Question

在我的代码中，我有MainActivity作为启动器活动。通过从checkLogin()调用SessionManagementActivity函数，它首先检查我们登录的位置。调用该函数，并满足＆＃34;未登录＆＃34;的条件。因此，它应该从LoginActivity开始，然后MainActivity结束FLAG_CLEAR_TOP。但控件再次传递给MainActivity，并在checkLogin()调用后开始执行更多代码。也就是说，MainActivity并未从SessionManagementActivity关闭。因此，我的应用首先没有响应，它意外关闭，然后也成功启动LoginActivity。当我回击时，它会在移动到MainActivity时意外关闭。任何人都可以说，为什么MainActivity之后CheckLogin()没有关闭？

这是代码

MainActivity.java

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    session = new SessionManagement(getApplicationContext());

    session.checkLogin();

    HashMap<String, String> user = session.getUserDetails();

    username = user.get(SessionManagement.KEY_NAME);

    school = user.get(SessionManagement.KEY_SCHOOL);

SessionManagement.java

// Editor for Shared preferences
Editor editor;

// Context
Context _context;

// Shared pref mode
int PRIVATE_MODE = 0;

// Sharedpref file name
private static final String PREF_NAME = "iguardian";

// All Shared Preferences Keys
private static final String IS_LOGIN = "IsLoggedIn";

// User name (make variable public to access from outside)
public static final String KEY_NAME = "name";

// Email address (make variable public to access from outside)
public static final String KEY_SCHOOL = "school";

// Constructor
public SessionManagement(Context context){
    this._context = context;
    pref = _context.getSharedPreferences(PREF_NAME, PRIVATE_MODE);
    editor = pref.edit();
}

/**
 * Create login session
 * */
public void createLoginSession(String username, String school){
    // Storing login value as TRUE
    editor.putBoolean(IS_LOGIN, true);

    // Storing name in pref
    editor.putString(KEY_NAME, username);

    // Storing email in pref
    editor.putString(KEY_SCHOOL, school);

    // commit changes
    editor.commit();
}   


/**
 * Check login method wil check user login status
 * If false it will redirect user to login page
 * Else won't do anything
 * */
public void checkLogin(){
    Log.i("Value of ","check");
    // Check login status
    if(!this.isLoggedIn()){


        Intent i = new Intent(_context, LoginActivity.class);

        i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);


        // Add new Flag to start new Activity
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);


        // Staring Login Activity
        _context.startActivity(i);



    }

}

日志

01-01 19:17:51.617: E/AndroidRuntime(12017): FATAL EXCEPTION: main
01-01 19:17:51.617: E/AndroidRuntime(12017): Process: com.litchi.iguardian, PID: 12017
01-01 19:17:51.617: E/AndroidRuntime(12017): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.litchi.iguardian/com.litchi.iguardian.MainActivity}: java.lang.NullPointerException
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread.access$800(ActivityThread.java:139)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.os.Handler.dispatchMessage(Handler.java:102)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.os.Looper.loop(Looper.java:136)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread.main(ActivityThread.java:5086)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at java.lang.reflect.Method.invokeNative(Native Method)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at java.lang.reflect.Method.invoke(Method.java:515)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at dalvik.system.NativeStart.main(Native Method)
01-01 19:17:51.617: E/AndroidRuntime(12017): Caused by: java.lang.NullPointerException
01-01 19:17:51.617: E/AndroidRuntime(12017):    at com.litchi.iguardian.MainActivity.onCreate(MainActivity.java:152)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.Activity.performCreate(Activity.java:5248)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
01-01 19:17:51.617: E/AndroidRuntime(12017):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
01-01 19:17:51.617: E/AndroidRuntime(12017):    ... 11 more

Answer 1

从 checkLogin（）获取布尔结果，并从 MainActivity 开始活动从

更改声明

_context.startActivity(i);

到

_context.startActivityForResult(i, requestCode);

参考此startActivityForResult

的链接

http://developer.android.com/training/basics/intents/result.html

编辑2： 的 SessionManagement.java

public boolean checkLogin(){ Log.i("Value of ","check"); // Check login status if(!this.isLoggedIn()){ return false; } return true; }

<强> MainActivity.java

boolean b = session.checkLogin(); if(!b) { Intent i = new Intent(MainActivity.this, LoginActivity.class); ... _context.startActivityForResult(i, 1); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { // Check which request we're responding to if (requestCode == 1) { // Make sure the request was successful if (resultCode == RESULT_OK) { // Do something } } }

Answer 2

if(!this.isLoggedIn()){


    Intent i = new Intent(_context, LoginActivity.class);

    i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);


    // Add new Flag to start new Activity
    i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);


    // Staring Login Activity
    _context.startActivity(i);

（（活动）_context）.finish（）;

即使在从其他活动关闭MainActivity后，它也不会关闭

2 个答案: