Android中的Parcel机制(下)

上一篇中我们透过源码看到了Parcel背后的机制，本质上把它当成一个Serialize就可以了，只是它是在内存中完成的序列化和反序列化，利用的是连续的内存空间，因此会更加高效。

我们接下来要说的是Parcel类如何应用。就应用程序而言，最常见使用Parcel类的场景就是在Activity间传递数据。没错，在Activity间使用Intent传递数据的时候，可以通过Parcelable机制传递复杂的对象。

下面来看一下简单的代码：

UserInfo类，实现了Parcelable接口:

package com.demo.entity;

import java.util.ArrayList;
import java.util.HashMap;

import android.os.Parcel;
import android.os.Parcelable;

/**
 * 用户信息，实现Parcelable接口
 * String,int,String[],ArrayList<HashMap<String,Object>>这四种类型测试
 * @author weijiang204321
 *
 */
public class UserInfo implements Parcelable{

	private String id;
	private String name;
	private int age;
	private String[] boyfriendAry = new String[3];
	private ArrayList<HashMap<String,SonInfo>> listData = new ArrayList<HashMap<String,SonInfo>>();
	private SonInfo sonInfo;

	public UserInfo(){
	}

	public UserInfo(String id,String name,int age,String[] boyfriendAry,ArrayList<HashMap<String,SonInfo>> listData){
		this.id = id;
		this.name = name;
		this.age = age;
		this.boyfriendAry = boyfriendAry;
		this.listData = listData;
	}

	public UserInfo(Parcel source){
		id = source.readString();
		name = source.readString();
		age = source.readInt();
		sonInfo = source.readParcelable(SonInfo.class.getClassLoader());
		source.readStringArray(boyfriendAry);
		source.readList(listData, SonInfo.class.getClassLoader());
	}

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public SonInfo getSonInfo(){
		return sonInfo;
	}

	public void setSonInfo(SonInfo sonInfo){
		this.sonInfo = sonInfo;
	}

	public String[] getBoyfriendAry() {
		return boyfriendAry;
	}

	public void setBoyfriendAry(String[] boyfriendAry) {
		this.boyfriendAry = boyfriendAry;
	}

	public ArrayList<HashMap<String, SonInfo>> getListData() {
		return listData;
	}

	public void setListData(ArrayList<HashMap<String, SonInfo>> listData) {
		this.listData = listData;
	}

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

	//进行序列化存储
	@Override
	public void writeToParcel(Parcel dest, int flags) {
		dest.writeString(id);
		dest.writeString(name);
		dest.writeInt(age);
		dest.writeParcelable(sonInfo, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);

		dest.writeStringArray(boyfriendAry);
		dest.writeList(listData);
	}

	public static final Parcelable.Creator<UserInfo> CREATOR = new Creator<UserInfo>() {
        @Override
        public UserInfo[] newArray(int size) {
            return new UserInfo[size];
        }   

        //将Parcel对象反序列化为UserInfo
        @Override
        public UserInfo createFromParcel(Parcel source) {
            return new UserInfo(source);
        }
    };   

}

同样SonInfo类也要实现Parcelable接口:

package com.demo.entity;

import android.os.Parcel;
import android.os.Parcelable;

public class SonInfo implements Parcelable{

	private String id;
	private String name;

	public SonInfo(){

	}

	public SonInfo(String id,String name){
		this.id = id;
		this.name = name;
	}

	public SonInfo(Parcel source){
		this.id = source.readString();
		this.name = source.readString();
	}

	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}

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

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

	public static final Parcelable.Creator<SonInfo> CREATOR = new Creator<SonInfo>() {
        @Override
        public SonInfo[] newArray(int size) {
            return new SonInfo[size];
        }   

        //将Parcel对象反序列化为UserInfo
        @Override
        public SonInfo createFromParcel(Parcel source) {
            return new SonInfo(source);
        }
    };   

}

下面来看一下测试类：

MainActivity类，在这里面进行数据的封装，然后传递到StubActivity类中：

package com.demo.parcel;

import java.util.ArrayList;
import java.util.HashMap;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

import com.demo.entity.SonInfo;
import com.demo.entity.UserInfo;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		Intent intent = new Intent(this,StubActivity.class);
		ArrayList<HashMap<String,SonInfo>> listData = new ArrayList<HashMap<String,SonInfo>>();
		HashMap<String,SonInfo> tempMap = new HashMap<String,SonInfo>();
		tempMap.put("one_child", new SonInfo("001_1","jiangwei_one_child"));
		listData.add(tempMap);

		UserInfo userInfo = new UserInfo("001","jiangwei",24,new String[]{"张三","李四","王五"},listData);
		SonInfo sonInfo = new SonInfo();
		sonInfo.setId("001_1");
		sonInfo.setName("jiangwei_child");
		userInfo.setSonInfo(sonInfo);
		intent.putExtra("userinfo", userInfo);
		startActivity(intent);

	}

}

下面就是StubActivity类，在这个类中将读出数据进行显示:

package com.demo.parcel;

import java.util.ArrayList;
import java.util.HashMap;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import com.demo.entity.SonInfo;
import com.demo.entity.UserInfo;

public class StubActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_stub);

		UserInfo userInfo = (UserInfo)this.getIntent().getParcelableExtra("userinfo");
		SonInfo sonInfo = userInfo.getSonInfo();

		String[] boyfriend = userInfo.getBoyfriendAry();
		for(int i=0;i<boyfriend.length;i++){
			Log.e("boyfriend_name:",boyfriend[i]);
		}

		ArrayList<HashMap<String,SonInfo>> listData = userInfo.getListData();
		for(int j=0;j<listData.size();j++){
			SonInfo temp_soninfo = listData.get(j).get("one_child");
			Log.e("OneChildId:",temp_soninfo.getId()+"");
			Log.e("OneChildName:",temp_soninfo.getName()+"");
		}

		Log.e("UserId:",userInfo.getId()+"");
		Log.e("UserName:",userInfo.getName()+"");
		Log.e("UserAge:",userInfo.getAge()+"");
		Log.e("Son_id:",sonInfo.getId()+"");
		Log.e("Son_name:",sonInfo.getName()+"");

	}

}

运行结果：

这样就成功了使用了Parcelable进行数据的传输