diff --git a/app/src/main/java/org/fdroid/fdroid/AppDetails.java b/app/src/main/java/org/fdroid/fdroid/AppDetails.java
index 71fa35b30..ead493e76 100644
--- a/app/src/main/java/org/fdroid/fdroid/AppDetails.java
+++ b/app/src/main/java/org/fdroid/fdroid/AppDetails.java
@@ -78,7 +78,6 @@ import com.nostra13.universalimageloader.core.DisplayImageOptions;
 import com.nostra13.universalimageloader.core.ImageLoader;
 import com.nostra13.universalimageloader.core.assist.ImageScaleType;
 
-import org.fdroid.fdroid.Utils.CommaSeparatedList;
 import org.fdroid.fdroid.data.Apk;
 import org.fdroid.fdroid.data.ApkProvider;
 import org.fdroid.fdroid.data.App;
@@ -93,7 +92,6 @@ import org.fdroid.fdroid.net.Downloader;
 import org.fdroid.fdroid.net.DownloaderService;
 
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
 
 public class AppDetails extends AppCompatActivity {
diff --git a/app/src/main/java/org/fdroid/fdroid/installer/ApkVerifier.java b/app/src/main/java/org/fdroid/fdroid/installer/ApkVerifier.java
index c818df9a5..7b38093b2 100644
--- a/app/src/main/java/org/fdroid/fdroid/installer/ApkVerifier.java
+++ b/app/src/main/java/org/fdroid/fdroid/installer/ApkVerifier.java
@@ -23,7 +23,7 @@ import android.content.Context;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.net.Uri;
-import android.util.Log;
+import android.text.TextUtils;
 
 import org.apache.commons.io.FileUtils;
 import org.fdroid.fdroid.Hasher;
@@ -37,14 +37,19 @@ import java.security.NoSuchAlgorithmException;
 import java.util.Arrays;
 import java.util.HashSet;
 
+/**
+ * This ApkVerifier verifies that the downloaded apk corresponds to the Apk information
+ * displayed to the user. This is especially important in case an unattended installer
+ * has been used which displays permissions before download.
+ */
 public class ApkVerifier {
 
     private static final String TAG = "ApkVerifier";
 
-    Context context;
-    Uri localApkUri;
-    Apk expectedApk;
-    PackageManager pm;
+    private final Context context;
+    private final Uri localApkUri;
+    private final Apk expectedApk;
+    private final PackageManager pm;
 
     ApkVerifier(Context context, Uri localApkUri, Apk expectedApk) {
         this.context = context;
@@ -54,14 +59,15 @@ public class ApkVerifier {
     }
 
     public void verifyApk() throws ApkVerificationException {
+        // parse downloaded apk file locally
         PackageInfo localApkInfo = pm.getPackageArchiveInfo(
                 localApkUri.getPath(), PackageManager.GET_PERMISSIONS);
         if (localApkInfo == null) {
-            throw new ApkVerificationException("parsing apk failed!");
+            throw new ApkVerificationException("parsing apk file failed!");
         }
 
         // check if the apk has the expected packageName
-        if (localApkInfo.packageName == null || !localApkInfo.packageName.equals(expectedApk.packageName)) {
+        if (!TextUtils.equals(localApkInfo.packageName, expectedApk.packageName)) {
             throw new ApkVerificationException("apk has unexpected packageName!");
         }
 
@@ -78,7 +84,10 @@ public class ApkVerifier {
             throw new ApkVerificationException("permissions of apk not equals expected permissions!");
         }
 
+        int localTargetSdkVersion = localApkInfo.applicationInfo.targetSdkVersion;
+        Utils.debugLog(TAG, "localTargetSdkVersion: " + localTargetSdkVersion);
         // TODO: check target sdk
+
     }
 
     private HashSet<String> getLocalPermissionsSet(PackageInfo localApkInfo) {
diff --git a/app/src/main/java/org/fdroid/fdroid/installer/ExtensionInstaller.java b/app/src/main/java/org/fdroid/fdroid/installer/ExtensionInstaller.java
index b9902bd58..a17565dd3 100644
--- a/app/src/main/java/org/fdroid/fdroid/installer/ExtensionInstaller.java
+++ b/app/src/main/java/org/fdroid/fdroid/installer/ExtensionInstaller.java
@@ -38,8 +38,6 @@ import java.io.File;
  */
 public class ExtensionInstaller extends Installer {
 
-    private static final String TAG = "ExtensionInstaller";
-
     ExtensionInstaller(Context context) {
         super(context);
     }
diff --git a/app/src/main/java/org/fdroid/fdroid/privileged/views/AppDiff.java b/app/src/main/java/org/fdroid/fdroid/privileged/views/AppDiff.java
index 58d10cfdb..3753093d2 100644
--- a/app/src/main/java/org/fdroid/fdroid/privileged/views/AppDiff.java
+++ b/app/src/main/java/org/fdroid/fdroid/privileged/views/AppDiff.java
@@ -18,18 +18,12 @@
 
 package org.fdroid.fdroid.privileged.views;
 
-import android.annotation.TargetApi;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
-import android.os.Build;
 
-import org.fdroid.fdroid.Permission;
 import org.fdroid.fdroid.data.Apk;
 
-import java.util.ArrayList;
-
-@TargetApi(Build.VERSION_CODES.M)
 public class AppDiff {
 
     private final PackageManager mPm;