Implements #3894, Only show Changelog on startup if hash code changed

- switched from version checking to checksum checking

3 files changed, 27 insertions, 12 deletions

diff --git a/main/src/cgeo/geocaching/MainActivity.java b/main/src/cgeo/geocaching/MainActivity.java
index d901e05..84bc960 100644
--- a/main/src/cgeo/geocaching/MainActivity.java
+++ b/main/src/cgeo/geocaching/MainActivity.java
@@ -23,6 +23,7 @@ import cgeo.geocaching.ui.Formatter;
 import cgeo.geocaching.ui.dialog.Dialogs;
 import cgeo.geocaching.utils.DatabaseBackupUtils;
 import cgeo.geocaching.utils.Log;
+import cgeo.geocaching.utils.TextUtils;
 import cgeo.geocaching.utils.Version;
 
 import com.google.zxing.integration.android.IntentIntegrator;
@@ -732,11 +733,11 @@ public class MainActivity extends AbstractActionBarActivity {
     }
 
     private void checkShowChangelog() {
-        final int lastVersion = Settings.getLastChangelogVersion();
-        final int version = Version.getVersionCode(this);
-        Settings.setLastChangelogVersion(version);
+        final long lastChecksum = Settings.getLastChangelogChecksum();
+        final long checksum = TextUtils.checksum(getString(R.string.changelog_master) + getString(R.string.changelog_release));
+        Settings.setLastChangelogChecksum(checksum);
         // don't show change log after new install...
-        if (lastVersion > 0 && version != lastVersion) {
+        if (lastChecksum > 0 && lastChecksum != checksum) {
             AboutActivity.showChangeLog(this);
         }
     }
diff --git a/main/src/cgeo/geocaching/settings/Settings.java b/main/src/cgeo/geocaching/settings/Settings.java
index 133df5c..0ed5aef 100644
--- a/main/src/cgeo/geocaching/settings/Settings.java
+++ b/main/src/cgeo/geocaching/settings/Settings.java
@@ -1007,13 +1007,13 @@ public class Settings {
         return getString(R.string.pref_ec_icons, "1");
     }
 
-    /* Store last version for the changelog display */
-    public static int getLastChangelogVersion() {
-        return getInt(R.string.pref_changelog_last_version, 0);
+    /* Store last checksum of changelog for changelog display */
+    public static long getLastChangelogChecksum() {
+        return getLong(R.string.pref_changelog_last_checksum, 0);
     }
 
-    public static void setLastChangelogVersion(final int version) {
-        putInt(R.string.pref_changelog_last_version, version);
+    public static void setLastChangelogChecksum(final long checksum) {
+        putLong(R.string.pref_changelog_last_checksum, checksum);
     }
 
     public static List<String> getLastOpenedCaches() {
diff --git a/main/src/cgeo/geocaching/utils/TextUtils.java b/main/src/cgeo/geocaching/utils/TextUtils.java
index ef09f32..77aa167 100644
--- a/main/src/cgeo/geocaching/utils/TextUtils.java
+++ b/main/src/cgeo/geocaching/utils/TextUtils.java
@@ -4,11 +4,13 @@
 package cgeo.geocaching.utils;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+
 import org.eclipse.jdt.annotation.Nullable;
 
 import java.nio.charset.Charset;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.zip.CRC32;
 
 /**
  * Misc. utils. All methods don't use Android specific stuff to use these methods in plain JUnit tests.
@@ -52,7 +54,7 @@ public final class TextUtils {
                 result = matcher.group(group);
             }
             if (null != result) {
-                Matcher remover = PATTERN_REMOVE_NONPRINTABLE.matcher(result);
+                final Matcher remover = PATTERN_REMOVE_NONPRINTABLE.matcher(result);
                 result = remover.replaceAll(" ");
 
                 return trim ? new String(result).trim() : new String(result);
@@ -134,7 +136,7 @@ public final class TextUtils {
         data.getChars(0, length, chars, 0);
         int resultSize = 0;
         boolean lastWasWhitespace = true;
-        for (char c : chars) {
+        for (final char c : chars) {
             if (c == ' ' || c == '\n' || c == '\r' || c == '\t') {
                 if (!lastWasWhitespace) {
                     chars[resultSize++] = ' ';
@@ -167,8 +169,20 @@ public final class TextUtils {
      * @return
      */
     public static String removeControlCharacters(final String input) {
-        Matcher remover = PATTERN_REMOVE_NONPRINTABLE.matcher(input);
+        final Matcher remover = PATTERN_REMOVE_NONPRINTABLE.matcher(input);
         return remover.replaceAll(" ").trim();
     }
 
+    /**
+     * Calculate a simple checksum for change-checking (not usable for security/cryptography!)
+     * 
+     * @param input
+     *            String to check
+     * @return resulting checksum
+     */
+    public static long checksum(final String input) {
+        final CRC32 checksum = new CRC32();
+        checksum.update(input.getBytes());
+        return checksum.getValue();
+    }
 }