Dialog一般用自定义的，系统自带的也有

//系统自带Dialog AlertDialog.Builder b=new AlertDialog.Builder(Reign.this);                            b.setTitle("是否登录");//设置标题                            b.setMessage("是否登录"); //设置内容                            b.setPositiveButton("是", new DialogInterface.OnClickListener() {                                @Override                                public void onClick(DialogInterface dialog, int which) {                                    Intent i = new Intent();                                    Bundle bundle=new Bundle();                                    i.setClass(Reign.this, Login.class);                                    bundle.putSerializable("data", (Serializable) user);                                    i.putExtras(bundle);                                    startActivity(i);                                    dialog.dismiss();                                }                            });                            b.setNegativeButton("否", new DialogInterface.OnClickListener() {                                @Override                                public void onClick(DialogInterface dialog, int which) {                                    Toast.makeText(Reign.this, "还是登录吧", Toast.LENGTH_SHORT).show();                                    dialog.dismiss();//销毁弹窗                                }                            });                            b.create().show();//先create，再show                      　　　　//b.setCancelable(true);点击空白处，是否消失弹窗，默认是true，消失

//学了自定义在说