1.向下一個活動傳遞資料。

意思是：該Intent類是在android四大元件之間傳遞資料的信使。

(Context packageContext,Class<?> cls)
          Create an intent for a specific component.
Intent           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. 

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

@1通過Intent向下一個活動傳送資料。
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");
 

A mapping from String values to various Parcelable types.

          Constructs a new, empty Bundle.

Bundle bundle = new Bundle();

bundle.putInt("operate",1);

2.返回資料給上一個活動。

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