共享偏好不起作用，默认值

Question

My app has a lot of checkboxes in it, a spinner, edittext and a button. When I choose an item from the spinner and then enter a certain value and hit a button, a certain checkbox text changes. Now I added shared preferences and I have two problems.

First problem is that when I try to use sharedpreferences the app crashes (as soon as I start the activity containing these sharedpreferences).

private String getItemQuantity(String key){
    SharedPreferences itemQuantitySP = getApplicationContext().getSharedPreferences("bifrostPrefs", android.content.Context.MODE_PRIVATE);
    String sp1 = "sp1";
    return itemQuantitySP.getString(key, sp1);
}
private void saveItemQuantity(String key, String value){
    SharedPreferences itemQuantitySP = getApplicationContext().getSharedPreferences("bifrostPrefs", android.content.Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = itemQuantitySP.edit();
    editor.putString(key, value);
    editor.commit();
}

Saving sharedpreferences:

if (Integer.parseInt(quantityEditText.getText().toString()) == 250)
{
    cb4.setText("Elaborate Totem (" + item1 + "/250)");
    saveItemQuantity("cb4", cb4.getText().toString());
    cb4.setChecked(true);
}
... //REST OF THE CODE

Getting sharedpreferences:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_bifrost);

    getItemQuantity("cb4");
... //REST OF THE CODE

Second problem is that I have a lot of checkboxes and setting default value for every single one of them would be very time consuming. So is there a way to simply read the default value from XML? As you can see, for now, I created a new variable called sp1 and set it as the default value, but ofcourse I want to get rid of that.

Logcat file:

06-27 16:31:44.782: E/AndroidRuntime(13139): FATAL EXCEPTION: main
06-27 16:31:44.782: E/AndroidRuntime(13139): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.matthewstudios.gw2legendary/com.example.gw2legendary.Bifrost}: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.os.Looper.loop(Looper.java:137)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread.main(ActivityThread.java:5041)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at java.lang.reflect.Method.invokeNative(Native Method)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at java.lang.reflect.Method.invoke(Method.java:511)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at dalvik.system.NativeStart.main(Native Method)
06-27 16:31:44.782: E/AndroidRuntime(13139): Caused by: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:224)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at com.example.gw2legendary.Bifrost.getItemQuantity(Bifrost.java:849)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at com.example.gw2legendary.Bifrost.onCreate(Bifrost.java:152)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.Activity.performCreate(Activity.java:5104)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
06-27 16:31:44.782: E/AndroidRuntime(13139):    ... 11 more
06-27 16:31:49.391: E/fb4a(:<default>):MmsConfig(13225): MmsConfig.loadMmsSettings mms_config.xml missing uaProfUrl setting

Part of the code:

public void submitQuantityButton (View v){
    final Spinner sItems = (Spinner)findViewById(R.id.spinner1);
    final Context context = this;
    final CheckBox cb4 = (CheckBox) findViewById(R.id.checkBox4);
    final CheckBox cb5 = (CheckBox) findViewById(R.id.checkBox5);
    final CheckBox cb6 = (CheckBox) findViewById(R.id.checkBox6);
    final CheckBox cb7 = (CheckBox) findViewById(R.id.checkBox7);
    final CheckBox cb9 = (CheckBox) findViewById(R.id.checkBox9);
    final CheckBox cb10 = (CheckBox) findViewById(R.id.checkBox10);
    final CheckBox cb11 = (CheckBox) findViewById(R.id.checkBox11);
    final CheckBox cb12 = (CheckBox) findViewById(R.id.checkBox12);
    final CheckBox cb13 = (CheckBox) findViewById(R.id.checkBox13);
    final CheckBox cb15 = (CheckBox) findViewById(R.id.checkBox15);
    final CheckBox cb16 = (CheckBox) findViewById(R.id.checkBox16);
    final CheckBox cb17 = (CheckBox) findViewById(R.id.checkBox17);
    final CheckBox cb18 = (CheckBox) findViewById(R.id.checkBox18);
    final CheckBox cb25 = (CheckBox) findViewById(R.id.checkBox25);
    final CheckBox cb27 = (CheckBox) findViewById(R.id.checkBox27);
    final CheckBox cb28 = (CheckBox) findViewById(R.id.checkBox28);
    final CheckBox cb29 = (CheckBox) findViewById(R.id.checkBox29);
    final CheckBox cb30 = (CheckBox) findViewById(R.id.checkBox30);
    final CheckBox cb31 = (CheckBox) findViewById(R.id.checkBox31);
    final CheckBox cb33 = (CheckBox) findViewById(R.id.checkBox33);
    final CheckBox cb34 = (CheckBox) findViewById(R.id.checkBox34);
    final CheckBox cb35 = (CheckBox) findViewById(R.id.checkBox35);
    final CheckBox cb36 = (CheckBox) findViewById(R.id.checkBox36);
    final CheckBox cb37 = (CheckBox) findViewById(R.id.checkBox37);

    //WRONG VALUE ERROR
    final AlertDialog.Builder wrongValueBuilder = new AlertDialog.Builder(context);
    wrongValueBuilder.setTitle("Warning");
    wrongValueBuilder.setMessage("The value you entered is too high!");
    wrongValueBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    //EMPTY TEXT ERROR
    final AlertDialog.Builder emptyETextErrorBuilder = new AlertDialog.Builder(context);
    emptyETextErrorBuilder.setTitle("Warning");
    emptyETextErrorBuilder.setMessage("Please enter a value before pressing this button");
    emptyETextErrorBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

            final int position = sItems.getSelectedItemPosition();
            EditText quantityEditText = (EditText)findViewById(R.id.editText1);

            switch (position){
            case 0:
                AlertDialog.Builder spinnerErrorBuilder = new AlertDialog.Builder(context);
                spinnerErrorBuilder.setTitle("Warning");
                spinnerErrorBuilder.setMessage("Please choose an item from the list above and then enter a certain value");
                spinnerErrorBuilder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

                    @Override
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });
                AlertDialog spinnerError = spinnerErrorBuilder.create();
                spinnerError.show();
                break;
            case 1:
                String item1 = quantityEditText.getText().toString();
                if (item1.matches(""))
                {
                    AlertDialog emptyETextError = emptyETextErrorBuilder.create();
                    emptyETextError.show();
                }
                else
                {
                    if (Integer.parseInt(quantityEditText.getText().toString()) <= 250)
                    {
                        if (Integer.parseInt(quantityEditText.getText().toString()) == 250)
                        {
                            cb4.setText("Elaborate Totem (" + item1 + "/250)");
                            saveItemQuantity("cb4", cb4.getText().toString());
                            cb4.setChecked(true);
                        }
                        else
                        {
                            cb4.setText("Elaborate Totem (" + item1 + "/250)");
                            saveItemQuantity("cb4", cb4.getText().toString());
                            cb4.setChecked(false);
                        }
                    }

Answer 1

The stacktrace, and the 3 following lines, shows where is the problem:

06-27 16:31:44.782: E/AndroidRuntime(13139): Caused by: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
06-27 16:31:44.782: E/AndroidRuntime(13139):    at android.app.SharedPreferencesImpl.getString(SharedPreferencesImpl.java:224)
06-27 16:31:44.782: E/AndroidRuntime(13139):    at com.example.gw2legendary.Bifrost.getItemQuantity(Bifrost.java:849)

So you have a problem in the file Bifrost.java, at line 849, in the getItemQuantity() method. And it corresponds to the call to getString() method. It's really interesting looking at the 3 lines and try to understand how you can get all these informations, because you'll have to do the same each time you have an exception in your code.

What I can suppose is that the value you try to get from the SharedPreferences has been saved as Boolean , and you try to get it as a String , so you have this ClassCastException. Just revise the value you saved in the SharedPreferences with that key.

To have more information, try to learn how to debug your application and use breakpoints to check the values of the variables at a moment of the execution. Breakpoints allow you to stop the execution exactly where you want and look for the state and values of all the variables. Debugging with an IDE like Eclipse or NetBeans is really easy and can help you in a lot of situations.

Answer 2

It should be obvious what the error is from reading the stacktrace:

java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String

And yes you can read default values from an XML file, read about arrays.xml and http://developer.android.com/guide/topics/resources/more-resources.html#TypedArray here