我正在创建一个需要登录的应用程序。我创建了主活动和登录活动。
在主活动onCreate方法中，我添加了以下条件:
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
...
loadSettings();
if(strSessionString == null)
{
login();
}
...
}
当登录表单终止时执行的onActivityResult方法看起来像这样:
@Override
public void onActivityResult(int requestCode,
int resultCode,
Intent data)
{
super.onActivityResult(requestCode, resultCode, data);
switch(requestCode)
{
case(SHOW_SUBACTICITY_LOGIN):
{
if(resultCode == Activity.RESULT_OK)
{
strSessionString = data.getStringExtra(Login.SESSIONSTRING);
connectionAvailable = true;
strUsername = data.getStringExtra(Login.USERNAME);
}
}
}
问题是登录表单有时出现两次(login()方法被调用两次)，也当电话键盘滑动登录表单再次出现，我猜问题是变量strSessionString。
有人知道如何设置变量全局，以避免登录表单出现后，用户已经成功验证?
你可以使用两种方法来做到这一点:
使用应用程序类
使用共享首选项
使用应用程序类
例子:
class SessionManager extends Application{
String sessionKey;
setSessionKey(String key){
this.sessionKey=key;
}
String getSessisonKey(){
return this.sessionKey;
}
}
你可以使用上面的类在MainActivity中实现登录。代码看起来像这样:
@override
public void onCreate (Bundle savedInstanceState){
// you will this key when first time login is successful.
SessionManager session= (SessionManager)getApplicationContext();
String key=getSessisonKey.getKey();
//Use this key to identify whether session is alive or not.
}
This method will work for temporary storage. You really do not any idea when operating system is gonna kill the application, because of low memory.
When your application is in background and user is navigating through other application which demands more memory to run, then your application will be killed since operating system given more priority to foreground processes than background.
Hence your application object will be null before user logs out. Hence for this I recommend to use second method Specified above.
使用共享首选项。
字符串MYPREF = " com.your.application.session "
SharedPreferences pref= context.getSharedPreferences(MyPREF,MODE_PRIVATE);
//插入键如下:
编辑器编辑= pre .edit();
editor.putString(“关键”、“价值”);
editor.commit ();
//获取密钥如下所示。
sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
String key= getResources().getString("key");
