关于Android重启机器，之前的任务还是会显示出来的修改

http://blog.csdn.net/qq_27062249/article/details/54645214

当系统重启的时候，会由ActivityManagerService操作TaskPersister类的restoreTasksLocked方法去读取，见下面代码：
ActivityManagerService在源码中的位置：./frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java:

[java] view plain copy

public void systemReady(final Runnable goingCallback) {

   synchronized(this) {  
       if (mSystemReady) {  
           // If we're done calling all the receivers, run the next "boot phase" passed in  
           // by the SystemServer  
           if (goingCallback != null) {  
               goingCallback.run();  
           }  
           return;  
       }  

       mLocalDeviceIdleController  
               = LocalServices.getService(DeviceIdleController.LocalService.class);  

       // Make sure we have the current profile info, since it is needed for  
       // security checks.  
       updateCurrentProfileIdsLocked();  
       mRecentTasks.clear();  
       mRecentTasks.addAll(mTaskPersister.restoreTasksLocked());  
       mRecentTasks.cleanupLocked(UserHandle.USER_ALL);  
       mTaskPersister.startPersisting();  
//省略部分代码,保留关键部分  

}

现在客户有一个需求，就是在设备重启的时候不需要显示上一次保存的应用。
这个需求其实很简单哟,TaskPersister类里添加删除保存的数据的方法,在ActivityManagerService初始化的时候调用就好了,见一下代码:
TaskPersister里添加删除的方法:

[java] view plain copy

private void removeAllTasks(File[] files) {
if (files == null) {
Slog.e(TAG, "File error accessing recents directory (too many files open?).");
return;
}

 for (int fileNdx = 0; fileNdx < files.length; ++fileNdx) {  
     File file = files[fileNdx];  
     file.delete();  
 }  

}

public void removeAllTasks() {

 removeAllTasks(sTasksDir.listFiles());  
 removeAllTasks(sImagesDir.listFiles());  

}

ActivityManagerService类初始化的时候调用:

[java] view plain copy

public void systemReady(final Runnable goingCallback) {
synchronized(this) {
if (mSystemReady) {
// If we're done calling all the receivers, run the next "boot phase" passed in
// by the SystemServer
if (goingCallback != null) {
goingCallback.run();
}
return;
}

       mLocalDeviceIdleController  
               = LocalServices.getService(DeviceIdleController.LocalService.class);  

       // Make sure we have the current profile info, since it is needed for  
       // security checks.  
       updateCurrentProfileIdsLocked();  

//这里读取数据之前就删除
mTaskPersister.removeAllTasks();

       mRecentTasks.clear();  
       mRecentTasks.addAll(mTaskPersister.restoreTasksLocked());  
       mRecentTasks.cleanupLocked(UserHandle.USER_ALL);  
       mTaskPersister.startPersisting();  

}
//省略部分代码,保留关键部分

就这样咯,可以去看一下TaskPersister和ActivityManagerService的源码了解更深。