【Harmony OS】【JAVA UI】鸿蒙系统中怎么使用Parcel进行存储数据或数据传递

 Parcel简介

在IPC过程中，发送方可以使用Parcel提供的写方法，将待发送的数据以特定格式写入Parcel对象。接收方可以使用Parcel提供的读取方法从Parcel对象中读取特定格式的数据。

Parcel实例的默认容量为200KB。如果您想要更多或更少，请使用setCapacity(int)更改它。

注意：只有以下数据类型的数据才能写入或从包裹中读取： byte, byteArray, short, shortArray, int, intArray, long, longArray, float, floatArray, double, doubleArray, boolean, booleanArray, char, charArray, String, StringArray、 PlainBooleanArray, Serializable, Sequenceable, 和 SequenceableArray。

方法介绍

2.1 addAppClassLoader(ClassLoader newClassLoader)public void addAppClassLoader（ClassLoader newClassLoader）添加第三方ClassLoader用于实例初始化。如果您需要封装或取消封装自定义序列化数据，请添加您自己的ClassLoader。

2.2 writeSequenceablepublic final void writeSequenceable(Sequenceable val)将可序列化对象写入Parcel实例。其余的方法参考文档Parcel资料

封装Sequenceable实体类我们参考Sequenceable资料

动手实践

今天将一个Sequenceable的集合存到Parcel然后读取出来
4.1 新建两个类 A类用户存放具体属性，B类用于存放A的实体类集合
A类代码如下

 public static class A implements Sequenceable {   private int a;private int b;private int c;public A() {    this(0, 0, 0);}public A(int a, int b, int c) {    this.a = a;    this.b = b;    this.c = c;}@Overridepublic boolean hasFileDescriptor() {    return false;}@Overridepublic boolean marshalling(Parcel out) {    out.writeInt(a);    out.writeInt(b);    out.writeInt(c);    return true;}@Overridepublic boolean unmarshalling(Parcel in) {    a = in.readInt();    b = in.readInt();    c = in.readInt();    return true;}public static final Sequenceable.Producer PRODUCER = new Sequenceable.Producer() {    public A createFromParcel(Parcel in) { A instance = new A(); instance.unmarshalling(in); return instance;    }};@Overridepublic boolean equals(Object o) {    if (this == o) return true;    if (o == null || getClass() != o.getClass()) return false;    A a1 = (A) o;    return a == a1.a &&     b == a1.b &&     c == a1.c;}@Overridepublic int hashCode() {    return Objects.hash(a, b, c);}@Overridepublic String toString() {    return "A{" +     "a=" + a +     ", b=" + b +     ", c=" + c +     '}';}

    public static class B implements Sequenceable {    private List list;  private B() {    }    private B(List list) { this.list = list;    }    @Override    public boolean hasFileDescriptor() { return false;    }    @Override    public boolean marshalling(Parcel out) { out.writeSequenceableList(list); return true;    }    @Override    public boolean unmarshalling(Parcel in) { in.addAppClassLoader(getClass().getClassLoader()); list = in.readSequenceableList(A.class); return true;    }    public static final Sequenceable.Producer PRODUCER = new Sequenceable.Producer() { public B createFromParcel(Parcel in) {     B instance = new B();     instance.unmarshalling(in);     return instance; }    };    @Override    public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; B b = (B) o; return Objects.equals(list, b.list);    }    @Override    public int hashCode() { return Objects.hash(list);    }}

 findComponentById(ResourceTable.Id_bt1).setClickedListener(new Component.ClickedListener() {     @Override     public void onClick(Component component) {  List list = new ArrayList();  A a = new A(1, 2, 3);  A a2 = new A(2, 2, 3);  A a3 = new A(3, 2, 3);  list.add(a);  list.add(a2);  list.add(a3);  B b = new B(list);  Parcel parcel = Parcel.create();  parcel.writeSequenceable(b);  B b1 = new B();  parcel.readSequenceable(b1);  StringBuilder stringBuilder=new StringBuilder();  if (b1.list.size() > 0) {      for (int i = 0; i " + b1.list.get(i).toString());   stringBuilder.append("\n");      }  }  mResult.setText(stringBuilder.toString());     } });