Parcelable in Android

晨曦之光 发布于 2012/03/01 18:59
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Parcelable(SDK)

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.Creatorinterface.


Passing data between activities is quite easy. 

You would normally do that using the Bundle packed into an intent. But sometimes you need to pass complex objects from one activity to another. 

One workaround would be to keep a static instance of the object int your Activity and access it from you new Activity. This might help, but it's definitely not a good way to do this. 

To pass such objects directly through the Bundle, your class would need to implement the Parcelable interface. 


Example:

MainActivity, SubActivity, Person


MainActivity

package com.learn;

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 MainActivity extends Activity implements OnClickListener {

	private static final String TAG = "Parcelable";
	
	public static final String KEY = "key";
	private Button btn;
	
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Log.d(TAG, "MainActivity");
        
        btn = (Button)findViewById(R.id.btn);
    	btn.setOnClickListener(this);
    	
    }
    
    
    @Override
    public void onClick(View v) {

        Log.d(TAG, "onClick");
        
    	if(R.id.btn == v.getId()){
    		
    		Person mPerson = new Person();
    		mPerson.setName("Bill");
    		mPerson.setAge(22);
    		
    		Bundle bundle = new Bundle();
    		bundle.putParcelable(KEY, mPerson);		// mPerson -> Parcelable

            Log.d(TAG, "mPerson=" + mPerson);
    		
    		Intent intent = new Intent(this, SubActivity.class);
    		intent.putExtras(bundle);
    		startActivity(intent);

            Log.d(TAG, "startActivity");
    	}
    	
    }
}

SubActivity

package com.learn;

import android.app.Activity;
import android.os.Bundle;
import android.os.Parcelable;
import android.util.Log;
import android.widget.TextView;

public class SubActivity extends Activity {

	private static final String TAG = "Parcelable";
	
	private TextView tv;

	@Override
	public void onCreate(Bundle savedInstanceState){
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

        Log.d(TAG, "SubActivity");
        
		Parcelable parcelable = getIntent().getParcelableExtra(MainActivity.KEY);
		Person mPerson = (Person)parcelable;		// Parcelable -> Person

        Log.d(TAG, "parcelable=" + parcelable + "; mPerson=" + mPerson);
        
		tv = (TextView)findViewById(R.id.tv);
		tv.setText("name=" + mPerson.getName() + "; age=" + mPerson.getAge());
	}
	
}

Person

package com.learn;

import android.os.Parcel;
import android.os.Parcelable;
import android.util.Log;

public class Person implements Parcelable{

	private static final String TAG = "Parcelable";
	
	private String name;
	private int age;
	
	public Person(){
		
	}

	public void setName(String name){
		this.name = name;
	}
	
	public String getName(){
		return this.name;
	}
	
	public void setAge(int age){
		this.age = age;
	}
	
	public int getAge(){
		return this.age;
	}
	
	
	public static final Parcelable.Creator<Person> CREATOR = new Creator<Person>() {

		@Override
		public Person createFromParcel(Parcel source) {

            Log.d(TAG, "createFromParcel(Parcel source)");
            
			Person mPerson = new Person();
			
			mPerson.name = source.readString();
			mPerson.age = source.readInt();
			
			return mPerson;
		}

		@Override
		public Person[] newArray(int size) {

            Log.d(TAG, "newArray(int size)");
            
			return new Person[size];
		}
		
	};
	
	@Override
	public int describeContents() {

        Log.d(TAG, "describeContents()");
        
		return 0;
	}

	@Override
	public void writeToParcel(Parcel dest, int flags) {

        Log.d(TAG, "writeToParcel(Parcel dest, int flags)");
        
		dest.writeString(name);
		dest.writeInt(age);
	}
	
}

main.xml

<?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/tv"
    	android:layout_width="fill_parent" 
    	android:layout_height="wrap_content" 
    	android:text="@string/hello" />
    
    <Button android:id="@+id/btn"
    	android:layout_width="wrap_content"
    	android:layout_height="wrap_content"
    	android:text="Parcelable" />
    
</LinearLayout>

Running Result


click, then



Log

D/Parcelable(  487): MainActivity
D/Parcelable(  487): onClick
D/Parcelable(  487): mPerson=com.learn.Person@40520b98
D/Parcelable(  487): writeToParcel(Parcel dest, int flags)
D/Parcelable(  487): startActivity
D/Parcelable(  487): SubActivity
D/Parcelable(  487): createFromParcel(Parcel source)
D/Parcelable(  487): parcelable=com.learn.Person@405269f8; mPerson=com.learn.Person@405269f8


Analyse

writeToParcel(Parcel dest, int flags)         ----          bundle.putParcelable(KEY, mPerson)

createFromParcel(Parcel source)             ----          (Person)getIntent().getParcelableExtra(MainActivity.KEY)

source                                                        ----          dest


Download


Parcelable - How to do that in Android

Writing Parcelable classes for Android


原文链接:http://blog.csdn.net/sunboy_2050/article/details/6949809
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