要实现Android键盘/输入法切换的监听器，可以使用以下步骤：

1. 在Activity或Fragment中，创建一个继承自ViewTreeObserver.OnGlobalLayoutListener的类，用于监听布局变化事件。

public class KeyboardChangeListener implements ViewTreeObserver.OnGlobalLayoutListener {
    private final View rootView;
    private final OnKeyboardChangeListener listener;

    private boolean isKeyboardShowing = false;
    private int keyboardHeight = 0;

    public interface OnKeyboardChangeListener {
        void onKeyboardShow(int keyboardHeight);
        void onKeyboardHide();
    }

    public KeyboardChangeListener(View rootView, OnKeyboardChangeListener listener) {
        this.rootView = rootView;
        this.listener = listener;
        rootView.getViewTreeObserver().addOnGlobalLayoutListener(this);
    }

    @Override
    public void onGlobalLayout() {
        Rect rect = new Rect();
        rootView.getWindowVisibleDisplayFrame(rect);
        int screenHeight = rootView.getRootView().getHeight();
        int heightDifference = screenHeight - rect.bottom;

        if (heightDifference > 200) { // 超过200像素则认为是键盘显示
            if (!isKeyboardShowing) {
                isKeyboardShowing = true;
                keyboardHeight = heightDifference;
                if (listener != null) {
                    listener.onKeyboardShow(keyboardHeight);
                }
            }
        } else {
            if (isKeyboardShowing) {
                isKeyboardShowing = false;
                if (listener != null) {
                    listener.onKeyboardHide();
                }
            }
        }
    }

    public void removeListener() {
        rootView.getViewTreeObserver().removeOnGlobalLayoutListener(this);
    }
}

2. 在Activity或Fragment中，实例化KeyboardChangeListener，并设置监听器。

public class MainActivity extends AppCompatActivity implements KeyboardChangeListener.OnKeyboardChangeListener {
    private KeyboardChangeListener keyboardChangeListener;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        View rootView = getWindow().getDecorView().findViewById(android.R.id.content);
        keyboardChangeListener = new KeyboardChangeListener(rootView, this);
    }

    @Override
    public void onKeyboardShow(int keyboardHeight) {
        // 键盘显示时的操作
    }

    @Override
    public void onKeyboardHide() {
        // 键盘隐藏时的操作
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (keyboardChangeListener != null) {
            keyboardChangeListener.removeListener();
        }
    }
}

在onKeyboardShow和onKeyboardHide方法中，可以进行相应的操作，例如调整布局、滚动内容等。注意在Activity或Fragment销毁时，移除监听器以避免内存泄漏。

这样，当键盘显示或隐藏时，就会触发相应的回调方法，你可以在这些方法中进行相应的处理。