Android Parcelable的使用

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在SDK中 Parcelable类的概述是这样的：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 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"    /><Buttonandroid: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";  @Overridepublic 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);} @Overridepublic 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。

 

package parcelable_test.com; import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.widget.TextView; public class ParcelableTest2 extends Activity{private static final String TAG = ParcelableTest.TAG;@Overridepublic void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);             Log.d(TAG, "ParcelableTest2");        TextView textView = new TextView(this);        Person mPerson = (Person)getIntent().getParcelableExtra(ParcelableTest.KEY);        textView.setText("name = " + mPerson.getName() + "  age = " + mPerson.getAge());        setContentView(textView);    } }

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>() {@Overridepublic Person createFromParcel(Parcel source) {Log.d(TAG,"createFromParcel");Person mPerson = new Person();mPerson.name = source.readString();mPerson.age = source.readInt();return mPerson;}@Overridepublic Person[] newArray(int size) {// TODO Auto-generated method stubreturn new Person[size];}};@Overridepublic int describeContents() {// TODO Auto-generated method stubLog.d(TAG,"describeContents");return 0;}@Overridepublic void writeToParcel(Parcel dest, int flags) {// TODO Auto-generated method stubLog.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): ParcelableTest05-18 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): fun05-18 16:09:49.263 D/Parcelable(  337): writeToParcel05-18 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): ParcelableTest205-18 16:09:49.453 D/Parcelable(  337): createFromParcel05-18 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。