/**

* 此方法为android程序写入sd文件文件，用到了android-annotation的支持库@

*

* @param buffer 写入文件的内容

* @param folder 保存文件的文件夹名称,如log；可为null，默认保存在sd卡根目录

* @param fileName 文件名称，默认app_log.txt

* @param append 是否追加写入，true为追加写入，false为重写文件

* @param autoLine 针对追加模式，true为增加时换行，false为增加时不换行

*/

public synchronized static void writeFileToSDCard(@NonNull final byte[] buffer, @Nullable final String folder,

@Nullable final String fileName, final boolean append, final boolean autoLine) {

new Thread(new Runnable() {

@Override

public void run() {

boolean sdCardExist = Environment.getExternalStorageState().equals(

android.os.Environment.MEDIA_MOUNTED);

String folderPath = "";

if (sdCardExist) {

//TextUtils为android自带的帮助类

if (TextUtils.isEmpty(folder)) {

//如果folder为空，则直接保存在sd卡的根目录

folderPath = Environment.getExternalStorageDirectory()

+ File.separator;

} else {

folderPath = Environment.getExternalStorageDirectory()

+ File.separator + folder + File.separator;

}

} else {

return;

}

File fileDir = new File(folderPath);

if (!fileDir.exists()) {

if (!fileDir.mkdirs()) {

return;

}

}

File file;

//判断文件名是否为空

if (TextUtils.isEmpty(fileName)) {

file = new File(folderPath + "app_log.txt");

} else {

file = new File(folderPath + fileName);

}

RandomAccessFile raf = null;

FileOutputStream out = null;

try {

if (append) {

//如果为追加则在原来的基础上继续写文件

raf = new RandomAccessFile(file, "rw");

raf.seek(file.length());

raf.write(buffer);

if (autoLine) {

raf.write("\n".getBytes());

}

} else {

//重写文件，覆盖掉原来的数据

out = new FileOutputStream(file);

out.write(buffer);

out.flush();

}

} catch (IOException e) {

e.printStackTrace();

} finally {

try {

if (raf != null) {

raf.close();

}

if (out != null) {

out.close();

}

} catch (IOException e) {

e.printStackTrace();

}

}

}

}).start();

}