/**
 * 文件转base64字符串
 *
 * @param file
 * @return
 */
public static String fileToBase64(File file) {
    String base64 = null;
    InputStream in = null;
    try {
        in = new FileInputStream(file);
        byte[] bytes = new byte[in.available()];
        int length = in.read(bytes);
        base64 = Base64.encodeToString(bytes, 0, length, Base64.DEFAULT);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } finally {
        try {
            if (in != null) {
                in.close();
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    return base64;
}

方法2：

String base64Img = "";
try {
    byte[] buf = readFile(file);

    base64Img = new String(Base64.encode(buf, Base64.NO_WRAP));


} catch (Exception e) {
    e.printStackTrace();
}

json文件转对象

public static String readStringFromFile(String fileName) {
    InputStream is = null;
    String msg = null;
    try {
        File file = new File(fileName);
        if(file.exists()){
            is = new FileInputStream(fileName);
            byte[] bytes = new byte[is.available()];
            is.read(bytes);
            msg = new String(bytes);
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (is != null){
                is.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    return msg;
}

public static DynamicLangBean loadDownLang(Context context, String lang){

    DynamicLangBean langBean = null;
    String filePathStr = getLangDownFileDir(context) + File.separator + getLangDownFileName(lang);
    String strContent = LangFileUtil.readStringFromFile(filePathStr);
    if (TextUtils.isEmpty(strContent)){
        return langBean;
    }
    try{
        langBean = new Gson().fromJson(strContent, DynamicLangBean.class);
    }catch (Exception e){
        e.printStackTrace();
        AppLog.Loge("语言包加载异常："+e.getMessage());
    }

    return langBean;

}