java - 共享首选项不起作用，默认值

标签 java android eclipse sharedpreferences

我的应用程序中有很多复选框、微调器、编辑文本和按钮。当我从微调器中选择一个项目然后输入某个值并点击一个按钮时，某个复选框文本会发生变化。现在我添加了共享首选项，但遇到了两个问题。

第一个问题是，当我尝试使用共享首选项时，应用程序崩溃(只要我启动包含这些共享首选项的 Activity )。

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();
}

保存共享首选项:

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

获取共享首选项:

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

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

第二个问题是我有很多复选框，为每个复选框设置默认值会非常耗时。那么有没有一种方法可以简单地从 XML 中读取默认值呢？如您所见，现在，我创建了一个名为 sp1 的新变量并将其设置为默认值，但当然我想摆脱它。

日志文件:

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

部分代码:

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);
                        }
                    }

最佳答案

堆栈跟踪和以下 3 行显示了问题出在哪里:

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)

所以您在文件 Bifrost.java 的第 849 行的 getItemQuantity() 方法中遇到了问题。并且对应于getString()方法的调用。查看这 3 行代码并尝试了解如何获取所有这些信息真的很有趣，因为每次代码中出现异常时，您都必须执行相同的操作。

我可以假设的是，您尝试从 SharedPreferences 获取的值已保存为 Boolean，并且您尝试将其作为 String ，所以你有这个 ClassCastException。只需使用该键修改您在 SharedPreferences 中保存的值。

要获得更多信息，请尝试了解如何调试您的应用程序并使用断点在执行时检查变量的值。断点允许您准确地在您想要的位置停止执行并查找所有变量的状态和值。使用 Eclipse 或 NetBeans 等 IDE 进行调试非常简单，并且可以在很多情况下为您提供帮助。

关于java - 共享首选项不起作用，默认值，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/17343269/

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