Use RxJava instead of AsyncTask in LicenseFragmentHelper.

app/src/main/java/org/schabi/newpipe/about/LicenseFragment.java

@@ -1,6 +1,5 @@
 package org.schabi.newpipe.about;
 
-import android.app.Activity;
 import android.os.Bundle;
 import android.view.ContextMenu;
 import android.view.LayoutInflater;
@@ -21,15 +20,19 @@ import java.io.Serializable;
 import java.util.Arrays;
 import java.util.Comparator;
 
+import io.reactivex.disposables.CompositeDisposable;
+
 /**
  * Fragment containing the software licenses.
  */
 public class LicenseFragment extends Fragment {
     private static final String ARG_COMPONENTS = "components";
+    private static final String LICENSE_KEY = "ACTIVE_LICENSE";
+
     private SoftwareComponent[] softwareComponents;
     private SoftwareComponent componentForContextMenu;
     private License activeLicense;
-    private static final String LICENSE_KEY = "ACTIVE_LICENSE";
+    private final CompositeDisposable compositeDisposable = new CompositeDisposable();
 
     public static LicenseFragment newInstance(final SoftwareComponent[] softwareComponents) {
         if (softwareComponents == null) {
@@ -42,16 +45,6 @@ public class LicenseFragment extends Fragment {
         return fragment;
     }
 
-    /**
-     * Shows a popup containing the license.
-     *
-     * @param context the context to use
-     * @param license the license to show
-     */
-    private static void showLicense(final Activity context, final License license) {
-        new LicenseFragmentHelper(context).execute(license);
-    }
-
     @Override
     public void onCreate(@Nullable final Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
@@ -68,6 +61,12 @@ public class LicenseFragment extends Fragment {
         Arrays.sort(softwareComponents, Comparator.comparing(SoftwareComponent::getName));
     }
 
+    @Override
+    public void onDestroy() {
+        compositeDisposable.dispose();
+        super.onDestroy();
+    }
+
     @Nullable
     @Override
     public View onCreateView(final LayoutInflater inflater, @Nullable final ViewGroup container,
@@ -78,7 +77,8 @@ public class LicenseFragment extends Fragment {
         final View licenseLink = rootView.findViewById(R.id.app_read_license);
         licenseLink.setOnClickListener(v -> {
             activeLicense = StandardLicenses.GPL3;
-                showLicense(getActivity(), StandardLicenses.GPL3);
+            compositeDisposable.add(LicenseFragmentHelper.showLicense(getActivity(),
+                    StandardLicenses.GPL3));
         });
 
         for (final SoftwareComponent component : softwareComponents) {
@@ -95,13 +95,15 @@ public class LicenseFragment extends Fragment {
             componentView.setTag(component);
             componentView.setOnClickListener(v -> {
                 activeLicense = component.getLicense();
-                showLicense(getActivity(), component.getLicense());
+                compositeDisposable.add(LicenseFragmentHelper.showLicense(getActivity(),
+                        component.getLicense()));
             });
             softwareComponentsView.addView(componentView);
             registerForContextMenu(componentView);
         }
         if (activeLicense != null) {
-            showLicense(getActivity(), activeLicense);
+            compositeDisposable.add(LicenseFragmentHelper.showLicense(getActivity(),
+                    activeLicense));
         }
         return rootView;
     }
@@ -129,7 +131,8 @@ public class LicenseFragment extends Fragment {
                 ShareUtils.openUrlInBrowser(getActivity(), component.getLink());
                 return true;
             case R.id.action_show_license:
-                showLicense(getActivity(), component.getLicense());
+                compositeDisposable.add(LicenseFragmentHelper.showLicense(getActivity(),
+                        component.getLicense()));
         }
         return false;
     }

app/src/main/java/org/schabi/newpipe/about/LicenseFragmentHelper.java

@@ -1,8 +1,6 @@
 package org.schabi.newpipe.about;
 
-import android.app.Activity;
 import android.content.Context;
-import android.os.AsyncTask;
 import android.util.Base64;
 import android.webkit.WebView;
 
@@ -16,18 +14,18 @@ import org.schabi.newpipe.util.ThemeHelper;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
-import java.lang.ref.WeakReference;
 import java.nio.charset.StandardCharsets;
 
+import io.reactivex.Observable;
+import io.reactivex.android.schedulers.AndroidSchedulers;
+import io.reactivex.disposables.Disposable;
+import io.reactivex.disposables.Disposables;
+import io.reactivex.schedulers.Schedulers;
+
 import static org.schabi.newpipe.util.Localization.assureCorrectAppLanguage;
 
-public class LicenseFragmentHelper extends AsyncTask<Object, Void, Integer> {
+public final class LicenseFragmentHelper {
-    private final WeakReference<Activity> weakReference;
+    private LicenseFragmentHelper() { }
-    private License license;
-
-    public LicenseFragmentHelper(@Nullable final Activity activity) {
-        weakReference = new WeakReference<>(activity);
-    }
 
     /**
      * @param context the context to use
@@ -62,7 +60,7 @@ public class LicenseFragmentHelper extends AsyncTask<Object, Void, Integer> {
      * @param context
      * @return String which is a CSS stylesheet according to the context's theme
      */
-    private static String getLicenseStylesheet(final Context context) {
+    private static String getLicenseStylesheet(@NonNull final Context context) {
         final boolean isLightTheme = ThemeHelper.isLightThemeSelected(context);
         return "body{padding:12px 15px;margin:0;"
                 + "background:#" + getHexRGBColor(context, isLightTheme
@@ -84,45 +82,31 @@ public class LicenseFragmentHelper extends AsyncTask<Object, Void, Integer> {
      * @param color   the color number from R.color
      * @return a six characters long String with hexadecimal RGB values
      */
-    private static String getHexRGBColor(final Context context, final int color) {
+    private static String getHexRGBColor(@NonNull final Context context, final int color) {
         return context.getResources().getString(color).substring(3);
     }
 
-    @Nullable
+    static Disposable showLicense(@Nullable final Context context, @NonNull final License license) {
-    private Activity getActivity() {
+        if (context == null) {
-        final Activity activity = weakReference.get();
+            return Disposables.empty();
-
-        if (activity != null && activity.isFinishing()) {
-            return null;
-        } else {
-            return activity;
-        }
         }
 
-    @Override
+        return Observable.fromCallable(() -> getFormattedLicense(context, license))
-    protected Integer doInBackground(final Object... objects) {
+                .subscribeOn(Schedulers.io())
-        license = (License) objects[0];
+                .observeOn(AndroidSchedulers.mainThread())
-        return 1;
+                .subscribe(formattedLicense -> {
-    }
+                    final String webViewData = Base64.encodeToString(formattedLicense
-
-    @Override
-    protected void onPostExecute(final Integer result) {
-        final Activity activity = getActivity();
-        if (activity == null) {
-            return;
-        }
-
-        final String webViewData = Base64.encodeToString(getFormattedLicense(activity, license)
                             .getBytes(StandardCharsets.UTF_8), Base64.NO_PADDING);
-        final WebView webView = new WebView(activity);
+                    final WebView webView = new WebView(context);
                     webView.loadData(webViewData, "text/html; charset=UTF-8", "base64");
 
-        final AlertDialog.Builder alert = new AlertDialog.Builder(activity);
+                    final AlertDialog.Builder alert = new AlertDialog.Builder(context);
                     alert.setTitle(license.getName());
                     alert.setView(webView);
-        assureCorrectAppLanguage(activity);
+                    assureCorrectAppLanguage(context);
-        alert.setNegativeButton(activity.getString(R.string.finish),
+                    alert.setNegativeButton(context.getString(R.string.finish),
                             (dialog, which) -> dialog.dismiss());
                     alert.show();
+                });
     }
 }