Android 如何加载内部存储对象

基本上，我保存了类服务器的一个对象，这是因为我可以读取保存的文件的名称并将它们放入微调器中，但我似乎不知道如何重新加载才能使用它

按照我使用的代码保存它并尝试加载它

EditText serverName;
EditText textGetter;
String filename;

public void saveServer(View view) {
    filename = serverName.getText().toString() + ".bin";

    Server newServer = new Server();
    textGetter = (EditText) findViewById(R.id.nameEdit);
    newServer.setName(textGetter.getText().toString());
    textGetter = (EditText) findViewById(R.id.serverEdit);
    newServer.setAddress(textGetter.getText().toString());
    textGetter = (EditText) findViewById(R.id.userEdit);
    newServer.setUser(textGetter.getText().toString());
    textGetter = (EditText) findViewById(R.id.passwordEdit);
    newServer.setPassword(textGetter.getText().toString());

    try {
        ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(filename));
        os.writeObject(newServer);
        os.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public void loadServer() {
    String selectedServer = String.valueOf(serverSpinner.getSelectedItem());
    selectedServer = selectedServer + ".bin";
    Server loadedServer = null;
    try {
        ObjectInputStream is = new ObjectInputStream(new FileInputStream(selectedServer));
        loadedServer = (Server) is.readObject();
        is.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    //following Line is highlited by logcat at app.FtpActivity.loadServer(FtpActivity.java:69)
    Toast.makeText(this, loadedServer.getName(), Toast.LENGTH_SHORT).show();
}

Logcat错误：

10-15 14:37:14.119 16083-16083/app E/AndroidRuntime: FATAL EXCEPTION: main
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime: java.lang.NullPointerException
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at app.FtpActivity.loadServer(FtpActivity.java:69)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at app.FtpActivity$1.onItemSelected(FtpActivity.java:44)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.widget.AdapterView.fireOnSelected(AdapterView.java:895)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.widget.AdapterView.access$200(AdapterView.java:50)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:863)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:615)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:92)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:4921)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
10-15 14:37:14.119 16083-16083/app E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)

指onClick中仅执行以下操作的行

loadServer();

---

它不起作用吗？什么不工作？当调用loadServer时，请参阅@TimCastelijns。应用程序停止工作并关闭。日志是什么output@TimCastelijns向我的loadServer抛出空指针异常，我真的不明白。。。

loadServer();