forceStopPackage与killBackgroundProcesses方法

最近了解一键清理功能，需要实现强制关闭进程的功能。下面介绍下killBackgroundProcesses()方法和forceStopPackage()方法。

killBackgroundProcesses()

ActivityManager的killBackgroundProcesses方法，可以立即杀死与指定包相关联的所有后台进程，这与内核杀死那些进程回收内存是一样的，但这些进程如果在将来某一时刻需要使用，会重新启动。该方法需要权限android.permission.KILL_BACKGROUND_PROCESSES。源码解释如下：

/**
 * Have the system immediately kill all background processes associated
 * with the given package.  This is the same as the kernel killing those
 * processes to reclaim memory; the system will take care of restarting
 * these processes in the future as needed.
 *
 * <p>You must hold the permission
 * {@link android.Manifest.permission#KILL_BACKGROUND_PROCESSES} to be able to
 * call this method.
 *
 * @param packageName The name of the package whose processes are to
 * be killed.
 */
public void killBackgroundProcesses(String packageName) {
    try {
        ActivityManagerNative.getDefault().killBackgroundProcesses(packageName,
                UserHandle.myUserId());
    } catch (RemoteException e) {
    }
}

forceStopPackage()

调用此方法，系统会强制停止与指定包关联的所有事情，将会杀死使用同一个uid的所有进程，停止所有服务，移除所有activity。所有注册的定时器和通知也会移除。forceStopPackage方法源码解释如下：

/**
 * Have the system perform a force stop of everything associated with
 * the given application package.  All processes that share its uid
 * will be killed, all services it has running stopped, all activities
 * removed, etc.  In addition, a {@link Intent#ACTION_PACKAGE_RESTARTED}
 * broadcast will be sent, so that any of its registered alarms can
 * be stopped, notifications removed, etc.
 *
 * <p>You must hold the permission
 * {@link android.Manifest.permission#FORCE_STOP_PACKAGES} to be able to
 * call this method.
 *
 * @param packageName The name of the package to be stopped.
 * @param userId The user for which the running package is to be stopped.
 *
 * @hide This is not available to third party applications due to
 * it allowing them to break other applications by stopping their
 * services, removing their alarms, etc.
 */
public void forceStopPackageAsUser(String packageName, int userId) {
    try {
        ActivityManagerNative.getDefault().forceStopPackage(packageName, userId);
    } catch (RemoteException e) {
    }
}

/**
 * @see #forceStopPackageAsUser(String, int)
 * @hide
 */
public void forceStopPackage(String packageName) {
    forceStopPackageAsUser(packageName, UserHandle.myUserId());
}

注意使用forceStopPackage方法时，需要添加权限android.permission.FORCE_STOP_PACKAGES。同时注意该方法是隐藏的方法，需要使用反射机制调用。如下：

ActivityManager mActivityManager = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);
Method method = Class.forName("android.app.ActivityManager").getMethod("forceStopPackage", String.class);
method.invoke(mActivityManager, packageName);  //packageName是需要强制停止的应用程序包名