fix: SymbolInputView is invalidated multiple times on tab reselection

app/src/main/java/com/itsaky/androidide/adapters/SymbolInputAdapter.java

@@ -23,17 +23,17 @@ import static com.itsaky.androidide.utils.ResourceUtilsKt.resolveAttr;
 import android.annotation.SuppressLint;
 import android.view.LayoutInflater;
 import android.view.ViewGroup;
-
 import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.DiffUtil;
 import androidx.recyclerview.widget.RecyclerView;
-
 import com.itsaky.androidide.R;
 import com.itsaky.androidide.databinding.LayoutSymbolItemBinding;
-import com.itsaky.androidide.ui.SymbolInputView.Symbol;
 import com.itsaky.androidide.editor.ui.IDEEditor;
-
+import com.itsaky.androidide.models.Symbol;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 public class SymbolInputAdapter extends RecyclerView.Adapter<SymbolInputAdapter.VH> {
 
@@ -49,24 +49,54 @@ public class SymbolInputAdapter extends RecyclerView.Adapter<SymbolInputAdapter.
     pairs.add('>');
   }
 
-  private final IDEEditor editor;
-  private Symbol[] symbols;
+  private IDEEditor editor;
+  private List<Symbol> symbols;
 
   public SymbolInputAdapter(IDEEditor editor) {
     this(editor, null);
   }
 
-  public SymbolInputAdapter(IDEEditor editor, Symbol[] symbols) {
+  public SymbolInputAdapter(IDEEditor editor, List<Symbol> symbols) {
     this.editor = editor;
-    this.symbols = symbols == null ? new Symbol[0] : symbols;
+    this.symbols = symbols == null ? Collections.emptyList() : symbols;
+    setHasStableIds(true);
   }
+  public void refresh(IDEEditor editor, List<Symbol> newSymbols) {
+    this.editor = Objects.requireNonNull(editor);
 
-  @SuppressLint("NotifyDataSetChanged")
-  public void setSymbols(boolean notify, Symbol... symbols) {
-    this.symbols = symbols;
-    if (notify) {
-      notifyDataSetChanged();
+    if (this.symbols.equals(newSymbols)) {
+      // no need to update symbols
+      return;
     }
+
+    Objects.requireNonNull(newSymbols, "Symbol list cannot be null");
+
+    final var callback = new DiffUtil.Callback() {
+      @Override
+      public int getOldListSize() {
+        return symbols.size();
+      }
+
+      @Override
+      public int getNewListSize() {
+        return newSymbols.size();
+      }
+
+      @Override
+      public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
+        return Objects.equals(symbols.get(oldItemPosition), newSymbols.get(newItemPosition));
+      }
+
+      @Override
+      public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
+        return areItemsTheSame(oldItemPosition, newItemPosition);
+      }
+    };
+
+    final var result = DiffUtil.calculateDiff(callback);
+
+    this.symbols = newSymbols;
+    result.dispatchUpdatesTo(this);
   }
 
   @NonNull
@@ -78,8 +108,10 @@ public class SymbolInputAdapter extends RecyclerView.Adapter<SymbolInputAdapter.
 
   @Override
   public void onBindViewHolder(@NonNull VH holder, int position) {
-    if (symbols == null || symbols[position] == null) return;
-    final Symbol symbol = symbols[position];
+    if (symbols == null || symbols.get(position) == null) {
+      return;
+    }
+    final Symbol symbol = symbols.get(position);
     holder.binding.symbol.setText(symbol.getLabel());
     holder.binding.symbol.setTextColor(
         resolveAttr(holder.binding.symbol.getContext(), R.attr.colorOnSurface));
@@ -87,9 +119,14 @@ public class SymbolInputAdapter extends RecyclerView.Adapter<SymbolInputAdapter.
         __ -> insertSymbol(symbol.getCommit(), symbol.getOffset()));
   }
 
+  @Override
+  public long getItemId(int position) {
+    return symbols.get(position).hashCode();
+  }
+
   @Override
   public int getItemCount() {
-    return symbols == null ? 0 : symbols.length;
+    return symbols == null ? 0 : symbols.size();
   }
 
   void insertSymbol(String text, int selectionOffset) {
@@ -131,6 +168,7 @@ public class SymbolInputAdapter extends RecyclerView.Adapter<SymbolInputAdapter.
   }
 
   public static class VH extends RecyclerView.ViewHolder {
+
     LayoutSymbolItemBinding binding;
 
     public VH(LayoutSymbolItemBinding binding) {

app/src/main/java/com/itsaky/androidide/models/Symbol.kt

@@ -0,0 +1,53 @@
+/*
+ *  This file is part of AndroidIDE.
+ *
+ *  AndroidIDE 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.
+ *
+ *  AndroidIDE 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 AndroidIDE.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package com.itsaky.androidide.models
+
+/**
+ * A symbol that is shown in the [SymbolInputView][com.itsaky.androidide.ui.SymbolInputView].
+ *
+ * @author Akash Yadav
+ */
+open class Symbol @JvmOverloads constructor(
+  open val label: String,
+  open val commit: String,
+  open val offset: Int = 1
+) {
+  @JvmOverloads
+  constructor(both: String, offset: Int = 1) : this(both, both, offset)
+
+  override fun equals(other: Any?): Boolean {
+    if (this === other) return true
+    if (other !is Symbol) return false
+
+    if (label != other.label) return false
+    if (commit != other.commit) return false
+    if (offset != other.offset) return false
+
+    return true
+  }
+
+  override fun hashCode(): Int {
+    var result = label.hashCode()
+    result = 31 * result + commit.hashCode()
+    result = 31 * result + offset
+    return result
+  }
+
+  override fun toString(): String {
+    return "Symbol(label='$label', commit='$commit', offset=$offset)"
+  }
+}

app/src/main/java/com/itsaky/androidide/ui/EditorBottomSheet.kt

@@ -244,8 +244,7 @@ constructor(
   }
 
   fun refreshSymbolInput(editor: CodeEditorView) {
-    binding.symbolInput.bindEditor(editor.editor)
-    binding.symbolInput.setSymbols(*forFile(editor.file))
+    binding.symbolInput.refresh(editor.editor, forFile(editor.file))
   }
 
   fun onSoftInputChanged() {

app/src/main/java/com/itsaky/androidide/ui/SymbolInputView.java

@@ -23,12 +23,14 @@ import androidx.recyclerview.widget.LinearLayoutManager;
 import androidx.recyclerview.widget.RecyclerView;
 import com.itsaky.androidide.adapters.SymbolInputAdapter;
 import com.itsaky.androidide.editor.ui.IDEEditor;
+import com.itsaky.androidide.models.Symbol;
 import com.itsaky.androidide.utils.Symbols;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
 
 public class SymbolInputView extends RecyclerView {
 
-  private SymbolInputAdapter adapter;
-
   public SymbolInputView(Context context) {
     this(context, null);
   }
@@ -42,55 +44,16 @@ public class SymbolInputView extends RecyclerView {
     setLayoutManager(new LinearLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, false));
   }
 
-  public void bindEditor(IDEEditor editor) {
-    adapter = new SymbolInputAdapter(editor);
-    setAdapter(adapter);
-  }
-
-  public void setSymbols(Symbol... symbols) {
-    if (adapter != null) {
-      if (symbols.length == 0) {
-        symbols = Symbols.INSTANCE.plainTextSymbols();
-      }
-
-      adapter.setSymbols(true, symbols);
-    }
-  }
-
-  public static class Symbol {
-
-    private final String label;
-    private final String commit;
-    private final int offset;
-
-    public Symbol(String both) {
-      this(both, 1);
+  public void refresh(IDEEditor editor, List<Symbol> symbols) {
+    if (symbols == null || symbols.isEmpty()) {
+      symbols = Symbols.INSTANCE.getPlainTextSymbols();
     }
 
-    public Symbol(String both, int offset) {
-      this(both, both, offset);
-    }
-
-    public Symbol(String label, String commit, int offset) {
-      this.label = label;
-      this.commit = commit;
-      this.offset = offset;
-    }
-
-    public Symbol(String label, String commit) {
-      this(label, commit, 1);
-    }
-
-    public String getLabel() {
-      return label;
-    }
-
-    public String getCommit() {
-      return commit;
-    }
-
-    public int getOffset() {
-      return offset;
+    final var adapter = getAdapter();
+    if (adapter instanceof SymbolInputAdapter) {
+      ((SymbolInputAdapter) adapter).refresh(editor, symbols);
+    } else {
+      setAdapter(new SymbolInputAdapter(editor));
     }
   }
 }

app/src/main/java/com/itsaky/androidide/utils/Symbols.kt

@@ -17,28 +17,29 @@
  */
 package com.itsaky.androidide.utils
 
-import com.itsaky.androidide.ui.SymbolInputView.Symbol
+import com.itsaky.androidide.models.Symbol
 import java.io.File
 
 object Symbols {
 
   @JvmStatic
-  fun forFile(file: File?): Array<Symbol?> {
+  fun forFile(file: File?): List<Symbol> {
     if (file == null || !file.isFile) {
-      return emptyArray()
+      return emptyList()
     }
 
     return when (file.extension) {
       "java",
       "gradle",
-      "kt" -> javaSymbols()
-      "xml" -> xmlSymbols()
-      else -> plainTextSymbols()
+      "kt" -> javaSymbols
+
+      "xml" -> xmlSymbols
+      else -> plainTextSymbols
     }
   }
 
-  fun javaSymbols(): Array<Symbol?> {
-    return arrayOf(
+  private val javaSymbols by lazy {
+    listOf(
       TabSymbol(),
       Symbol("{", "{}"),
       Symbol("}"),
@@ -64,8 +65,8 @@ object Symbols {
     )
   }
 
-  fun xmlSymbols(): Array<Symbol?> {
-    return arrayOf(
+  private val xmlSymbols by lazy {
+    listOf(
       TabSymbol(),
       Symbol("<", "<>"),
       Symbol(">"),
@@ -93,8 +94,8 @@ object Symbols {
     )
   }
 
-  fun plainTextSymbols(): Array<Symbol?> {
-    return arrayOf(
+  val plainTextSymbols by lazy {
+    listOf(
       TabSymbol(),
       Symbol("{", "{}"),
       Symbol("}"),
@@ -121,12 +122,11 @@ object Symbols {
   }
 
   private class TabSymbol : Symbol("↹") {
-    override fun getCommit(): String {
-      return "\t"
-    }
 
-    override fun getOffset(): Int {
-      return 1
-    }
+    override val commit: String
+      get() = "\t"
+
+    override val offset: Int
+      get() = 1
   }
 }