Android应用程序：当我尝试获取Parcelable时出现运行时错误，该Parcelable作为额外传递

Question

我有一个onItemClickListener，它启动一个Intent并将一个Parcelable对象作为额外的。

这是onItemClickListener代码：

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
//This is the value of the clicked Item
String clickedProjectName = (String) parent.getItemAtPosition(position);

//Create intent to start ProjectdetailActivity
Intent projectdetailIntent = new Intent(getActivity(),ProjectdetailActivity.class);

//get the Parcelable object
ProjectParcelable projectParcelable =  mProjectParcelableMap.get(clickedProjectName);

//put the Parcelable object as extra
projectdetailIntent.putExtra("ProjectParcelable", (ProjectParcelable)  projectParcelable);

//start activity
startActivity(projectdetailIntent);

Membervariable mProjectParcelableMap是ProjectParcelables的HashMap，其中Projectname（保存在clickedProjectName中）是Key。

这是目标Intent的onCreate方法中的代码：

//get received Intent
Intent receivedIntent = getActivity().getIntent();

//get ProjectParcelable from received Intent
ProjectParcelable projectParcelable = (ProjectParcelable)receivedIntent.getParcelableExtra("ProjectParcelable");
</pre>

最后一个命令不起作用。应用程序关闭并抛出以下错误：

11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime: FATAL EXCEPTION: main
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime: Process: com.example.application, PID: 19192
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.application/com.example.application.ProjectdetailActivity}: android.view.InflateException: Binary XML file line #2: Error inflating class fragment
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.access$800(ActivityThread.java:156)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:211)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5373)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:372)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:  Caused by: android.view.InflateException: Binary XML file line #2: Error inflating class fragment
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.view.LayoutInflater.inflate(LayoutInflater.java:482)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:257)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectdetailActivity.onCreate(ProjectdetailActivity.java:16)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5990)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2332)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.access$800(ActivityThread.java:156) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:211) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5373) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:372) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1020) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815) 
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:  Caused by: java.lang.NullPointerException: Attempt to get length of null array
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readStringArray(Parcel.java:1031)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.PersonParcelable.<init>(PersonParcelable.java:54)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.PersonParcelable.<init>(PersonParcelable.java:9)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.PersonParcelable$1.createFromParcel(PersonParcelable.java:96)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.PersonParcelable$1.createFromParcel(PersonParcelable.java:90)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readParcelable(Parcel.java:2283)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readParcelableArray(Parcel.java:2369)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectParcelable.<init>(ProjectParcelable.java:30)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectParcelable.<init>(ProjectParcelable.java:9)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectParcelable$1.createFromParcel(ProjectParcelable.java:71)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectParcelable$1.createFromParcel(ProjectParcelable.java:63)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readParcelable(Parcel.java:2283)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readValue(Parcel.java:2183)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Parcel.readArrayMapInternal(Parcel.java:2516)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.BaseBundle.unparcel(BaseBundle.java:221)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.os.Bundle.getParcelable(Bundle.java:755)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.content.Intent.getParcelableExtra(Intent.java:5089)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at com.example.application.ProjectdetailFragment.onCreateView(ProjectdetailFragment.java:40)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1965)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1047)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1237)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1339)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2295)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentController.onCreateView(FragmentController.java:111)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:314)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:31)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
11-12 17:51:58.840 19192-19192/com.example.application E/AndroidRuntime:    ...

这是ProjectParcelable的代码：

public class ProjectParcelable implements Parcelable {
   private String name;
   private PersonParcelable[] personParcelables;

   @Override
   public void writeToParcel(Parcel dest, int flags) {
       dest.writeString(name);
       dest.writeParcelableArray(personParcelables, flags);
   }

   private ProjectParcelable(Parcel in) {
       this.name = in.readString();
       in.readParcelableArray(PersonParcelable.class.getClassLoader());
   }

   public ProjectParcelable(String newName, PersonParcelable[] newPersonParcelables) {
       this.name = newName;
       this.personParcelables = newPersonParcelables;
   }

   //Getter
   public String getName() {
       return this.name;
   }

   public String[] getAllPersonNames() {
       String[] result = new String[personParcelables.length];
       for (int i = 0; i < personParcelables.length; i++) {
           result[i] = personParcelables[i].getName();
       }
       return result;
   }

   @Override
   public int describeContents() {
       return 0;
   }

   public static final Parcelable.Creator<ProjectParcelable> CREATOR = new Parcelable.Creator<ProjectParcelable>() {

       @Override
       public ProjectParcelable createFromParcel(Parcel source) {
           return new ProjectParcelable(source);
       }

       //We just need to copy this and change the type to match our class.

       @Override
       public ProjectParcelable[] newArray(int size) {
           return new ProjectParcelable[size];
       }
   };
}

这是personParcelable：

public class PersonParcelable implements Parcelable {
   private String role;
   private String name;
   private String job;
   private String company;
   private String birthday;
   private String street;
   private String city;
   private String country;
   private String[] phones;
   private String[] mails;
   private String[] links;

   @Override
   public void writeToParcel(Parcel dest, int flags) {
       dest.writeString(role);
       dest.writeString(name);
       dest.writeString(job);
       dest.writeString(company);
       dest.writeString(birthday);
       dest.writeString(street);
       dest.writeString(city);
       dest.writeString(country);
       dest.writeStringArray(phones);
       dest.writeStringArray(mails);
       dest.writeStringArray(links);
   }

   private PersonParcelable(Parcel in) {
       this.role = in.readString();
       this.name = in.readString();
       this.job = in.readString();
       this.company = in.readString();
       this.birthday = in.readString();
       this.street = in.readString();
       this.city = in.readString();
       this.country = in.readString();
       in.readStringArray(phones);
       in.readStringArray(mails);
       in.readStringArray(links);
   }

   public PersonParcelable(String newRole, String newName, String newJob, String newCompany, String newBirthday, String newStreet, String newCity, String newCountry, String[] newPhones, String[] newMails, String[] newLinks) {
       this.role = newRole;
       this.name = newName;
       this.job = newJob;
       this.company = newCompany;
       this.birthday = newBirthday;
       this.street = newStreet;
       this.city = newCity;
       this.country = newCountry;
       this.phones = newPhones;
       this.mails = newMails;
       this.links = newLinks;
   }

   //Getter
   public String getName() {
       return this.name;
   }


   @Override
   public int describeContents() {
       return 0;
   }

   public static final Parcelable.Creator<PersonParcelable> CREATOR = new Parcelable.Creator<PersonParcelable>() {

       @Override
       public PersonParcelable createFromParcel(Parcel source) {
           return new PersonParcelable(source);
       }


       @Override
       public PersonParcelable[] newArray(int size) {
           return new PersonParcelable[size];
       }
   };
}    

Answer 1

所以，有两件事：

这里发生了崩溃：

private PersonParcelable(Parcel in) {
    ...
    in.readStringArray(phones);
    in.readStringArray(mails);
    in.readStringArray(links);
}

不使用readStringArray，而是使用createStringArray()并分配结果，如下所示：

private PersonParcelable(Parcel in) {
    ...
    this.phones = in.createStringArray();
    this.mails = in.createStringArray();
    this.links = in.createStringArray();
}

使用readStringArray()要求您事先知道数组的大小，并预先分配数组，这很少是您真正想要的。

对于第二个问题，使用readParcelableArray()是因类型擦除而导致的痛苦。我们有一个自定义实用程序方法，可以执行一些可怕的通用数组分配和警告抑制 - 我建议使用List代替：

private List<PersonParcelable> personParcelables;

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeString(name);
    dest.writeList(personParcelables);
}

private ProjectParcelable(Parcel in) {
    this.name = in.readString();
    this.personParcelables = in.readArrayList(PersonParcelable.class.getClassLoader());
}