intent 使用（2）

前面提到建立intent 的方式的含义，这里记录下intent的作用，activity之间的值传递

     当程序中需要调用一个外部功能（命令，类）来得到想要的结果时，可以用 startActivityForResult(Intent, int) 。 其中intent是想要做的事情，int 是request_code; intent中的功能执行结束时，需要返回一个resultCode，当然也可以附加更多的参数(intent.putExtra())。 

     然后再在该类中重载  onActivityResult(int, int, Intent) 函数来处理返回结果。

下边是activity官方文档：

http://www.android-doc.com/reference/android/app/Activity.html

Sometimes you want to get a result back from an activity when it ends. For example, you may start an activity that lets the user pick a person in a list of contacts; when it ends, it returns the person that was selected. To do this, you call the startActivityForResult(Intent, int) version with a second integer parameter identifying the call. The result will come back through your onActivityResult(int, int, Intent) method.

public class MyActivity extends Activity {     ...

     static final int PICK_CONTACT_REQUEST = 0;

     protected boolean onKeyDown(int keyCode, KeyEvent event) {         if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) {             // When the user center presses, let them pick a contact.             startActivityForResult(                 new Intent(Intent.ACTION_PICK,                 new Uri("content://contacts")),                 PICK_CONTACT_REQUEST);            return true;         }         return false;     }

     protected void onActivityResult(int requestCode, int resultCode,             Intent data) {         if (requestCode == PICK_CONTACT_REQUEST) {             if (resultCode == RESULT_OK) {                 // A contact was picked.  Here we will just display it                 // to the user.                 startActivity(new Intent(Intent.ACTION_VIEW, data));             }         }     } }