Android应用程序中的“记住我"的SharedPreferences按钮 [英] SharedPreferences in Android app for remember me button

问题描述

我不确定自己在做什么错.在我的应用程序中，我试图让它记住提交时在文本字段中输入的先前密码.根据使用共享首选项进行的研究，即使应用重新启动，也可以保存该变量.我的代码顶部:

Im not to sure what I'm doing wrong. In my app I'm trying to have it remember a previous password entered into the textfield on submit. From research done using shared preferences saving the variable even if the app it restarted. Top of my code:

public class AK_Voucher_access extends BT_fragment{

View thisScreensView = null;

String errormessage = "";
String errormessageTextColor = "";
String errormessageText = "";
String rememberTextText = "";
String rememberTextTextColor = "";
String voucherTextfieldPlaceholder = "";
String voucherTextfieldSecureTextEntry = "";
boolean voucherTextfieldSecureTextEntryBool = false;
String iphoneImage = "";
String ipadImage = "";
String errormessageInvalid = "";
String errormessageRemember = "";

private TextView errormessageTextView = null;
private EditText voucherTextfieldEditText = null;
private ImageView imageView = null;
private Button submitButton = null;
private Switch rememberSwitch = null;

private Drawable myHeaderImageDrawable = null;
private String alphaImage = "", pass;
private static BT_item screenObjectToLoad = null;
private static final String PASSVALUE = "value";
//private static final String appPassword = "appPassword";
Context context;

要在设置时检索文本字段:

To retrieve textfield when set:

if (rememberSwitch.isChecked()) {
            BT_debugger.showIt(fragmentName + ":rememberSwitch is ON");

        SharedPreferences settings = context.getSharedPreferences(PASSVALUE, MODE_PRIVATE);

        String rpass= settings.getString("rpassword","");


            if (rpass!=null) {
                    voucherTextfieldEditText.setText(rpass);
            } else {
                voucherTextfieldEditText.setText("nono");
            }

    }
    else {
        BT_debugger.showIt(fragmentName + ":rememberSwitch is OFF");
        // switchStatus.setText("Switch is currently OFF");
    }

然后我的代码在提交时保存字符串:

Then my code to save the String on submit:

if (loadScreenNickname.length() > 1 && !loadScreenNickname.equalsIgnoreCase("none")) {

                // before we launch the next screen...
                if (!rememberSwitch.isChecked()) {
                    voucherTextfieldEditText.setText("");
                }

                if (rememberSwitch.isChecked()){
                    //voucherTextfieldEditText.setText("");

                    String pass = voucherTextfieldEditText.getText().toString();
                    BT_debugger.showIt(pass + ":CODE");

                    SharedPreferences settings = context.getSharedPreferences(PASSVALUE, MODE_PRIVATE);
                    settings.edit().putString("rpassword", pass).apply();

                    rememberSwitch.setChecked(true);



                }
                errormessageTextView.setVisibility(View.GONE);
                errormessageTextView.invalidate();

                //loadScreenObject(null, thisScreen);
                try {
                    loadScreenWithNickname(loadScreenNickname);

                    foundIt = 1;

                } catch (Exception ex){
                    Log.e ("eTutorPrism Error", "Caught this exception " + ex);
                    ex.printStackTrace();
                }
                break;
            }
        }

但是我加班却在我的应用程序中运行插件，但在logcat中却收到此错误:

However overtime I run the plugin within my app I receive this error in the logcat:

E/UncaughtException: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
                                                               at com.asfapp.ui.bt_plugins.AK_Voucher_access.onCreateView(AK_Voucher_access.java:210)


E/AndroidRuntime: FATAL EXCEPTION: main
                                                        Process: com.asfapp, PID: 24771
                                                        java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
                                                            at com.asfapp.ui.bt_plugins.AK_Voucher_access.onCreateView(AK_Voucher_access.java:210)

不能确定这次代码有什么问题，但是应该有帮助.

Not to sure whats wrong with the code this time but anything should help.

推荐答案

使用此代码在fragment

SharedPreferences preferences = this.getActivity().getSharedPreferences("myPref", Context.MODE_PRIVATE);

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