【Harmony OS】【JAVA UI】鴻蒙系統中怎么使用 Parcel 進行存盤資料或資料傳遞-有解無憂

1. Parcel 簡介

在 IPC 程序中，發送方可以使用 Parcel 提供的寫方法，將待發送的資料以特定格式寫入Parcel物件，接收方可以使用 Parcel 提供的讀取方法從 Parcel 物件中讀取特定格式的資料，

Parcel 實體的默認容量為200KB，如果您想要更多或更少，請使用 setCapacity(int) 更改它，

注意：只有以下資料型別的資料才能寫入或從包裹中讀取： byte, byteArray, short, shortArray, int, intArray, long, longArray, float, floatArray, double, doubleArray, boolean, booleanArray, char, charArray, String, StringArray、 PlainBooleanArray, Serializable, Sequenceable, 和 SequenceableArray，

2. 方法介紹

2.1 addAppClassLoader(ClassLoader newClassLoader)public void addAppClassLoader（ClassLoader newClassLoader）添加第三方ClassLoader用于實體初始化，如果您需要封裝或取消封裝自定義序列化資料，請添加您自己的ClassLoader，

2.2 writeSequenceablepublic final void writeSequenceable(Sequenceable val)將可序列化物件寫入Parcel實體，其余的方法參考檔案Parcel資料

3. 封裝Sequenceable物體類我們參考Sequenceable資料

4. 動手實踐

今天將一個 Sequenceable 的集合存到 Parcel 然后讀取出來

4.1 新建兩個類 A類用戶存放具體屬性，B類用于存放A的物體類集合

A類代碼如下

 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類用于存放A的物體類集合，代碼如下

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);
    }
}

需要注意的是我們需要呼叫addAppClassLoader方法，這個地方比較容易出錯，如下圖

4.3 新建abilitySlice ，然后在xml寫一個控制元件用于存讀Parcel中資料，xml代碼如下

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

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

4.4 實作點擊按鈕事件，然后存讀資料，代碼如下

 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. 運行效果

全部代碼如下

5.1 xml

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

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

5.2 java 代碼

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

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