<?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" 
    >  
<EditText    
    android:id="@+id/first" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    />  
<EditText    
    android:id="@+id/second" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    />  
<Button    
    android:id="@+id/start" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="start" 
    />  
<TextView    
    android:id="@+id/text" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="...is waiting" 
    />  
</LinearLayout> 

first = (EditText) findViewById(R.id.first);  
        second = (EditText) findViewById(R.id.second); 

Intent i = new Intent(this, Activity2.class);  

        Bundle b = new Bundle();  

        b.putString("first", first.getText().toString());  
        b.putString("second", second.getText().toString());  

        i.putExtras(b);  

        startActivityForResult(i,10); 

public void startActivityForResult (Intent intent, int requestCode)   

Intent intent：系統會根據這個確定目的Activity  

int requestCode:用于標識該Intent 回來后確定是不是想要的返回 

findViewById(R.id.start).setOnClickListener(new OnClickListener(){  
            public void onClick(View v) {  
                // TODO Auto-generated method stub  
                sendCalculate();  
            }  
        }); 

<?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" 
    >  
<Button    
    android:id="@+id/reply" 
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:text="reply" 
    />  
</LinearLayout> 

Intent i = this.getIntent();  

        Bundle b = i.getExtras();  

        String v1 = b.getString("first");  
        String v2 = b.getString("second");  

        value = v1 + v2; 

Intent i = new Intent();  

        Bundle b = new Bundle();  
        b.putString("CALCULATION", value);  

        i.putExtras(b);  

        this.setResult(RESULT_OK, i);  
        this.finish(); 

protected void onActivityResult(int requestCode, int resultCode,  
                                    Intent data){  
        switch (resultCode){  
        case RESULT_OK:  
            Bundle b = data.getExtras();  

            String string = b.getString("CALCULATION");  

            updateText(string);  
        }  
    }