我很难弄清楚如何使用 SharedPreferences 将用户名存储在手机中并保持 session 状态直到注销。我还需要知道它如何同时在 session 中将用户名与用户在 ListView 中单击的数据一起发送出去。以下是我正在使用的代码，我想知道为了实现这个目标而放置的位置和代码。作为登录，它将转到菜单并停留在菜单上(避免后退按钮返回登录屏幕)每个菜单都有一个注销项，它将返回登录屏幕。

我之前看过的问题是 this和 this

日志详细信息

05-26 10:42:19.146: WARN/KeyCharacterMap(26071): Using default keymap: /system/usr/keychars/qwerty.kcm.bin
05-26 10:42:23.926: DEBUG/AndroidRuntime(26071): Shutting down VM
05-26 10:42:23.926: WARN/dalvikvm(26071): threadid=3: thread exiting with uncaught exception (group=0x40013140)
05-26 10:42:23.926: ERROR/AndroidRuntime(26071): Uncaught handler: thread main exiting due to uncaught exception
05-26 10:42:23.936: ERROR/AndroidRuntime(26071): java.lang.NullPointerException
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.merrill2.Login$1.onClick(Login.java:42)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.View.performClick(View.java:2232)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.View.onTouchEvent(View.java:3905)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.widget.TextView.onTouchEvent(TextView.java:6414)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.View.dispatchTouchEvent(View.java:3421)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:906)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1707)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1197)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.app.Activity.dispatchTouchEvent(Activity.java:1993)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1691)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1533)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.os.Looper.loop(Looper.java:123)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at android.app.ActivityThread.main(ActivityThread.java:3992)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at java.lang.reflect.Method.invokeNative(Native Method)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at java.lang.reflect.Method.invoke(Method.java:521)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
05-26 10:42:23.936: ERROR/AndroidRuntime(26071):     at dalvik.system.NativeStart.main(Native Method)
05-26 10:42:23.946: INFO/Process(899): Sending signal. PID: 26071 SIG: 3
05-26 10:42:23.956: INFO/dalvikvm(26071): threadid=7: reacting to signal 3
05-26 10:42:23.966: INFO/dalvikvm(26071): Wrote stack trace to '/data/anr/traces.txt'
05-26 10:42:25.646: DEBUG/dalvikvm(25722): GC freed 973 objects / 63040 bytes in 93ms
05-26 10:42:27.777: DEBUG/DispatchService(945): Handled message = TIMED_SERVICE_UNMASK
05-26 10:42:29.856: DEBUG/DispatchService(945): DISPATCH SERVICE getIdenPacketDataState: returning: 4
05-26 10:42:29.876: INFO/iDENWAPReceiver(953): Received a android.intent.action.ANY_DATA_STATE

登录.java

public class Login extends Activity {
    protected static final SharedPreferences settings = null;
    private EditText etUsername;
    private Button btnLogin;
    private Button btnCancel;
    private TextView lblResult;
    /** Called when the activity is first created. */
    //@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        etUsername = (EditText)findViewById(R.id.username);
        btnLogin = (Button)findViewById(R.id.login_button);
        btnCancel = (Button)findViewById(R.id.cancel_button);
        lblResult = (TextView)findViewById(R.id.result);

        btnLogin.setOnClickListener(new OnClickListener() {
            //@Override
            public void onClick(View v) {
            // Check Login
            String username = etUsername.getText().toString();

            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
            SharedPreferences.Editor editor = settings.edit();
            editor.putString("username", username);

            if(username.equals("1111")){
                lblResult.setText("Login successful.");

                //startActivity(new Intent(this, Activity2.class));


                Intent i = new Intent(getApplicationContext(), Customer.class);
                startActivity(i);

如果我去掉下面的行:

protected static final SharedPreferences settings = null;

我把这个:

btnLogin.setOnClickListener(new OnClickListener() {
            private SharedPreferences settings;

“设置”出错所以我不得不使用上面提到的那些行之一

最佳答案

要添加用户，只需执行以下操作:

import android.preference.PreferenceManager;
....
SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
SharedPreferences.Editor editor = settings.edit();
editor.putString("username", username);

并在注销中删除它:

SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
SharedPreferences.Editor editor = settings.edit();
editor.remove("username");

通过这种方式，您可以确保用户只持续一个 session ，直到注销。当您打开您的应用程序时，您应该进行检查(以防万一)，如果发生错误，请查看是否已经从上一个 session 设置了用户名。

至于在 ListView 中传递数据，您必须手动完成。 SharedPreference 框架负责处理其他一切。

关于Android:将用户名保留在 session 中直到注销，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6112269/