我开发孩子们的数学应用程序。在用户自定义的问题的选项,我要开始另一项活动。我想送一个 QuestionOptions
对象的活动,以便它可以根据选项生成的问题。所以,我创建了一个 QuestionnOptions
类,并实现 Parcelable
作为其他的答案给我看。但是,在我的课枚举。所以我不知道该怎么办,让机器人工作室生成所需要的东西:
包com.smartkidslovemaths;
进口android.os.Parcel;
进口android.os.Parcelable;
公共类QuestionOptions实现Parcelable {
保护QuestionOptions(包裹中){
digitCount = in.readInt();
}
公共静态最终的创造者和LT; QuestionOptions> CREATOR =新的创造者和LT; QuestionOptions> (){
@覆盖
公共QuestionOptions createFromParcel(包裹中){
返回新QuestionOptions(中);
}
@覆盖
公共QuestionOptions [] newArray(INT尺寸){
返回新QuestionOptions【尺寸】;
}
};
公共QuestionOptions(OperationType operationType,INT digitCount,布尔timerEnabled){
this.operationType = operationType;
this.digitCount = digitCount;
this.timerEnabled = timerEnabled;
}
@覆盖
公众诠释describeContents(){
返回0;
}
@覆盖
公共无效writeToParcel(包裹DEST,INT标志){
}
@覆盖
公众诠释哈希code(){
int值;
开关(operationType){
案例增加:
值= 0;
打破;
案例加减:
值= 4;
打破;
案例ADD_AND_SUB:
值= 8;
案例乘法:
值= 12;
打破;
默认:
值= 0;
打破;
}
值+ = digitCount;
如果(timerEnabled)
值+ = 100;
返回值;
}
@覆盖
公共布尔等于(对象o){
返回o.hash code()== this.hash code();
}
公共枚举OperationType {
加成,
减法,
ADD_AND_SUB,
乘法
}
公共布尔isTimerEnabled(){
返回timerEnabled;
}
公共无效setTimerEnabled(布尔timerEnabled){
this.timerEnabled = timerEnabled;
}
公共OperationType getOperationType(){
返回operationType;
}
公共无效setOperationType(OperationType operationType){
this.operationType = operationType;
}
公众诠释getDigitCount(){
返回digitCount;
}
公共无效setDigitCount(INT digitCount){
this.digitCount = digitCount;
}
私人OperationType operationType;
私人诠释digitCount;
私人布尔timerEnabled;
}
现在我送了 QuestionOptions
其他活动:
QuestionOptions选项=新QuestionOptions(
操作,digitCount,
cbTimerEnabled.isChecked());
意图I =新的意图(MainActivity.this,QuestionsActivity.class);
i.putExtra(com.smartkidslovemaths.option选项);
startActivity(ⅰ);
我不知道我是否叫 putExtra
正确的方法,但我继续写code以获得在其他活动的问题选项:
意图I = getIntent();
选项= i.getExtras().getParcelable(com.smartkidslovemaths.options);
的System.out.println(options.getDigitCount());
的System.out.println(options.getOperationType());
的System.out.println(options.isTimerEnabled());
我打印出来,只是因为我想看看它是否有正确的东西的选项。但是,当我运行code,A NullPointerException异常
发生。现在我真的不知道为什么会这样。我试图改变第二行
选项= i.getExtras().getParcelable(「购股权」);
但结果还是一样。我想我必须做一些错误的 QuestionOptions
类,可能是因为我没有写信给包裹,但有一个枚举!没有一个叫方法 writeEnum()
!所以,你能告诉我,我做错了什么,以及如何解决它?如果我没有别的东西错了,请告诉我为好。
编辑:
下面是我的logcat:
08-24 16:14:20.841 530-750 /? E / Diag_Lib:[IMS_FATAL] | 251 | 750 | qvp_rtp_handle_signals IRET:0
08-24 16:14:20.841 530-750 /? E / Diag_Lib:[IMS_FATAL] | 238 | 750 | qvp_rtp_handle_signals qpDplMainLoop:调用imsSignalHandler
08-24 16:14:20.841 530-750 /? E / Diag_Lib:[IMS_FATAL] | 155 | 750 | qpdpl:imsSignalHandler:全球数据NULL或事件列表大小为0
08-24 16:14:20.841 530-750 /? E / Diag_Lib:[IMS_FATAL] | 243 | 750 | qvp_rtp_handle_signals加FD阅读:9
08-24 16:14:22.823 389-389 /? E /包裹:在这里读不支持空字符串。
08-24 16:14:22.823 389-389 /? E /包裹:在这里读不支持空字符串。
08-24 16:14:25.836 530-750 /? E / Diag_Lib:[IMS_FATAL] | 251 | 750 | qvp_rtp_handle_signals IRET:0
08-24 16:14:25.836 530-750 /? E / Diag_Lib:[IMS_FATAL] | 238 | 750 | qvp_rtp_handle_signals qpDplMainLoop:调用imsSignalHandler
08-24 16:14:25.836 530-750 /? E / Diag_Lib:[IMS_FATAL] | 155 | 750 | qpdpl:imsSignalHandler:全球数据NULL或事件列表大小为0
08-24 16:14:25.836 530-750 /? E / Diag_Lib:[IMS_FATAL] | 243 | 750 | qvp_rtp_handle_signals加FD阅读:9
08-24 16:14:29.730 7104-7104 /? E / AndroidRuntime:致命异常:主要
java.lang.RuntimeException的:无法启动的活动ComponentInfo {com.smartkidslovemaths / com.smartkidslovemaths.QuestionsActivity}:显示java.lang.NullPointerException
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2266)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
在android.app.ActivityThread.access $ 600(ActivityThread.java:150)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1298)
在android.os.Handler.dispatchMessage(Handler.java:99)
在android.os.Looper.loop(Looper.java:213)
在android.app.ActivityThread.main(ActivityThread.java:5225)
在java.lang.reflect.Method.invokeNative(本机方法)
在java.lang.reflect.Method.invoke(Method.java:525)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:741)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
在dalvik.system.NativeStart.main(本机方法)
显示java.lang.NullPointerException:产生的原因
在com.smartkidslovemaths.QuestionsActivity.onCreate(QuestionsActivity.java:16)
在android.app.Activity.performCreate(Activity.java:5133)
在android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2230)
在android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
在android.app.ActivityThread.access $ 600(ActivityThread.java:150)
在android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1298)
在android.os.Handler.dispatchMessage(Handler.java:99)
在android.os.Looper.loop(Looper.java:213)
在android.app.ActivityThread.main(ActivityThread.java:5225)
在java.lang.reflect.Method.invokeNative(本机方法)
在java.lang.reflect.Method.invoke(Method.java:525)
在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:741)
在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
在dalvik.system.NativeStart.main(本机方法)
08-24 16:14:30.842 530-750 /? E / Diag_Lib:[IMS_FATAL] | 251 | 750 | qvp_rtp_handle_signals IRET:0
08-24 16:14:30.842 530-750 /? E / Diag_Lib:[IMS_FATAL] | 238 | 750 | qvp_rtp_handle_signals qpDplMainLoop:调用imsSignalHandler
08-24 16:14:30.842 530-750 /? E / Diag_Lib:[IMS_FATAL] | 155 | 750 | qpdpl:imsSignalHandler:全球数据NULL或事件列表大小为0
08-24 16:14:30.842 530-750 /? E / Diag_Lib:[IMS_FATAL] | 243 | 750 | qvp_rtp_handle_signals加FD阅读:9
发生
例外执行行时:
的System.out.println(options.getDigitCount());
解决方案
我试过你的code,似乎问题出在parcelable对象。 请更新以下内容,将工作:
这是接受一个包裹对象的构造函数。
保护QuestionOptions(包裹中){
this.operationType = OperationType.valueOf(in.readString());
this.digitCount = in.readInt();
this.timerEnabled = in.readByte()!= 0;
}
和writeToParcel方法。
@覆盖
公共无效writeToParcel(包裹DEST,INT标志){
dest.writeString(this.operationType.name());
dest.writeInt(this.digitCount);
dest.writeByte((字节)(this.timerEnabled?1:0));
}
您可以从意向对象通过以下方式:
最后QuestionOptions选项= getIntent()getParcelableExtra(com.smartkidslovemaths.option)。
I am developing a math app for kids. After the user customizes the question options, I want to start another activity. I want to send a QuestionOptions
object to the activity so that it can generate questions according to the options. So I created a QuestionnOptions
class and implement Parcelable
as the other answers showed me. However, there is an enum in my class. So I don't know what to do and let Android Studio generate the stuff needed:
package com.smartkidslovemaths;
import android.os.Parcel;
import android.os.Parcelable;
public class QuestionOptions implements Parcelable{
protected QuestionOptions(Parcel in) {
digitCount = in.readInt ();
}
public static final Creator<QuestionOptions> CREATOR = new Creator<QuestionOptions> () {
@Override
public QuestionOptions createFromParcel(Parcel in) {
return new QuestionOptions (in);
}
@Override
public QuestionOptions[] newArray(int size) {
return new QuestionOptions[size];
}
};
public QuestionOptions (OperationType operationType, int digitCount, boolean timerEnabled) {
this.operationType = operationType;
this.digitCount = digitCount;
this.timerEnabled = timerEnabled;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
}
@Override
public int hashCode () {
int value;
switch (operationType) {
case ADDITION:
value = 0;
break;
case SUBTRACTION:
value = 4;
break;
case ADD_AND_SUB:
value = 8;
case MULTIPLICATION:
value = 12;
break;
default:
value = 0;
break;
}
value += digitCount;
if (timerEnabled)
value += 100;
return value;
}
@Override
public boolean equals(Object o) {
return o.hashCode() == this.hashCode();
}
public enum OperationType {
ADDITION,
SUBTRACTION,
ADD_AND_SUB,
MULTIPLICATION
}
public boolean isTimerEnabled() {
return timerEnabled;
}
public void setTimerEnabled(boolean timerEnabled) {
this.timerEnabled = timerEnabled;
}
public OperationType getOperationType() {
return operationType;
}
public void setOperationType(OperationType operationType) {
this.operationType = operationType;
}
public int getDigitCount() {
return digitCount;
}
public void setDigitCount(int digitCount) {
this.digitCount = digitCount;
}
private OperationType operationType;
private int digitCount;
private boolean timerEnabled;
}
Now I send the QuestionOptions
to the other activity:
QuestionOptions options = new QuestionOptions (
operation, digitCount,
cbTimerEnabled.isChecked ());
Intent i = new Intent (MainActivity.this, QuestionsActivity.class);
i.putExtra ("com.smartkidslovemaths.option", options);
startActivity (i);
I don't know whether I called the putExtra
method correctly, but I continued to write code to get the question options in the other activity:
Intent i = getIntent ();
options = i.getExtras ().getParcelable ("com.smartkidslovemaths.options");
System.out.println (options.getDigitCount ());
System.out.println (options.getOperationType ());
System.out.println (options.isTimerEnabled ());
I printed out the options just because I want to see whether it has the correct stuff. But when I run the code, a NullPointerException
occurred. Now I really don't know why this is happening. I tried changing the second line to
options = i.getExtras ().getParcelable ("options");
but the result is still the same. I think I must be doing something wrong in the QuestionOptions
class, possibly because I didn't write to parcel but there's an enum! There isn't a method called writeEnum()
! So can you tell me what I did wrong and how to fix it? And if I did something else wrong please tell me as well.
EDIT:
Here is my logcat:
08-24 16:14:20.841 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 251 | 750 |qvp_rtp_handle_signals iRet : 0
08-24 16:14:20.841 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 238 | 750 |qvp_rtp_handle_signals qpDplMainLoop: Calling imsSignalHandler
08-24 16:14:20.841 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 155 | 750 |qpdpl:imsSignalHandler: GLobal data NULL or Event list size is 0
08-24 16:14:20.841 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 243 | 750 |qvp_rtp_handle_signals add read fd : 9
08-24 16:14:22.823 389-389/? E/Parcel﹕ Reading a NULL string not supported here.
08-24 16:14:22.823 389-389/? E/Parcel﹕ Reading a NULL string not supported here.
08-24 16:14:25.836 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 251 | 750 |qvp_rtp_handle_signals iRet : 0
08-24 16:14:25.836 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 238 | 750 |qvp_rtp_handle_signals qpDplMainLoop: Calling imsSignalHandler
08-24 16:14:25.836 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 155 | 750 |qpdpl:imsSignalHandler: GLobal data NULL or Event list size is 0
08-24 16:14:25.836 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 243 | 750 |qvp_rtp_handle_signals add read fd : 9
08-24 16:14:29.730 7104-7104/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.smartkidslovemaths/com.smartkidslovemaths.QuestionsActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2266)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
at android.app.ActivityThread.access$600(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:213)
at android.app.ActivityThread.main(ActivityThread.java:5225)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.smartkidslovemaths.QuestionsActivity.onCreate(QuestionsActivity.java:16)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2316)
at android.app.ActivityThread.access$600(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:213)
at android.app.ActivityThread.main(ActivityThread.java:5225)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:741)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
at dalvik.system.NativeStart.main(Native Method)
08-24 16:14:30.842 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 251 | 750 |qvp_rtp_handle_signals iRet : 0
08-24 16:14:30.842 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 238 | 750 |qvp_rtp_handle_signals qpDplMainLoop: Calling imsSignalHandler
08-24 16:14:30.842 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 155 | 750 |qpdpl:imsSignalHandler: GLobal data NULL or Event list size is 0
08-24 16:14:30.842 530-750/? E/Diag_Lib﹕ [IMS_FATAL]| 243 | 750 |qvp_rtp_handle_signals add read fd : 9
The exception occurred when executing the line:
System.out.println (options.getDigitCount ());
解决方案
I've tried your code and it seems the problem is with the parcelable object. Please update the following and it will work:
The constructor that accepts a Parcel object.
protected QuestionOptions(Parcel in) {
this.operationType = OperationType.valueOf(in.readString());
this.digitCount = in.readInt();
this.timerEnabled = in.readByte() != 0;
}
and the writeToParcel method.
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(this.operationType.name());
dest.writeInt(this.digitCount);
dest.writeByte((byte) (this.timerEnabled ? 1 : 0));
}
You can get the object from the intent in the following way:
final QuestionOptions options = getIntent().getParcelableExtra("com.smartkidslovemaths.option");