Android Parcel学习

最新推荐文章于 2022-03-10 14:12:53 发布

herbert5069

最新推荐文章于 2022-03-10 14:12:53 发布

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分类专栏： Android 文章标签： android serialization object string list integer

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本文探讨了Parcel作为轻量级对象序列化的应用，特别关注如何通过实现Parcelable接口来高效地在Android应用中进行进程间通信。通过实例展示了如何封装对象并将其作为Intent的额外参数传递，从而在不同Activity间共享复杂的数据结构。

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Parcel是一个轻量级的对象序列化，（类似Serierlizable），可用于进程间通信，用的时候需要写个static CREATOR，写入数据和读出的顺序必需一致。

这里是一个Stackoverflow上的例子

研究了下怎么样传送List<T>，下面这个例子直接传ArrayList<String>:

public class MyParcelInfo implements Parcelable {
	private int feildCount;
	private ArrayList<String> feildNameList;
	
	public MyParcelInfo(Parcel in) {
		feildCount = in.readInt();
		feildNameList = new ArrayList<String>();
		in.readList(feildNameList, ClassLoader.getSystemClassLoader());
	}

	public MyParcelInfo() {
	}

	public int describeContents() {
		return 0;
	}

	public void writeToParcel(Parcel dest, int flags) {
		dest.writeInt(feildCount);
		dest.writeList(feildNameList);

	}

	public static final Parcelable.Creator<MyParcelInfo> CREATOR = new Parcelable.Creator<MyParcelInfo>() {
		public MyParcelInfo createFromParcel(Parcel in) {
			return new MyParcelInfo(in);
		}

		public MyParcelInfo[] newArray(int size) {
			return new MyParcelInfo[size];
		}
	};
	
	public void setFeildCount(int count) {
		this.feildCount = count;
	}

	public int getFeildCount() {
		return this.feildCount;
	}
	
	public ArrayList<String> getFeildList() {
		return this.feildNameList;
	}
	
	public void setFeildList(ArrayList<String> list){
		this.feildNameList = list;
	}
}

下面是发送代码：
protected void sendParcel() {
		
		MyParcelInfo info = new MyParcelInfo();
		
		info.setFeildCount(4);
		
		ArrayList<String> list = new ArrayList<String>();
		list.add("Lisp");
		list.add("JNI");
		list.add("Net");
		list.add("Box2d");
		info.setFeildList(list);
		
		Intent it = new Intent(MainActivity.this, ParcelReceiverActivity.class);
		it.putExtra("info", info);
		this.startActivity(it);
	}




下面是接收代码： 

MyParcelInfo info = this.getIntent().getParcelableExtra("info");
		ArrayList<String> infoList = info.getFeildList();






和String一样，如下的类型可以传送：


   
   null 
String 
Byte 
Short 
Integer 
Long 
Float 
Double 
Boolean 
String[] 
boolean[] 
byte[] 
int[] 
long[] 
Object[] (supporting objects of the same type defined here). 
Bundle 
Map (as supported by writeMap). 
Any object that implements the Parcelable protocol.
Parcelable[] 
CharSequence (as supported by TextUtils.writeToParcel).
List (as supported by writeList). 
SparseArray (as supported by writeSparseArray).
IBinder 
Any object that implements Serializable (but see writeSerializable for caveats). Note that all of the previous types have relatively efficient implementations for writing to a Parcel; having to rely on the generic serialization
 approach is much less efficient and should be avoided whenever possible. 
注意如果要传送其它自定义类型的对象，这个对象必须要implements Parcelable.



parcel可以用于Activity之间传送对象，相比于用Bundle传送，Parcel的好处是可以把数据打包成对象传送，可读性和可维性比用Bundle传一大堆Key,Value键值对要好，同时也可以扩展为传递其它类型的对象(implements Serializalbe or Parcelable).



关于进程间通信的应用，有待进一步研究。