Android，如何在 Parcelable 类中正确使用 readTypedList 方法? [英] Android, How to use readTypedList method correctly in a Parcelable class?
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问题描述
我有两个活动，在第一个活动中，我实例化了对象 myObject 的 ArrayList.在第二个活动中，我需要获取这个 Arraylist.我找到了一个教程:http://prasanta-paul.blogspot.com/2010/06/android-parcelable-example.html我已经实现了我的课程，就像它的解释一样.
I have two Activities, in the first one, I instanciate an ArrayList of Object myObject. In the second activity, i need to get this Arraylist. I've found a tutorial : http://prasanta-paul.blogspot.com/2010/06/android-parcelable-example.html I have implemented my class liked it's explain.
公共类 Chapitre 实现 Parcelable{
public class Chapitre implements Parcelable{
private int numero;
private String titre;
private String description;
private int nbVideo;
private ArrayList<Video> listeVideo;
public Chapitre(int numero, String titre, String description,
ArrayList<Video> listeVideo) {
this.numero = numero;
this.titre = titre;
this.description = description;
this.listeVideo = listeVideo;
this.nbVideo = listeVideo.size();
}
//Getters and Setters ...
private Chapitre(Parcel source) {
numero = source.readInt();
titre = source.readString();
description = source.readString();
nbVideo = source.readInt();
source.readTypedList(listeVideo, Video.CREATOR);
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(numero);
dest.writeString(titre);
dest.writeString(description);
dest.writeInt(nbVideo);
dest.writeTypedList(listeVideo);
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
public Chapitre createFromParcel(Parcel in) {
return new Chapitre(in);
}
public Chapitre[] newArray(int size) {
return new Chapitre[size];
}
};
}
公共类 Video 实现 Parcelable{
public class Video implements Parcelable{
private String titre;
private int numero;
private String url;
private String description;
private String imageUrl;
private Bitmap image;
private String duree;
/**
*
* @param nom
* @param numero
* @param url
* @param description
*/
public Video(String titre, String url, String description) {
super();
this.titre = titre;
this.url = url;
this.description = description;
}
public Video(int numero, String titre, String url, String description) {
super();
this.titre = titre;
this.url = url;
this.description = description;
this.numero = numero;
}
public Video(String titre,int numero, String url, String description, String imageUrl) {
super();
this.titre = titre;
this.url = url;
this.description = description;
this.imageUrl = imageUrl;
this.numero = numero;
setImage(fetchImage(imageUrl));
}
//Getters and Setters ...
@Override
public int describeContents() {
// TODO Auto-generated method stub
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(titre);
dest.writeInt(numero);
dest.writeString(url);
dest.writeString(description);
dest.writeString(imageUrl);
dest.writeString(duree);
}
public Video(Parcel source){
/*
* Reconstruct from the Parcel
*/
Log.v("TAG", "ParcelData(Parcel source): time to put back parcel data");
titre = source.readString();
numero = source.readInt();
url = source.readString();
description = source.readString();
imageUrl = source.readString();
duree = source.readString();
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
public Video createFromParcel(Parcel in) {
return new Video(in);
}
public Video[] newArray(int size) {
return new Video[size];
}
};
}
但是我在source.readTypedList(listeVideo, Video.CREATOR);"这一行得到了 nullPointException在课堂上.
But I get nullPointException on the line "source.readTypedList(listeVideo, Video.CREATOR);" in the class Chapitre.
07-21 10:07:28.212: ERROR/AndroidRuntime(682): FATAL EXCEPTION: main
07-21 10:07:28.212: ERROR/AndroidRuntime(682): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.genicorp.video.proto/com.genicorp.video.proto.Lecture}: java.lang.NullPointerException
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1736)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1752)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread.access$1500(ActivityThread.java:123)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:993)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Handler.dispatchMessage(Handler.java:99)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Looper.loop(Looper.java:126)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread.main(ActivityThread.java:3997)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at java.lang.reflect.Method.invokeNative(Native Method)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at java.lang.reflect.Method.invoke(Method.java:491)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at dalvik.system.NativeStart.main(Native Method)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): Caused by: java.lang.NullPointerException
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readTypedList(Parcel.java:1630)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.genicorp.video.proto.Chapitre.<init>(Chapitre.java:70)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.genicorp.video.proto.Chapitre.<init>(Chapitre.java:65)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.genicorp.video.proto.Chapitre$1.createFromParcel(Chapitre.java:89)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.genicorp.video.proto.Chapitre$1.createFromParcel(Chapitre.java:1)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readParcelable(Parcel.java:1981)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readValue(Parcel.java:1846)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readListInternal(Parcel.java:2092)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readArrayList(Parcel.java:1536)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readValue(Parcel.java:1867)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Parcel.readMapInternal(Parcel.java:2083)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Bundle.unparcel(Bundle.java:215)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.os.Bundle.getParcelableArrayList(Bundle.java:1151)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.content.Intent.getParcelableArrayListExtra(Intent.java:3634)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at com.genicorp.video.proto.Lecture.onCreate(Lecture.java:37)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1700)
07-21 10:07:28.212: ERROR/AndroidRuntime(682): ... 11 more
我已经浪费了 1 天时间，所以如果有人可以帮助我，那就太好了，
I've already waste 1 day on this, so if anyone could help me, it would be great,
提前致谢
推荐答案
希望您现在已经弄清楚了.但对于任何偶然发现这一点的人来说.您得到的 NullPointerException 是由从未初始化的 ArrayList 引起的.
Hopefully, you've figured this out by now. But for anyone else who stumbles upon this one. The NullPointerException you were getting was caused by the ArrayList never being initialized.
这会解决它:
private Chapitre(){
listVideo = new ArrayList<Video>();
}
private Chapitre(Parcel source) {
// Call the above constructor
this();
numero = source.readInt();
titre = source.readString();
description = source.readString();
nbVideo = source.readInt();
source.readTypedList(listeVideo, Video.CREATOR);
}
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