我对Android很新，所以请温柔地对待我。我有一个扩展Object的自定义类。它被称为Word，并且通过应用程序的过程，某些单词被添加到ArrayList中。在活动结束时，此ArrayList通过Intent传递给另一个活动。在测试它时，我只是设置了两个单词，我知道它们都是在传递给新活动之前都在ArrayList中。当我进入第二个活动时，如果我只想获得第一个单词（即[get（0）]），我访问ArrayList没有问题。问题是，当我也尝试获取（1）时，它会抛出异常：＆＃34; java.lang.RuntimeException：无法启动活动ComponentInfo {chase_crawford_69001.ltoj / chase_crawford_69001.ltoj.Finished}：java.lang。 ClassCastException：java.lang.String无法强制转换为chase_crawford_69001.ltoj.Word＆＃34;
这就是我所拥有的：
public class Word extends Object implements Parcelable{
private String vocabWord;
private String definition;
private Boolean flagged = Boolean.FALSE;
public Word (String vocabWord, String definition) {
this.vocabWord = vocabWord;
this.definition = definition;}
public Word (String vocabWord){ //Used to make ten Language words so that all TextViews are full,
// but this will never be the correct answer.
this.vocabWord = vocabWord;}
public String getVocabWord(){return vocabWord;}
public String getDefinition(){return definition;}
public Boolean getFlagged(){return flagged;}
public void setVocabWord(String vocabWord) {this.vocabWord = vocabWord;}
public void setDefinition(String definition) {this.definition = definition;}
public void setFlag(Boolean used){this.flagged = used;}
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel out, int flags) {
out.writeString(vocabWord);
out.writeString(definition);
out.writeValue(flagged);
// out.writeByte((byte) (flagged ? 1:0));//1 == TRUE, 0== FALSE
}
public static final Parcelable.Creator<Word> CREATOR
= new Parcelable.Creator<Word>() {
public Word createFromParcel(Parcel in) {
return new Word(in);
}
public Word[] newArray(int size) {
return new Word[size];
}
};
private Word(Parcel in) {
vocabWord = in.readString();
definition = in.readString();
flagged = in.readByte()!=0;//If not 0, flagged is true.
}
} 来自第一项活动：
ArrayList<Word> missedWords = new ArrayList<>(); //this was instantiated at the beginning of the activity
else {
view.setText("Try Again!");
view.setBackgroundColor(getResources().getColor(R.color.red));
if (!missedWords.contains(correctWord)) {
missedWords.add(correctWord);}
public void FinalMessage(View view) {
Intent toFinished = new Intent(this, Finished.class);
missedWordsBundle.putParcelableArrayList("missedWords", missedWords);
toFinished.putExtra("missedWordsList", missedWordsBundle);
startActivity(toFinished);
}
第二项活动：
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_finished);
Intent words = getIntent();
Bundle missedWordsBundle;
ArrayList<Word> missedWords = new ArrayList();
//missedWords = getIntent().getParcelableArrayListExtra("missedWords");
missedWordsBundle = this.getIntent().getBundleExtra("missedWordsList");
missedWords = missedWordsBundle.getParcelableArrayList("missedWords");
MissedWords(missedWords);
}
public void MissedWords(ArrayList missedWords) {
wordOne = (Word) missedWords.get(0);
wordTwo = (Word) missedWords.get(1);
String sWordOne = wordOne.getVocabWord();
String sWordTwo = wordTwo.getVocabWord();
TextView finished = (TextView) findViewById(R.id.finished);
TextView finishedOne = (TextView) findViewById(R.id.finished1);
String wrongList = sWordOne;// + " " +
String wrongList1 = sWordTwo;
finished.setText(wrongList);
finishedOne.setText(wrongList1);}
请您帮我弄清楚为什么我无法从ArrayList获取第二项？我已经在这几个星期里一直在努力，我准备把头发拉出来。我确信这是我想念的简单事。谢谢!!!
以下是完整的错误跟踪：
10-12 04:24:48.789 353-353/chase_crawford_69001.ltoj E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{chase_crawford_69001.ltoj/chase_crawford_69001.ltoj.Finished}: java.lang.ClassCastException: java.lang.String cannot be cast to chase_crawford_69001.ltoj.Word
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2080)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2105)
at android.app.ActivityThread.access$600(ActivityThread.java:133)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1211)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4795)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.ClassCastException: java.lang.String cannot be cast to chase_crawford_69001.ltoj.Word
at chase_crawford_69001.ltoj.Finished.missedWords(Finished.java:30)
at chase_crawford_69001.ltoj.Finished.onCreate(Finished.java:25)
at android.app.Activity.performCreate(Activity.java:5008)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2044)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2105)
at android.app.ActivityThread.access$600(ActivityThread.java:133)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1211)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4795)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
at dalvik.system.NativeStart.main(Native Method)
Line 30 is: wordTwo = missedWords.get(1);
Line 25 is: missedWords(missedWords);
答案 0 :(得分：0)
首先，如果您创建自己的对象模型，则不需要扩展Object。所以就像这样
public class Word {
private String vocabWord;
private String definition;
private Boolean flagged = Boolean.FALSE;
public Word(String vocabWord, String definition) {
this.vocabWord = vocabWord;
this.definition = definition;
}
public Word(String vocabWord) { //Used to make ten Language words so that all TextViews are full,
// but this will never be the correct answer.
this.vocabWord = vocabWord;
}
public String getVocabWord() {
return vocabWord;
}
public String getDefinition() {
return definition;
}
public Boolean getFlagged() {
return flagged;
}
public void setVocabWord(String vocabWord) {
this.vocabWord = vocabWord;
}
public void setDefinition(String definition) {
this.definition = definition;
}
public void setFlag(Boolean used) {
this.flagged = used;
}
然后你可以将你的ArrayList转换为像这样的Gson类的String
String stringList = new Gson().toJson(yourList);
然后将Extras添加到Intent
intent.putExtra(EXTRA_KEY, stringList);
在第二个活动中，您可以获取stringList并将其转换为ArrayList
ArrayList<Word> list = new Gson().fromJson(br, new TypeToken<ArrayList<Word>>(){}.getType());
请注意，这是不好的做法，对性能不利，但只是简单的短代码
答案 1 :(得分：0)
首先，正如Hank Moody刚才所说，你不需要从Object扩展。也许你的错误可能出现在MissedWords方法中（你应该将它重命名为missWords以便遵循Java代码风格），因为你没有定义arraylist的类型而你需要进行转换。如果你重构这样的方法，你就不再需要施法了：
public void missedWords(ArrayList<Word> missedWords) {
Word wordOne = missedWords.get(0);
Word wordTwo = missedWords.get(1);
此外，你需要知道missWords中是否有第二个单词（你不能拥有，甚至不能拥有它们）。如果我们不知道你想要做什么，那就很难说了。
答案 2 :(得分：0)
Parcel in和Parcel out方法的类型不匹配。 包裹在：
flagged = in.readByte()!=0;
虽然包裹出来了：
out.writeValue(flagged);
他们需要同时调用相同类型的方法（值或字节） 最后，有效的代码是：
out.writeByte((byte) (flagged ? 1:0));//1 == TRUE, 0== FALSE
flagged = in.readByte()!=0;//If not 0, flagged is true.
感谢大家的帮助。