feat: 添加笔记导出功能支持文本、图片和PDF格式

- 新增菜单项和按钮用于触发导出功能
- 实现单条笔记导出（文本、图片、PDF）及批量导出
- 添加 FileProvider 配置以支持文件分享
- 新增 PdfExportHelper 和 ImageExportHelper 工具类
- 修改 BackupUtils 支持单条笔记和批量导出

src/Notesmaster/app/src/main/AndroidManifest.xml

@@ -62,6 +62,7 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Notesmaster"
+        android:requestLegacyExternalStorage="true"
         tools:targetApi="31">
 
         <!-- ==================== 笔记列表活动 ==================== -->
@@ -155,6 +156,16 @@
             android:authorities="micode_notes"
             android:multiprocess="true" />
 
+        <provider
+            android:name="androidx.core.content.FileProvider"
+            android:authorities="net.micode.notes.fileprovider"
+            android:exported="false"
+            android:grantUriPermissions="true">
+            <meta-data
+                android:name="android.support.FILE_PROVIDER_PATHS"
+                android:resource="@xml/file_paths" />
+        </provider>
+
         <!-- ==================== 桌面小部件接收器 ==================== -->
         <!-- 2x2大小的笔记桌面小部件 -->
         <receiver

src/Notesmaster/app/src/main/java/net/micode/notes/MainActivity.java

@@ -5,6 +5,7 @@ import android.os.Bundle;
 import android.util.Log;
 import android.view.Gravity;
 import android.view.View;
+import android.widget.Toast;
 
 import androidx.activity.EdgeToEdge;
 import androidx.appcompat.app.AppCompatActivity;
@@ -15,6 +16,7 @@ import androidx.drawerlayout.widget.DrawerLayout;
 
 import net.micode.notes.data.Notes;
 import net.micode.notes.databinding.ActivityMainBinding;
+import net.micode.notes.tool.BackupUtils;
 import net.micode.notes.ui.BaseActivity;
 import net.micode.notes.ui.SidebarFragment;
 
@@ -130,7 +132,23 @@ public class MainActivity extends BaseActivity implements SidebarFragment.OnSide
     @Override
     public void onExportSelected() {
         Log.d(TAG, "Export selected");
-        // TODO: 实现导出功能
+        BackupUtils backupUtils = BackupUtils.getInstance(this);
+        int state = backupUtils.exportToText();
+        switch (state) {
+            case BackupUtils.STATE_SUCCESS:
+                Toast.makeText(this, getString(R.string.format_exported_file_location,
+                        backupUtils.getExportedTextFileName(),
+                        backupUtils.getExportedTextFileDir()), Toast.LENGTH_SHORT).show();
+                break;
+            case BackupUtils.STATE_SD_CARD_UNMOUONTED:
+                Toast.makeText(this, R.string.error_sdcard_unmounted, Toast.LENGTH_SHORT).show();
+                break;
+            case BackupUtils.STATE_SYSTEM_ERROR:
+            default:
+                Toast.makeText(this, R.string.error_sdcard_export, Toast.LENGTH_SHORT).show();
+                break;
+        }
+        closeSidebar();
     }
 
     @Override

src/Notesmaster/app/src/main/java/net/micode/notes/data/NotesRepository.java

@@ -429,6 +429,23 @@ public class NotesRepository {
         return notes;
     }
 
+    /**
+     * 查询单个笔记信息（异步版本）
+     *
+     * @param noteId 笔记ID
+     * @param callback 回调接口
+     */
+    public void getNoteInfo(long noteId, Callback<NoteInfo> callback) {
+        executor.execute(() -> {
+            try {
+                NoteInfo noteInfo = getFolderInfo(noteId);
+                callback.onSuccess(noteInfo);
+            } catch (Exception e) {
+                callback.onError(e);
+            }
+        });
+    }
+
     /**
      * 查询单个文件夹信息
      *
@@ -1542,6 +1559,23 @@ public class NotesRepository {
         });
     }
 
+    /**
+     * 获取笔记完整内容（异步版本）
+     *
+     * @param noteId 笔记ID
+     * @param callback 回调接口
+     */
+    public void getNoteContent(long noteId, Callback<String> callback) {
+        executor.execute(() -> {
+            try {
+                String content = getNoteContent(noteId);
+                callback.onSuccess(content);
+            } catch (Exception e) {
+                callback.onError(e);
+            }
+        });
+    }
+
     private String getNoteContent(long noteId) {
         String content = "";
         Cursor cursor = contentResolver.query(

src/Notesmaster/app/src/main/java/net/micode/notes/tool/BackupUtils.java

@@ -116,6 +116,27 @@ public class BackupUtils {
         return mTextExport.exportToText();
     }
 
+    /**
+     * 导出单条笔记为文本文件
+     *
+     * @param noteId 笔记 ID
+     * @param title 笔记标题（用于文件名）
+     * @return 导出状态码
+     */
+    public int exportNoteToText(String noteId, String title) {
+        return mTextExport.exportNoteToText(noteId, title);
+    }
+
+    /**
+     * 批量导出指定笔记为文本文件
+     *
+     * @param noteIds 笔记 ID 列表
+     * @return 导出状态码
+     */
+    public int exportNotesToText(java.util.List<Long> noteIds) {
+        return mTextExport.exportNotesToText(noteIds);
+    }
+
     /**
      * 获取导出的文本文件名
      * 
@@ -310,6 +331,72 @@ public class BackupUtils {
             }
         }
 
+        /**
+         * 导出单条笔记为文本文件
+         *
+         * @param noteId 笔记 ID
+         * @param title 笔记标题
+         * @return 导出状态码
+         */
+        public int exportNoteToText(String noteId, String title) {
+            if (!externalStorageAvailable()) {
+                Log.d(TAG, "Media was not mounted");
+                return STATE_SD_CARD_UNMOUONTED;
+            }
+
+            PrintStream ps = getExportNotePrintStream(title);
+            if (ps == null) {
+                Log.e(TAG, "get print stream error");
+                return STATE_SYSTEM_ERROR;
+            }
+
+            exportNoteToText(noteId, ps);
+            ps.close();
+
+            return STATE_SUCCESS;
+        }
+
+        /**
+         * 批量导出指定笔记为文本文件
+         *
+         * @param noteIds 笔记 ID 列表
+         * @return 导出状态码
+         */
+        public int exportNotesToText(java.util.List<Long> noteIds) {
+            if (!externalStorageAvailable()) {
+                Log.d(TAG, "Media was not mounted");
+                return STATE_SD_CARD_UNMOUONTED;
+            }
+
+            PrintStream ps = getExportToTextPrintStream();
+            if (ps == null) {
+                Log.e(TAG, "get print stream error");
+                return STATE_SYSTEM_ERROR;
+            }
+
+            for (Long noteId : noteIds) {
+                Cursor noteCursor = mContext.getContentResolver().query(
+                        net.micode.notes.data.Notes.CONTENT_NOTE_URI,
+                        NOTE_PROJECTION,
+                        net.micode.notes.data.Notes.NoteColumns.ID + "=?",
+                        new String[]{String.valueOf(noteId)},
+                        null);
+
+                if (noteCursor != null) {
+                    if (noteCursor.moveToFirst()) {
+                        ps.println(String.format(getFormat(FORMAT_NOTE_DATE), DateFormat.format(
+                                mContext.getString(R.string.format_datetime_mdhm),
+                                noteCursor.getLong(NOTE_COLUMN_MODIFIED_DATE))));
+                        exportNoteToText(String.valueOf(noteId), ps);
+                    }
+                    noteCursor.close();
+                }
+            }
+            ps.close();
+
+            return STATE_SUCCESS;
+        }
+
         /**
          * 导出笔记数据为文本文件
          * <p>
@@ -383,6 +470,31 @@ public class BackupUtils {
             return STATE_SUCCESS;
         }
 
+        /**
+         * 获取导出单条笔记文本文件的输出流
+         *
+         * @param title 笔记标题
+         * @return PrintStream 对象，如果创建失败则返回 null
+         */
+        private PrintStream getExportNotePrintStream(String title) {
+            File file = generateFileWithTitle(mContext, R.string.file_path, title);
+            if (file == null) {
+                Log.e(TAG, "create file to exported failed");
+                return null;
+            }
+            mFileName = file.getName();
+            mFileDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();
+            PrintStream ps = null;
+            try {
+                FileOutputStream fos = new FileOutputStream(file);
+                ps = new PrintStream(fos);
+            } catch (FileNotFoundException e) {
+                e.printStackTrace();
+                return null;
+            }
+            return ps;
+        }
+
         /**
          * 获取导出文本文件的输出流
          * <p>
@@ -399,7 +511,7 @@ public class BackupUtils {
                 return null;
             }
             mFileName = file.getName();
-            mFileDirectory = mContext.getString(R.string.file_path);
+            mFileDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();
             PrintStream ps = null;
             try {
                 FileOutputStream fos = new FileOutputStream(file);
@@ -416,31 +528,62 @@ public class BackupUtils {
     }
 
     /**
-     * 在 SD 卡上生成导出文本文件
+     * 在公用下载目录上生成指定标题的文本文件
+     *
+     * @param context 应用上下文
+     * @param filePathResId 文件路径资源 ID (不再使用，改为公用下载目录)
+     * @param title 笔记标题
+     * @return 生成的文件对象，如果创建失败则返回 null
+     */
+    private static File generateFileWithTitle(Context context, int filePathResId, String title) {
+        // 清理文件名中的非法字符
+        String fileName = title.replaceAll("[\\\\/:*?\"<>|]", "_");
+        if (TextUtils.isEmpty(fileName)) {
+            fileName = "untitled";
+        }
+        fileName = fileName + "_" + System.currentTimeMillis() + ".txt";
+
+        File filedir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
+        File file = new File(filedir, fileName);
+
+        try {
+            if (!filedir.exists()) {
+                filedir.mkdirs();
+            }
+            if (!file.exists()) {
+                file.createNewFile();
+            }
+            return file;
+        } catch (SecurityException | IOException e) {
+            e.printStackTrace();
+        }
+
+        return null;
+    }
+
+    /**
+     * 在公用下载目录上生成导出文本文件
      * <p>
      * 在指定的路径下创建导出文件，如果目录不存在则创建目录。
      * </p>
      * 
      * @param context 应用上下文
-     * @param filePathResId 文件路径资源 ID
+     * @param filePathResId 文件路径资源 ID (不再使用，改为公用下载目录)
      * @param fileNameFormatResId 文件名格式资源 ID
      * @return 生成的文件对象，如果创建失败则返回 null
      */
     private static File generateFileMountedOnSDcard(Context context, int filePathResId, int fileNameFormatResId) {
-        StringBuilder sb = new StringBuilder();
-        sb.append(Environment.getExternalStorageDirectory());
-        sb.append(context.getString(filePathResId));
-        File filedir = new File(sb.toString());
-        sb.append(context.getString(
+        File filedir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
+        String fileName = context.getString(
                 fileNameFormatResId,
                 DateFormat.format(context.getString(R.string.format_date_ymd),
-                        System.currentTimeMillis())));
-        File file = new File(sb.toString());
+                        System.currentTimeMillis()));
+        File file = new File(filedir, fileName);
 
         try {
             if (!filedir.exists()) {
                 // 创建目录
-                filedir.mkdir();
+                filedir.mkdirs();
             }
             if (!file.exists()) {
                 // 创建文件

src/Notesmaster/app/src/main/java/net/micode/notes/tool/ImageExportHelper.java

@@ -0,0 +1,117 @@
+package net.micode.notes.tool;
+
+import android.content.Context;
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.Paint;
+import android.net.Uri;
+import android.view.View;
+import android.widget.ScrollView;
+
+import androidx.core.widget.NestedScrollView;
+import androidx.core.content.FileProvider;
+
+import android.os.Environment;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * 图片导出工具类
+ * <p>
+ * 提供将 View 转换为图片并分享的功能。
+ * </p>
+ */
+public class ImageExportHelper {
+    private static final String TAG = "ImageExportHelper";
+
+    /**
+     * 将 View 转换为 Bitmap
+     *
+     * @param view 要转换的 View
+     * @return 转换后的 Bitmap
+     */
+    public static Bitmap viewToBitmap(View view) {
+        if (view instanceof ScrollView || view instanceof NestedScrollView) {
+            int height = 0;
+            if (view instanceof ScrollView) {
+                ScrollView scrollView = (ScrollView) view;
+                for (int i = 0; i < scrollView.getChildCount(); i++) {
+                    height += scrollView.getChildAt(i).getHeight();
+                }
+            } else {
+                NestedScrollView nestedScrollView = (NestedScrollView) view;
+                for (int i = 0; i < nestedScrollView.getChildCount(); i++) {
+                    height += nestedScrollView.getChildAt(i).getHeight();
+                }
+            }
+            Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), height, Bitmap.Config.ARGB_8888);
+            Canvas canvas = new Canvas(bitmap);
+            canvas.drawColor(Color.WHITE);
+            view.draw(canvas);
+            return bitmap;
+        } else {
+            Bitmap bitmap = Bitmap.createBitmap(view.getWidth(), view.getHeight(), Bitmap.Config.ARGB_8888);
+            Canvas canvas = new Canvas(bitmap);
+            canvas.drawColor(Color.WHITE);
+            view.draw(canvas);
+            return bitmap;
+        }
+    }
+
+    /**
+     * 保存 Bitmap 到公用下载目录
+     *
+     * @param context 应用上下文
+     * @param bitmap  要保存的 Bitmap
+     * @param title   笔记标题
+     * @return 生成的文件 Uri，如果保存失败则返回 null
+     */
+    public static Uri saveBitmapToExternal(Context context, Bitmap bitmap, String title) {
+        String fileName = title.replaceAll("[\\\\/:*?\"<>|]", "_");
+        if (fileName.isEmpty()) {
+            fileName = "untitled";
+        }
+        fileName += "_" + System.currentTimeMillis() + ".png";
+
+        File filedir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
+        File file = new File(filedir, fileName);
+
+        try {
+            if (!filedir.exists()) {
+                filedir.mkdirs();
+            }
+            FileOutputStream stream = new FileOutputStream(file);
+            bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
+            stream.close();
+            return FileProvider.getUriForFile(context, context.getPackageName() + ".fileprovider", file);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+    /**
+     * 保存 Bitmap 到缓存目录并返回 Uri
+     *
+     * @param context 应用上下文
+     * @param bitmap  要保存的 Bitmap
+     * @return 文件的 Uri，如果保存失败则返回 null
+     */
+    public static Uri saveBitmapToCache(Context context, Bitmap bitmap) {
+        File cachePath = new File(context.getCacheDir(), "images");
+        cachePath.mkdirs();
+        try {
+            File file = new File(cachePath, "note_export_" + System.currentTimeMillis() + ".png");
+            FileOutputStream stream = new FileOutputStream(file);
+            bitmap.compress(Bitmap.CompressFormat.PNG, 100, stream);
+            stream.close();
+            return FileProvider.getUriForFile(context, context.getPackageName() + ".fileprovider", file);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}

src/Notesmaster/app/src/main/java/net/micode/notes/tool/PdfExportHelper.java

@@ -0,0 +1,98 @@
+package net.micode.notes.tool;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.graphics.pdf.PdfDocument;
+import android.os.Environment;
+import android.text.Layout;
+import android.text.StaticLayout;
+import android.text.TextPaint;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * PDF 导出工具类
+ * <p>
+ * 使用 Android PdfDocument API 将笔记导出为 PDF 文件。
+ * </p>
+ */
+public class PdfExportHelper {
+    private static final String TAG = "PdfExportHelper";
+
+    /**
+     * 将笔记导出为 PDF
+     *
+     * @param context 应用上下文
+     * @param title   笔记标题
+     * @param content 笔记内容
+     * @return 生成的 PDF 文件，如果失败则返回 null
+     */
+    public static File exportToPdf(Context context, String title, String content) {
+        PdfDocument document = new PdfDocument();
+        // A4 纸张大小 (595 x 842 points)
+        PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(595, 842, 1).create();
+        PdfDocument.Page page = document.startPage(pageInfo);
+
+        Canvas canvas = page.getCanvas();
+        TextPaint titlePaint = new TextPaint();
+        titlePaint.setColor(Color.BLACK);
+        titlePaint.setTextSize(24);
+        titlePaint.setFakeBoldText(true);
+
+        TextPaint contentPaint = new TextPaint();
+        contentPaint.setColor(Color.BLACK);
+        contentPaint.setTextSize(14);
+
+        int x = 50;
+        int y = 50;
+
+        // 绘制标题
+        canvas.drawText(title, x, y, titlePaint);
+        y += 40;
+
+        // 绘制正文（自动换行）
+        StaticLayout staticLayout;
+        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
+            staticLayout = StaticLayout.Builder.obtain(content, 0, content.length(), contentPaint, pageInfo.getPageWidth() - 100)
+                    .setAlignment(Layout.Alignment.ALIGN_NORMAL)
+                    .setLineSpacing(0.0f, 1.2f)
+                    .setIncludePad(false)
+                    .build();
+        } else {
+            staticLayout = new StaticLayout(content, contentPaint, pageInfo.getPageWidth() - 100,
+                    Layout.Alignment.ALIGN_NORMAL, 1.2f, 0.0f, false);
+        }
+
+        canvas.save();
+        canvas.translate(x, y);
+        staticLayout.draw(canvas);
+        canvas.restore();
+
+        document.finishPage(page);
+
+        // 生成文件名
+        String fileName = title.replaceAll("[\\\\/:*?\"<>|]", "_");
+        if (fileName.isEmpty()) {
+            fileName = "untitled";
+        }
+        fileName += "_" + System.currentTimeMillis() + ".pdf";
+
+        File file = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS), fileName);
+
+        try {
+            FileOutputStream fos = new FileOutputStream(file);
+            document.writeTo(fos);
+            fos.close();
+        } catch (IOException e) {
+            e.printStackTrace();
+            file = null;
+        } finally {
+            document.close();
+        }
+
+        return file;
+    }
+}

src/Notesmaster/app/src/main/java/net/micode/notes/ui/NoteEditActivity.java

@@ -53,6 +53,8 @@ import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 import android.widget.Toast;
+import android.graphics.Bitmap;
+import android.net.Uri;
 
 import net.micode.notes.R;
 import net.micode.notes.data.Notes;
@@ -61,7 +63,10 @@ import net.micode.notes.model.NoteCommand;
 import net.micode.notes.model.UndoRedoManager;
 import net.micode.notes.model.WorkingNote;
 import net.micode.notes.model.WorkingNote.NoteSettingChangedListener;
+import net.micode.notes.tool.BackupUtils;
 import net.micode.notes.tool.DataUtils;
+import net.micode.notes.tool.ImageExportHelper;
+import net.micode.notes.tool.PdfExportHelper;
 import net.micode.notes.tool.ResourceParser;
 import net.micode.notes.tool.ResourceParser.TextAppearanceResources;
 import net.micode.notes.ui.DateTimePickerDialog.OnDateTimeSetListener;
@@ -88,6 +93,12 @@ import net.micode.notes.tool.SmartParser;
 
 import net.micode.notes.data.FontManager;
 
+import android.widget.RadioButton;
+import android.widget.RadioGroup;
+
+import java.io.File;
+import java.util.ArrayList;
+
 public class NoteEditActivity extends BaseActivity implements OnClickListener,
         NoteSettingChangedListener, OnTextViewChangeListener {
     /**
@@ -1035,6 +1046,9 @@ public class NoteEditActivity extends BaseActivity implements OnClickListener,
                 getWorkingText();
                 sendTo(this, mWorkingNote.getContent());
                 break;
+            case R.id.menu_export:
+                showExportDialog();
+                break;
             case R.id.menu_send_to_desktop:
                 sendToDesktop();
                 break;
@@ -1082,6 +1096,135 @@ public class NoteEditActivity extends BaseActivity implements OnClickListener,
         context.startActivity(intent);
     }
 
+    /**
+     * 显示导出选项对话框
+     */
+    private void showExportDialog() {
+        if (mWorkingNote.getNoteId() == 0) {
+            saveNote();
+        }
+        getWorkingText();
+        String content = mWorkingNote.getContent();
+        if (TextUtils.isEmpty(content)) {
+            showToast(R.string.error_note_empty_for_send_to_desktop);
+            return;
+        }
+
+        AlertDialog.Builder builder = new AlertDialog.Builder(this);
+        builder.setTitle("导出便签");
+
+        LinearLayout layout = new LinearLayout(this);
+        layout.setOrientation(LinearLayout.VERTICAL);
+        layout.setPadding(50, 20, 50, 20);
+
+        final RadioGroup group = new RadioGroup(this);
+        RadioButton rbText = new RadioButton(this);
+        rbText.setText("导出为文本 (.txt)");
+        rbText.setId(View.generateViewId());
+        group.addView(rbText);
+
+        RadioButton rbImage = new RadioButton(this);
+        rbImage.setText("导出为图片 (.png)");
+        rbImage.setId(View.generateViewId());
+        group.addView(rbImage);
+
+        RadioButton rbPdf = new RadioButton(this);
+        rbPdf.setText("导出为 PDF (.pdf)");
+        rbPdf.setId(View.generateViewId());
+        group.addView(rbPdf);
+
+        group.check(rbText.getId());
+        layout.addView(group);
+
+        final CheckBox cbShare = new CheckBox(this);
+        cbShare.setText("导出后立即分享");
+        layout.addView(cbShare);
+
+        builder.setView(layout);
+
+        builder.setPositiveButton("开始导出", (dialog, which) -> {
+            int checkedId = group.getCheckedRadioButtonId();
+            boolean share = cbShare.isChecked();
+
+            if (checkedId == rbText.getId()) {
+                performExport(0, share);
+            } else if (checkedId == rbImage.getId()) {
+                performExport(1, share);
+            } else if (checkedId == rbPdf.getId()) {
+                performExport(2, share);
+            }
+        });
+
+        builder.setNegativeButton("取消", null);
+        builder.show();
+    }
+
+    private void performExport(int format, boolean share) {
+        String content = mWorkingNote.getContent();
+        String title = getTitleFromContent(content);
+        String noteId = String.valueOf(mWorkingNote.getNoteId());
+
+        switch (format) {
+            case 0: // Text
+                BackupUtils backupUtils = BackupUtils.getInstance(this);
+                int state = backupUtils.exportNoteToText(noteId, title);
+                if (state == BackupUtils.STATE_SUCCESS) {
+                    File file = new File(backupUtils.getExportedTextFileDir(), backupUtils.getExportedTextFileName());
+                    showToast("已导出至下载目录: " + file.getName());
+                    if (share) shareFile(file, "text/plain");
+                } else {
+                    showToast("导出文本失败");
+                }
+                break;
+            case 1: // Image
+                binding.svNoteEditScroll.post(() -> {
+                    Bitmap bitmap = ImageExportHelper.viewToBitmap(binding.cvEditorSurface);
+                    Uri uri = ImageExportHelper.saveBitmapToExternal(NoteEditActivity.this, bitmap, title);
+                    if (uri != null) {
+                        showToast("已导出图片至下载目录");
+                        if (share) shareUri(uri, "image/png");
+                    } else {
+                        showToast("生成图片失败");
+                    }
+                });
+                break;
+            case 2: // PDF
+                File pdfFile = PdfExportHelper.exportToPdf(this, title, content);
+                if (pdfFile != null) {
+                    showToast("已导出 PDF 至下载目录: " + pdfFile.getName());
+                    if (share) shareFile(pdfFile, "application/pdf");
+                } else {
+                    showToast("导出 PDF 失败");
+                }
+                break;
+        }
+    }
+
+    private String getTitleFromContent(String content) {
+        String title = content.trim();
+        int firstNewLine = title.indexOf('\n');
+        if (firstNewLine > 0) {
+            title = title.substring(0, firstNewLine);
+        }
+        if (title.length() > 30) {
+            title = title.substring(0, 30);
+        }
+        return title;
+    }
+
+    private void shareFile(File file, String mimeType) {
+        Uri uri = androidx.core.content.FileProvider.getUriForFile(this, getPackageName() + ".fileprovider", file);
+        shareUri(uri, mimeType);
+    }
+
+    private void shareUri(Uri uri, String mimeType) {
+        Intent intent = new Intent(Intent.ACTION_SEND);
+        intent.setType(mimeType);
+        intent.putExtra(Intent.EXTRA_STREAM, uri);
+        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        startActivity(Intent.createChooser(intent, "分享便签"));
+    }
+
     /**
      * 创建新笔记
      * <p>
@@ -1747,6 +1890,17 @@ public class NoteEditActivity extends BaseActivity implements OnClickListener,
         }
     }
 
+    /**
+     * 显示Toast提示
+     * <p>
+     * 显示指定文本的Toast提示消息。
+     * </p>
+     * @param text 提示文本
+     */
+    private void showToast(String text) {
+        Toast.makeText(this, text, Toast.LENGTH_SHORT).show();
+    }
+
     /**
      * 显示Toast提示
      * <p>

src/Notesmaster/app/src/main/java/net/micode/notes/ui/NotesListActivity.java

@@ -3,14 +3,31 @@ package net.micode.notes.ui;
 import android.app.AlertDialog;
 import android.content.BroadcastReceiver;
 import android.content.Context;
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.IntentFilter;
+import android.graphics.Bitmap;
+import android.graphics.Canvas;
+import android.graphics.Color;
+import android.net.Uri;
 import android.os.Bundle;
+import android.text.TextUtils;
 import android.util.Log;
 import android.view.View;
+import android.widget.CheckBox;
 import android.widget.EditText;
+import android.widget.LinearLayout;
+import android.widget.RadioButton;
+import android.widget.RadioGroup;
 import android.widget.Toast;
 
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+
+import net.micode.notes.tool.ImageExportHelper;
+import net.micode.notes.tool.PdfExportHelper;
+
 import androidx.annotation.NonNull;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.core.view.GravityCompat;
@@ -24,6 +41,7 @@ import net.micode.notes.data.Notes;
 import net.micode.notes.data.NotesRepository;
 import net.micode.notes.databinding.ActivityHomeBinding;
 import net.micode.notes.sync.SyncManager;
+import net.micode.notes.tool.BackupUtils;
 import net.micode.notes.tool.SecurityManager;
 import net.micode.notes.viewmodel.NotesListViewModel;
 
@@ -138,6 +156,11 @@ public class NotesListActivity extends BaseActivity implements SidebarFragment.O
             viewModel.setIsSelectionMode(false);
         });
 
+        binding.btnActionExport.setOnClickListener(v -> {
+            exportSelectedNotes();
+            viewModel.setIsSelectionMode(false);
+        });
+
         binding.btnActionLock.setOnClickListener(v -> {
             SecurityManager securityManager = SecurityManager.getInstance(this);
             if (!securityManager.isPasswordSet()) {
@@ -375,7 +398,11 @@ public class NotesListActivity extends BaseActivity implements SidebarFragment.O
     @Override public void onSyncSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); SyncManager.getInstance().syncNotes(null); }
     @Override public void onLoginSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); startActivity(new Intent(this, LoginActivity.class)); }
     @Override public void onLogoutSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); viewModel.refreshNotes(); }
-    @Override public void onExportSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); Toast.makeText(this, "导出功能待实现", Toast.LENGTH_SHORT).show(); }
+    @Override public void onExportSelected() { 
+        binding.drawerLayout.closeDrawer(GravityCompat.START); 
+        viewModel.setIsSelectionMode(true);
+        Toast.makeText(this, "请选择要导出的便签", Toast.LENGTH_SHORT).show();
+    }
     @Override public void onTemplateSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); viewModel.enterFolder(Notes.ID_TEMPLATE_FOLDER); }
     @Override public void onSettingsSelected() { binding.drawerLayout.closeDrawer(GravityCompat.START); startActivity(new Intent(this, SettingsActivity.class)); }
     @Override public void onCapsuleSelected() { 
@@ -410,6 +437,176 @@ public class NotesListActivity extends BaseActivity implements SidebarFragment.O
         });
     }
     
+    private void exportSelectedNotes() {
+        java.util.List<Long> selectedIds = viewModel.getSelectedNoteIds();
+        if (selectedIds.isEmpty()) {
+            Toast.makeText(this, "请先选择要导出的便签", Toast.LENGTH_SHORT).show();
+            return;
+        }
+
+        AlertDialog.Builder builder = new AlertDialog.Builder(this);
+        builder.setTitle("批量导出便签");
+
+        LinearLayout layout = new LinearLayout(this);
+        layout.setOrientation(LinearLayout.VERTICAL);
+        layout.setPadding(50, 20, 50, 20);
+
+        final RadioGroup group = new RadioGroup(this);
+        RadioButton rbText = new RadioButton(this);
+        rbText.setText("导出为文本 (.txt)");
+        rbText.setId(View.generateViewId());
+        group.addView(rbText);
+
+        RadioButton rbImage = new RadioButton(this);
+        rbImage.setText("导出为图片 (.png)");
+        rbImage.setId(View.generateViewId());
+        group.addView(rbImage);
+
+        RadioButton rbPdf = new RadioButton(this);
+        rbPdf.setText("导出为 PDF (.pdf)");
+        rbPdf.setId(View.generateViewId());
+        group.addView(rbPdf);
+
+        group.check(rbText.getId());
+        layout.addView(group);
+
+        final CheckBox cbShare = new CheckBox(this);
+        cbShare.setText("导出后立即分享");
+        layout.addView(cbShare);
+
+        builder.setView(layout);
+
+        builder.setPositiveButton("开始导出", (dialog, which) -> {
+            int checkedId = group.getCheckedRadioButtonId();
+            boolean share = cbShare.isChecked();
+
+            if (checkedId == rbText.getId()) {
+                 performBatchExport(0, selectedIds, share);
+             } else if (checkedId == rbImage.getId()) {
+                 performBatchExport(1, selectedIds, share);
+             } else if (checkedId == rbPdf.getId()) {
+                 performBatchExport(2, selectedIds, share);
+             }
+         });
+
+        builder.setNegativeButton("取消", null);
+        builder.show();
+    }
+
+    private void performBatchExport(int format, java.util.List<Long> selectedIds, boolean share) {
+        if (format == 0) { // Text (Combined)
+            BackupUtils backupUtils = BackupUtils.getInstance(this);
+            int state = backupUtils.exportNotesToText(selectedIds);
+            if (state == BackupUtils.STATE_SUCCESS) {
+                File file = new File(backupUtils.getExportedTextFileDir(), backupUtils.getExportedTextFileName());
+                Toast.makeText(this, "已导出至下载目录: " + file.getName(), Toast.LENGTH_SHORT).show();
+                if (share) shareFile(file, "text/plain");
+            } else {
+                Toast.makeText(this, "导出失败", Toast.LENGTH_SHORT).show();
+            }
+        } else {
+            final ArrayList<Uri> uris = new ArrayList<>();
+            final int total = selectedIds.size();
+            final int[] successCount = {0};
+            final String mimeType = (format == 1) ? "image/png" : "application/pdf";
+
+            for (Long id : selectedIds) {
+                viewModel.getNoteContent(id, new NotesRepository.Callback<String>() {
+                    @Override
+                    public void onSuccess(String content) {
+                        if (!TextUtils.isEmpty(content)) {
+                            String title = getTitleFromContent(content);
+                            File exportedFile = null;
+                            if (format == 1) { // Image
+                                Bitmap bitmap = renderTextToBitmap(content);
+                                Uri uri = ImageExportHelper.saveBitmapToExternal(NotesListActivity.this, bitmap, title);
+                                if (uri != null) {
+                                    successCount[0]++;
+                                    uris.add(uri);
+                                }
+                            } else { // PDF
+                                exportedFile = PdfExportHelper.exportToPdf(NotesListActivity.this, title, content);
+                                if (exportedFile != null) {
+                                    successCount[0]++;
+                                    uris.add(androidx.core.content.FileProvider.getUriForFile(NotesListActivity.this, getPackageName() + ".fileprovider", exportedFile));
+                                }
+                            }
+                        }
+                        checkBatchFinished(successCount[0], total, uris, mimeType, share);
+                    }
+
+                    @Override
+                    public void onError(Exception error) {
+                        checkBatchFinished(successCount[0], total, uris, mimeType, share);
+                    }
+                });
+            }
+        }
+    }
+
+    private Bitmap renderTextToBitmap(String text) {
+        android.widget.TextView textView = new android.widget.TextView(this);
+        textView.setText(text);
+        textView.setTextColor(Color.BLACK);
+        textView.setBackgroundColor(Color.WHITE);
+        textView.setTextSize(16);
+        textView.setPadding(40, 40, 40, 40);
+        textView.setWidth(800);
+        
+        int widthMeasureSpec = View.MeasureSpec.makeMeasureSpec(800, View.MeasureSpec.EXACTLY);
+        int heightMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
+        textView.measure(widthMeasureSpec, heightMeasureSpec);
+        textView.layout(0, 0, textView.getMeasuredWidth(), textView.getMeasuredHeight());
+        
+        Bitmap bitmap = Bitmap.createBitmap(textView.getMeasuredWidth(), textView.getMeasuredHeight(), Bitmap.Config.ARGB_8888);
+        Canvas canvas = new Canvas(bitmap);
+        textView.draw(canvas);
+        return bitmap;
+    }
+
+    private synchronized void checkBatchFinished(int success, int total, ArrayList<Uri> uris, String mimeType, boolean share) {
+        // Since we are doing this sequentially or with callbacks, we need to track progress
+        // For simplicity in this implementation, I'll just check if we have reached total count
+        if (uris.size() + (total - success) >= total) {
+            if (success > 0) {
+                Toast.makeText(this, "成功导出 " + success + " 个文件至下载目录", Toast.LENGTH_SHORT).show();
+                if (share) shareUris(uris, mimeType);
+            } else {
+                Toast.makeText(this, "导出失败", Toast.LENGTH_SHORT).show();
+            }
+        }
+    }
+
+    private String getTitleFromContent(String content) {
+        if (TextUtils.isEmpty(content)) return "untitled";
+        String title = content.trim();
+        int firstNewLine = title.indexOf('\n');
+        if (firstNewLine > 0) {
+            title = title.substring(0, firstNewLine);
+        }
+        if (title.length() > 30) {
+            title = title.substring(0, 30);
+        }
+        return title;
+    }
+
+    private void shareFile(File file, String mimeType) {
+        Uri uri = androidx.core.content.FileProvider.getUriForFile(this, getPackageName() + ".fileprovider", file);
+        Intent intent = new Intent(Intent.ACTION_SEND);
+        intent.setType(mimeType);
+        intent.putExtra(Intent.EXTRA_STREAM, uri);
+        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        startActivity(Intent.createChooser(intent, "分享便签"));
+    }
+
+    private void shareUris(ArrayList<Uri> uris, String mimeType) {
+        Intent intent = new Intent(Intent.ACTION_SEND_MULTIPLE);
+        intent.setType(mimeType);
+        intent.putParcelableArrayListExtra(Intent.EXTRA_STREAM, uris);
+        intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        startActivity(Intent.createChooser(intent, "分享便签"));
+    }
+
     private void showRenameFolderDialog(long folderId, String currentName) {
         final EditText input = new EditText(this);
         input.setText(currentName);

src/Notesmaster/app/src/main/java/net/micode/notes/viewmodel/NotesListViewModel.java

@@ -942,6 +942,26 @@ public class NotesListViewModel extends AndroidViewModel {
         });
     }
 
+    /**
+     * 获取单个笔记的详细信息
+     *
+     * @param noteId 笔记ID
+     * @param callback 回调接口
+     */
+    public void getNoteInfo(long noteId, NotesRepository.Callback<NotesRepository.NoteInfo> callback) {
+        repository.getNoteInfo(noteId, callback);
+    }
+
+    /**
+     * 获取单个笔记的完整内容
+     *
+     * @param noteId 笔记ID
+     * @param callback 回调接口
+     */
+    public void getNoteContent(long noteId, NotesRepository.Callback<String> callback) {
+        repository.getNoteContent(noteId, callback);
+    }
+
     /**
      * 获取文件夹信息
      * <p>

src/Notesmaster/app/src/main/res/layout/activity_home.xml

@@ -196,6 +196,7 @@
             
             <TextView android:id="@+id/btn_action_hide" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="隐藏" android:drawableTop="@android:drawable/ic_menu_close_clear_cancel" android:gravity="center" android:visibility="gone"/>
             <TextView android:id="@+id/btn_action_pin" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="置顶" android:drawableTop="@android:drawable/ic_menu_upload" android:gravity="center"/>
+            <TextView android:id="@+id/btn_action_export" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="导出" android:drawableTop="@android:drawable/ic_menu_save" android:gravity="center"/>
             <TextView android:id="@+id/btn_action_move" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="移动到" android:drawableTop="@drawable/ic_folder" android:gravity="center"/>
             <TextView android:id="@+id/btn_action_lock" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="加锁" android:drawableTop="@android:drawable/ic_lock_lock" android:gravity="center"/>
             <TextView android:id="@+id/btn_action_delete" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" android:text="删除" android:drawableTop="@android:drawable/ic_menu_delete" android:gravity="center"/>

src/Notesmaster/app/src/main/res/menu/note_edit.xml

@@ -71,6 +71,10 @@
         android:id="@+id/menu_share"
         android:title="@string/menu_share"/>
 
+    <item
+        android:id="@+id/menu_export"
+        android:title="导出" />
+
     <item
         android:id="@+id/menu_send_to_desktop"
         android:title="@string/menu_send_to_desktop"/>

src/Notesmaster/app/src/main/res/xml/file_paths.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<paths>
+    <external-path name="external_files" path="." />
+    <cache-path name="cache_files" path="." />
+</paths>