Android 共享内存

Parcelable 和 Serializable 区别

Serializable IO完成（通过磁盘文件读写）
Parcelable C++ 对象指针来实现共享内存

import android.os.Parcel;
import androidx.annotation.NonNull;

public class ApiResponseBean extends Throwable implements Parcelable {

    private boolean success;
    private String msg;

    protected ApiResponseBean(Parcel in) {
        success = in.readByte() != 0;
        msg = in.readString();
    }

    public static final Creator<ApiResponseBean> CREATOR = new Creator<ApiResponseBean>() {
        @Override
        public ApiResponseBean createFromParcel(Parcel in) {
            return new ApiResponseBean(in);
        }

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

    @Override
    public int describeContents() {
        return 0;
    }
    
    @Override
    public void writeToParcel(@NonNull Parcel dest, int flags) {
        dest.writeInt(success?1:0);
        dest.writeString(msg);
    }
}

数据序列化的部分写入和读取的顺序不能乱，C++根据指针下标来读取数据；

Parcel.obtain 对象池 Handler message.obtain

私有 Parcel 防止直接 new 通过 obtain 获取；
单例同步锁对象池
静态链表的结构形成一个对象池；

/**
     * Retrieve a new Parcel object from the pool.
     */
    @NonNull
    public static Parcel obtain() {
        Parcel res = null;
        synchronized (sPoolSync) {
            if (sOwnedPool != null) {
                res = sOwnedPool;
                sOwnedPool = res.mPoolNext;
                res.mPoolNext = null;
                sOwnedPoolSize--;
            }
        }

        // When no cache found above, create from scratch; otherwise prepare the
        // cached object to be used
        if (res == null) {
            res = new Parcel(0);
        } else {
            if (DEBUG_RECYCLE) {
                res.mStack = new RuntimeException();
            }
            res.mReadWriteHelper = ReadWriteHelper.DEFAULT;
        }
        return res;
    }