将资源文件转换成本地文件：

读取到流中，转换成bitmap，再从bitmap转变成file

InputStream is = getResources().openRawResource(R.drawable.icon);

Bitmap bitmap = BitmapFactory.decodeStream(is);

String defaultPath = getApplicationContext().getFilesDir()
.getAbsolutePath() + "/defaultGoodInfo";
File file = new File(defaultPath);
if (!file.exists()) {
file.mkdirs();
} else {
return;
}
String defaultImgPath = defaultPath + "/messageImg.jpg";
file = new File(defaultImgPath);
try {
file.createNewFile();

FileOutputStream fOut = new FileOutputStream(file);

bitmap.compress(Bitmap.CompressFormat.PNG, 20, fOut);
is.close();
fOut.flush();
fOut.close();
} catch (Exception e) {
e.printStackTrace();

        }