Android判断用户2G/3G/4G移动数据网络
作者:lijiao 发布时间:2022-12-13 03:21:49
在做 Android App 的时候,为了给用户省流量,为了不激起用户的愤怒,为了更好的用户体验,是需要根据用户当前网络情况来做一些调整的,也可以在 App 的设置模块里,让用户自己选择,在 2G / 3G / 4G 网络条件下,是否允许请求一些流量比较大的数据。
通过 Android 提供的 TelephonyManager 和 ConnectivityManager 都可以获取到 NetworksInfo 对象,可以通过 getType() 获取类型,判断是 wifi 还是 mobile ,如果是 mobile ,可以通过 NetworksInfo 对象的 getSubType() 和 getSubTypeName() 可以获取到对于的网络类型和名字。
网络类型和名字定义在 TelephonyManager 类里。
/** Network type is unknown */
public static final int NETWORK_TYPE_UNKNOWN = 0;
/** Current network is GPRS */
public static final int NETWORK_TYPE_GPRS = 1;
/** Current network is EDGE */
public static final int NETWORK_TYPE_EDGE = 2;
/** Current network is UMTS */
public static final int NETWORK_TYPE_UMTS = 3;
/** Current network is CDMA: Either IS95A or IS95B*/
public static final int NETWORK_TYPE_CDMA = 4;
/** Current network is EVDO revision 0*/
public static final int NETWORK_TYPE_EVDO_0 = 5;
/** Current network is EVDO revision A*/
public static final int NETWORK_TYPE_EVDO_A = 6;
/** Current network is 1xRTT*/
public static final int NETWORK_TYPE_1xRTT = 7;
/** Current network is HSDPA */
public static final int NETWORK_TYPE_HSDPA = 8;
/** Current network is HSUPA */
public static final int NETWORK_TYPE_HSUPA = 9;
/** Current network is HSPA */
public static final int NETWORK_TYPE_HSPA = 10;
/** Current network is iDen */
public static final int NETWORK_TYPE_IDEN = 11;
/** Current network is EVDO revision B*/
public static final int NETWORK_TYPE_EVDO_B = 12;
/** Current network is LTE */
public static final int NETWORK_TYPE_LTE = 13;
/** Current network is eHRPD */
public static final int NETWORK_TYPE_EHRPD = 14;
/** Current network is HSPA+ */
public static final int NETWORK_TYPE_HSPAP = 15;
看到这个代码和注释,相信没有这方面知识的人很难看懂,都啥玩意?这注释跟没注释有啥区别?!就是让人看着更加闹心而已。所以说,注释对阅读代码的人很重 要。当然这些东西可能太专业了,写这些代码的人估计是想写也不知道该怎么了,得写多大一坨啊?!我在最后会贴上一些我整理的资料,可以供大家参考一下,不 是很详细,也不专业,就是大概有个印象。
TelephonyManager 还提供了 getNetworkTypeName(int type) 的方法,这个方法可以返回一个字符串,但是信息量不大。
那怎么判断是 2G , 3G 还是 4G 网络呢?TelephonyManager 还提供了另外一个方法,getNetworkClass(int networkType) ,但这个方法被隐藏掉了,我把代码贴一下。
public static int getNetworkClass(int networkType) {
switch (networkType) {
case NETWORK_TYPE_GPRS:
case NETWORK_TYPE_EDGE:
case NETWORK_TYPE_CDMA:
case NETWORK_TYPE_1xRTT:
case NETWORK_TYPE_IDEN:
return NETWORK_CLASS_2_G;
case NETWORK_TYPE_UMTS:
case NETWORK_TYPE_EVDO_0:
case NETWORK_TYPE_EVDO_A:
case NETWORK_TYPE_HSDPA:
case NETWORK_TYPE_HSUPA:
case NETWORK_TYPE_HSPA:
case NETWORK_TYPE_EVDO_B:
case NETWORK_TYPE_EHRPD:
case NETWORK_TYPE_HSPAP:
return NETWORK_CLASS_3_G;
case NETWORK_TYPE_LTE:
return NETWORK_CLASS_4_G;
default:
return NETWORK_CLASS_UNKNOWN;
}
}
然后下面是这几个常量的值。
/** Unknown network class. {@hide} */
public static final int NETWORK_CLASS_UNKNOWN = 0;
/** Class of broadly defined "2G" networks. {@hide} */
public static final int NETWORK_CLASS_2_G = 1;
/** Class of broadly defined "3G" networks. {@hide} */
public static final int NETWORK_CLASS_3_G = 2;
/** Class of broadly defined "4G" networks. {@hide} */
public static final int NETWORK_CLASS_4_G = 3;
不知道为啥要把这些东西给隐藏起来,不靠谱?还是其他的更好的方式?!不知道,先这样吧,现在通过上面的手段,是可以知道用户用的是什么网络,当 然也可以区分出来用户使用的是 2G , 3G 还是 4G 了。当然,你获取到这些数据后,你也可以推算出用户用的是哪家公司的网络,移动的,联通的,还是电信的,当然,只在中国。而且虚拟运营商开始真正上市后, 这个就区分不出来是京东的,还是国美,苏宁的了,但是你可以知道你的手机号用的是联通的网还是移动的网。
最后贴上我收集整理的一些资料,可以参考一下。
GPRS 2G(2.5) General Packet Radia Service 114kbps
EDGE 2G(2.75G) Enhanced Data Rate for GSM Evolution 384kbps
UMTS 3G WCDMA 联通3G Universal Mobile Telecommunication System 完整的3G移动通信技术标准
CDMA 2G 电信 Code Division Multiple Access 码分多址
EVDO_0 3G (EVDO 全程 CDMA2000 1xEV-DO) Evolution - Data Only (Data Optimized) 153.6kps - 2.4mbps 属于3G
EVDO_A 3G 1.8mbps - 3.1mbps 属于3G过渡,3.5G
1xRTT 2G CDMA2000 1xRTT (RTT - 无线电传输技术) 144kbps 2G的过渡,
HSDPA 3.5G 高速下行分组接入 3.5G WCDMA High Speed Downlink Packet Access 14.4mbps
HSUPA 3.5G High Speed Uplink Packet Access 高速上行链路分组接入 1.4 - 5.8 mbps
HSPA 3G (分HSDPA,HSUPA) High Speed Packet Access
IDEN 2G Integrated Dispatch Enhanced Networks 集成数字增强型网络 (属于2G,来自 * )
EVDO_B 3G EV-DO Rev.B 14.7Mbps 下行 3.5G
LTE 4G Long Term Evolution FDD-LTE 和 TDD-LTE , 3G过渡,升级版 LTE Advanced 才是4G
EHRPD 3G CDMA2000向LTE 4G的中间产物 Evolved High Rate Packet Data HRPD的升级
HSPAP 3G HSPAP 比 HSDPA 快些
实例:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.text.DecimalFormat;
import java.util.List;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.wifi.WifiInfo;
import android.net.wifi.WifiManager;
import android.telephony.NeighboringCellInfo;
import android.telephony.TelephonyManager;
import android.telephony.cdma.CdmaCellLocation;
import android.telephony.gsm.GsmCellLocation;
import android.util.Log;
public class NetWorkUtil {
public static boolean isWifiAvailable() {
ConnectivityManager connectivityManager = (ConnectivityManager) ConfigManager
.getContext().getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
return (networkInfo != null && networkInfo.isConnected() && networkInfo
.getType() == ConnectivityManager.TYPE_WIFI);
}
/**
* 获取MAC地址
*
* @param context
* @return
*/
public static String getMacAddress(Context context) {
if (context == null) {
return "";
}
String localMac = null;
if (isWifiAvailable()) {
localMac = getWifiMacAddress(context);
}
if (localMac != null && localMac.length() > 0) {
localMac = localMac.replace(":", "-").toLowerCase();
return localMac;
}
localMac = getMacFromCallCmd();
if (localMac != null) {
localMac = localMac.replace(":", "-").toLowerCase();
}
return localMac;
}
private static String getWifiMacAddress(Context context) {
String localMac = null;
try {
WifiManager wifi = (WifiManager) context
.getSystemService(Context.WIFI_SERVICE);
WifiInfo info = wifi.getConnectionInfo();
if (wifi.isWifiEnabled()) {
localMac = info.getMacAddress();
if (localMac != null) {
localMac = localMac.replace(":", "-").toLowerCase();
return localMac;
}
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
/**
* 通过callCmd("busybox ifconfig","HWaddr")获取mac地址
*
* @attention 需要设备装有busybox工具
* @return Mac Address
*/
private static String getMacFromCallCmd() {
String result = "";
result = callCmd("busybox ifconfig", "HWaddr");
if (result == null || result.length() <= 0) {
return null;
}
DebugLog.v("tag", "cmd result : " + result);
// 对该行数据进行解析
// 例如:eth0 Link encap:Ethernet HWaddr 00:16:E8:3E:DF:67
if (result.length() > 0 && result.contains("HWaddr") == true) {
String Mac = result.substring(result.indexOf("HWaddr") + 6,
result.length() - 1);
if (Mac.length() > 1) {
result = Mac.replaceAll(" ", "");
}
}
return result;
}
public static String callCmd(String cmd, String filter) {
String result = "";
String line = "";
try {
Process proc = Runtime.getRuntime().exec(cmd);
InputStreamReader is = new InputStreamReader(proc.getInputStream());
BufferedReader br = new BufferedReader(is);
// 执行命令cmd,只取结果中含有filter的这一行
while ((line = br.readLine()) != null
&& line.contains(filter) == false) {
}
result = line;
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
/**
* 网络是否可用
*
* @param context
* @return
*/
public static boolean IsNetWorkEnable(Context context) {
try {
ConnectivityManager connectivity = (ConnectivityManager) context
.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivity == null) {
ToastUtil.showMessage(context, "无法连接网络");
return false;
}
NetworkInfo info = connectivity.getActiveNetworkInfo();
if (info != null && info.isConnected()) {
// 判断当前网络是否已经连接
if (info.getState() == NetworkInfo.State.CONNECTED) {
return true;
}
}
} catch (Exception e) {
e.printStackTrace();
}
ToastUtil.showMessage(context, "无法连接网络");
return false;
}
private static final int NETWORK_TYPE_UNAVAILABLE = -1;
// private static final int NETWORK_TYPE_MOBILE = -100;
private static final int NETWORK_TYPE_WIFI = -101;
private static final int NETWORK_CLASS_WIFI = -101;
private static final int NETWORK_CLASS_UNAVAILABLE = -1;
/** Unknown network class. */
private static final int NETWORK_CLASS_UNKNOWN = 0;
/** Class of broadly defined "2G" networks. */
private static final int NETWORK_CLASS_2_G = 1;
/** Class of broadly defined "3G" networks. */
private static final int NETWORK_CLASS_3_G = 2;
/** Class of broadly defined "4G" networks. */
private static final int NETWORK_CLASS_4_G = 3;
private static DecimalFormat df = new DecimalFormat("#.##");
// 适配低版本手机
/** Network type is unknown */
public static final int NETWORK_TYPE_UNKNOWN = 0;
/** Current network is GPRS */
public static final int NETWORK_TYPE_GPRS = 1;
/** Current network is EDGE */
public static final int NETWORK_TYPE_EDGE = 2;
/** Current network is UMTS */
public static final int NETWORK_TYPE_UMTS = 3;
/** Current network is CDMA: Either IS95A or IS95B */
public static final int NETWORK_TYPE_CDMA = 4;
/** Current network is EVDO revision 0 */
public static final int NETWORK_TYPE_EVDO_0 = 5;
/** Current network is EVDO revision A */
public static final int NETWORK_TYPE_EVDO_A = 6;
/** Current network is 1xRTT */
public static final int NETWORK_TYPE_1xRTT = 7;
/** Current network is HSDPA */
public static final int NETWORK_TYPE_HSDPA = 8;
/** Current network is HSUPA */
public static final int NETWORK_TYPE_HSUPA = 9;
/** Current network is HSPA */
public static final int NETWORK_TYPE_HSPA = 10;
/** Current network is iDen */
public static final int NETWORK_TYPE_IDEN = 11;
/** Current network is EVDO revision B */
public static final int NETWORK_TYPE_EVDO_B = 12;
/** Current network is LTE */
public static final int NETWORK_TYPE_LTE = 13;
/** Current network is eHRPD */
public static final int NETWORK_TYPE_EHRPD = 14;
/** Current network is HSPA+ */
public static final int NETWORK_TYPE_HSPAP = 15;
/**
* 格式化大小
*
* @param size
* @return
*/
public static String formatSize(long size) {
String unit = "B";
float len = size;
if (len > 900) {
len /= 1024f;
unit = "KB";
}
if (len > 900) {
len /= 1024f;
unit = "MB";
}
if (len > 900) {
len /= 1024f;
unit = "GB";
}
if (len > 900) {
len /= 1024f;
unit = "TB";
}
return df.format(len) + unit;
}
public static String formatSizeBySecond(long size) {
String unit = "B";
float len = size;
if (len > 900) {
len /= 1024f;
unit = "KB";
}
if (len > 900) {
len /= 1024f;
unit = "MB";
}
if (len > 900) {
len /= 1024f;
unit = "GB";
}
if (len > 900) {
len /= 1024f;
unit = "TB";
}
return df.format(len) + unit + "/s";
}
public static String format(long size) {
String unit = "B";
float len = size;
if (len > 1000) {
len /= 1024f;
unit = "KB";
if (len > 1000) {
len /= 1024f;
unit = "MB";
if (len > 1000) {
len /= 1024f;
unit = "GB";
}
}
}
return df.format(len) + "\n" + unit + "/s";
}
/**
* 获取运营商
*
* @return
*/
public static String getProvider() {
String provider = "未知";
try {
TelephonyManager telephonyManager = (TelephonyManager) ConfigManager
.getContext().getSystemService(Context.TELEPHONY_SERVICE);
String IMSI = telephonyManager.getSubscriberId();
Log.v("tag", "getProvider.IMSI:" + IMSI);
if (IMSI == null) {
if (TelephonyManager.SIM_STATE_READY == telephonyManager
.getSimState()) {
String operator = telephonyManager.getSimOperator();
Log.v("tag", "getProvider.operator:" + operator);
if (operator != null) {
if (operator.equals("46000")
|| operator.equals("46002")
|| operator.equals("46007")) {
provider = "中国移动";
} else if (operator.equals("46001")) {
provider = "中国联通";
} else if (operator.equals("46003")) {
provider = "中国电信";
}
}
}
} else {
if (IMSI.startsWith("46000") || IMSI.startsWith("46002")
|| IMSI.startsWith("46007")) {
provider = "中国移动";
} else if (IMSI.startsWith("46001")) {
provider = "中国联通";
} else if (IMSI.startsWith("46003")) {
provider = "中国电信";
}
}
} catch (Exception e) {
e.printStackTrace();
}
return provider;
}
/**
* 获取网络类型
*
* @return
*/
public static String getCurrentNetworkType() {
int networkClass = getNetworkClass();
String type = "未知";
switch (networkClass) {
case NETWORK_CLASS_UNAVAILABLE:
type = "无";
break;
case NETWORK_CLASS_WIFI:
type = "Wi-Fi";
break;
case NETWORK_CLASS_2_G:
type = "2G";
break;
case NETWORK_CLASS_3_G:
type = "3G";
break;
case NETWORK_CLASS_4_G:
type = "4G";
break;
case NETWORK_CLASS_UNKNOWN:
type = "未知";
break;
}
return type;
}
private static int getNetworkClassByType(int networkType) {
switch (networkType) {
case NETWORK_TYPE_UNAVAILABLE:
return NETWORK_CLASS_UNAVAILABLE;
case NETWORK_TYPE_WIFI:
return NETWORK_CLASS_WIFI;
case NETWORK_TYPE_GPRS:
case NETWORK_TYPE_EDGE:
case NETWORK_TYPE_CDMA:
case NETWORK_TYPE_1xRTT:
case NETWORK_TYPE_IDEN:
return NETWORK_CLASS_2_G;
case NETWORK_TYPE_UMTS:
case NETWORK_TYPE_EVDO_0:
case NETWORK_TYPE_EVDO_A:
case NETWORK_TYPE_HSDPA:
case NETWORK_TYPE_HSUPA:
case NETWORK_TYPE_HSPA:
case NETWORK_TYPE_EVDO_B:
case NETWORK_TYPE_EHRPD:
case NETWORK_TYPE_HSPAP:
return NETWORK_CLASS_3_G;
case NETWORK_TYPE_LTE:
return NETWORK_CLASS_4_G;
default:
return NETWORK_CLASS_UNKNOWN;
}
}
private static int getNetworkClass() {
int networkType = NETWORK_TYPE_UNKNOWN;
try {
final NetworkInfo network = ((ConnectivityManager) ConfigManager
.getContext()
.getSystemService(Context.CONNECTIVITY_SERVICE))
.getActiveNetworkInfo();
if (network != null && network.isAvailable()
&& network.isConnected()) {
int type = network.getType();
if (type == ConnectivityManager.TYPE_WIFI) {
networkType = NETWORK_TYPE_WIFI;
} else if (type == ConnectivityManager.TYPE_MOBILE) {
TelephonyManager telephonyManager = (TelephonyManager) ConfigManager
.getContext().getSystemService(
Context.TELEPHONY_SERVICE);
networkType = telephonyManager.getNetworkType();
}
} else {
networkType = NETWORK_TYPE_UNAVAILABLE;
}
} catch (Exception ex) {
ex.printStackTrace();
}
return getNetworkClassByType(networkType);
}
public static String getWifiRssi() {
int asu = 85;
try {
final NetworkInfo network = ((ConnectivityManager) ConfigManager
.getContext()
.getSystemService(Context.CONNECTIVITY_SERVICE))
.getActiveNetworkInfo();
if (network != null && network.isAvailable()
&& network.isConnected()) {
int type = network.getType();
if (type == ConnectivityManager.TYPE_WIFI) {
WifiManager wifiManager = (WifiManager) ConfigManager
.getContext()
.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wifiManager.getConnectionInfo();
if (wifiInfo != null) {
asu = wifiInfo.getRssi();
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return asu + "dBm";
}
public static String getWifiSsid() {
String ssid = "";
try {
final NetworkInfo network = ((ConnectivityManager) ConfigManager
.getContext()
.getSystemService(Context.CONNECTIVITY_SERVICE))
.getActiveNetworkInfo();
if (network != null && network.isAvailable()
&& network.isConnected()) {
int type = network.getType();
if (type == ConnectivityManager.TYPE_WIFI) {
WifiManager wifiManager = (WifiManager) ConfigManager
.getContext()
.getSystemService(Context.WIFI_SERVICE);
WifiInfo wifiInfo = wifiManager.getConnectionInfo();
if (wifiInfo != null) {
ssid = wifiInfo.getSSID();
if (ssid == null) {
ssid = "";
}
ssid = ssid.replaceAll("\"", "");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return ssid;
}
/**
* 检查sim卡状态
*
* @param ctx
* @return
*/
public static boolean checkSimState() {
TelephonyManager tm = (TelephonyManager) ConfigManager.getContext()
.getSystemService(Context.TELEPHONY_SERVICE);
if (tm.getSimState() == TelephonyManager.SIM_STATE_ABSENT
|| tm.getSimState() == TelephonyManager.SIM_STATE_UNKNOWN) {
return false;
}
return true;
}
/**
* 获取imei
*/
public static String getImei() {
TelephonyManager mTelephonyMgr = (TelephonyManager) ConfigManager
.getContext().getSystemService(Context.TELEPHONY_SERVICE);
String imei = mTelephonyMgr.getDeviceId();
if (imei == null) {
imei = "000000000000000";
}
return imei;
}
public static String getPhoneImsi() {
TelephonyManager mTelephonyMgr = (TelephonyManager) ConfigManager
.getContext().getSystemService(Context.TELEPHONY_SERVICE);
return mTelephonyMgr.getSubscriberId();
}
public static CellInfo getNetInfo() {
CellInfo info = new CellInfo();
try {
TelephonyManager mTelephonyManager = (TelephonyManager) ConfigManager
.getContext().getSystemService(Context.TELEPHONY_SERVICE);
String operator = mTelephonyManager.getNetworkOperator();
if (operator != null) {
/** 通过operator获取 MCC 和MNC */
if (operator.length() > 3) {
String mcc = operator.substring(0, 3);
String mnc = operator.substring(3);
info.setMcc(mcc);
info.setMnc(mnc);
}
}
int lac = 0;
int cellId = 0;
int phoneType = mTelephonyManager.getPhoneType();
if (phoneType == TelephonyManager.PHONE_TYPE_GSM) {
GsmCellLocation location = (GsmCellLocation) mTelephonyManager
.getCellLocation();
/** 通过GsmCellLocation获取中国移动和联通 LAC 和cellID */
lac = location.getLac();
cellId = location.getCid();
} else if (phoneType == TelephonyManager.PHONE_TYPE_CDMA) {
CdmaCellLocation location = (CdmaCellLocation) mTelephonyManager
.getCellLocation();
lac = location.getNetworkId();
cellId = location.getBaseStationId();
cellId /= 16;
}
if (lac == 0 || cellId == 0) {
List<NeighboringCellInfo> infos = mTelephonyManager
.getNeighboringCellInfo();
int lc = 0;
int ci = 0;
int rssi = 0;
for (NeighboringCellInfo cell : infos) {
// 根据邻区总数进行循环
if (lc == 0 || ci == 0) {
lc = cell.getLac();
ci = cell.getCid();
rssi = cell.getRssi();
}
// sb.append(" LAC : " + info.getLac());
// // 取出当前邻区的LAC
// sb.append(" CID : " + info.getCid());
// // 取出当前邻区的CID
// sb.append(" BSSS : " + (-113 + 2 * info.getRssi()) +
// "\n"); // 获取邻区基站信号强度
}
rssi = -113 + 2 * rssi;
}
} catch (Exception e) {
e.printStackTrace();
}
return info;
}
}
希望本文所述对大家学习Android软件编程有所帮助。
猜你喜欢
- Spark的算子的分类从大方向来说,Spark 算子大致可以分为以下两类:1)Transformation 变换/转换算子:这种变换并不触发
- 相信大家对 String 和 StringBuffer 的区别也已经很了解了,但是估计还是会有很多同志对这两个类的工作原理有些不清楚的地方,
- 在本文中,我们将介绍一个非常有用的Spring功能,该功能允许我们基于一个或多个Spring注释创建自己的注释。假设我们有一组经常一起使用的
- 前言idea作为一个java开发的便利IDE工具,个人是比较喜欢的,今天来探索个小功能: 导出单个类文件为jar包!JAR文件的全称是Jav
- 要求: * 对用户输入的每个字符的值进行加密,将解密后的字符串输出 * 对用户输入的已加密字符串进行解密并
- JMMJMM是指Java内存模型,不是Java内存布局,不是所谓的栈、堆、方法区。每个Java线程都有自己的工作内存。操作数据,首先从主内存
- 本文实例为大家分享了Java使用MulticastSocket实现群聊应用程序的具体代码,供大家参考,具体内容如下在这篇文章中,讨论了一个使
- 最近滑动验证码在很多网站逐步流行起来,一方面对用户体验来说,比较新颖,操作简单,另一方面相对图形验证码来说,安全性并没有很大的降低。当然到目
- 1.问题引出源码: public static void main(String[] args) { List&l
- 本文实例汇总了C#常用GDI+文字操作,包含了文字的投影、倒影、旋转等常见的效果,在进行C#应用程序开发中有不错的实用价值。分享给大家供大家
- 实践过程效果代码/** * https://zhima.blog.csdn.net/ */public partial class Form
- 需要记录日志的地方包括:进入方法的时候,传参的时候,统计执行时间,方法返回参数的时候,退出语句块的时候,出现异常的时候,等等。先来体验不使用
- 本文实例讲述了C#实现图片加相框的方法。分享给大家供大家参考,具体如下://加边框try{ Bitmap Backbmp = n
- 首先给一个简单的Builder设计模式的例子:主实现类代码如下:/** * 实体类 包含一个静态内部类 Builder */public c
- 淘宝返回的数据为:{"code":0,"data":{"country":&qu
- 在Web应用系统开发中,文件上传和下载功能是非常常用的功能,今天来讲一下JavaWeb中的文件上传和下载功能的实现。对于文件上传,浏览器在上
- 直译过来就是倒计数(CountDown)门闩(Latch)。倒计数不用说,门闩的意思顾名思义就是阻止前进。在这里就是指 CountDownL
- 自定义对象作为HashMap的Key这个问题在很多面试者面试时都会被提及,本人也是最近在看effective java第九条:覆盖equal
- 本文句句走心,希望老铁们用心阅读并实战,一定会有收获的。摘要:本文主要讨论生产环境中枚举类的使用。首先会通过对枚举类概念进行简单的介绍,引入
- 我们知道在编程时许多操作(如更新UI)需要在主线程中完成,而且,耗时操作(如网络连接)需要放在子线程中,否则会引起ANR。所以我们常使用Ha