我的应用中有很多复选框，一个微调器，一个edittext和一个按钮。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，我有两个问题。
第一个问题是，当我尝试使用共享偏好时，应用程序崩溃（一旦我启动包含这些共享偏好的活动）。
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();
}
保存共享偏好：
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
获取共享偏好：
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，并且为每一个复选框设置默认值会非常耗时。那么有没有办法简单地从XML中读取默认值？正如你所看到的，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。
Logcat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);
}
}
答案 0 :(得分：4)
堆栈跟踪和以下3行显示问题所在：
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)
所以你在getItemQuantity()方法的第849行文件Bifrost.java中遇到了问题。它对应于getString()方法的调用。查看3行并尝试了解如何获取所有这些信息非常有趣，因为每次在代码中出现异常时都必须这样做。
我可以假设您尝试从SharedPreferences获得的值已保存为Boolean，并且您尝试将其设为String，因此您拥有此值ClassCastException异常。只需使用该密钥修改您在SharedPreferences中保存的值。
要获得更多信息，请尝试学习如何调试应用程序并使用断点在执行时检查变量的值。断点允许您在所需的位置停止执行，并查找所有变量的状态和值。使用像Eclipse或NetBeans这样的IDE进行调试非常简单，可以在很多情况下为您提供帮助。
答案 1 :(得分：0)
显然，读取堆栈跟踪的错误是什么：
java.lang.ClassCastException：java.lang.Boolean无法强制转换为java.lang.String
是的，你可以从XML文件读取默认值，在这里阅读arrays.xml和http://developer.android.com/guide/topics/resources/more-resources.html#TypedArray