Demo4的github地址 模拟器有点慢之后贴图
https://git.oschina.net/annie_guo/study.git

在登陆注册界面中java的提示语言(Login.java)
if(LN.length()<=0&&LP.length()<=0){
Toast.makeText(LoginActivity.this, "用户名和密码不能为空", Toast.LENGTH_SHORT).show();
}else if (LN.length()<=0){
Toast.makeText(LoginActivity.this, "用户名不能为空", Toast.LENGTH_SHORT).show();
}else if (LP.length()<=0){
Toast.makeText(LoginActivity.this, "密码不能为空", Toast.LENGTH_SHORT).show();
}else if (LN!=null&&LP!=null)