java - 如何在 Android 中使用 sharedpreferences 更改 Pin Number？

Question

我正在使用共享首选项为应用程序 pin 实现 android 演示，我输入 pin 并确认 pin。问题是当我访问这个值时，它没有返回更新的值，它给了我NullPointerException。

String strGetPin;
public final String pref_filename = "settings";
String myPassword;
static SharedPreferences shaedPref;
public static String strdataReturned = "";

public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.settings_list);
  activity = this;
  edtxt_EnterPin = (EditText) findViewById(R.id.edtxt_Pin);
  edtxt_NewPin = (EditText) findViewById(R.id.edtxt_NewPin);
  edtxt_ConfirmPin = (EditText) findViewById(R.id.edtxt_ConfirmPin);
  shaedPref = getSharedPreferences(pref_filename, 0);
  strdataReturned = shaedPref.getString("user", "");
  if (strdataReturned.equals("")) {
    SharedPreferences.Editor editor = shaedPref.edit();
    editor.putString("user", "1234"); // newData is new pass,passwordKey is key
    editor.commit();
  }
  btnChangePin = (Button) findViewById(R.id.btn_ChangePin);

  btnChangePin.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
      // TODO Auto-generated method stub
      myDialog = new Dialog(Settings_Activity.this);
      myDialog.setContentView(R.layout.pin_change);
      myDialog.setTitle("Application PIN Change");
      myDialog.setCancelable(false);
      //Button For Change Pin save
      Button btnChange = (Button) myDialog.findViewById(R.id.btn_Save);

      btnChange.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View arg0) {
          // TODO Auto-generated method stub
          String stringData = edtxt_EnterPin.getText().toString().trim();
          strdataReturned = shaedPref.getString("user", ""); // key/def message
          // if stored password is equal to entered password
          if (strdataReturned.equals(stringData)) {
            String newData = edtxt_NewPin.getText().toString().trim();
            SharedPreferences.Editor editor = shaedPref.edit();
            editor.putString("user", newData); // newData is new pass, passwordKey is key
            editor.commit();
            Toast.makeText(getApplicationContext(), "PIN Change successfully", Toast.LENGTH_LONG).show();
            edtxt_EnterPin.setText("");
            edtxt_NewPin.setText("");
          } else {
            Toast.makeText(getApplicationContext(), "Wrong Pin!", Toast.LENGTH_LONG).show();
            edtxt_EnterPin.setText("");
            edtxt_NewPin.setText("");
          }
        }
      });
      Button btnCancel = (Button) myDialog.findViewById(R.id.btn_Cancel);

      btnCancel.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
          // TODO Auto-generated method stub
          myDialog.dismiss();
        }
      });
      myDialog.show();
    }
  });
}

日志猫：

04-09 18:42:12.694: D/(29235): onClick: Stoping Service
04-09 18:42:12.781: E/(29235): Service Stopped
04-09 18:42:19.861: D/dalvikvm(29235): GREF has increased to 201
04-09 18:42:50.712: D/AndroidRuntime(29235): Shutting down VM
04-09 18:42:50.712: W/dalvikvm(29235): threadid=1: thread exiting with uncaught exception (group=0x40015560)
04-09 18:42:50.721: E/AndroidRuntime(29235): FATAL EXCEPTION: main
04-09 18:42:50.721: E/AndroidRuntime(29235): java.lang.NullPointerException
04-09 18:42:50.721: E/AndroidRuntime(29235):    at com.sms_alert.Settings_Activity$1$1.onClick(Settings_Activity.java:95)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.view.View.performClick(View.java:2485)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.view.View$PerformClick.run(View.java:9080)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.os.Handler.handleCallback(Handler.java:587)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.os.Handler.dispatchMessage(Handler.java:92)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.os.Looper.loop(Looper.java:123)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at android.app.ActivityThread.main(ActivityThread.java:3683)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at java.lang.reflect.Method.invokeNative(Native Method)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at java.lang.reflect.Method.invoke(Method.java:507)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-09 18:42:50.721: E/AndroidRuntime(29235):    at dalvik.system.NativeStart.main(Native Method)
04-09 18:42:53.932: I/Process(29235): Sending signal. PID: 29235 SIG: 9

Answer 1

在写入之前尝试清除 SharedPreferences。

editor.clear();