Android Parcelable接口使用介绍

在SDK中 Parcelable类的概述是这样的：Interface for classes whose instances can be written to and restored from aParcel. Classes implementing the Parcelable interface must also have a static field calledCREATOR, which is an object implementing theParcelable.Creator interface.

这个接口的实例是通过Parcel进行存储的，在使用Parcelable的时候必须使用Parcelable.Creator。

下面上代码：

首先修改main.xml，增加一个button

 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView 
android:id="@+id/text"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    />
<Button
android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Parcelable">
</Button>
</LinearLayout>

 

然后是主Activity ParcelableTest.java,这个类显示UI，并通过button点击事件启动另一个Activity -- ParcelableTest2,同时通过Parcelable接口传递一些数据。

package parcelable_test.com;
 
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
 
public class ParcelableTest extends Activity implements OnClickListener{
public static final String KEY = "key";
private Button button;
public static final String TAG = "Parcelable";
 
@Override
public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main);
        init();
        Log.d(TAG, "ParcelableTest");
    }
 
private void init(){
button = (Button)findViewById(R.id.button);
button.setOnClickListener(this);
}
 
private void fun(){
Log.d(TAG, "fun");
Person mPerson = new Person();
mPerson.setName("tom");
mPerson.setAge(25);
Intent mIntent = new Intent(this,parcelable_test.com.ParcelableTest2.class);
Bundle mBundle = new Bundle();
mBundle.putParcelable(KEY, mPerson);
mIntent.putExtras(mBundle);
startActivity(mIntent);
}
 
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button:
fun();
break;
 
default:
break;
}
}
}

 

ParcelableTest2.java,这个类用于获取ParcelableTest传出的数据，并显示在UI上。

 

1. package parcelable_test.com;
3. import android.app.Activity;
4. import android.os.Bundle;
5. import android.util.Log;
6. import android.widget.TextView;
8. public class ParcelableTest2extends Activity{
9. private staticfinal String TAG = ParcelableTest.TAG;
10. @Override
11. public void onCreate(Bundle savedInstanceState) {
12. super.onCreate(savedInstanceState);
13. setContentView(R.layout.main);
14. Log.d(TAG, "ParcelableTest2");
15. TextView textView = new TextView(this);
16. Person mPerson = (Person)getIntent().getParcelableExtra(ParcelableTest.KEY);
17. textView.setText("name = " + mPerson.getName() +" age = " + mPerson.getAge());
18. setContentView(textView);
19. }
20. }

下面就是最重要的类Person,Person类引用了Parcelable接口

package parcelable_test.com;
import android.os.Parcel; 
import android.os.Parcelable;
import android.util.Log;
public class Person implements Parcelable{
private String name;
private int age;
private static final String TAG = ParcelableTest.TAG;
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 static final Parcelable.Creator<Person> CREATOR = new Creator<Person>() {
@Override
public Person createFromParcel(Parcel source) {
Log.d(TAG,"createFromParcel");
Person mPerson = new Person();
mPerson.name = source.readString();
mPerson.age = source.readInt();
return mPerson;
}
@Override
public Person[] newArray(int size) {
// TODO Auto-generated method stub
return new Person[size];
}
};
@Override
public int describeContents() {
// TODO Auto-generated method stub
Log.d(TAG,"describeContents");
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
// TODO Auto-generated method stub
Log.d(TAG,"writeToParcel");
dest.writeString(name);
dest.writeInt(age);
}
}

 

最后在AndroidManifest.xml加入<activity android:name=".ParcelableTest2"></activity>

程序运行效果如下：

输出的log如下：

05-18 16:09:47.243 I/ActivityManager(   59): Starting activity: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=parcelable_test.com/.ParcelableTest }
05-18 16:09:47.383 D/Parcelable(  337): ParcelableTest
05-18 16:09:48.003 I/ActivityManager(   59): Displayed activity parcelable_test.com/.ParcelableTest: 724 ms (total 724 ms)
05-18 16:09:49.263 D/Parcelable(  337): fun
05-18 16:09:49.263 D/Parcelable(  337): writeToParcel
05-18 16:09:49.273 I/ActivityManager(   59): Starting activity: Intent { cmp=parcelable_test.com/.ParcelableTest2 (has extras) }
05-18 16:09:49.453 D/Parcelable(  337): ParcelableTest2
05-18 16:09:49.453 D/Parcelable(  337): createFromParcel
05-18 16:09:49.952 I/ActivityManager(   59): Displayed activity parcelable_test.com/.ParcelableTest2: 562 ms (total 562 ms)

 

通过log可知程序的运行情况，在mBundle.putParcelable(KEY, mPerson);时，调用了Person类中的public void writeToParcel(Parcel dest, int flags)方法，并向dest写数据，在 Person mPerson = (Person)getIntent().getParcelableExtra(ParcelableTest.KEY);的时候，调用了Person类中的public Person createFromParcel(Parcel source) 方法，创建了一个Person对象，并给这个对象的属性赋值，这里的Parcel source和Parcel dest,是相同的，然后返回这个Person对象。最后就可以打印出mPerson的属性信息了。