intent不仅是activity通信的中介，是各个组件的通信媒介，这里紧紧举一个小例子：
MainActivity[java]
package com.example.getmessage;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity {
public static final String EXTRA_MESSAGE = "com.example.getmessage.MESSAGE";

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

public void sendMessage(View view) {
Intent intent = new Intent(this, ActivityMessage.class);
EditText editText = (EditText) findViewById(R.id.editText1);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);
// Log.v("debug", message);

}

}[/java]
ActivityMessage.java[java]
package com.example.getmessage;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.widget.TextView;

public class ActivityMessage extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Log.v("debug", "jiji");
// setContentView(R.layout.activity_activity_message);
//
Intent intent = getIntent();
Bundle bundle = intent.getExtras();
String message = bundle.getString(MainActivity.EXTRA_MESSAGE);

TextView textView = new TextView(this);
textView.setWidth(40);
textView.setText(message);
setContentView(textView);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_message, menu);
return true;
}

}[/java]
xml布局文件：
activity_main.xml[xml]
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<EditText
android:id="@+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10" >

<requestFocus />
</EditText>

<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
android:onClick="sendMessage" />

</LinearLayout>[/xml]
activity_activity_message.xml[xml]
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".ActivityMessage" >

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/hello_world" />

</RelativeLayout>[/xml]