Retain TextView selection after list updating

1 files changed, 201 insertions, 0 deletions

diff --git a/src/main/java/de/pixart/messenger/ui/widget/ListSelectionManager.java b/src/main/java/de/pixart/messenger/ui/widget/ListSelectionManager.java
new file mode 100644
index 000000000..4cf1a9e42
--- /dev/null
+++ b/src/main/java/de/pixart/messenger/ui/widget/ListSelectionManager.java
@@ -0,0 +1,201 @@
+package de.pixart.messenger.ui.widget;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Message;
+import android.text.Selection;
+import android.text.Spannable;
+import android.view.ActionMode;
+import android.view.Menu;
+import android.view.MenuItem;
+import android.widget.TextView;
+
+public class ListSelectionManager {
+
+    private static final int MESSAGE_SEND_RESET = 1;
+    private static final int MESSAGE_RESET = 2;
+    private static final int MESSAGE_START_SELECTION = 3;
+
+    private static final Handler HANDLER = new Handler(Looper.getMainLooper(), new Handler.Callback() {
+
+        @Override
+        public boolean handleMessage(Message msg) {
+            switch (msg.what) {
+                case MESSAGE_SEND_RESET: {
+                    // Skip one more message queue loop
+                    HANDLER.obtainMessage(MESSAGE_RESET, msg.obj).sendToTarget();
+                    return true;
+                }
+                case MESSAGE_RESET: {
+                    final ListSelectionManager listSelectionManager = (ListSelectionManager) msg.obj;
+                    listSelectionManager.futureSelectionIdentifier = null;
+                    return true;
+                }
+                case MESSAGE_START_SELECTION: {
+                    final StartSelectionHolder holder = (StartSelectionHolder) msg.obj;
+                    holder.listSelectionManager.futureSelectionIdentifier = null;
+                    startSelection(holder.textView, holder.start, holder.end);
+                    return true;
+                }
+            }
+            return false;
+        }
+    });
+
+    private static class StartSelectionHolder {
+
+        public final ListSelectionManager listSelectionManager;
+        public final TextView textView;
+        public final int start;
+        public final int end;
+
+        public StartSelectionHolder(ListSelectionManager listSelectionManager, TextView textView,
+                                    int start, int end) {
+            this.listSelectionManager = listSelectionManager;
+            this.textView = textView;
+            this.start = start;
+            this.end = end;
+        }
+    }
+
+    private ActionMode selectionActionMode;
+    private Object selectionIdentifier;
+    private TextView selectionTextView;
+
+    private Object futureSelectionIdentifier;
+    private int futureSelectionStart;
+    private int futureSelectionEnd;
+
+    public void onCreate(TextView textView) {
+        final CustomCallback callback = new CustomCallback(textView);
+        textView.setCustomSelectionActionModeCallback(callback);
+    }
+
+    public void onUpdate(TextView textView, Object identifier) {
+        if (SUPPORTED) {
+            CustomCallback callback = (CustomCallback) textView.getCustomSelectionActionModeCallback();
+            callback.identifier = identifier;
+            if (futureSelectionIdentifier == identifier) {
+                HANDLER.obtainMessage(MESSAGE_START_SELECTION, new StartSelectionHolder(this,
+                        textView, futureSelectionStart, futureSelectionEnd)).sendToTarget();
+            }
+        }
+    }
+
+    public void onBeforeNotifyDataSetChanged() {
+        if (SUPPORTED) {
+            HANDLER.removeMessages(MESSAGE_SEND_RESET);
+            HANDLER.removeMessages(MESSAGE_RESET);
+            HANDLER.removeMessages(MESSAGE_START_SELECTION);
+            if (selectionActionMode != null) {
+                final CharSequence text = selectionTextView.getText();
+                futureSelectionIdentifier = selectionIdentifier;
+                futureSelectionStart = Selection.getSelectionStart(text);
+                futureSelectionEnd = Selection.getSelectionEnd(text);
+                selectionActionMode.finish();
+                selectionActionMode = null;
+                selectionIdentifier = null;
+                selectionTextView = null;
+            }
+        }
+    }
+
+    public void onAfterNotifyDataSetChanged() {
+        if (SUPPORTED && futureSelectionIdentifier != null) {
+            HANDLER.obtainMessage(MESSAGE_SEND_RESET, this).sendToTarget();
+        }
+    }
+
+    private class CustomCallback implements ActionMode.Callback {
+
+        private final TextView textView;
+        public Object identifier;
+
+        public CustomCallback(TextView textView) {
+            this.textView = textView;
+        }
+
+        @Override
+        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
+            selectionActionMode = mode;
+            selectionIdentifier = identifier;
+            selectionTextView = textView;
+            return true;
+        }
+
+        @Override
+        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
+            return true;
+        }
+
+        @Override
+        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
+            return false;
+        }
+
+        @Override
+        public void onDestroyActionMode(ActionMode mode) {
+            if (selectionActionMode == mode) {
+                selectionActionMode = null;
+                selectionIdentifier = null;
+                selectionTextView = null;
+            }
+        }
+    }
+
+    private static final Field FIELD_EDITOR;
+    private static final Method METHOD_START_SELECTION;
+    private static final boolean SUPPORTED;
+
+    static {
+        Field editor;
+        try {
+            editor = TextView.class.getDeclaredField("mEditor");
+            editor.setAccessible(true);
+        } catch (Exception e) {
+            editor = null;
+        }
+        FIELD_EDITOR = editor;
+        Method startSelection = null;
+        if (editor != null) {
+            String[] startSelectionNames = {"startSelectionActionMode", "startSelectionActionModeWithSelection"};
+            for (String startSelectionName : startSelectionNames) {
+                try {
+                    startSelection = editor.getType().getDeclaredMethod(startSelectionName);
+                    startSelection.setAccessible(true);
+                    break;
+                } catch (Exception e) {
+                    startSelection = null;
+                }
+            }
+        }
+        METHOD_START_SELECTION = startSelection;
+        SUPPORTED = FIELD_EDITOR != null && METHOD_START_SELECTION != null;
+    }
+
+    public static boolean isSupported() {
+        return SUPPORTED;
+    }
+
+    public static void startSelection(TextView textView) {
+        startSelection(textView, 0, textView.getText().length());
+    }
+
+    public static void startSelection(TextView textView, int start, int end) {
+        final CharSequence text = textView.getText();
+        if (SUPPORTED && start >= 0 && end > start && textView.isTextSelectable() && text instanceof Spannable) {
+            final Spannable spannable = (Spannable) text;
+            start = Math.min(start, spannable.length());
+            end = Math.min(end, spannable.length());
+            Selection.setSelection(spannable, start, end);
+            try {
+                final Object editor = FIELD_EDITOR != null ? FIELD_EDITOR.get(textView) : textView;
+                METHOD_START_SELECTION.invoke(editor);
+            } catch (Exception e) {
+            }
+        }
+    }
+}
\ No newline at end of file