android Parcelable完全解析

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2024-08-06 08:20:40 222人阅读

title: android.os.Parcelable文档自译 date: 2014-12-05 09:16:06

tags:

android.os.Parcelable接口的已知间接子类很多，这里就不列举了：

Class Overview

Interface for classes whose instances can be written to and restored from a

Parcel. Classes implementing the Parcelable interface must also have a static

field called CREATOR, which is an object implementing the Parcelable.Creator

interface.

该Interface用于实例可以被写入，并且可以从Parcel中恢复的classes(对于Parcel暂时只要知道它是一个存放数据的容器就好了，我会在android IPC中写到它)。实现android.os.Parcelable接口的类必须持有一个实现了android.os.Parcelable接口的名为 CREATOR 的静态字段。

android.os.Parcelable接口典型使用方式,这是官网的例子：

package me.androiddemo.canglangwenyue.androiddemo;

import android.os.Parcel;

import android.os.Parcelable;

/**

* Created by canglangwenyue on 12/5/14.

public class MyParcelable implements Parcelable {

private int mData;

public int describeContents() {

return 0;

}

public void writeToParcel(Parcel out, int flags) {

out.writeInt(mData);

}

public static final Parcelable.Creator<MyParcelable> CREATOR

= new Parcelable.Creator<MyParcelable>() {

public MyParcelable createFromParcel(Parcel in) {

return new MyParcelable(in);

}

public MyParcelable[] newArray(int size) {

return new MyParcelable[size];

}

};

private MyParcelable(Parcel in) {

mData = http://www.mamicode.com/in.readInt();

}

Summary(简介)

Nested Classes(嵌套类)

1.interface Parcelable.ClassLoaderCreator<T>

Specialization of Parcelable.Creator that allows you to receive

the ClassLoader the object is being created in.

解析：专业化的 Parcelable.Creator，允许你接收的Object内部创建的 ClassLoader 对象.

2.interface Parcelable.Creator<T>

Interface that must be implemented and provided as a public CREATOR field that

generates instances of your Parcelable class from a Parcel.

解析：该接口必须被子类实现，而且CREATOR 作为公有字段来提供，CREATOR 用于从 Parcel中实例化你的可包装类.

Constants(常量)

1.int CONTENTS_FILE_DESCRIPTOR

Bit masks for use with describeContents(): each bit represents a kind of object

considered to have potential special significance when marshalled.

解析：用于 describeContents() 的位掩码，每一位代表它编组时附加的特殊含义。

2.int PARCELABLE_WRITE_RETURN_VALUE

Flag for use with writeToParcel(Parcel, int): the object being written is a

return value, that is the result of a function such as "Parcelable

someFunction()", "void someFunction(out Parcelable)", or "void

someFunction(inout Parcelable)".

解析：writeToParcel(Parcel, int)的标志位：作为一个返回值，是"Parcelable

someFunction()", "void someFunction(out Parcelable)", or "void

someFunction(inout Parcelable)"返回的result。

Public Methods(公共method)

1.abstract int describeContents()

Describe the kinds of special objects contained in this Parcelable‘s marshalled

representation.

解析：描述各种特殊对象，它们包含在可包装对象的编组形式中.

2.abstract void writeToParcel(Parcel dest, int flags)

Flatten this object in to a Parcel.

解析：将该对象展开到Parcel(存放数据的容器)中。

Parcelable适用于通过Intent来传递自定义对象。最后给出一个用Parcelable进行数据传送的例子

1.发送Object的Activity，内容很简单，点击Button，Intent携带Object跳转到MainActivity2(用来接收Object的Activity)。

package me.androiddemo.canglangwenyue.androiddemo;

import android.content.Intent;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.MenuItem;

import android.view.View;

import android.widget.Button;

import java.util.HashMap;

/**

* @author canglangwenyue

* 用来发送信息的Activity

public class MainActivity extends ActionBarActivity {

private Button sendButton;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

sendButton = (Button) findViewById(R.id.send_button);

sendButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

Intent intent = new Intent();

Person person = new Person();

person.name = "WenYue";

intent.putExtra("WenYue",person);

intent.setClass(MainActivity.this,MainActivity2.class);

startActivity(intent);

}

});

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.menu_main, menu);

return true;

}

@Override

public boolean onOptionsItemSelected(MenuItem item) {

// Handle action bar item clicks here. The action bar will

// automatically handle clicks on the Home/Up button, so long

// as you specify a parent activity in AndroidManifest.xml.

int id = item.getItemId();

//noinspection SimplifiableIfStatement

if (id == R.id.action_settings) {

return true;

}

return super.onOptionsItemSelected(item);

}

2.MainActivity2用来接收来自MainActivity的Object，并打印Person.name的长度和content。

package me.androiddemo.canglangwenyue.androiddemo;

import android.content.Intent;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.util.Log;

import android.view.Menu;

import android.view.MenuItem;

/**

@author canglangwenyue
接收数据的Intent */
public class MainActivity2 extends ActionBarActivity {
@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main_activity2);
Intent intent = getIntent();
Person person = intent.getParcelableExtra("WenYue");
Log.e("MainActivity2 received message‘s length----->",String.valueOf(person.name.length()));
Log.e("MainActivity2 received message content------>",person.name);
}
@Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main_activity2, menu); return true; }
@Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
} }

3.Parcelable的实现，具体细节前面已经讲到了，就不多说了。

package me.androiddemo.canglangwenyue.androiddemo;

import android.os.Parcel;

import android.os.Parcelable;

/**

* Created by canglangwenyue on 12/5/14.

* Parcelable常用于Intent中进行自定义对象的传递

public class Person implements Parcelable {

public String name;

@Override

public int describeContents() {

return 0;

}

@Override

public void writeToParcel(Parcel dest, int flags) {

dest.writeString(name);

}

需要重写Creator实现android.os.Parcelable接口的类必须持有一个实现了android.os.Parcelable接口的名为 CREATOR 的静态字段

public static final Creator<Person> CREATOR = new Parcelable.Creator<Person>() {

重写Creator方法

@Override

public Person createFromParcel(Parcel source) {

Person person = new Person();

person.name = source.readString();

return person;

}

@Override

public Person[] newArray(int size) {

return new Person[0];

}

};

}

最后给出在MainActivity2中log打印的结果，眼见为实，哈哈：

再附上demo下载地址，希望对大家与帮助：苍狼问月

android Parcelable完全解析

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android Parcelable完全解析

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