android技术特别成熟了,热修复,组件化…等框架已经层出不穷,如果还仅限于使用框架,技术永远很难得到成长,只有我们懂得他的原理,能够娓娓道来,能够自己动手的写出来,技术才会越来越好,与其想着未来怎么办,不如把握现在。这一篇文章教大家手写出插件化框架,插件化技术是Android工程师必备的技术之一,我们要懂其思想,知其原理。
那么在 android中,什么是「 插件化 」,顾名思义啊,就是把一些核心复杂依赖度高的业务模块封装成独立的插件,然后根据不同业务需求进行不同组合,动态进行替换,可对插件进行管理、更新,后期对插件也可进行版本管理等操作。在插件化中有两个概念需要讲解下:
宿主:
所谓宿主,就是需要能提供运行环境,给资源调用提供上下文环境,一般也就是我们主 APK ,要运行的应用,它作为应用的主工程所在,实现了一套插件的加载和管理的框架,插件都是依托于宿主的APK而存在的。
插件:
插件可以想象成每个独立的功能模块封装为一个小的 APK ,可以通过在线配置和更新实现插件 APK 在宿主 APK 中的上线和下线,以及动态更新等功能。
那么为何要使用插件化技术,它有何优势,能给我们带来什么样好处,这里简单列举了以下几点:
让用户不用重新安装 APK 就能升级应用功能,减少发版本频率,增加用户体验。 提供一种快速修复线上 BUG 和更新的能力。 按需加载不同的模块,实现灵活的功能配置,减少服务器对旧版本接口兼容压力。 模块化、解耦合、并行开发、 65535 问题。
简单描述一下入门的知识
首先我们要知道插件化技术是属于比较复杂一个领域,复杂点在于它涉及知识点广泛,不仅仅是上层做应用架构能力,还要求我们对 Android 系统底层知识需要有一定的认知,这里简单罗列了其中会涉及的知识点:
然后这一篇文章我带大家来熟悉及实现广播插件,广播主要分两种,一种动态广播,一种静态广播。
启动插件中的动态广播其实和启动Activity和Service是一样的流程.
首先我们需要在 通用库里面新建一个接口,插件中的广播都要实现此接口
public interface PluginInterfaceBroadcast {
void attach(Context context);
void onReceive(Context context, Intent intent);
}
然后在BaseActivity中重写registerReceiver 和sendBroadcast、unregisterReceiver,因为这两个方法都用到了上下文(Context),我们需要用宿主(app)的Context来注册和发送广播.代码如下:
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
if (mActivity != null) {
return mActivity.registerReceiver(receiver, filter);
}
return super.registerReceiver(receiver, filter);
}
@Override
public void sendBroadcast(Intent intent) {
if (null != mActivity) {
mActivity.sendBroadcast(intent);
} else {
super.sendBroadcast(intent);
}
}
@Override
public void unregisterReceiver(BroadcastReceiver receiver) {
if (null != mActivity) {
mActivity.unregisterReceiver(receiver);
} else {
super.unregisterReceiver(receiver);
}
}
上述代码其实就是,调用了宿主(app)的里面方法,就是启动了宿主定义好的第一个空壳的广播,然后通过DexClassLoader反射插件中的广播类,然后通过继承的接口,来进行方法的调用和参数的传递.
public class ProxyBroadcast extends BroadcastReceiver {
private String className;
private PluginInterfaceBroadcast bordcast;
private static final String TAG = "ProxyBroadcast";
public ProxyBroadcast(String name, Context context) {
this.className = name;
Class loadClass = null;
try {
loadClass = PluginManager.getInstance().getClassLoader().loadClass(className);
Constructor constructor = loadClass.getConstructor(new Class[]{});
bordcast = (PluginInterfaceBroadcast) constructor.newInstance(new Object[]{});
bordcast.attach(context);
} catch (Exception e) {
e.printStackTrace();
}
}
//class --- object --- p
@Override
public void onReceive(Context context, Intent intent) {
Log.e(TAG, "ProxyBroadcast onReceive: ");
if (bordcast != null) {
bordcast.onReceive(context, intent);
}
}
}
同理,在宿主方法中需要做一些处理,new ProxyBroadcast 然后注册此广播,实际上就是注册了宿主的空壳的一个广播:
private List proxyBroadcastList = new ArrayList<>();
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
//重写真正注册的是ProxyBroadcast 转发
IntentFilter filter1 = new IntentFilter();
for (int i = 0; i < filter.countActions(); i++) {
filter1.addAction(filter.getAction(i));
Log.e(TAG, "sendBroadcast: 注册插件的广播 -> " + filter1.getAction(i));
}
ProxyBroadcast proxyBroadcast = new ProxyBroadcast(receiver.getClass().getName(), this);
proxyBroadcastList.add(proxyBroadcast);
return super.registerReceiver(proxyBroadcast, filter1);
}
@Override
public void unregisterReceiver(BroadcastReceiver receiver) {
if (proxyBroadcastList != null && proxyBroadcastList.size() > 0) {
for (ProxyBroadcast proxyBroadcast : proxyBroadcastList) {
if (proxyBroadcast.getClass().getName().equals(receiver.getClass().getName())) {
super.unregisterReceiver(proxyBroadcast);
}
}
} else {
super.unregisterReceiver(receiver);
}
}
我们来看一个插件中的广播实现,通过继承PluginInterfaceBroadcast,宿主调用接口的方法:
public class MyReceive extends BroadcastReceiver implements PluginInterfaceBroadcast {
@Override
public void attach(Context context) {
Toast.makeText(context, "注册广播成功", Toast.LENGTH_SHORT).show();
}
@Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context, "接收广播成功", Toast.LENGTH_SHORT).show();
}
}
这样我们就实现了,插件动态广播的实现,是不是的非常简单,几乎没有什么难点,接下来我们来看插件静态广播如何来实现
我们知道任何插件都是没有安装到手机上的,静态广播是注册在AndroidManifest中,那么,我们就不能通过上述那样轻松的拿到类名进行反射了,如下
需要通过PMS来解析xml,拿到在xml注册的类名,和intent-filter,然后和上面讲的动态广播一样,宿主动态注册插件中的静态广播,以达到这样的效果.实际上宿主就是做了动态注册静态广播,都是天马行空的想象.
apk安装时并有做很多操作,那么它是如何真正的加载静态广播? 真正的加载广播,是在系统启动时发生的, 系统启动就可以理解成 将所有app重新安装一遍到系统中,会重复上述过程.
为了方便阅读,我已经将PackageManagerService 和PackageParser的源码放到了代码中,结合起来阅读本文更容易理解.
PMS 全称(PackageManagerService) ,当安装apk时会调用PackageManagerService的main方法
public static final PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
ServiceManager.addService("package", m);
return m;
}
很显然上述代码,new PackageManagerService,我们接着看PackageManagerService的构造方法.然后我们可以看到data app 这样创建的目录,着重关注mAppInstallDir,字面意思就是app的安装路径
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
.....
synchronized (mPackages) {
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_BACKGROUND, true /*allowIo*/);
mHandlerThread.start();
mHandler = new PackageHandler(mHandlerThread.getLooper());
Watchdog.getInstance().addThread(mHandler, WATCHDOG_TIMEOUT);
//TODO
File dataDir = Environment.getDataDirectory();
mAppDataDir = new File(dataDir, "data");
mAppInstallDir = new File(dataDir, "app");
mAppLib32InstallDir = new File(dataDir, "app-lib");
mAsecInternalPath = new File(dataDir, "app-asec").getPath();
mUserAppDataDir = new File(dataDir, "user");
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
......
if (!mOnlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
scanDirLI(mAppInstallDir, 0, scanFlags, 0);
scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
scanFlags, 0);
.....
}
}
接着会调用scanDirLI去扫面apk文件,点击去看一下它做了什么? 内部有调用scanPackageLI方法.
private void scanDirLI(File dir, int parseFlags, int scanFlags, long currentTime) {
for (File file : files) {
final boolean isPackage = (isApkFile(file) || file.isDirectory())
&& !PackageInstallerService.isStageName(file.getName());
if (!isPackage) {
// Ignore entries which are not packages
continue;
}
try {
scanPackageLI(file, parseFlags | PackageParser.PARSE_MUST_BE_APK,
scanFlags, currentTime, null);
} catch (PackageManagerException e) {
Slog.w(TAG, "Failed to parse " + file + ": " + e.getMessage());
// Delete invalid userdata apps
if ((parseFlags & PackageParser.PARSE_IS_SYSTEM) == 0 &&
e.error == PackageManager.INSTALL_FAILED_INVALID_APK) {
logCriticalInfo(Log.WARN, "Deleting invalid package at " + file);
if (file.isDirectory()) {
FileUtils.deleteContents(file);
}
file.delete();
}
}
}
}
接着点scanPackageLI,从字面意思上看是解析包,我们看看它做了什么?返回了一个Package,这个Package是不是我们想要的呢?
private PackageParser.Package scanPackageLI(File scanFile, int parseFlags, int scanFlags,
long currentTime, UserHandle user) throws PackageManagerException {
....
final PackageParser.Package pkg;
try {
pkg = pp.parsePackage(scanFile, parseFlags);
} catch (PackageParserException e) {
throw PackageManagerException.from(e);
}
.....
}
看一下Package 里面有什么? 很显然它是我们想要的Package存放的就是AndroidManifest.xml 注册的四大组件.
public final static class Package {
....
public final ArrayList activities = new ArrayList(0);
public final ArrayList receivers = new ArrayList(0);
public final ArrayList providers = new ArrayList(0);
public final ArrayList services = new ArrayList(0);
......
}
注意这里的Activity不是四大组件的Activity而是PackageParser的一个内部类,activity 与receivers 在 AndroidManifest里面属性都差不多一样,很显然Google复用了Activity.
我们来看一下Activity里面存放了什么?
public final static class Activity extends Component {
public final ActivityInfo info;
public Activity(final ParseComponentArgs args, final ActivityInfo _info) {
super(args, _info);
info = _info;
info.applicationInfo = args.owner.applicationInfo;
}
public void setPackageName(String packageName) {
super.setPackageName(packageName);
info.packageName = packageName;
}
.......
}
Activity中只存放了ActivityInfo,继续点进去ActivityInfo中是否有我们想要的类名等信息
ActivityInfo extends ComponentInfo
ComponentInfo extends PackageItemInfo
/**
* Public name of this item. From the "android:name" attribute.
*/
public String name;
PackageItemInfo中找到了这样的一个属性,终于找到了我们想要的类名了.只要我们拿到ActivityInfo就可以拿到类名
但是还忽略了一点,intent-filter 还没有找到,从代码中看
final static class Activity extends Component
public static class Component {
public final Package owner;
public final ArrayList intents;
public final String className;
public Bundle metaData;
}
ArrayList intents 看起来像是intent-filter,II泛型 --> IntentInfo
public static class IntentInfo extends IntentFilter {
public boolean hasDefault;
public int labelRes;
public CharSequence nonLocalizedLabel;
public int icon;
public int logo;
public int banner;
public int preferred;
}
可以看到IntentInfo 继承 IntentFilter,找到了IntentFilter.
从上述代码中,我们可以知道通过,parsePackage解析包,得到Package,就可以拿到AndroidManifeast的信息.
PackageParser pp = new PackageParser();
final PackageParser.Package pkg;
//解析apk 得到pkg
pkg = pp.parsePackage(scanFile, parseFlags);
但是很不幸的是,Google将这个类写成了@hide 隐藏的API那我们就只能通过反射去获取了,感觉瞬间脑壳痛了.
没有办法嘞,我们就只能硬来咯
首先我们实例化PackageParser然后调用parsePackage得到Package
//反射获取解析apk包的类
Class packageParserClass = Class.forName("android.content.pm.PackageParser");
//获取方法
Method parsePackage = packageParserClass.getDeclaredMethod("parsePackage",
File.class, int.class);
//实例化PackageParser类
Object packageParser = packageParserClass.newInstance();
//Package 得到
Object packageObj = parsePackage.invoke(packageParser, new File(absolutePath), PackageManager.GET_ACTIVITIES);
//拿到注册的静态广播
然后通过Package拿到xml注册的静态广播
//拿到注册的静态广播
Field receiversField = packageObj.getClass().getDeclaredField("receivers");
//获取List
List receivers = (List) receiversField.get(packageObj);
然后循环Activity,拿到类名和intent-fliter
//循环receivers
for (Object activity : receivers) {
//拿到ActivityInfo
ActivityInfo info = (ActivityInfo) generateReceiverInfo.invoke(packageParser, activity, 0, defaltUserState, userId);
//根据ActivityInfo,拿到BroadCastReceiver
BroadcastReceiver broadcastReceiver = (BroadcastReceiver) classLoader.loadClass(info.name).newInstance();
//拿到intentFilter
List intentFilters = (List) intentsField.get(activity);
for (IntentFilter filter : intentFilters) {
//动态注册插件中的静态广播
context.registerReceiver(broadcastReceiver, filter);
}
}
SystemService -> main
->scanDirLI 扫描apk的文件 --》scanPackageLI 解析apk PackageParser -> parsePackage get Package (一个apk对应一个package)
-> parseBaseApk loadApkIntoAssetManager -> parseBaseApk -> parseBaseApplication -> parseActivity -> parseIntent
/**
* 解析xml静态注册的广播
*
* @param context
* @param absolutePath
*/
private void parserReceive(Context context, String absolutePath) {
try {
//反射获取解析apk包的类
Class packageParserClass = Class.forName("android.content.pm.PackageParser");
//获取方法
Method parsePackage = packageParserClass.getDeclaredMethod("parsePackage",
File.class, int.class);
//实例化PackageParser类
Object packageParser = packageParserClass.newInstance();
//Package 得到
Object packageObj = parsePackage.invoke(packageParser, new File(absolutePath), PackageManager.GET_ACTIVITIES);
//拿到注册的静态广播
Field receiversField = packageObj.getClass().getDeclaredField("receivers");
//获取List
List receivers = (List) receiversField.get(packageObj);
//public final static class Activity extends Component
//获取Component
Class componentClass = Class.forName("android.content.pm.PackageParser$Component");
//获取intents
Field intentsField = componentClass.getDeclaredField("intents");
//generatePackageInfo(PackageParser.Package p,
// int gids[], int flags, long firstInstallTime, long lastUpdateTime,
// HashSet grantedPermissions, PackageUserState state, int userId)
// 调用generateActivityInfo 方法, 把PackageParser.Activity 转换成
Class packageParser$ActivityClass = Class.forName("android.content.pm.PackageParser$Activity");
// generateActivityInfo方法
Class packageUserStateClass = Class.forName("android.content.pm.PackageUserState");
Object defaltUserState = packageUserStateClass.newInstance();
Method generateReceiverInfo = packageParserClass.getDeclaredMethod("generateActivityInfo",
packageParser$ActivityClass, int.class, packageUserStateClass, int.class);
//获取userID
Class userHandler = Class.forName("android.os.UserHandle");
Method getCallingUserIdMethod = userHandler.getDeclaredMethod("getCallingUserId");
int userId = (int) getCallingUserIdMethod.invoke(null);
//循环receivers
for (Object activity : receivers) {
//拿到ActivityInfo
ActivityInfo info = (ActivityInfo) generateReceiverInfo.invoke(packageParser, activity, 0, defaltUserState, userId);
//根据ActivityInfo,拿到BroadCastReceiver
BroadcastReceiver broadcastReceiver = (BroadcastReceiver) classLoader.loadClass(info.name).newInstance();
//拿到intentFilter
List intentFilters = (List) intentsField.get(activity);
for (IntentFilter filter : intentFilters) {
//动态注册插件中的静态广播
context.registerReceiver(broadcastReceiver, filter);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
插件中的静态广播就不需要实现接口PluginInterfaceBroadcast
public class StaticBroadcastReceiver extends BroadcastReceiver {
private static final String ACTION = "com.prim.plugin.host";
@Override
public void onReceive(Context context, Intent intent) {
Toast.makeText(context, "我是插件,收到发送的广播,我将向宿主发送广播", Toast.LENGTH_SHORT).show();
//接收到广播,然后给宿主发送广播
context.sendBroadcast(new Intent(ACTION));
}
}
如果前面我说的还有点不理解,我在举个例子:
(以下的静A 表示静态广播接收器,同理动B。)
1、 静A (优先级1)
2、 动B(优先级1)
3、 静C (优先级2,后扫描)
4、静D (优先级2,先扫描)
5 、动E (优先级2,先注册)
6、 动F (优先级2,后注册)
当来了一个 有序广播,接收顺序如下:动E > 动F > 静D > 静C > 动B > 静A
当来了一个 普通广播,接收顺序如下:动E > 动F > 动B > 静D > 静C > 静A
Android插件化的发展方向
Android插件化方向主要有2个方向: