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安卓开发避不开的一个点就是权限申请，从以前的只需简单声明所用权限到Android M开始的动态权限申请，安卓变得更安全了，但是开发时候需要考虑的东西也就多了。关于动态权限申请，你可以借助一些第三方的库，使用很简单。当然，动态权限申请其实也不是什么复杂的过程，所以完全可以自己简单地实现。本笔记主要介绍博主常用的处理方式，附带一个简单的demo，请求存储和相机权限。下面进入正题。为了操作更直观更方便，首先新建一个工具类：PermissionCheck.java。里面封装了权限检查方法。代码如下： package org.devsong.permissionrequest; import android.content.Context; import android.content.pm.PackageManager; import android.support.v4.content.ContextCompat; public class PermissionCheck { private Context context; public PermissionCheck(Context context){ this.context = context; } /** * 检查是否获取了所有权限 * @param permissions ：权限集合 * @return ：检查结果 */ public boolean hasPermissions(String...permissions){ for(String permission : permissions){ if(!isGrantedPermission(permission)){ return false; } } return true; } /** * 判断是否获取权限 * @param permission 权限 * @return */ public boolean isGrantedPermission(String permission){ return ContextCompat.checkSelfPermission(context, permission) == PackageManager.PERMISSION_GRANTED; } /** * 从请求结果中判断是否获取了所有权限 * @param res 请求结果集合 * @return */ public boolean hasAllPermission(int[] res){ for(int i : res){ if(i == PackageManager.PERMISSION_DENIED){ return false; } } return true; } } 由于上述工具需要用到运行上下文，所以需要在activity里面初始化一下。下面是MainActivity的代码： package org.devsong.permissionrequest; import android.content.DialogInterface; import android.content.Intent; import android.net.Uri; import android.os.Build; import android.provider.Settings; import android.support.annotation.NonNull; import android.support.v4.app.ActivityCompat; import android.support.v7.app.AlertDialog; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.widget.Toast; public class MainActivity extends AppCompatActivity { private boolean isGotPermission = false; private PermissionCheck permissionCheck; private AlertDialog dialog; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); permissionCheck = new PermissionCheck(getApplicationContext()); //初始化 } /** * 结合 Activity 的生命周期来看，权限检查放到 onResume 里面是比较合适的 * 因为在引导用户跳转到 App 详情页面后并不能保证用户一定会开启权限，所以当用户返回 App 时需要再次检查权限 */ @Override protected void onResume() { super.onResume(); if (!isGotPermission && Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && !permissionCheck.hasPermissions(IConst.PERMISSION_ARR)) { if (!shouldAlertPermissionRequestDialog()) { //如果不需要弹出自定义的引导开启权限窗口则用系统默认的处理方式（默认权限请求窗口）请求权限 ActivityCompat.requestPermissions(this, IConst.PERMISSION_ARR, IConst.PERMISSION_REQUEST_CODE); } else if (dialog == null) { //否则如果没有弹出自定义的权限开启引导窗口则开启 showPermissionReqDialog(); } } } /** * 权限请求结果处理 * @param requestCode 请求代号 * @param permissions 权限数组 * @param grantResults 请求结果 */ @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { super.onRequestPermissionsResult(requestCode, permissions, grantResults); if (requestCode == IConst.PERMISSION_REQUEST_CODE && permissionCheck.hasAllPermission(grantResults)) { Toast.makeText(getApplicationContext(), "获取权限成功", Toast.LENGTH_SHORT).show(); isGotPermission = true; } else if (shouldAlertPermissionRequestDialog()) { //如果没有请求成功，则弹出自定义的权限引导对话框，引导用户到设置里面开启权限 showPermissionReqDialog(); } } /** * 自定义的权限请求引导对话框 */ private void showPermissionReqDialog() { AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setTitle("权限申请").setMessage("程序缺少必要权限，请打开点击\"设置\"->开启相关权限。"); builder.setNegativeButton("退出", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialogInterface, int i) { //如果用户点击退出，则表示用户不想授予必要权限，结束运行 Toast.makeText(getApplicationContext(), "未获取权限，结束运行。", Toast.LENGTH_SHORT).show(); finish(); } }); builder.setPositiveButton("设置", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialogInterface, int i) { //若用户点击了设置，则跳转到app的详情页面 startSetting(); } }); builder.setCancelable(false); dialog = builder.show(); } /** * 跳转到软件详情页面 */ public void startSetting() { dialog.dismiss(); //关闭自定义的权限请求对话框 dialog = null; Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS); intent.setData(Uri.parse(IConst.PACKAGE_URL_SCHEME + getPackageName())); startActivity(intent); } /** * 判断是否应该弹出用户自定义对话框引导用户开启权限 */ public boolean shouldAlertPermissionRequestDialog() { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { for (String permission : IConst.PERMISSION_ARR) { //shouldShowRequestPermissionRationale：默认返回false, 实测对应的权限点击了拒绝就会返回true，并不是网上描述的点击了不再提醒才返回true //可能是安卓太自由，定制化系统太多，产生了差异，不能说谁对谁错 if (shouldShowRequestPermissionRationale(permission)) { return true; } } } return false; } } 最后是一些常量，单独放到一个类里面方便维护：IConst.java package org.devsong.permissionrequest; import android.Manifest; public class IConst { //测试权限：存储、相机 public static final String[] PERMISSION_ARR = {Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.CAMERA}; public static final int PERMISSION_REQUEST_CODE = 1; public static final String PACKAGE_URL_SCHEME = "package:"; } 一些需要注意的地方代码里也做了说明。按照上面过程可以方便地完成动态权限的申请。下面是运行结果的展示。测试环境：原生安卓 6.0

熟悉安卓开发的朋友应该对OKHttp这个网络框架不陌生，使用OKHttp框架可以轻松地进行网络操作。但是奇怪的一点是OKHttp并未提供Session持久化选项，这就导致如果我们需要用session记录一些东西，如登录状态时，就不行了。所以我们需要手动编写session持久化的代码。本篇笔记围绕的就是Session的持久化操作，网络上也有很多相关的博文，我整理了一些优秀且实测可用的内容。在文章末尾，你可根据需要下载我写的简单Demo，可以参考操作。 HttpSession 持久化主要涉及三个类：（1）PersistentCookieStore ，这个类主要是将Cookie缓存在内存中以及从内存中将持久化文件重新转换为Cookie。代码如下： package org.devsong.okhttpsessionpersistent.httputil; import android.content.Context; import android.content.SharedPreferences; import android.text.TextUtils; import android.util.Log; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Locale; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import okhttp3.Cookie; import okhttp3.HttpUrl; /** * Created by SONG on 2018/3/9. */ public class PersistentCookieStore { private static final String LOG_TAG = "PersistentCookieStore"; private static final String COOKIE_PREFS = "Cookies_Prefs"; private final Map<String, ConcurrentHashMap<String, Cookie>> cookies; private final SharedPreferences cookiePrefs; public PersistentCookieStore(Context context) { cookiePrefs = context.getSharedPreferences(COOKIE_PREFS, 0); cookies = new HashMap<>(); //将持久化的cookies缓存到内存中即map cookies Map<String, > prefsMap = cookiePrefs.getAll(); for (Map.Entry<String, > entry : prefsMap.entrySet()) { String[] cookieNames = TextUtils.split((String) entry.getValue(), ","); for (String name : cookieNames) { String encodedCookie = cookiePrefs.getString(name, null); if (encodedCookie != null) { Cookie decodedCookie = decodeCookie(encodedCookie); if (decodedCookie != null) { if (!cookies.containsKey(entry.getKey())) { cookies.put(entry.getKey(), new ConcurrentHashMap<String, Cookie>()); } cookies.get(entry.getKey()).put(name, decodedCookie); } } } } } protected String getCookieToken(Cookie cookie) { return cookie.name() + "@" + cookie.domain(); } public void add(HttpUrl url, Cookie cookie) { String name = getCookieToken(cookie); //将cookies缓存到内存中如果缓存过期就重置此cookie if (!cookie.persistent()) { if (!cookies.containsKey(url.host())) { cookies.put(url.host(), new ConcurrentHashMap<String, Cookie>()); } cookies.get(url.host()).put(name, cookie); } else { if (cookies.containsKey(url.host())) { cookies.get(url.host()).remove(name); } } //将cookies持久化到本地 SharedPreferences.Editor prefsWriter = cookiePrefs.edit(); prefsWriter.putString(url.host(), TextUtils.join(",", cookies.get(url.host()).keySet())); prefsWriter.putString(name, encodeCookie(new SerializableOkHttpCookies(cookie))); prefsWriter.apply(); } public List<Cookie> get(HttpUrl url) { ArrayList<Cookie> ret = new ArrayList<>(); if (cookies.containsKey(url.host())) ret.addAll(cookies.get(url.host()).values()); return ret; } public boolean removeAll() { SharedPreferences.Editor prefsWriter = cookiePrefs.edit(); prefsWriter.clear(); prefsWriter.apply(); cookies.clear(); return true; } public boolean remove(HttpUrl url, Cookie cookie) { String name = getCookieToken(cookie); if (cookies.containsKey(url.host()) && cookies.get(url.host()).containsKey(name)) { cookies.get(url.host()).remove(name); SharedPreferences.Editor prefsWriter = cookiePrefs.edit(); if (cookiePrefs.contains(name)) { prefsWriter.remove(name); } prefsWriter.putString(url.host(), TextUtils.join(",", cookies.get(url.host()).keySet())); prefsWriter.apply(); return true; } else { return false; } } public List<Cookie> getCookies() { ArrayList<Cookie> ret = new ArrayList<>(); for (String key : cookies.keySet()) ret.addAll(cookies.get(key).values()); return ret; } /** * cookies 序列化成 string * * @param cookie 要序列化的cookie * @return 序列化之后的string */ protected String encodeCookie(SerializableOkHttpCookies cookie) { if (cookie == null) return null; ByteArrayOutputStream os = new ByteArrayOutputStream(); try { ObjectOutputStream outputStream = new ObjectOutputStream(os); outputStream.writeObject(cookie); } catch (IOException e) { Log.d(LOG_TAG, "IOException in encodeCookie", e); return null; } return byteArrayToHexString(os.toByteArray()); } /** * 将字符串反序列化成cookies * * @param cookieString cookies string * @return cookie object */ protected Cookie decodeCookie(String cookieString) { byte[] bytes = hexStringToByteArray(cookieString); ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes); Cookie cookie = null; try { ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream); cookie = ((SerializableOkHttpCookies) objectInputStream.readObject()).getCookies(); } catch (IOException e) { Log.d(LOG_TAG, "IOException in decodeCookie", e); } catch (ClassNotFoundException e) { Log.d(LOG_TAG, "ClassNotFoundException in decodeCookie", e); } return cookie; } /** * 二进制数组转十六进制字符串 * * @param bytes byte array to be converted * @return string containing hex values */ protected String byteArrayToHexString(byte[] bytes) { StringBuilder sb = new StringBuilder(bytes.length * 2); for (byte element : bytes) { int v = element & 0xff; if (v < 16) { sb.append('0'); } sb.append(Integer.toHexString(v)); } return sb.toString().toUpperCase(Locale.US); } /** * 十六进制字符串转二进制数组 * * @param hexString string of hex-encoded values * @return decoded byte array */ protected byte[] hexStringToByteArray(String hexString) { int len = hexString.length(); byte[] data = new byte[len / 2]; for (int i = 0; i < len; i += 2) { data[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character.digit(hexString.charAt(i + 1), 16)); } return data; } } 另一个重要的类是SerializableOkHttpCookies，也就是序列化Cookie，以便进行网络传输。代码如下： package org.devsong.okhttpsessionpersistent.httputil; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import okhttp3.Cookie; /** * Created by SONG on 2018/3/9. */ public class SerializableOkHttpCookies implements Serializable { private transient final Cookie cookies; private transient Cookie clientCookies; public SerializableOkHttpCookies(Cookie cookies) { this.cookies = cookies; } public Cookie getCookies() { Cookie bestCookies = cookies; if (clientCookies != null) { bestCookies = clientCookies; } return bestCookies; } private void writeObject(ObjectOutputStream out) throws IOException { out.writeObject(cookies.name()); out.writeObject(cookies.value()); out.writeLong(cookies.expiresAt()); out.writeObject(cookies.domain()); out.writeObject(cookies.path()); out.writeBoolean(cookies.secure()); out.writeBoolean(cookies.httpOnly()); out.writeBoolean(cookies.hostOnly()); out.writeBoolean(cookies.persistent()); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { String name = (String) in.readObject(); String value = (String) in.readObject(); long expiresAt = in.readLong(); String domain = (String) in.readObject(); String path = (String) in.readObject(); boolean secure = in.readBoolean(); boolean httpOnly = in.readBoolean(); boolean hostOnly = in.readBoolean(); boolean persistent = in.readBoolean(); Cookie.Builder builder = new Cookie.Builder(); builder = builder.name(name); builder = builder.value(value); builder = builder.expiresAt(expiresAt); builder = hostOnly builder.hostOnlyDomain(domain) : builder.domain(domain); builder = builder.path(path); builder = secure builder.secure() : builder; builder = httpOnly builder.httpOnly() : builder; clientCookies = builder.build(); } } 最后是CookiesManager ，这个作为最顶层的管理文件，从response中读取并存储信息到Cookie，从存储的Cookie文件中加载信息放到Request传输至服务器。代码如下： /** * Cookie 管理类，自动管理Cookie */ public class CookiesManager implements CookieJar { private final PersistentCookieStore cookieStore = new PersistentCookieStore(getApplicationContext()); @Override public void saveFromResponse(@NonNull HttpUrl url, @NonNull List<Cookie> cookies) { if (cookies.size() > 0) { for (Cookie item : cookies) { cookieStore.add(url, item); } } } @Override public List<Cookie> loadForRequest(@NonNull HttpUrl url) { return cookieStore.get(url); } } Demo测试，服务器部分有了以上三个类，我们就能进行下一步的工作了，首先，得先写一个服务端。这里我只是简单写了一个servlet，当收到请求时，以文本的形式回复客户端。servlet如下： package org.devsong.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @WebServlet(urlPatterns={"/"}, name="SessionIdServlet") public class SessionServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String sessionId = req.getSession().getId(); System.out.println("当前SessionId:" + sessionId); resp.setContentType("text/plain; charseet=utf-8"); PrintWriter writer = resp.getWriter(); writer.print("当前SessionId:" + sessionId); writer.flush(); writer.close(); } } 服务端其他文件就不贴出来，如果您需要，可以到文章末尾选择下载。安卓客户端Demo 服务器端构建完成，下面就是客户端了，客户端也很简单，就是发送请求，然后将接收到的信息加载到一个TextView。由于网络操作是一个耗时的操作，直接在ui线程中操作显然是不合理的，所以需要单独创建一个线程：HttpThread，代码如下： HttpThread.java package org.devsong.okhttpsessionpersistent.httputil; import android.util.Log; import java.io.IOException; import okhttp3.Call; import okhttp3.Callback; import okhttp3.OkHttpClient; import okhttp3.Request; import okhttp3.Response; public class HttpThread extends Thread { private static OkHttpClient okHttpClient; private IDataProcess dataProcess; private String url; public static void initHttpThread(OkHttpClient okHttpClient) { HttpThread.okHttpClient = okHttpClient; } public HttpThread(String url, IDataProcess dataProcess) { this.url = url; this.dataProcess = dataProcess; } @Override public void run() { if (okHttpClient == null) { Log.e("HttpThread", "error: HTTPThread 尚未初始化"); return; } //如果需要传数据，那么只需要新建一个RequestBody，然后build进去就行了 Request.Builder builder = new Request.Builder(); Request request = builder.url(url).build(); Call call = okHttpClient.newCall(request); call.enqueue(new Callback() { @Override public void onFailure(Call call, IOException e) { e.printStackTrace(); dataProcess.process("error: 数据请求失败！描述：" + e.getMessage()); } @Override public void onResponse(Call call, Response response) throws IOException { dataProcess.process(response.body().string()); } }); } } 为方便查看，这里也贴出MainActivity.java package org.devsong.okhttpsessionpersistent; import android.support.annotation.NonNull; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.text.method.ScrollingMovementMethod; import android.view.View; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast; import org.devsong.okhttpsessionpersistent.httputil.HttpThread; import org.devsong.okhttpsessionpersistent.httputil.IDataProcess; import org.devsong.okhttpsessionpersistent.httputil.PersistentCookieStore; import org.devsong.okhttpsessionpersistent.utils.MyTools; import java.util.List; import java.util.concurrent.TimeUnit; import okhttp3.Cookie; import okhttp3.CookieJar; import okhttp3.HttpUrl; import okhttp3.OkHttpClient; public class MainActivity extends AppCompatActivity { private TextView tv; private String ip = "172.31.241.22:8080"; private EditText et_ip; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); tv = findViewById(R.id.tv_res_disp); tv.setMovementMethod(new ScrollingMovementMethod()); et_ip = findViewById(R.id.ip); et_ip.setText(ip); //新建OKHttpClient对象 OkHttpClient client = new OkHttpClient.Builder().connectTimeout(10, TimeUnit.SECONDS).cookieJar(new CookiesManager()).build(); //初始化HttpThread HttpThread.initHttpThread(client); } /** * Cookie 管理类，自动管理Cookie */ public class CookiesManager implements CookieJar { private final PersistentCookieStore cookieStore = new PersistentCookieStore(getApplicationContext()); @Override public void saveFromResponse(@NonNull HttpUrl url, @NonNull List<Cookie> cookies) { if (cookies.size() > 0) { for (Cookie item : cookies) { cookieStore.add(url, item); } } } @Override public List<Cookie> loadForRequest(@NonNull HttpUrl url) { return cookieStore.get(url); } } public void click(View view){ switch (view.getId()){ case R.id.btn_send: doSend(); break; } } /** * 发送一次请求，将服务器返回结果显示在文本区 */ public void doSend(){ ip = et_ip.getText().toString(); if("".equals(ip.trim())){ Toast.makeText(MainActivity.this, "请输入IP或网址", Toast.LENGTH_SHORT).show(); return; } //访问本机端口8080 //安卓虚拟机访问电脑不能用Localhost:8080, 要将localhost替换为本机IP new HttpThread("http://" + ip + "/", new IDataProcess() { @Override public void process(final String data) { runOnUiThread(new Runnable() { @Override public void run() { tv.setText(String.format("%s%s\n\n%s", MyTools.getDateStr(System.currentTimeMillis(), "yyyy/MM/dd HH:mm:ss ->"), data, tv.getText().toString())); } }); } }).start(); } } 最终测试效果最后效果如下，可以看到每次请求服务器返回的 SessionId 是一致的：附件下载：服务器端工程（Eclipse）：点此下载客户端工程（AndroidStudio）：点此下载客户端APK文件：点此下载