【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

1. 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。

2. 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

3. 封装Sequenceable实体类我们参考Sequenceable资料

4. 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;
    }

    @Override
    public boolean hasFileDescriptor() {
        return false;
    }

    @Override
    public boolean marshalling(Parcel out) {
        out.writeInt(a);
        out.writeInt(b);
        out.writeInt(c);
        return true;
    }

    @Override
    public boolean unmarshalling(Parcel in) {
        a = in.readInt();
        b = in.readInt();
        c = in.readInt();
        return true;
    }

    public static final Sequenceable.Producer<A> PRODUCER = new Sequenceable.Producer<A>() {
        public A createFromParcel(Parcel in) {
            A instance = new A();
            instance.unmarshalling(in);
            return instance;
        }
    };

    @Override
    public 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;
    }

    @Override
    public int hashCode() {
        return Objects.hash(a, b, c);
    }

    @Override
    public String toString() {
        return "A{" +
            "a=" + a +
            ", b=" + b +
            ", c=" + c +
            '}';
    }
}

4.2 B类用于存放A的实体类集合，代码如下

public static class B implements Sequenceable {
    private List<A> list;
         private B() {
    }

    private B(List<A> 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<B> PRODUCER = new Sequenceable.Producer<B>() {
        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);
    }
}

需要注意的是我们需要调用addAppClassLoader方法，这个地方比较容易出错，如下图

4.3 新建abilitySlice ，然后在xml写一个控件用于存读Parcel中数据，xml代码如下

<?xml version="1.0" encoding="utf-8"?>
<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:height="match_parent"
    ohos:width="match_parent"
    ohos:orientation="vertical">

    <Text
        ohos:id="$+id:bt1"
        ohos:height="100vp"
        ohos:background_element="#Ed6262"
        ohos:width="match_parent"
        ohos:text_alignment="center"
        ohos:text_size="30fp"
        ohos:text_color="#ffffff"
        ohos:text="存储数据"/>
    <Text
        ohos:top_margin="10vp"
        ohos:id="$+id:Result"
        ohos:height="100vp"
        ohos:multiple_lines="true"
        ohos:width="match_parent"
        ohos:text_alignment="center|left"
        ohos:text_size="20fp"
        ohos:text_color="#ed6262"
        />
</DirectionalLayout>

4.4 实现点击按钮事件，然后存读数据，代码如下

 findComponentById(ResourceTable.Id_bt1).setClickedListener(new Component.ClickedListener() {
    @Override
    public void onClick(Component component) {
        List<A> 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.size(); i++) {
                stringBuilder.append(" b1.list====>" + b1.list.get(i).toString());
                stringBuilder.append("\n");
            }
        }
        mResult.setText(stringBuilder.toString());
    }
});

5. 运行效果

全部代码如下

5.1 xml

<DirectionalLayout
    xmlns:ohos="http://schemas.huawei.com/res/ohos"
    ohos:height="match_parent"
    ohos:width="match_parent"
    ohos:orientation="vertical">

    <Text
        ohos:id="$+id:bt1"
        ohos:height="100vp"
        ohos:background_element="#Ed6262"
        ohos:width="match_parent"
        ohos:text_alignment="center"
        ohos:text_size="30fp"
        ohos:text_color="#ffffff"
        ohos:text="存储数据"/>
    <Text
        ohos:top_margin="10vp"
        ohos:id="$+id:Result"
        ohos:height="100vp"
        ohos:multiple_lines="true"
        ohos:width="match_parent"
        ohos:text_alignment="center|left"
        ohos:text_size="20fp"
        ohos:text_color="#ed6262"
        />
</DirectionalLayout>

5.2 java 代码

package com.harmony.alliance.mydemo.slice;
import com.harmony.alliance.mydemo.ResourceTable;
import ohos.aafwk.ability.AbilitySlice;
import ohos.aafwk.content.Intent;
import ohos.agp.components.Component;
import ohos.agp.components.Text;
import ohos.utils.Parcel;
import ohos.utils.Sequenceable;
import java.util.*;

public class ParcelTestSlice extends AbilitySlice {
    private Text mResult;
    @Override
    protected void onStart(Intent intent) {
        super.onStart(intent);
        setUIContent(ResourceTable.Layout_slice_main2);
        mResult= (Text) findComponentById(ResourceTable.Id_Result);
        findComponentById(ResourceTable.Id_bt1).setClickedListener(new Component.ClickedListener() {
            @Override
            public void onClick(Component component) {
                List<A> 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.size(); i++) {
                        stringBuilder.append(" b1.list====>" + b1.list.get(i).toString());
                        stringBuilder.append("\n");
                    }
                }
                mResult.setText(stringBuilder.toString());
            }
        });
    }

    public static class B implements Sequenceable {
        private List<A> list;
        private B() {}
        private B(List<A> 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<B> PRODUCER = new Sequenceable.Producer<B>() {
            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);
        }
    }

    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;
        }

        @Override
        public boolean hasFileDescriptor() {
            return false;
        }

        @Override
        public boolean marshalling(Parcel out) {
            out.writeInt(a);
            out.writeInt(b);
            out.writeInt(c);
            return true;
        }

        @Override
        public boolean unmarshalling(Parcel in) {
            a = in.readInt();
            b = in.readInt();
            c = in.readInt();
            return true;
        }

        public static final Sequenceable.Producer<A> PRODUCER = new Sequenceable.Producer<A>() {
            public A createFromParcel(Parcel in) {
                A instance = new A();
                instance.unmarshalling(in);
                return instance;
            }
        };

        @Override
        public 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;
        }

        @Override
        public int hashCode() {
            return Objects.hash(a, b, c);
        }

        @Override
        public String toString() {
            return "A{" +
                    "a=" + a +
                    ", b=" + b +
                    ", c=" + c +
                    '}';
        }
    }
}

5.3 效果如下

posted @ 2022-04-07 17:00 华为开发者论坛阅读(411) 评论(0) 收藏举报

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