Android离线缓存 _Android

莫问天涯路几重，轻衫侧帽且从容。这篇文章主要讲述Android离线缓存相关的知识，希望能为你提供帮助。
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。
【Android离线缓存】（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 = https://www.songbingjia.com/android/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;
}