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：