feat: 원격 FTP 서버 파일 다운로드 기능 구현

.gitignore

@@ -29,3 +29,6 @@ captures/
 
 # Google Services (safety)
 /app/google-services.json
+
+# temp
+/.temp

app/src/main/java/be/gyu/android/file/explorer/FTPClientHelper.java

@@ -5,6 +5,7 @@ import org.apache.commons.net.ftp.FTPFile;
 import org.apache.commons.net.ftp.FTPReply;
 
 import java.io.IOException;
+import java.io.OutputStream;
 
 public class FTPClientHelper {
 
@@ -23,6 +24,7 @@ public class FTPClientHelper {
                 return false;
             }
             ftpClient.enterLocalPassiveMode();
+            ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
             return true;
         } catch (IOException e) {
             e.printStackTrace();
@@ -43,13 +45,9 @@ public class FTPClientHelper {
 
     public FTPFile[] listFiles(String path) {
         try {
-            // First, try to change the working directory.
             if (ftpClient.changeWorkingDirectory(path)) {
-                // If successful, list files in the new directory.
                 return ftpClient.listFiles();
             } else {
-                // If changing directory fails, it might be a file path, not a directory.
-                // Or the path is invalid. For now, we return null for simplicity.
                 return null;
             }
         } catch (IOException e) {
@@ -57,4 +55,14 @@ public class FTPClientHelper {
             return null;
         }
     }
+
+    public boolean downloadFile(String remoteFileName, OutputStream out) {
+        try {
+            // retrieveFile works on the current working directory.
+            return ftpClient.retrieveFile(remoteFileName, out);
+        } catch (IOException e) {
+            e.printStackTrace();
+            return false;
+        }
+    }
 }

app/src/main/java/be/gyu/android/file/explorer/MainActivity.java

@@ -28,6 +28,9 @@ import androidx.recyclerview.widget.RecyclerView;
 import org.apache.commons.net.ftp.FTPFile;
 
 import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -118,6 +121,28 @@ public class MainActivity extends AppCompatActivity implements FileAdapter.OnIte
         }).start();
     }
 
+    private void downloadAndOpenFile(FileItem item) {
+        runOnUiThread(() -> Toast.makeText(this, "Downloading " + item.getName(), Toast.LENGTH_SHORT).show());
+
+        new Thread(() -> {
+            File localFile = new File(getCacheDir(), item.getName());
+            try (OutputStream out = new FileOutputStream(localFile)) {
+                boolean success = ftpHelper.downloadFile(item.getName(), out);
+                runOnUiThread(() -> {
+                    if (success) {
+                        Toast.makeText(this, "Download complete", Toast.LENGTH_SHORT).show();
+                        openFile(localFile);
+                    } else {
+                        Toast.makeText(this, "Download failed", Toast.LENGTH_SHORT).show();
+                    }
+                });
+            } catch (IOException e) {
+                e.printStackTrace();
+                runOnUiThread(() -> Toast.makeText(this, "Download failed: " + e.getMessage(), Toast.LENGTH_SHORT).show());
+            }
+        }).start();
+    }
+
     // --- Local Storage Methods ---
     private void loadFiles(File directory) {
         this.currentDirectory = directory;
@@ -143,8 +168,7 @@ public class MainActivity extends AppCompatActivity implements FileAdapter.OnIte
             if (item.isDirectory()) {
                 loadFtpFiles(item.getPath());
             } else {
-                // TODO: Implement file download/open for FTP
-                Toast.makeText(this, "Opening remote files is not implemented yet.", Toast.LENGTH_SHORT).show();
+                downloadAndOpenFile(item);
             }
         } else {
             File file = new File(item.getPath());