EditText控件如何自定義撤銷操作

要自定義EditText控件的撤銷操作，可以使用SpannableStringBuilder和TextWatcher來實現。以下是一個示例代碼：

public class CustomEditText extends AppCompatEditText {
    private Stack<CharSequence> mUndoStack = new Stack<>();
    private Stack<CharSequence> mRedoStack = new Stack<>();

    public CustomEditText(Context context) {
        super(context);
        init();
    }

    public CustomEditText(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CustomEditText(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                // do nothing
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                mUndoStack.push(new SpannableStringBuilder(s));
                mRedoStack.clear();
            }

            @Override
            public void afterTextChanged(Editable s) {
                // do nothing
            }
        });
    }

    public void undo() {
        if (!mUndoStack.isEmpty()) {
            CharSequence currentText = getText();
            mRedoStack.push(new SpannableStringBuilder(currentText));

            Editable editable = getText();
            editable.clear();
            editable.append(mUndoStack.pop());
        }
    }

    public void redo() {
        if (!mRedoStack.isEmpty()) {
            CharSequence currentText = getText();
            mUndoStack.push(new SpannableStringBuilder(currentText));

            Editable editable = getText();
            editable.clear();
            editable.append(mRedoStack.pop());
        }
    }
}

在這個自定義EditText控件中，我們使用兩個棧來保存撤銷和重做的操作。在TextWatcher中，每當文字發生改變時，我們將當前的文字內容保存到撤銷棧中。通過調用undo()和redo()方法，可以實現撤銷和重做操作。