Android如何将文件保存到指定路径？自定义应用存储路径方法

Hey there! I see you want to switch from saving files to the internal app private directory (/data/data/com.mypackage.app/files/) to the external app private directory (Internal Storage/Android/data/com.mypackage.app/files/). Let's break down how to fix this properly.

Key Background #

The path you're targeting (Internal Storage/Android/data/...) is Android's recommended external storage private directory for your app. Unlike public external storage, this directory:

• Doesn't require the WRITE_EXTERNAL_STORAGE permission (for Android 4.4 / API 19 and above)
• Gets automatically deleted when your app is uninstalled
• Is private to your app (other apps can't access it without special permissions)

Fixing Your Code #

The main issue with your current code is that you're using getFilesDir(), which points to the internal storage private directory. Instead, use getExternalFilesDir(null) to get the correct external private directory path.

Here's the modified version of your createFile() method:

public void createFile() {
    // Get the external app private directory (this is the path you want)
    File externalFilesDir = this.getExternalFilesDir(null);
    
    // Check if external storage is available to avoid null pointer exceptions
    if (externalFilesDir == null) {
        // Handle unavailable external storage (e.g., SD card unmounted)
        Toast.makeText(this, "External storage is not available", Toast.LENGTH_SHORT).show();
        return;
    }

    String fileName = "myfiles.txt"; // Matches your desired filename
    String value = "example value";
    File output = new File(externalFilesDir, fileName); // Safe path joining via File constructor

    try {
        FileOutputStream fileout = new FileOutputStream(output);
        OutputStreamWriter outputWriter = new OutputStreamWriter(fileout);
        outputWriter.write(value);
        outputWriter.close();
        fileout.close();
        // Optional: Confirm success to the user
        Toast.makeText(this, "File created successfully", Toast.LENGTH_SHORT).show();
    } catch (IOException e) {
        e.printStackTrace();
        Toast.makeText(this, "Error creating file", Toast.LENGTH_SHORT).show();
    }
}

Important Notes #

• Why getExternalFilesDir(null)? Passing null gives you the root of your app's external private files directory. If you wanted to organize files into subfolders (like "documents" or "images"), you could pass a specific type (e.g., Environment.DIRECTORY_DOCUMENTS), but null works perfectly for your root files path.
• Path Safety: Using new File(externalFilesDir, fileName) is safer than manually joining paths with File.separator—it handles OS-specific path separators automatically.
• Error Handling: Always check if getExternalFilesDir() returns null—this can happen if the external storage is unmounted (e.g., user removed the SD card on older devices).

内容的提问来源于stack exchange，提问作者qwerty