Android离线缓存

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;    }