/*** Return a new Context object for the given application name. This* Context is the same as what the named application gets when it is* launched, containing the same resources and class loader. Each call to* this method returns a new instance of a Context object; Context objects* are not shared, however they share common state (Resources, ClassLoader,* etc) so the Context instance itself is fairly lightweight.** <p>Throws {@link PackageManager.NameNotFoundException} if there is no* application with the given package name.** <p>Throws {@link java.lang.SecurityException} if the Context requested* can not be loaded into the caller’s process for security reasons (see* {@link #CONTEXT_INCLUDE_CODE} for more information}.** @param packageName Name of the application’s package.* @param flags Option flags, one of {@link #CONTEXT_INCLUDE_CODE}*or {@link #CONTEXT_IGNORE_SECURITY}.** @return A Context for the application.** @throws java.lang.SecurityException* @throws PackageManager.NameNotFoundException if there is no application with* the given package name*/Overridepublic Context createPackageContext(String packageName, int flags)throws PackageManager.NameNotFoundException {if (packageName.equals("system") || packageName.equals("android")) {final ContextImpl context = new ContextImpl(mMainThread.getSystemContext());context.mBasePackageName = mBasePackageName;return context;}LoadedApk pi =mMainThread.getPackageInfo(packageName, mResources.getCompatibilityInfo(), flags);if (pi != null) {ContextImpl c = new ContextImpl();c.mRestricted = (flags & CONTEXT_RESTRICTED) == CONTEXT_RESTRICTED;c.init(pi, null, mMainThread, mResources, mBasePackageName);if (c.mResources != null) {return c;}}// Should be a better exception.throw new PackageManager.NameNotFoundException("Application package " + packageName + " not found");} 主要作用是:创建其它程序的Context,通过创建的这个Context，就可以访问该软件包的资源，甚至可以执行其它软件包的代码。 使用： try {Context c = createPackageContext("com.dolphin.demo", Context.CONTEXT_INCLUDE_CODE | Context.CONTEXT_IGNORE_SECURITY);} catch (SecurityException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();} 通常一个软件是不能创建其它程序的Context的，除非它们拥有相同的用户ID与签名。用户ID是一个字符串标识，在程序的AndroidManifest.xml文件的manifest标签中指定，格式为android:shareUserId="**"。安装在设备中的每一个apk程序，，Android系统会给其分配一个单独的用户空间,其中android:shareUserId就是对应一个Linux用户ID，并且为它创建一个沙箱，以防止与其它应用程序产生影响。用户ID 在应用程序被安装到设备中时分配。通过SharedUserid,拥有同一个Userid的多个APK可以配置成运行在同一个进程中，所以默认就是可以互相访问任意数据，也可以配置成运行在不同的进程中, 同时可以访问其APK的数据目录下的资源(图片，数据库和文件），就像访问本程序的数据一样。 经常的用途： 如经常一些应用提供的换皮肤功能，实现方法大致有两种： 1）把需要替换的资源图片打包好之后，放在客户端指定的目录下面，切换皮肤，查找相应的资源时，直接切换资源查找的路径到该打包文件中对应的资源路径即可。 2）把需要替换的资源，放在一个空的android 应用程序的drawable-**目录下面即可，编译，运行该apk，查找资源时，就需要用到createPackageContext获取对应包名的Context实例，然后通过context来查找对应的资源。查找时，也有两种方式： 2.1）通过ID来查找资源图片； Context context;try {context = createPackageContext("com.dolphin.demo", Context.CONTEXT_INCLUDE_CODE| Context.CONTEXT_IGNORE_SECURITY);txvA.setText(context.getResources().getText(R.string.message));} catch (NameNotFoundException e) {e.printStackTrace();} 2.2）通过资源Name，反推出资源ID，然后查找对应的资源图片； /**** @param clazz 目标资源的R.java* @param className R.java的内部类，如layout,string,drawable…* @param name 资源名称* @return*/private int getResourseIdByName(Class clazz, String className, String name) {int id = 0;try {Class[] classes = clazz.getClasses(); // 获取R.java里的所有静态内部类Class desireClass = null;for (int i = 0; i < classes.length; i++) {if (classes[i].getName().split("\\$")[1].equals(className)) {desireClass = classes[i];break;}}if (desireClass != null)id = desireClass.getField(name).getInt(desireClass);} catch (IllegalArgumentException e) {e.printStackTrace();} catch (SecurityException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (NoSuchFieldException e) {e.printStackTrace();}return id;}Context context;try {context = createPackageContext("com.dolphin.demo", Context.CONTEXT_INCLUDE_CODE| Context.CONTEXT_IGNORE_SECURITY);Class cls = context.getClassLoader().loadClass("com.dolphin.demo.R"); // 获得目标apk的R类txvA.setText(context.getResources().getText(getResourseIdByName(cls, "string", "message")));} catch (NameNotFoundException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();}
唯有讲述此间途经的美景，分享没有男主角的相片。
