// 定义一个文本视图变化监听器的接口，用于监听文本编辑框中的变化事件
private OnTextViewChangeListener mOnTextViewChangeListener;

// NoteEditText的构造函数，当从AttributeSet创建时调用
public NoteEditText(Context context) {
    super(context, null);
    mIndex = 0;
}

// 设置当前文本编辑框的索引，用于标识编辑框的位置
public void setIndex(int index) {
    mIndex = index;
}

// 设置文本视图变化监听器
public void setOnTextViewChangeListener(OnTextViewChangeListener listener) {
    mOnTextViewChangeListener = listener;
}

// NoteEditText的构造函数，当从AttributeSet和 defStyle创建时调用
public NoteEditText(Context context, AttributeSet attrs) {
    super(context, attrs, android.R.attr.editTextStyle);
}

// NoteEditText的构造函数，当从AttributeSet、defStyle和 defStyle创建时调用
public NoteEditText(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
}

// 处理触摸事件，用于实现自定义的文本选择行为
@Override
public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // 计算触摸点在文本中的位置，并设置光标
            int x = (int) event.getX();
            int y = (int) event.getY();
            x -= getTotalPaddingLeft();
            y -= getTotalPaddingTop();
            x += getScrollX();
            y += getScrollY();

            Layout layout = getLayout();
            int line = layout.getLineForVertical(y);
            int off = layout.getOffsetForHorizontal(line, x);
            Selection.setSelection(getText(), off);
            break;
    }

    return super.onTouchEvent(event);
}

// 处理按键事件，例如Enter和Delete键
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
        case KeyEvent.KEYCODE_ENTER:
            // 如果设置了监听器，消费Enter键事件
            if (mOnTextViewChangeListener != null) {
                return false;
            }
            break;
        case KeyEvent.KEYCODE_DEL:
            // 在删除之前记录光标的位置
            mSelectionStartBeforeDelete = getSelectionStart();
            break;
        default:
            break;
    }
    return super.onKeyDown(keyCode, event);
}

// 处理按键释放事件，例如Enter和Delete键
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
    switch(keyCode) {
        case KeyEvent.KEYCODE_DEL:
            // 如果设置了监听器，并且在删除之前光标位于文本开头，则通知监听器删除事件
            if (mOnTextViewChangeListener != null) {
                if (0 == mSelectionStartBeforeDelete && mIndex != 0) {
                    mOnTextViewChangeListener.onEditTextDelete(mIndex, getText().toString());
                    return true;
                }
            } else {
                Log.d(TAG, "OnTextViewChangeListener was not seted");
            }
            break;
        case KeyEvent.KEYCODE_ENTER:
            // 如果设置了监听器，通知监听器Enter键事件，创建新的文本行
            if (mOnTextViewChangeListener != null) {
                int selectionStart = getSelectionStart();
                String text = getText().subSequence(selectionStart, length()).toString();
                setText(getText().subSequence(0, selectionStart));
                mOnTextViewChangeListener.onEditTextEnter(mIndex + 1, text);
            } else {
                Log.d(TAG, "OnTextViewChangeListener was not seted");
            }
            break;
        default:
            break;
    }
    return super.onKeyUp(keyCode, event);
}

// 处理焦点变化事件，用于在文本编辑框失去焦点时通知监听器
@Override
protected void onFocusChanged(boolean focused, int direction, Rect previouslyFocusedRect) {
    if (mOnTextViewChangeListener != null) {
        // 如果文本编辑框失去焦点且文本为空，通知监听器文本变化
        if (!focused && TextUtils.isEmpty(getText())) {
            mOnTextViewChangeListener.onTextChange(mIndex, false);
        } else {
            mOnTextViewChangeListener.onTextChange(mIndex, true);
        }
    }
    super.onFocusChanged(focused, direction, previouslyFocusedRect);
}

// 创建上下文菜单，用于实现长按文本时弹出的菜单
@Override
protected void onCreateContextMenu(ContextMenu menu) {
    if (getText() instanceof Spanned) {
        int selStart = getSelectionStart();
        int selEnd = getSelectionEnd();

        int min = Math.min(selStart, selEnd);
        int max = Math.max(selStart, selEnd);

        // 如果选中的文本包含URL，添加一个菜单项用于打开链接
        final URLSpan[] urls = ((Spanned) getText()).getSpans(min, max, URLSpan.class);
        if (urls.length == 1) {
            int defaultResId = 0;
            for(String schema: sSchemaActionResMap.keySet()) {
                if(urls[0].getURL().indexOf(schema) >= 0) {
                    defaultResId = sSchemaActionResMap.get(schema);
                    break;
                }
            }

            if (defaultResId == 0) {
                defaultResId = R.string.note_link_other;
            }

            menu.add(0, 0, 0, defaultResId).setOnMenuItemClickListener(
                    new OnMenuItemClickListener() {
                        public boolean onMenuItemClick(MenuItem item) {
                            // 打开链接
                            urls[0].onClick(NoteEditText.this);
                            return true;
                        }
                    });
        }
    }
    super.onCreateContextMenu(menu);
}