筆記（活動（activity）之間的通信）

1.向下一個活動傳遞資料。

在此就先簡單介紹一下Intent：

An intent is an abstract description of an operation to be performed. It can be used with

startActivity

to launch an

Activity

,

broadcastIntent

to send it to any interested

BroadcastReceiver

components, and

Context.startService(android.content.Intent)

or

Context.bindService(android.content.Intent, android.content.ServiceConnection, int)

to communicate with a background

Service

. 

意思是：該Intent類是在android四大元件之間傳遞資料的信使。

Intent(Context packageContext,Class<?> cls)

          Create an intent for a specific component.

Intent

putExtra(String name, String value)

          Add extended data to the intent.

Add extended data to the intent. The name must include a package prefix, for example the app com.android.contacts would use names like "com.android.contacts.ShowAll".

String getStringExtra(String name)Retrieve extended data from the intent. 

參數：

name

- The name of the desired item. 傳回：the value of an item that previously added with putExtra() or null if no String value was found.

例子：

@1通過Intent向下一個活動發送資料。
String data = "nihao";                                                                      Intent intent = new Intent(activity1.this,activity2.class);
intent.putExtra("send_data",data);
startActivity(intent);
@2通過intent接收來自上一個活動的資料。
Intent intent = getIntent();
String data = intent.getStringExtra("send_data");
           

接着介紹一下Bundle:

A mapping from String values to various Parcelable types.

Bundle()

          Constructs a new, empty Bundle.

putInt(String key, int value)

          Inserts an int value into the mapping of this Bundle, replacing any existing value for the given key.

Bundle bundle = new Bundle();

bundle.putInt("operate",1);

Intent intent = new Intent(); intent.putExtra(bundle); 這樣的程式可以根據鍵值找到數值1，進而進行其他操作。 這隻是簡單的介紹一下Bundle,還有很多方法用來操作。

2.傳回資料給上一個活動。

setResult(int resultCode, Intent data)           Call this to set the result that your activity will return to its caller. 參數： resultCode - The result code to propagate back to the originating activity, often RESULT_CANCELED or RESULT_OK data - The data to propagate back to the originating activity.    資料傳播回caller activity.

Call this to set the result that your activity will return to its caller.

意思是：調用此函數将會把結果回調回caller activity.

3.開啟目前活動的onActivityResult(int requestCode, int resultCode, Intent data)方法。

startActivityForResult(Intent intent, int requestCode)           Launch an activity for which you would like a result when it finished. 參數：      intent - The intent to start.      requestCode - If >= 0, this code will be returned in onActivityResult() when the activity exits.

Launch an activity for which you would like a result when it finished. When this activity exits, your onActivityResult() method will be called with the given requestCode. Using a negative requestCode is the same as calling

startActivity(android.content.Intent)

(the activity is not launched as a sub-activity). 

意思是：需要一個活動結束時傳回結果。目前活動退出，onActivityResult()方法将會被調用，如果

requestCode

 < 0 時，startActivityForResult()與startActivity()效果是一樣的。