Android如何使用DecorView实现对话框功能

public class TipsDialog {  private Activity activity;  private View rootView;  private TextView confirmTextView;  private TextView cancelTextView;  private TextView contentTextView;  private boolean isShowing;  public TipsDialog(Activity activity) {    this.activity = activity;    isShowing = false;    rootView = LayoutInflater.from(activity).inflate(R.layout.view_tips_dialog,null);    confirmTextView = (TextView) rootView.findViewById(R.id.view_tips_dialog_tv_confirm);    cancelTextView = (TextView) rootView.findViewById(R.id.view_tips_dialog_tv_cancel);    contentTextView = (TextView) rootView.findViewById(R.id.view_tips_dialog_tv_content);  }  public void show(){    if(activity == null){      return;    }    if(isShowing){      return;    }    ViewGroup decorView = (ViewGroup) activity.getWindow().getDecorView();    FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT);    params.gravity = Gravity.CENTER;    rootView.setLayoutParams(params);    decorView.addView(rootView);    rootView.setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View v) {        dismiss();      }    });    RotateAnimation rotateAnimation = new RotateAnimation(0,720f,RotateAnimation.RELATIVE_TO_SELF,0.5f,RotateAnimation.RELATIVE_TO_SELF,0.5f);    rotateAnimation.setDuration(2000);    contentTextView.startAnimation(rotateAnimation);    isShowing = true;  }  public void dismiss(){    if(!isShowing){      return;    }    isShowing = false;    if(rootView.getParent() == null){      return;    }    ViewGroup parent = (ViewGroup) rootView.getParent();    parent.removeView(rootView);  }  public int getRandomColor(){    Random random = new Random();    return Color.argb(random.nextInt(200),random.nextInt(240),random.nextInt(240),random.nextInt(240));  }  public boolean isShowing() {    return isShowing;  }}