Autocomplete @ mentions in the composer. Closes #103

app/src/main/java/com/keylesspalace/tusky/ComposeActivity.java

@@ -18,6 +18,7 @@ package com.keylesspalace.tusky;
 import android.Manifest;
 import android.app.ProgressDialog;
 import android.content.ContentResolver;
+import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ -39,6 +40,7 @@ import android.os.Parcel;
 import android.os.Parcelable;
 import android.provider.MediaStore;
 import android.support.annotation.AttrRes;
+import android.support.annotation.LayoutRes;
 import android.support.annotation.NonNull;
 import android.support.annotation.StringRes;
 import android.support.design.widget.Snackbar;
@@ -60,14 +62,18 @@ import android.util.Log;
 import android.view.MenuItem;
 import android.view.View;
 import android.webkit.MimeTypeMap;
+import android.widget.ArrayAdapter;
 import android.widget.Button;
 import android.widget.EditText;
+import android.widget.Filter;
+import android.widget.Filterable;
 import android.widget.ImageButton;
 import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.ProgressBar;
 import android.widget.TextView;
 
+import com.keylesspalace.tusky.entity.Account;
 import com.keylesspalace.tusky.entity.Media;
 import com.keylesspalace.tusky.entity.Status;
 import com.keylesspalace.tusky.fragment.ComposeOptionsFragment;
@@ -75,6 +81,7 @@ import com.keylesspalace.tusky.util.CountUpDownLatch;
 import com.keylesspalace.tusky.util.DownsizeImageTask;
 import com.keylesspalace.tusky.util.IOUtils;
 import com.keylesspalace.tusky.util.MediaUtils;
+import com.keylesspalace.tusky.util.MentionTokenizer;
 import com.keylesspalace.tusky.util.ParserUtils;
 import com.keylesspalace.tusky.util.SpanUtils;
 import com.keylesspalace.tusky.util.ThemeUtils;
@@ -313,6 +320,10 @@ public class ComposeActivity extends BaseActivity implements ComposeOptionsFragm
             }
         });
 
+        textEditor.setAdapter(new MentionAutoCompleteAdapter(this,
+                android.R.layout.simple_dropdown_item_1line));
+        textEditor.setTokenizer(new MentionTokenizer());
+
         // Add any mentions to the text field when a reply is first composed.
         if (mentionedUsernames != null) {
             StringBuilder builder = new StringBuilder();
@@ -1220,7 +1231,6 @@ public class ComposeActivity extends BaseActivity implements ComposeOptionsFragm
         }
     }
 
-
     // remove the precedent paste from the edit text
     private void cleanBaseUrl(ParserUtils.HeaderInfo headerInfo) {
         int lengthBaseUrl = headerInfo.baseUrl.length();
@@ -1236,6 +1246,28 @@ public class ComposeActivity extends BaseActivity implements ComposeOptionsFragm
         displayTransientError(R.string.error_generic);
     }
 
+    /**
+     * Does a synchronous search request for usernames fulfilling the given partial mention text.
+     */
+    private ArrayList<String> autocompleteMention(String mention) {
+        ArrayList<String> resultList = new ArrayList<>();
+        try {
+            List<Account> accountList = mastodonAPI.searchAccounts(mention, false, 5)
+                    .execute()
+                    .body();
+            /* Match only accounts whose username contains the partial mention text, because
+               searches also return matches for display names, which aren't relevant here. */
+            for (Account account : accountList) {
+                if (account.username.toLowerCase().contains(mention.toLowerCase())) {
+                    resultList.add(account.username);
+                }
+            }
+        } catch (IOException e) {
+            Log.e(TAG, String.format("Autocomplete search for %s failed.", mention));
+        }
+        return resultList;
+    }
+
     private static class QueuedMedia {
         Type type;
         ImageView preview;
@@ -1311,4 +1343,47 @@ public class ComposeActivity extends BaseActivity implements ComposeOptionsFragm
             dest.writeLong(mediaSize);
         }
     }
+
+    private class MentionAutoCompleteAdapter extends ArrayAdapter<String> implements Filterable {
+        private ArrayList<String> resultList;
+
+        MentionAutoCompleteAdapter(Context context, @LayoutRes int resource) {
+            super(context, resource);
+        }
+
+        @Override
+        public int getCount() {
+            return resultList.size();
+        }
+
+        @Override
+        public String getItem(int index) {
+            return resultList.get(index);
+        }
+
+        @Override @NonNull
+        public Filter getFilter() {
+            return new Filter() {
+                @Override
+                protected FilterResults performFiltering(CharSequence constraint) {
+                    FilterResults filterResults = new FilterResults();
+                    if (constraint != null) {
+                        resultList = autocompleteMention(constraint.toString());
+                        filterResults.values = resultList;
+                        filterResults.count = resultList.size();
+                    }
+                    return filterResults;
+                }
+
+                @Override
+                protected void publishResults(CharSequence constraint, FilterResults results) {
+                    if (results != null && results.count > 0) {
+                        notifyDataSetChanged();
+                    } else {
+                        notifyDataSetInvalidated();
+                    }
+                }
+            };
+        }
+    }
 }

app/src/main/java/com/keylesspalace/tusky/util/MediaUtils.java

@@ -1,3 +1,18 @@
+/* Copyright 2017 Andrew Dawson
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
 package com.keylesspalace.tusky.util;
 
 import android.content.ContentResolver;

app/src/main/java/com/keylesspalace/tusky/util/MentionTokenizer.java

@@ -0,0 +1,66 @@
+/* Copyright 2017 Andrew Dawson
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.util;
+
+import android.text.SpannableString;
+import android.text.Spanned;
+import android.text.TextUtils;
+import android.widget.MultiAutoCompleteTextView;
+
+public class MentionTokenizer implements MultiAutoCompleteTextView.Tokenizer {
+    @Override
+    public int findTokenStart(CharSequence text, int cursor) {
+        int i = cursor;
+        while (i > 0 && text.charAt(i - 1) != '@') {
+            i--;
+        }
+        if (i < 1 || text.charAt(i - 1) != '@') {
+            return cursor;
+        }
+        return i;
+    }
+
+    @Override
+    public int findTokenEnd(CharSequence text, int cursor) {
+        int i = cursor;
+        int length = text.length();
+        while (i < length) {
+            if (text.charAt(i) == ' ') {
+                return i;
+            } else {
+                i++;
+            }
+        }
+        return length;
+    }
+
+    @Override
+    public CharSequence terminateToken(CharSequence text) {
+        int i = text.length();
+        while (i > 0 && text.charAt(i - 1) == ' ') {
+            i--;
+        }
+        if (i > 0 && text.charAt(i - 1) == ' ') {
+            return text;
+        } else if (text instanceof Spanned) {
+            SpannableString s = new SpannableString(text + " ");
+            TextUtils.copySpansFrom((Spanned) text, 0, text.length(), Object.class, s, 0);
+            return s;
+        } else {
+            return text + " ";
+        }
+    }
+}

app/src/main/java/com/keylesspalace/tusky/view/EditTextTyped.java

@@ -18,18 +18,18 @@ package com.keylesspalace.tusky.view;
 import android.content.Context;
 import android.support.v13.view.inputmethod.EditorInfoCompat;
 import android.support.v13.view.inputmethod.InputConnectionCompat;
-import android.support.v7.widget.AppCompatEditText;
+import android.support.v7.widget.AppCompatMultiAutoCompleteTextView;
 import android.util.AttributeSet;
 import android.view.inputmethod.EditorInfo;
 import android.view.inputmethod.InputConnection;
 
 import com.keylesspalace.tusky.util.Assert;
 
-public class EditTextTyped extends AppCompatEditText {
+public class EditTextTyped extends AppCompatMultiAutoCompleteTextView {
 
     InputConnectionCompat.OnCommitContentListener onCommitContentListener;
     String[] mimeTypes;
-    private OnPasteListener mOnPasteListener;
+    private OnPasteListener onPasteListener;
 
     public EditTextTyped(Context context) {
         super(context);
@@ -40,7 +40,7 @@ public class EditTextTyped extends AppCompatEditText {
     }
 
     public void addOnPasteListener(OnPasteListener mOnPasteListener) {
-        this.mOnPasteListener = mOnPasteListener;
+        this.onPasteListener = mOnPasteListener;
     }
 
     public void setMimeTypes(String[] types,
@@ -68,6 +68,7 @@ public class EditTextTyped extends AppCompatEditText {
         switch (id) {
             case android.R.id.paste:
                 onPaste();
+                break;
         }
         return consumed;
     }
@@ -76,8 +77,9 @@ public class EditTextTyped extends AppCompatEditText {
      * Text was pasted into the EditText.
      */
     public void onPaste() {
-        if (mOnPasteListener != null)
-            mOnPasteListener.onPaste();
+        if (onPasteListener != null) {
+            onPasteListener.onPaste();
+        }
     }
 
     public interface OnPasteListener {

app/src/main/res/layout/activity_compose.xml

@@ -62,7 +62,9 @@
                 android:ems="10"
                 android:gravity="start|top"
                 android:hint="@string/hint_compose"
-                android:inputType="text|textMultiLine|textCapSentences" />
+                android:inputType="text|textMultiLine|textCapSentences"
+                android:dropDownWidth="wrap_content"
+                android:completionThreshold="2" />
 
             <HorizontalScrollView
                 android:layout_width="match_parent"