> 編寫:[kesenhoo](https://github.com/kesenhoo) - 原文:[http://developer.android.com/training/basics/intents/result.html](http://developer.android.com/training/basics/intents/result.html) 啟動另外一個[activity](# "An activity represents a single screen with a user interface.")并不一定是單向的。我們也可以啟動另外一個[activity](# "An activity represents a single screen with a user interface.")然后接受一個返回的result。為接受result，我們需要使用[startActivityForResult()](http://developer.android.com/reference/android/app/Activity.html#startActivityForResult(android.content.Intent, int)) ，而不是[startActivity()](http://developer.android.com/reference/android/app/Activity.html#startActivity(android.content.Intent))。 例如，我們的app可以啟動一個camera程序并接受拍的照片作為result。或者可以啟動聯系人程序并獲取其中聯系的人的詳情作為result。 當然，被啟動的[activity](# "An activity represents a single screen with a user interface.")需要指定返回的result。它需要把這個result作為另外一個intent對象返回，我們的[activity](# "An activity represents a single screen with a user interface.")需要在[onActivityResult()](http://developer.android.com/reference/android/app/Activity.html#onActivityResult(int, int, android.content.Intent))的回調方法里面去接收result。 > **Note:**在執行`startActivityForResult()`時，可以使用explicit 或者 implicit 的intent。當啟動另外一個位于的程序中的[activity](# "An activity represents a single screen with a user interface.")時，我們應該使用explicit intent來確保可以接收到期待的結果。 ### 啟動[Activity](# "An activity represents a single screen with a user interface.") 對于startActivityForResult() 方法中的intent與之前介紹的并無太大差異，不過是需要在這個方法里面多添加一個int類型的參數。 該integer參數稱為"request code"，用于標識請求。當我們接收到result Intent時，可從回調方法里面的參數去判斷這個result是否是我們想要的。 例如，下面是一個啟動[activity](# "An activity represents a single screen with a user interface.")來選擇聯系人的例子： ~~~ 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); } ~~~ ### 接收Result 當用戶完成了啟動之后[activity](# "An activity represents a single screen with a user interface.")操作之后，系統會調用我們[activity](# "An activity represents a single screen with a user interface.")中的onActivityResult() 回調方法。該方法有三個參數： - 通過startActivityForResult()傳遞的request code。 - 第二個[activity](# "An activity represents a single screen with a user interface.")指定的result code。如果操作成功則是`RESULT_OK` ，如果用戶沒有操作成功，而是直接點擊回退或者其他什么原因，那么則是`RESULT_CANCELED` - 第它包含了返回的result數據的intent。 例如，下面顯示了如何處理pick a contact的result： ~~~ @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) } } } ~~~ 本例中被返回的Intent使用Uri的形式來表示返回的聯系人。 為正確處理這些result，我們必須了解那些result intent的格式。對于自己程序里面的返回result是比較簡單的。Apps都會有一些自己的api來指定特定的數據。例如，People app (Contacts app on some older versions) 總是返回一個URI來指定選擇的contact，Camera app 則是在`data`數據區返回一個 Bitmap （see the class about [Capturing Photos](http://developer.android.com/training/camera/index.html)). ### 讀取聯系人數據 上面的代碼展示了如何獲取聯系人的返回結果，但沒有說清楚如何從結果中讀取數據，因為這需要更多關于[content providers](http://developer.android.com/guide/topics/providers/content-providers.html)的知識。但如果想知道的話，下面是一段代碼，展示如何從被選的聯系人中讀出電話號碼。 ~~~ @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { // Check which request it is that we're responding to if (requestCode == PICK_CONTACT_REQUEST) { // Make sure the request was successful if (resultCode == RESULT_OK) { // Get the URI that points to the selected contact Uri contactUri = data.getData(); // We only need the NUMBER column, because there will be only one row in the result String[] projection = {Phone.NUMBER}; // Perform the query on the contact to get the NUMBER column // We don't need a selection or sort order (there's only one result for the given URI) // CAUTION: The query() method should be called from a separate thread to avoid blocking // your app's UI thread. (For simplicity of the sample, this code doesn't do that.) // Consider using CursorLoader to perform the query. Cursor cursor = getContentResolver() .query(contactUri, projection, null, null, null); cursor.moveToFirst(); // Retrieve the phone number from the NUMBER column int column = cursor.getColumnIndex(Phone.NUMBER); String number = cursor.getString(column); // Do something with the phone number... } } } ~~~ > **Note**:在Android 2.3 (API level 9)之前對`Contacts Provider`的請求(比如上面的代碼)，需要聲明`READ_CONTACTS`權限(更多詳見[Security and Permissions](http://developer.android.com/guide/topics/security/security.html))。但如果是Android 2.3以上的系統就不需要這么做。但這種臨時權限也僅限于特定的請求，所以仍無法獲取除返回的Intent以外的聯系人信息，除非聲明了`READ_CONTACTS`權限。