Android 防止Toast重复弹出相同的信息

private Toast mToast;
    public void showToast(String text) {  
        if(mToast == null) {  
            mToast = Toast.makeText(OrderDetail.this, text, Toast.LENGTH_SHORT);  
        } else {  
            mToast.setText(text);    
            mToast.setDuration(Toast.LENGTH_SHORT);  
        }  
        mToast.show();  
    }  
      
    public void cancelToast() {  
            if (mToast != null) {  
                mToast.cancel();  
            }  
        }  
      
    public void onBackPressed() {  
            cancelToast();  
            super.onBackPressed();  
        }