check for Storage Access Framework features

* creating files though saf
* picking folder though saf

app/src/main/java/org/schabi/newpipe/download/DownloadDialog.java

@@ -569,7 +569,7 @@ public class DownloadDialog extends DialogFragment implements RadioGroup.OnCheck
             // This part is called if with SAF preferred:
             //  * older android version running
             //  * save path not defined (via download settings)
-            //  * the user as checked the "ask where to download" option
+            //  * the user checked the "ask where to download" option
 
             if (!askForSavePath)
                 Toast.makeText(context, getString(R.string.no_available_dir), Toast.LENGTH_LONG).show();
@@ -728,7 +728,7 @@ public class DownloadDialog extends DialogFragment implements RadioGroup.OnCheck
         try {
             if (storage.length() > 0) storage.truncate();
         } catch (IOException e) {
-            Log.e(TAG, "failed to overwrite the file: " + storage.getUri().toString(), e);
+            Log.e(TAG, "failed to truncate the file: " + storage.getUri().toString(), e);
             showFailedDialog(R.string.overwrite_failed);
             return;
         }

app/src/main/java/org/schabi/newpipe/settings/DownloadSettingsFragment.java

@@ -35,8 +35,6 @@ public class DownloadSettingsFragment extends BasePreferenceFragment {
     private String DOWNLOAD_PATH_VIDEO_PREFERENCE;
     private String DOWNLOAD_PATH_AUDIO_PREFERENCE;
 
-    private String DOWNLOAD_STORAGE_ASK;
-
     private Preference prefPathVideo;
     private Preference prefPathAudio;
     private Preference prefStorageAsk;
@@ -49,14 +47,14 @@ public class DownloadSettingsFragment extends BasePreferenceFragment {
 
         DOWNLOAD_PATH_VIDEO_PREFERENCE = getString(R.string.download_path_video_key);
         DOWNLOAD_PATH_AUDIO_PREFERENCE = getString(R.string.download_path_audio_key);
-        DOWNLOAD_STORAGE_ASK = getString(R.string.downloads_storage_ask);
+        final String downloadStorageAsk = getString(R.string.downloads_storage_ask);
 
         prefPathVideo = findPreference(DOWNLOAD_PATH_VIDEO_PREFERENCE);
         prefPathAudio = findPreference(DOWNLOAD_PATH_AUDIO_PREFERENCE);
-        prefStorageAsk = findPreference(DOWNLOAD_STORAGE_ASK);
+        prefStorageAsk = findPreference(downloadStorageAsk);
 
         updatePreferencesSummary();
-        updatePathPickers(!defaultPreferences.getBoolean(DOWNLOAD_STORAGE_ASK, false));
+        updatePathPickers(!defaultPreferences.getBoolean(downloadStorageAsk, false));
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
             prefStorageAsk.setSummary(R.string.downloads_storage_ask_summary);
@@ -180,7 +178,7 @@ public class DownloadSettingsFragment extends BasePreferenceFragment {
         }
 
         Intent i;
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && NewPipeSettings.hasOpenDocumentTreeSupport) {
             i = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE)
                     .putExtra("android.content.extra.SHOW_ADVANCED", true)
                     .addFlags(Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION | StoredDirectoryHelper.PERMISSION_FLAGS);
@@ -221,16 +219,17 @@ public class DownloadSettingsFragment extends BasePreferenceFragment {
             return;
         }
 
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+
-            // steps:
+        // revoke permissions on the old save path (required for SAF only)
-            //       1. revoke permissions on the old save path
-            //       2. acquire permissions on the new save path
-            //       3. save the new path, if step(2) was successful
         final Context ctx = getContext();
         if (ctx == null) throw new NullPointerException("getContext()");
 
         forgetSAFTree(ctx, defaultPreferences.getString(key, ""));
 
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && NewPipeSettings.hasOpenDocumentTreeSupport) {
+            // steps to acquire the selected path:
+            //     1. acquire permissions on the new save path
+            //     2. save the new path, if step(2) was successful
             try {
                 ctx.grantUriPermission(ctx.getPackageName(), uri, StoredDirectoryHelper.PERMISSION_FLAGS);
 

app/src/main/java/org/schabi/newpipe/settings/NewPipeSettings.java

@@ -21,7 +21,10 @@
 package org.schabi.newpipe.settings;
 
 import android.content.Context;
+import android.content.Intent;
 import android.content.SharedPreferences;
+import android.content.pm.PackageManager;
+import android.content.pm.ResolveInfo;
 import android.os.Build;
 import android.os.Environment;
 import android.preference.PreferenceManager;
@@ -30,6 +33,7 @@ import android.support.annotation.NonNull;
 import org.schabi.newpipe.R;
 
 import java.io.File;
+import java.util.List;
 
 /**
  * Helper for global settings
@@ -58,6 +62,20 @@ public class NewPipeSettings {
     private NewPipeSettings() {
     }
 
+    /**
+     * Indicates if is possible pick a directory though the Storage Access Framework.
+     * {@code true} if at least one provider can handle {@link Intent#ACTION_OPEN_DOCUMENT_TREE}
+     * otherwise {@code false}
+     */
+    public static boolean hasOpenDocumentTreeSupport = false;
+
+    /**
+     * Indicates if is possible create a file though the Storage Access Framework.
+     * {@code true} if at least one provider can handle {@link Intent#ACTION_CREATE_DOCUMENT}
+     * otherwise {@code false}
+     */
+    public static boolean hasCreateDocumentSupport = false;
+
     public static void initSettings(Context context) {
         PreferenceManager.setDefaultValues(context, R.xml.appearance_settings, true);
         PreferenceManager.setDefaultValues(context, R.xml.content_settings, true);
@@ -67,7 +85,14 @@ public class NewPipeSettings {
         PreferenceManager.setDefaultValues(context, R.xml.video_audio_settings, true);
         PreferenceManager.setDefaultValues(context, R.xml.debug_settings, true);
 
-        if (android.os.Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            hasOpenDocumentTreeSupport = testFor(context, Intent.ACTION_OPEN_DOCUMENT_TREE);
+        }
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
+            hasCreateDocumentSupport = testFor(context, Intent.ACTION_CREATE_DOCUMENT);
+        }
+
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP || !hasOpenDocumentTreeSupport) {
             getVideoDownloadFolder(context);
             getAudioDownloadFolder(context);
         }
@@ -100,4 +125,19 @@ public class NewPipeSettings {
     private static String getNewPipeChildFolderPathForDir(File dir) {
         return new File(dir, "NewPipe").toURI().toString();
     }
+
+    private static boolean testFor(@NonNull Context ctx, @NonNull String intentAction) {
+        Intent queryIntent = new Intent(intentAction);
+        queryIntent.addFlags(Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION);
+
+        List<ResolveInfo> infoList = ctx.getPackageManager()
+                .queryIntentActivities(queryIntent, PackageManager.MATCH_DEFAULT_ONLY);
+
+        int availableProviders = 0;
+        for (ResolveInfo info : infoList) {
+            if (info.activityInfo.exported) availableProviders++;
+        }
+
+        return availableProviders > 0;
+    }
 }