added a service to handle the caching, this'll ensure the cache works while no activity is around, which is better for k9mail integration

it also is a more efficient and much smarter cache, not requiring an own timer thread, just a service that sleeps must of the time, it also is more accurate in cleaning up the entries, ensuring that the worst case of too late removal is 5 seconds

AndroidManifest.xml

@@ -128,6 +128,8 @@
             android:label="@string/title_preferences"
             android:configChanges="keyboardHidden|orientation|keyboard"/>
 
+        <service android:name=".Service" />
+
         <provider
             android:readPermission="org.thialfihar.android.apg.permission.READ_KEY_DETAILS"
             android:name="org.thialfihar.android.apg.provider.DataProvider"

src/org/thialfihar/android/apg/Apg.java

@@ -225,19 +225,30 @@ public class Apg {
         return cpp.passPhrase;
     }
 
-    public static void cleanUpCache(int ttl) {
+    public static int cleanUpCache(int ttl, int initialDelay) {
+        int delay = initialDelay;
+        long realTtl = ttl * 1000;
         long now = new Date().getTime();
-
         Vector<Long> oldKeys = new Vector<Long>();
         for (Map.Entry<Long, CachedPassPhrase> pair : mPassPhraseCache.entrySet()) {
-            if ((now - pair.getValue().timestamp) >= 1000 * ttl) {
+            long lived = now - pair.getValue().timestamp;
+            if (lived >= realTtl) {
                 oldKeys.add(pair.getKey());
+            } else {
+                // see, whether the remaining time for this cache entry improves our
+                // check delay
+                long nextCheck = realTtl - lived + 1000;
+                if (nextCheck < delay) {
+                    delay = (int)nextCheck;
+                }
             }
         }
 
         for (long keyId : oldKeys) {
             mPassPhraseCache.remove(keyId);
         }
+
+        return delay;
     }
 
     public static PGPSecretKey createKey(Context context,

src/org/thialfihar/android/apg/BaseActivity.java

@@ -17,8 +17,6 @@
 package org.thialfihar.android.apg;
 
 import java.io.File;
-import java.util.Timer;
-import java.util.TimerTask;
 
 import org.bouncycastle2.bcpg.HashAlgorithmTags;
 import org.bouncycastle2.openpgp.PGPEncryptedData;
@@ -53,8 +51,6 @@ public class BaseActivity extends Activity
     private String mDeleteFile = null;
     protected static SharedPreferences mPreferences = null;
 
-    private static Timer mCacheTimer = new Timer();
-
     private Handler mHandler = new Handler() {
         @Override
         public void handleMessage(Message msg) {
@@ -80,29 +76,9 @@ public class BaseActivity extends Activity
             }
         }
 
-        if (mCacheTimer == null) {
-            setPassPhraseCacheTimer();
-        }
-    }
-
-    private void setPassPhraseCacheTimer() {
-        if (mCacheTimer != null) {
-            mCacheTimer.cancel();
-            mCacheTimer = null;
-        }
-        int ttl = getPassPhraseCacheTtl();
-        if (ttl == 0) {
-            // no timer needed
-            return;
-        }
-        // check every ttl/2 seconds, which shouldn't be heavy on the device (even if ttl = 15),
-        // and makes sure the longest a pass phrase survives int the cache is 1.5 * ttl
-        mCacheTimer = new Timer();
-        mCacheTimer.scheduleAtFixedRate(new TimerTask() {
-            public void run() {
-                Apg.cleanUpCache(BaseActivity.this.getPassPhraseCacheTtl());
-            }
-        }, 0, ttl * 1000 / 2);
+        Intent intent = new Intent(this, Service.class);
+        intent.putExtra(Service.EXTRA_TTL, getPassPhraseCacheTtl());
+        startService(intent);
     }
 
     @Override
@@ -400,7 +376,9 @@ public class BaseActivity extends Activity
         editor.putInt(Constants.pref.pass_phrase_cache_ttl, value);
         editor.commit();
 
-        setPassPhraseCacheTimer();
+        Intent intent = new Intent(this, Service.class);
+        intent.putExtra(Service.EXTRA_TTL, getPassPhraseCacheTtl());
+        startService(intent);
     }
 
     public int getDefaultEncryptionAlgorithm() {

src/org/thialfihar/android/apg/PreferencesActivity.java

@@ -50,7 +50,6 @@ public class PreferencesActivity extends BaseActivity {
                 new Choice(180, getString(R.string.choice_3mins)),
                 new Choice(300, getString(R.string.choice_5mins)),
                 new Choice(600, getString(R.string.choice_10mins)),
-                new Choice(0, getString(R.string.choice_untilQuit)),
         };
         ArrayAdapter<Choice> adapter =
                 new ArrayAdapter<Choice>(this, android.R.layout.simple_spinner_item, choices);

src/org/thialfihar/android/apg/Service.java

@@ -0,0 +1,79 @@
+package org.thialfihar.android.apg;
+
+import android.content.Intent;
+import android.os.Binder;
+import android.os.Handler;
+import android.os.IBinder;
+
+public class Service extends android.app.Service {
+    private final IBinder mBinder = new LocalBinder();
+
+    public static final String EXTRA_TTL = "ttl";
+
+    private int mPassPhraseCacheTtl = 15;
+    private Handler mCacheHandler = new Handler();
+    private Runnable mCacheTask = new Runnable() {
+        public void run() {
+            // TODO: I suppose we could read out the time left until the first cache entry
+            // expiration, then use that for the timer...
+
+            // check every ttl/2 seconds, which shouldn't be heavy on the device (even if ttl = 15),
+            // and makes sure the longest a pass phrase survives in the cache is 1.5 * ttl
+            int delay = mPassPhraseCacheTtl * 1000 / 2;
+            // also make sure the delay is not longer than one minute
+            if (delay > 60000) {
+                delay = 60000;
+            }
+
+            delay = Apg.cleanUpCache(mPassPhraseCacheTtl, delay);
+            // don't check too often, even if we were close
+            if (delay < 5000) {
+                delay = 5000;
+            }
+
+            mCacheHandler.postDelayed(this, delay);
+        }
+    };
+
+    static private boolean mIsRunning = false;
+
+    @Override
+    public void onCreate() {
+        super.onCreate();
+
+        mIsRunning = true;
+    }
+
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        mIsRunning = false;
+    }
+
+    @Override
+    public void onStart(Intent intent, int startId) {
+        super.onStart(intent, startId);
+
+        mPassPhraseCacheTtl = intent.getIntExtra(EXTRA_TTL, 15);
+        if (mPassPhraseCacheTtl < 15) {
+            mPassPhraseCacheTtl = 15;
+        }
+        mCacheHandler.removeCallbacks(mCacheTask);
+        mCacheHandler.postDelayed(mCacheTask, 1000);
+    }
+
+    static public boolean isRunning() {
+        return mIsRunning;
+    }
+
+    public class LocalBinder extends Binder {
+        Service getService() {
+            return Service.this;
+        }
+    }
+
+    @Override
+    public IBinder onBind(Intent intent) {
+        return mBinder;
+    }
+}