);
+        lgn_login.setOnClickListener(new View.OnClickListener() {
+                                         @Override
+                                         public void onClick(View v) {
+                                             SharedPreferences pref = getSharedPreferences("user management", MODE_PRIVATE);
+                                             String password = pref.getString("password", "");
+                                             if (password.equals(" ") == false && password.equals(lgn_password.getText().toString()) == true) {
+                                                 Intent intent = new Intent(LoginActivity.this, NotesListActivity.class);
+                                                 startActivity(intent);
+                                                 finish();
+                                             } else {
+                                                 Toast.makeText(LoginActivity.this, "密码错误", Toast.LENGTH_SHORT).show();
+                                                 lgn_password.setText(""); //清空密码框内的输入
+                                             }
+
+                                         }
+                                     }
+        );
+    }
+}
+
+
diff --git a/src/net/micode/notes/ui/SettingPassword.java b/src/net/micode/notes/ui/SettingPassword.java
new file mode 100644
index 0000000..abc2fe5
--- /dev/null
+++ b/src/net/micode/notes/ui/SettingPassword.java
@@ -0,0 +1,66 @@
+package net.micode.notes.ui;
+
+import static android.content.Context.MODE_PRIVATE;
+import android.app.Activity;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.View;
+import android.view.WindowManager;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.Toast;
+
+import net.micode.notes.R;
+
+
+public class SettingPassword extends Activity {
+    EditText password;
+    EditText password_ack;
+    Button acknowledge;
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_set_loginpassword);
+        getWindow().setSoftInputMode(
+                WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE
+                        | WindowManager.LayoutParams.SOFT_INPUT_STATE_VISIBLE);
+        password = (EditText) findViewById(R.id.password);
+        password_ack = (EditText) findViewById(R.id.password_ack);
+        acknowledge = (Button)findViewById(R.id.acknowledge);
+        acknowledge.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                String text02 = password.getText().toString();
+                String text03 = password_ack.getText().toString();
+                if(text02.equals("")==true) {
+                    Toast.makeText(SettingPassword.this, "密码不能为空", Toast.LENGTH_SHORT).show();
+                }
+                else if (text02.equals(text03) == false) {
+                    Toast.makeText(SettingPassword.this, "密码错误，请重新输入密码 ", Toast.LENGTH_SHORT).show();
+                            password_ack.setText("");
+                }
+                else if (text02.equals(text03) == true){
+                    SharedPreferences.Editor editor=getSharedPreferences("user management", MODE_PRIVATE).edit();
+                    editor.putBoolean("user",true); //true 表示已经设置登录密码
+                    editor.putString("password",text02);
+                    editor.apply();
+                    Log.d("RegisterLoginPassword","password is "+text02);
+                    Toast.makeText(SettingPassword.this, "密码设置成功",
+                            Toast.LENGTH_SHORT).show();
+                    Intent intent=new
+                            Intent(SettingPassword.this,NotesListActivity.class);
+                    startActivity(intent);
+                    finish();
+                }
+            }
+        });
+    }
+    @Override
+    public void onBackPressed() {
+        Intent intent=new Intent(SettingPassword.this,NotesListActivity.class);
+        startActivity(intent);
+        finish();
+    }
+}
\ No newline at end of file