Getting a Result from an Activity

一般情况下我们会通过startActivity()来启动一个activity，但是如果我们想获得要启动的activity的结果的时候就需要调用startActivityForResult().并且重写 onActivityResult() 。
static final int PICK_CONTACT_REQUEST = 1;  // The request code
...
private void pickContact() {
    Intent pickContactIntent = new Intent(Intent.ACTION_PICK, Uri.parse("content://contacts"));
    pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers
    startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST);
}
得到结果
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // Check which request we're responding to
    if (requestCode == PICK_CONTACT_REQUEST) {
        // Make sure the request was successful
        if (resultCode == RESULT_OK) {
            // The user picked a contact.
            // The Intent's data Uri identifies which contact was selected.


            // Do something with the contact here (bigger example below)
        }
    }
}
注意要判断requestCode == PICK_CONTACT_REQUEST 且resultCode == RESULT_OK。
如上所示：onActivityResult 是用Intent 来返回数据的。这个时候我们就可以通过Intent的getData()来获得数据.