APP开发

1. 创建菜单资源文件

在 res/menu 目录下创建一个新的菜单资源文件 main_menu.xml。

main_menu.xml

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/nav_my_notes" android:title="我的"/> <item android:id="@+id/nav_settings" android:title="设置"/> </menu>

2. 修改 `MainActivity` 布局文件

在 activity_main.xml 中，设置 Toolbar 以支持菜单的显示。

activity_main.xml

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <androidx.appcompat.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/colorPrimary" android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"/> <FrameLayout android:id="@+id/fragment_container" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_below="@id/toolbar"/> </RelativeLayout>

3. 修改 `MainActivity` 代码

MainActivity.java

package com.example.notesapp; import android.content.Intent; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.widget.Toast; import androidx.annotation.NonNull; import androidx.appcompat.app.AppCompatActivity; import androidx.fragment.app.Fragment; public class MainActivity extends AppCompatActivity { 
    private String username; @Override protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); // 设置Toolbar androidx.appcompat.widget.Toolbar toolbar = findViewById(R.id.toolbar); setSupportActionBar(toolbar); username = getIntent().getStringExtra("username"); if (username == null) { 
    Toast.makeText(this, "请先登录", Toast.LENGTH_SHORT).show(); startActivity(new Intent(this, LoginActivity.class)); finish(); return; } // 默认显示"我的"页面 if (savedInstanceState == null) { 
    getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new MyNotesFragment()).commit(); } } @Override public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.main_menu, menu); return true; } @Override public boolean onOptionsItemSelected(@NonNull MenuItem item) { 
    Fragment selectedFragment = null; switch (item.getItemId()) { 
    case R.id.nav_my_notes: selectedFragment = new MyNotesFragment(); break; case R.id.nav_settings: selectedFragment = new SettingsFragment(); break; default: return super.onOptionsItemSelected(item); } getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, selectedFragment).commit(); return true; } }

4. 添加依赖和主题配置

确保在 build.gradle 文件中添加了 appcompat 库依赖，并在 styles.xml 中配置主题。

build.gradle

dependencies { implementation 'androidx.appcompat:appcompat:1.3.0' implementation 'com.google.android.material:material:1.3.0' // 其他依赖项... }

styles.xml

<resources> <!-- Base application theme. --> <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"> <!-- Customize your theme here. --> <item name="colorPrimary">@color/colorPrimary</item> <item name="colorPrimaryDark">@color/colorPrimaryDark</item> <item name="colorAccent">@color/colorAccent</item> </style> </resources>

5. 测试应用

在 MainActivity 中运行应用程序，右上角的菜单按钮，应该会显示“我的”和“设置”选项。这些选项将会加载相应的Fragment。

这样可以实现你提供的截图中所展示的界面。下面是 MyNotesFragment 和 SettingsFragment 的代码示例，供参考。

MyNotesFragment 示例

MyNotesFragment.java

package com.example.notesapp; import android.content.Intent; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.ListView; import android.widget.Toast; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.appcompat.app.AlertDialog; import androidx.fragment.app.Fragment; import java.util.ArrayList; public class MyNotesFragment extends Fragment { 
    private SQLiteDatabase db; private ListView listView; private ArrayAdapter<String> adapter; private ArrayList<String> notesList; private String username; @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_my_notes, container, false); // 初始化数据库 NotesDBHelper dbHelper = new NotesDBHelper(getActivity()); db = dbHelper.getWritableDatabase(); listView = view.findViewById(R.id.notes_list); Button addButton = view.findViewById(R.id.add_note_button); // 获取用户名 MainActivity activity = (MainActivity) getActivity(); if (activity != null) { 
    username = activity.getIntent().getStringExtra("username"); } notesList = new ArrayList<>(); adapter = new ArrayAdapter<>(getActivity(), android.R.layout.simple_list_item_1, notesList); listView.setAdapter(adapter); loadNotes(); addButton.setOnClickListener(new View.OnClickListener() { 
    @Override public void onClick(View v) { 
    // 跳转到新增笔记页面 Intent intent = new Intent(getActivity(), EditNoteActivity.class); intent.putExtra("username", username); startActivity(intent); } }); listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
    @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
    // 跳转到编辑笔记页面 String note = notesList.get(position); Intent intent = new Intent(getActivity(), EditNoteActivity.class); intent.putExtra("note", note); intent.putExtra("username", username); startActivity(intent); } }); listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() { 
    @Override public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) { 
    new AlertDialog.Builder(getActivity()) .setTitle("删除笔记") .setMessage("确定要删除这条笔记吗？") .setPositiveButton("删除", (dialog, which) -> { 
    String note = notesList.get(position); deleteNote(note); notesList.remove(position); adapter.notifyDataSetChanged(); }) .setNegativeButton("取消", null) .show(); return true; } }); return view; } private void loadNotes() { 
    notesList.clear(); Cursor cursor = db.query("notes", null, "username=?", new String[]{ 
   username}, null, null, "timestamp DESC"); if (cursor != null) { 
    while (cursor.moveToNext()) { 
    String title = cursor.getString(cursor.getColumnIndex("title")); String content = cursor.getString(cursor.getColumnIndex("content")); notesList.add(title + "\n" + content); } cursor.close(); } adapter.notifyDataSetChanged(); } private void deleteNote(String note) { 
    db.delete("notes", "username=? AND content=?", new String[]{ 
   username, note}); } }

fragment_my_notes.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:padding="16dp"> <Button android:id="@+id/add_note_button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="新增笔记" /> <ListView android:id="@+id/notes_list" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_marginTop="16dp" /> </LinearLayout>

SettingsFragment 示例

SettingsFragment.java

package com.example.notesapp; import android.content.ContentValues; import android.content.Intent; import android.os.Bundle; import android.text.TextUtils; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.Button; import android.widget.EditText; import android.widget.Toast; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.fragment.app.Fragment; public class SettingsFragment extends Fragment { 
    private EditText nicknameEditText, passwordEditText, confirmPasswordEditText; private Button saveButton, logoutButton; private SQLiteDatabase db; private String username; @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_settings, container, false); nicknameEditText = view.findViewById(R.id.nickname); passwordEditText = view.findViewById(R.id.password); confirmPasswordEditText = view.findViewById(R.id.confirmPassword); saveButton = view.findViewById(R.id.save); logoutButton = view.findViewById(R.id.logout); NotesDBHelper dbHelper = new NotesDBHelper(getActivity()); db = dbHelper.getWritableDatabase(); MainActivity activity = (MainActivity) getActivity(); if (activity != null) { 
    username = activity.getIntent().getStringExtra("username"); } saveButton.setOnClickListener(new View.OnClickListener() { 
    @Override public void onClick(View v) { 
    String nickname = nicknameEditText.getText().toString(); String password = passwordEditText.getText().toString(); String confirmPassword = confirmPasswordEditText.getText().toString(); if (!TextUtils.isEmpty(password) && !password.equals(confirmPassword)) { 
    Toast.makeText(getActivity(), "密码和确认密码不一致", Toast.LENGTH_SHORT).show(); return; } ContentValues values = new ContentValues(); if (!TextUtils.isEmpty(nickname)) { 
    values.put("nickname", nickname); } if (!TextUtils.isEmpty(password)) { 
    values.put("password", password); } if (values.size() > 0) { 
    db.update("users", values, "username=?", new String[]{ 
   username}); Toast.makeText(getActivity(), "信息已更新", Toast.LENGTH_SHORT).show(); } else { 
    Toast.makeText(getActivity(), "没有要更新的信息", Toast.LENGTH_SHORT).show(); } } }); logoutButton.setOnClickListener(new View.OnClickListener() { 
    @Override public void onClick(View v) { 
    Intent intent = new Intent(getActivity(), LoginActivity.class); startActivity(intent); if (getActivity() != null) { 
    getActivity().finish(); } } }); return view; } }

fragment_settings.xml

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:padding="16dp"> <EditText android:id="@+id/nickname" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="昵称" /> <EditText android:id="@+id/password" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="密码" android:inputType="textPassword" /> <EditText android:id="@+id/confirmPassword" android:layout_width="match_parent" android:layout_height="wrap_content" android:hint="确认密码" android:inputType="textPassword" /> <Button android:id="@+id/save" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="保存" /> <Button android:id="@+id/logout" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="退出登录" /> </LinearLayout>

完整代码总结

main_menu.xml

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/nav_my_notes" android:title="我的"/> <item android:id="@+id/nav_settings" android:title="设置"/> </menu>

2.activity_main.xml

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <androidx.appcompat.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="?attr/colorPrimary" android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"/> <FrameLayout android:id="@+id/fragment_container" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_below="@id/toolbar"/> </RelativeLayout>