背景:
近来有学员朋友在群里有问到一个很特别的需求,他的原文疑问如下:
转化一下他的需求如下2个要求:
1、要控制一些app在行车过程禁止打开
2、要求不可以修改任何的系统源,即不修改系统相关代码,即最好可以apk直接实现(当然可以系统app)
需求剖析:
这里其实只是第一个要求很多人可能觉得很简单,学员们纷纷回答直接startActivity时候搞个名单不就好了
这个需要修改system_server代码,所以pass
也有的回答直接在桌面Launcher的applist进行入口判断不然启动
这个学员大概思路就是,可以在桌面applist图标点击进行屏蔽,这个明显不行哈,首先不说改了Launcher代码,最重要是只是applist点击进行屏蔽根本无法覆盖,你能保证你的app启动都是通过桌面点击么,完全有可能其他场景,比如后台service启动,或者其他Activity拉起。
所以关键难度是第二个要求,不允许修改任何的系统代码,那么就需要寻找到系统是否现成有相关的接口可以直接。
实现线索寻找
学员朋友们也在积极的寻找相关的方案,最后有一个积极学员找到了一个如下方法:
frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java
/**
* Executing activity start request and starts the journey of starting an activity. Here
* begins with performing several preliminary checks. The normally activity launch flow will
* go through {@link #startActivityUnchecked} to {@link #startActivityInner}.
*/
private int executeRequest(Request request) {
//省略
if (mService.mController != null) {
//这里会调用activityStarting来返回abort,这个abort值决定是否启动
abort |= !mService.mController.activityStarting(watchIntent,
aInfo.applicationInfo.packageName);
} catch (RemoteException e) {
mService.mController = null;
}
}
//省略
if (abort) {
//判断如果是abort,则直接返回,不进行启动
return START_ABORTED;
}
上面核心就是在系统启动Activity时候,会调用一下mController的activityStarting方法来确定是否要抛弃启动。那么这里的activityStarting具体如何实现呢?这里需要先了解mController是啥类型
IActivityController mController = null;
实际上就是一个binder通讯的bp,看看对应aidl的接口说明:
frameworks/base/core/java/android/app/IActivityController.aidl
/**
* Testing interface to monitor what is happening in the activity manager
* while tests are running. Not for normal application development.
* {@hide}
*/
interface IActivityController
{
/**
* The system is trying to start an activity. Return true to allow
* it to be started as normal, or false to cancel/reject this activity.
*/
boolean activityStarting(in Intent intent, String pkg);
/**
* The system is trying to return to an activity. Return true to allow
* it to be resumed as normal, or false to cancel/reject this activity.
*/
boolean activityResuming(String pkg);
/**
* An application process has crashed (in Java). Return true for the
* normal error recovery (app crash dialog) to occur, false to kill
* it immediately.
*/
boolean appCrashed(String processName, int pid,
String shortMsg, String longMsg,
long timeMillis, String stackTrace);
/**
* Early call as soon as an ANR is detected.
*/
int appEarlyNotResponding(String processName, int pid, String annotation);
/**
* An application process is not responding. Return 0 to show the "app
* not responding" dialog, 1 to continue waiting, or -1 to kill it
* immediately.
*/
int appNotResponding(String processName, int pid, String processStats);
/**
* The system process watchdog has detected that the system seems to be
* hung. Return 1 to continue waiting, or -1 to let it continue with its
* normal kill.
*/
int systemNotResponding(String msg);
}
注释明显看出IActivityController实际上是监测AMS一些实际的发生接口,一般用于一些测试来监测系统的Activity的一些状态,这个不针对普通第三方app,属于一个隐藏api,不过对于系统app肯定是可见的。
那么下面重点就是看看这个IActivityController怎么用的,这里找到了一个am命令案例,主要有如下几步:
frameworks/base/services/core/java/com/android/server/am/ActivityManagerShellCommand.java
1 构造出IActivityController的实现类
可以看到,主要是对IActivityController.Stub
static final class MyActivityController extends IActivityController.Stub {
//省略
@Override
public boolean activityResuming(String pkg) {
//省略
return true;
}
@Override
public boolean activityStarting(Intent intent, String pkg) {
if (!shouldHandlePackageOrProcess(pkg)) {
return true;
}
//省略
return true;
}
2 调用ams接口设置Controller
frameworks/base/services/core/java/com/android/server/am/ActivityManagerShellCommand.java
void run() throws RemoteException {
mInterface.setActivityController(this, mMonkey);
最后这里会跨进程到atms,设置到atms的mController,其实就是IActivityController的bp传递到了atms,方便atms有啥动作时候进行回调
frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java
@Override
public void setActivityController(IActivityController controller, boolean imAMonkey) {
mAmInternal.enforceCallingPermission(android.Manifest.permission.SET_ACTIVITY_WATCHER,
"setActivityController()");//注意这类有权限检测
synchronized (mGlobalLock) {
mController = controller;
mControllerIsAMonkey = imAMonkey;
Watchdog.getInstance().setActivityController(controller);
}
}
上面分析完成后总结流图如下:
实战体验验证:
根据源码可以知道其实am命令就可以测试这个接口:
emu64x:/ # am -h | grep monitor
monitor [--gdb <port>] [-p <TARGET>] [-s] [-c] [-k]
Start monitoring for crashes or ANRs.
大家只需要关心-p参数就是指定的进程名字,一般就是包名。
不做任何修改使用am monitor命令监测一下短信Activity的启动
emu64x:/ # am monitor -p com.android.messaging
Monitoring activity manager... available commands:
(q)uit: finish monitoring
** Activity starting: com.android.messaging
** Activity starting: com.android.messaging
可以看到这里有输出 Activity starting: com.android.messaging,而且画面也正常显示短信,那么如果我们对 IActivityController.Stub的实现方法activityStarting返回false呢?
发现点击短信时候再也无法打开Activity,点击其他的Activity没有问题.
上图可以看到短信无法打开,但是其他电话可以打开。
其实其他Monkey等也有相关的案例可以参考:
development/cmds/monkey/src/com/android/commands/monkey/Monkey.java
所以大家完全可以在自己系统app上也类似做一个。
使用要注意以下几点:
1、继承实现 IActivityController.Stub里面的任何方法,一定不要做任何的耗时操作,因为这里是atms同步binder调用的
2、调用setActivityController注意声明相关权限SET_ACTIVITY_WATCHER
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