1 files changed, 114 insertions, 0 deletions
diff --git a/src/edu/umich/PowerTutor/util/ForegroundDetector.java b/src/edu/umich/PowerTutor/util/ForegroundDetector.java
new file mode 100644
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+++ b/src/edu/umich/PowerTutor/util/ForegroundDetector.java
@@ -0,0 +1,114 @@
+/*
+Copyright (C) 2011 The University of Michigan
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Please send inquiries to powertutor@umich.edu
+*/
+
+package edu.umich.PowerTutor.util;
+
+import edu.umich.PowerTutor.util.SystemInfo;
+
+import android.app.ActivityManager;
+
+import java.util.Arrays;
+import java.util.BitSet;
+import java.util.List;
+
+/* This detector looks for transitions where one app leaves the foreground and
+ * another enters the foreground to detect apps that are legitimately in the
+ * foreground.  If no application is known to be legitimate system is returned.
+ */
+public class ForegroundDetector {
+  int lastSize;
+  int[] lastUids;
+  int nowSize;
+  int[] nowUids;
+
+  private BitSet validated;
+
+  private ActivityManager activityManager;
+
+  public ForegroundDetector(ActivityManager activityManager) {
+    lastSize = nowSize = 0;
+    lastUids = new int[10];
+    nowUids = new int[10];
+    validated = new BitSet(1 << 16);
+    validated.set(android.os.Process.myUid());
+    this.activityManager = activityManager;
+  }
+
+  // Figure out what uid should be charged for screen usage.
+  public int getForegroundUid() {
+    SystemInfo sysInfo = SystemInfo.getInstance();
+    List<ActivityManager.RunningAppProcessInfo> appProcs =
+        activityManager.getRunningAppProcesses();
+
+    // Move the last iteration to last and resize the other array if needed.
+    int[] tmp = lastUids;
+    lastUids = nowUids;
+    lastSize = nowSize;
+    if(tmp.length < appProcs.size()) {
+      tmp = new int[appProcs.size()];
+    }
+    nowUids = tmp;
+
+    // Fill in the uids from appProcs.
+    nowSize = 0;
+    for(ActivityManager.RunningAppProcessInfo app : appProcs) {
+      if(app.importance ==
+             ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
+        int uid = sysInfo.getUidForPid(app.pid);
+        if(SystemInfo.AID_APP <= uid && uid < 1 << 16) {
+          nowUids[nowSize++] = uid;
+        }
+      }
+    }
+    Arrays.sort(nowUids, 0, nowSize);
+
+    // Find app-exit app-enter transitions.
+    int appExit = -1;
+    int appEnter = -1;
+    int indNow = 0;
+    int indLast = 0;
+    while(indNow < nowSize && indLast < lastSize) {
+      if(nowUids[indNow] == lastUids[indLast]) {
+        indNow++; indLast++;
+      } else if(nowUids[indNow] < lastUids[indLast]) {
+        appEnter = nowUids[indNow++];
+      } else {
+        appExit = lastUids[indLast++];
+      }
+    }
+    if(indNow < nowSize) appEnter = nowUids[indNow];
+    if(indLast < lastSize) appExit = lastUids[indLast];
+
+    // Found an interesting transition.  Validate both applications.
+    if(appEnter != -1 && appExit != -1) {
+      validated.set(appEnter);
+      validated.set(appExit);
+    }
+    
+    // Now find a valid application now.  Hopefully there is only one.  If there
+    // are none return system.  If there are several return the one with the
+    // highest uid.
+    for(int i = nowSize - 1; i >= 0; i--) {
+      if(validated.get(nowUids[i])) {
+        return nowUids[i];
+      }
+    }
+    return SystemInfo.AID_SYSTEM;
+  }
+}