两个activity之间传递数据用startActivityForResult方法。

 package com.example.testactivityresquest;

 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.Toast;

 public class MainActivity extends Activity {

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

         Button btn = (Button) findViewById(R.id.button1);
         btn.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {

                 Intent intent = new Intent(MainActivity.this, Activityb.class);
                 int[] nums = { 15, 15 };
                 intent.putExtra(Changliang.KEY, nums);
                 //有别于startActivity，如果启动的其他Activity多了以后。相当于定一个特定KEY值，返回根据KEY值返回。
                 startActivityForResult(intent, Changliang.requestCode);

             }
         });
     }
    //Activityb传回来的数据在这个方法中获取
     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {

         int s = data.getIntExtra(Changliang.Activity_b_KEY, 1);

         Toast.makeText(getApplicationContext(), "传递两个数得到的和是：" + s, 1).show();

     }

 }

 package com.example.testactivityresquest;

 import android.app.Activity;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.Toast;

 public class Activityb extends Activity {

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

         Intent intent = this.getIntent();
         int[] n = intent.getIntArrayExtra(Changliang.KEY);

         final int nums = n[0] + n[1];

         Toast.makeText(this, n[0] + " " + n[1], 1).show();

         Button btn = (Button) findViewById(R.id.button2);
         btn.setOnClickListener(new OnClickListener() {

             @Override
             public void onClick(View v) {

                 Intent intent1 = new Intent(Activityb.this, MainActivity.class);

                 intent1.putExtra(Changliang.Activity_b_KEY, nums);
                 // 将数据根据特定键值的意图事件导入
                 Activityb.this.setResult(Changliang.requestCode, intent1);
                 //关闭后返回主Activity
                 Activityb.this.finish();

             }
         });
     }

 }

package com.example.testactivityresquest;

public class Changliang {

public static final String KEY="key";

public static final String Activity_b_KEY="key1";

public static final int requestCode=1987;

}

xml文件：

 <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:background="#ff0000" >

     <Button
         android:id="@+id/button1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentTop="true"
         android:layout_centerHorizontal="true"
         android:layout_marginTop="88dp"
         android:text="启动Activityb" />

 </RelativeLayout>

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="#00ff00"
     android:orientation="vertical" >

     <Button
         android:id="@+id/button2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="返回Activity" />

 </LinearLayout>

别忘在AndroidManifast中注册activityb。

运行效果图：