android SharedReferences空键、值和集<>；-角落案例

一直在广泛测试

SharedReferences

框架。虽然大多数都能如期工作，但我遇到过一些案例，我想知道它们背后的原因是什么。我给出了一些测试，所有测试都通过-它们的常见设置是：

Context ctx;
SharedPreferences prefs;
Editor ed;
protected void setUp() throws Exception {
    super.setUp();
    ctx = getContext();
    prefs = PreferenceManager.getDefaultSharedPreferences(ctx);
    ed = prefs.edit();
}
protected void tearDown() throws Exception {
    if (ed != null) ed.clear().commit();
    super.tearDown();
}

现在奇怪的是：

当我把一个空值放进去时，我必须用一个空的默认值要求它把它取回来——如果默认值是非空的，我就把这个默认值取回来。即使默认值与我输入的类型不同。适用于

字符串

和

集

（但我可以返回一个布尔值，例如）：

我可以很容易地将

集合

放在prefs内：

@SuppressWarnings("unchecked")
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public void testNullStringSetsRaw() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        @SuppressWarnings("rawtypes")
        final Set integerHashSet = new HashSet();
        integerHashSet.add(1);
        ed.putStringSet("set_key", integerHashSet);
        ed.commit();
        final Set<String> defValues = new HashSet<String>();
        defValues.add("a string");
        Set<String> s = prefs.getStringSet("set_key", defValues);
        final String msg = "The set I put in: " + integerHashSet
            + " and what I got out :" + s;
        Log.e(TAG, msg); // the same - [1]
        assertTrue(msg, integerHashSet.equals(s));
        assertTrue(s.contains(1)); // !
    }
}

但是我在我的日志中看到了如下内容：

org.xmlpull.v1.XmlPullParserException:Map value without name属性：boolean

-请参阅以获取讨论。我想知道这是否与

null

键有关编辑：它是相关的-复制器：

public class XmlExceptionTest extends AndroidTestCase {

    /** Run it twice - on the second run the exception is thrown */
    public void testXmlException() {
        Context ctx = getContext();
        SharedPreferences prefs = PreferenceManager
            .getDefaultSharedPreferences(ctx);//exception thrown here(line 18)
        // and apparently it clears the prefs as the condition below is false
        if (prefs.contains("run_once")) { // false
            Log.w("XmlExceptionTest",
                "contains null key :" + prefs.contains(null));
        }
        Editor e = prefs.edit();
        e.putBoolean("run_once", true).commit();
        e.putString(null, "I put a sting with null key").commit();
        assertTrue("Contains null", prefs.contains(null));
        PreferenceManager.getDefaultSharedPreferences(ctx); // exception
        // NOT thrown here  - why ? - apparently there is a static factory
        // returning the instance it already constructed
        // e.clear().commit(); // this eliminates the exception
    }
}

例外情况：

W/ApplicationContext(): getSharedPreferences
W/ApplicationContext(): org.xmlpull.v1.XmlPullParserException: Map value without name attribute: string
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readThisMapXml(XmlUtils.java:521)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readThisValueXml(XmlUtils.java:733)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readValueXml(XmlUtils.java:667)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readMapXml(XmlUtils.java:470)
W/ApplicationContext():     at android.app.ContextImpl.getSharedPreferences(ContextImpl.java:361)
W/ApplicationContext():     at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:348)
W/ApplicationContext():     at gr.uoa.di.android.helpers.test.XmlExceptionTest.testXmlException(XmlExceptionTest.java:18)
W/ApplicationContext():     at java.lang.reflect.Method.invokeNative(Native Method)
W/ApplicationContext():     at java.lang.reflect.Method.invoke(Method.java:521)
W/ApplicationContext():     at junit.framework.TestCase.runTest(TestCase.java:154)
W/ApplicationContext():     at junit.framework.TestCase.runBare(TestCase.java:127)
W/ApplicationContext():     at junit.framework.TestResult$1.protect(TestResult.java:106)
W/ApplicationContext():     at junit.framework.TestResult.runProtected(TestResult.java:124)
W/ApplicationContext():     at junit.framework.TestResult.run(TestResult.java:109)
W/ApplicationContext():     at junit.framework.TestCase.run(TestCase.java:118)
W/ApplicationContext():     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169)
W/ApplicationContext():     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154)
W/ApplicationContext():     at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:520)
W/ApplicationContext():     at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1447)

显然，当抛出异常时，首选项被清除（坏）

所以我的问题是：我所说的行为真的是这样吗（或者我错过了一些愚蠢的事情）？背后的动机是什么（尤其是空值行为）？是否有文件记录并保证保持不变？或者可能发生变化？第二点是疏忽吗

它是

是我不懂泛型：

在这里发布了一个问题：（在谷歌群组中以通常的noop结果开始了一次搜索之后）。事实上，截至2014年1月7日，该版本标记为未来版本：）

public class XmlExceptionTest extends AndroidTestCase {

    /** Run it twice - on the second run the exception is thrown */
    public void testXmlException() {
        Context ctx = getContext();
        SharedPreferences prefs = PreferenceManager
            .getDefaultSharedPreferences(ctx);//exception thrown here(line 18)
        // and apparently it clears the prefs as the condition below is false
        if (prefs.contains("run_once")) { // false
            Log.w("XmlExceptionTest",
                "contains null key :" + prefs.contains(null));
        }
        Editor e = prefs.edit();
        e.putBoolean("run_once", true).commit();
        e.putString(null, "I put a sting with null key").commit();
        assertTrue("Contains null", prefs.contains(null));
        PreferenceManager.getDefaultSharedPreferences(ctx); // exception
        // NOT thrown here  - why ? - apparently there is a static factory
        // returning the instance it already constructed
        // e.clear().commit(); // this eliminates the exception
    }
}

W/ApplicationContext(): getSharedPreferences
W/ApplicationContext(): org.xmlpull.v1.XmlPullParserException: Map value without name attribute: string
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readThisMapXml(XmlUtils.java:521)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readThisValueXml(XmlUtils.java:733)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readValueXml(XmlUtils.java:667)
W/ApplicationContext():     at com.android.internal.util.XmlUtils.readMapXml(XmlUtils.java:470)
W/ApplicationContext():     at android.app.ContextImpl.getSharedPreferences(ContextImpl.java:361)
W/ApplicationContext():     at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:348)
W/ApplicationContext():     at gr.uoa.di.android.helpers.test.XmlExceptionTest.testXmlException(XmlExceptionTest.java:18)
W/ApplicationContext():     at java.lang.reflect.Method.invokeNative(Native Method)
W/ApplicationContext():     at java.lang.reflect.Method.invoke(Method.java:521)
W/ApplicationContext():     at junit.framework.TestCase.runTest(TestCase.java:154)
W/ApplicationContext():     at junit.framework.TestCase.runBare(TestCase.java:127)
W/ApplicationContext():     at junit.framework.TestResult$1.protect(TestResult.java:106)
W/ApplicationContext():     at junit.framework.TestResult.runProtected(TestResult.java:124)
W/ApplicationContext():     at junit.framework.TestResult.run(TestResult.java:109)
W/ApplicationContext():     at junit.framework.TestCase.run(TestCase.java:118)
W/ApplicationContext():     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169)
W/ApplicationContext():     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154)
W/ApplicationContext():     at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:520)
W/ApplicationContext():     at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1447)