Android项目中怎么显示与隐藏软键盘

import android.app.Activity;import android.content.Context;import android.graphics.Rect;import android.os.Build;import android.util.Log;import android.util.TypedValue;import android.view.View;import android.view.ViewGroup;import android.view.ViewTreeObserver;public class KeyBoardShowListener {  private Context ctx;  public KeyBoardShowListener(Context ctx) {    this.ctx = ctx;  }  OnKeyboardVisibilityListener keyboardListener;  public OnKeyboardVisibilityListener getKeyboardListener() {    return keyboardListener;  }  public interface OnKeyboardVisibilityListener {    void onVisibilityChanged(boolean visible);  }  public void setKeyboardListener(final OnKeyboardVisibilityListener listener, Activity activity) {    final View activityRootView = ((ViewGroup) activity.findViewById(android.R.id.content)).getChildAt(0);    activityRootView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {      private boolean wasOpened;      private final int DefaultKeyboardDP = 100;      // From @nathanielwolf answer... Lollipop includes button bar in the root. Add height of button bar (48dp) to maxDiff      private final int EstimatedKeyboardDP = DefaultKeyboardDP + (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP ? 48 : 0);      private final Rect r = new Rect();      @Override      public void onGlobalLayout() {        // Convert the dp to pixels.        int estimatedKeyboardHeight = (int) TypedValue            .applyDimension(TypedValue.COMPLEX_UNIT_DIP, EstimatedKeyboardDP, activityRootView.getResources().getDisplayMetrics());        // Conclude whether the keyboard is shown or not.        activityRootView.getWindowVisibleDisplayFrame(r);        int heightDiff = activityRootView.getRootView().getHeight() - (r.bottom - r.top);        boolean isShown = heightDiff >= estimatedKeyboardHeight;        if (isShown == wasOpened) {          Log.e("Keyboard state", "Ignoring global layout change...");          return;        }        wasOpened = isShown;        listener.onVisibilityChanged(isShown);      }    });  }}