Android离线缓存的实例代码

android做到一定程度，需要考虑缓存的问题，不信可以掏出手机看看淘宝等一些app是否无网的情况下还可以浏览，不过大部分app并没有考虑到这些问题，解决android的缓存有哪些方法呢

1.io流读写文件

2.数据库

3.lrucache和disklrucache

个人比较喜欢sd卡文件读写的方式，原因自己可以去分析。

（1）权限

<uses-permission android:name="android.permission.write_external_storage" />
<uses-permission android:name="android.permission.internet"></uses-permission>
<uses-permission android:name="android.permission.access_network_state"></uses-permission>
<!-- 在sdcard中创建与删除文件权限 -->
<uses-permission android:name="android.permission.mount_unmount_filesystems"/>
<!-- 往sdcard写入数据权限 -->
<uses-permission android:name="android.permission.write_external_storage"/>

（2）判断网络连接的状态，有什么用呢？自己想

if (isnetworkavailable(mainactivity.this)) {
  toast.maketext(getapplicationcontext(), "当前有可用网络！", toast.length_long).show();

} else {
  toast.maketext(getapplicationcontext(), "当前wu可用网络！", toast.length_long).show();
}
public boolean isnetworkavailable(activity activity)
{
  context context = activity.getapplicationcontext();
  // 获取手机所有连接管理对象（包括对wi-fi,net等连接的管理）
  connectivitymanager connectivitymanager = (connectivitymanager) context.getsystemservice(context.connectivity_service);

  if (connectivitymanager == null)
  {
    return false;
  }
  else
  {
    // 获取networkinfo对象
    networkinfo[] networkinfo = connectivitymanager.getallnetworkinfo();

    if (networkinfo != null && networkinfo.length > 0)
    {
      for (int i = 0; i < networkinfo.length; i++)
      {
        system.out.println(i + "===状态===" + networkinfo[i].getstate());
        system.out.println(i + "===类型===" + networkinfo[i].gettypename());
        // 判断当前网络状态是否为连接状态
        if (networkinfo[i].getstate() == networkinfo.state.connected)
        {
          return true;
        }
      }
    }
  }
  return false;
}

（3）端口写入数据
 

  if(environment.getexternalstoragestate().equals(environment.media_mounted)){
  file sdcarddir = environment.getexternalstoragedirectory();//获取sdcard目录
  file savefile = new file(sdcarddir, "itcast.txt");
  fileoutputstream outstream = new fileoutputstream(savefile);
  outstream.write(result.getbytes());
  outstream.close();
}

（4）读取数据

file sdcarddir = environment.getexternalstoragedirectory();//获取sdcard目录
file savefile1  = new file(sdcarddir, "itcast.txt");
bufferedreader br = null;
try {
  br = new bufferedreader(new filereader(savefile1));
  string readline = "";
  stringbuffer sb = new stringbuffer();
  while ((readline = br.readline()) != null) {
    system.out.println("readline:" + readline);
    sb.append(readline);
  }
  string str = sb.tostring();

(5)部分完整demo1

if (isnetworkavailable(mainactivity.this)) {
  toast.maketext(getapplicationcontext(), "当前有可用网络！", toast.length_long).show();

} else {
  toast.maketext(getapplicationcontext(), "当前wu可用网络！", toast.length_long).show();
  file sdcarddir = environment.getexternalstoragedirectory();//获取sdcard目录
  file savefile1  = new file(sdcarddir, "itcast.txt");
  bufferedreader br = null;
  try {
    br = new bufferedreader(new filereader(savefile1));
    string readline = "";
    stringbuffer sb = new stringbuffer();
    while ((readline = br.readline()) != null) {
      system.out.println("readline:" + readline);
      sb.append(readline);
    }
    string str = sb.tostring();
    jsonobject jsonobject = new jsonobject(str);
    jsonarray jsonarray = jsonobject.getjsonarray("data");
    for (int i = 0; i < jsonarray.length(); i++) {
      jsonobject object = jsonarray.getjsonobject(i);
      string title = object.getstring("name");
      string content = object.getstring("description");
      string url = object.getstring("picsmall");
      domainbean newsinfo = new domainbean(title, content, url);

      //string path = environment.getexternalstoragedirectory() + "/" + name;
      //objectoutputstream out =new objectoutputstream(new fileoutputstream(path));
      //out.writeobject(newsinfo);
      list.add(newsinfo);
      //新建适配器
      beanadapter = new beanadapter(list, mainactivity.this);
      //配置适配器
      xlistview.setadapter(beanadapter);
      br.close();

    }

  } catch (ioexception e) {
    e.printstacktrace();
  } catch (jsonexception e) {
    e.printstacktrace();
  }
}

(6)部分完整demo2

 public string logoutpost(string url){
    string result = "";
    try {
      string data = urlencoder.encode("utf-8");
// + "&password=" + urlencoder.encode(password, "utf-8");//传递的数据
      url url = new url(url);
//2、url.openconnection()打开网络链接
      httpurlconnection conn = (httpurlconnection) url.openconnection();
//3、设置请求的方式
      conn.setrequestmethod("post");
      conn.setdoinput(true);//发送post请求必须设置允许输出
      conn.setdooutput(true);//发送post请求必须设置允许输入
      conn.setrequestproperty("content-type", "application/x-www-form-urlencoded");
      conn.setrequestproperty("charset", "utf-8");
      conn.setrequestproperty("content-length", string.valueof(data.getbytes().length));
//5、获取输出流
      outputstream os = conn.getoutputstream();
      os.write(data.getbytes());
      os.flush();
      bufferedreader in=new bufferedreader(new inputstreamreader(conn.getinputstream()));
      string line;
      while((line=in.readline())!=null){result+="\n"+line;}
            if(environment.getexternalstoragestate().equals(environment.media_mounted)){
        file sdcarddir = environment.getexternalstoragedirectory();//获取sdcard目录
        file savefile = new file(sdcarddir, "itcast.txt");
        fileoutputstream outstream = new fileoutputstream(savefile);
        outstream.write(result.getbytes());
        outstream.close();
      }
    } catch (unsupportedencodingexception e) {
      e.printstacktrace();
    } catch (protocolexception e) {
      e.printstacktrace();
    } catch (malformedurlexception e) {
      e.printstacktrace();
    } catch (ioexception e) {
      e.printstacktrace();
    }

    return result;
  }

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。