Android文件讀寫實例代碼

轉載：http://rnmichelle.javaeye.com/blog/923217

本文轉載自本人在javaeye.com 上發表的原創博客，有興趣的朋友可以看看。

Android文件讀寫實例代碼

1.Manifest文件中權限的聲明
爲了能對sdcard進行讀寫操作，即可創建文件或目錄，需要在AndroidManifest.xml中添加權限的聲明：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

2.創建目錄及目標文件，並以"utf-8"編碼格式對文件寫入
首先可在目標文件開頭定義一下目錄及文件名常量，方便創建文件時用

final static String FOLDER = "/sample/";
final static String FILENAME = "sample";
final static String SUFFIX = ".txt"; // suffix could be replaced on demand

writeFile函數按命名創建目錄和文件並寫入字串

private void writeFile(StringBuilder sb) {
 String foldername = Environment.getExternalStorageDirectory().getPath()
                             + FOLDER;
    File folder = new File(foldername);
    if (folder != null && !folder.exists()) {
        if (!folder.mkdir() && !folder.isDirectory())
        {
            Log.d(TAG, "Error: make dir failed!");
            return;
        }
    }

    String stringToWrite = sb.toString();
    String targetPath = foldername + FILENAME + SUFFIX;
    File targetFile = new File(targetPath);
    if (targetFile != null) {
        if (targetFile.exists()) {
            targetFile.delete();
        }

        OutputStreamWriter osw;
        try{
            osw = new OutputStreamWriter(
                        new FileOutputStream(targetFile),"utf-8");
            try {
            osw.write(stringToWrite);
                osw.flush();
                osw.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (UnsupportedEncodingException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
 }
}

注意在new FileOutputStream時用到編碼方式爲"utf-8",即以"utf-8"格式來保存這個，如果想用別的格式來保存，可換成"GB2312","Big5"等。
此外，待寫入的字串可以將字串樣式先用StringBuilder構造好，直接用StringBuilder變量；也可以直接傳入String類型的變量。

3.以"utf-8"解碼格式讀入文

private String readFile(String filepath) {
    String path = filepath;
    if (null == path) {
        Log.d(TAG, "Error: Invalid file name!");
        return null;
    }

    String filecontent = null;
    File f = new File(path);
    if (f != null && f.exists())
    {
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(f);
        } catch (FileNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
            Log.d(TAG, "Error: Input File not find!");
            return null;
        }

        CharBuffer cb;
        try {
            cb = CharBuffer.allocate(fis.available());
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
            Log.d(TAG, "Error: CharBuffer initial failed!");
            return null;
        }

        InputStreamReader isr;
        try {
            isr = new InputStreamReader(fis, "utf-8");
            try {
                if (cb != null) {
                   isr.read(cb);
                }
                filecontent = new String(cb.array());
                isr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    Log.d(TAG, "readFile filecontent = " + filecontent);
    return filecontent;
}