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从Android Activity开始
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       至于Activity是什么，不做详细述说可参考 Google Android 开发文档。生命在于运动，Activity是怎么动起来的？它的“能量“又是怎么传递的？看两个东西
 
1.Starting an Activity
2.Starting an activity for a result
 
详细：
 
1 Starting an Activity
startActivity Param: intent
Extra:(参考：Intents and Intent Filters)
Intent 包括 activity action data(small amounts of data)
 
e.g
 

//简单开始一个Activity
Intent intent = new Intent(this, SignInActivity.class);
startActivity(intent);

 
 

/*
*发送email
*Intent.Action_SEND <-添加发送事件 启动send Activity
*Intent.EXTRA_EMAIL <-添加邮件事件 IF case Email
*/
Intent intent = new Intent(Intent.ACTION_SEND);
intent.putExtra(Intent.EXTRA_EMAIL, recipientArray);
startActivity(intent);

 
 
 
 
2 Starting an activity for a result
a.A Activity:startActivityForResult  Param:intent requestcode
b.B Activity:setResult Param:resultCode || setResult Param: resultcode data
c.A Activity:onActivityResult Param: requestCode resultCode data 
 
e.g
 
 

//请求获取系统联系人
private void pickContact() {
// Create an intent to "pick" a contact, as defined by the content provider URI
Intent intent = new Intent(Intent.ACTION_PICK, Contacts.CONTENT_URI);
startActivityForResult(intent, PICK_CONTACT_REQUEST);
}

 

 

 
 

//返回获取到的联系人
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// If the request went well (OK) and the request was PICK_CONTACT_REQUEST
if (resultCode == Activity.RESULT_OK && requestCode == PICK_CONTACT_REQUEST) {
// Perform a query to the contact's content provider for the contact's name
Cursor cursor = getContentResolver().query(data.getData(),
new String[] {Contacts.DISPLAY_NAME}, null, null, null);
if (cursor.moveToFirst()) { // True if the cursor is not empty
int columnIndex = cursor.getColumnIndex(Contacts.DISPLAY_NAME);
String name = cursor.getString(columnIndex);
// Do something with the selected contact's name...
}
}
}

 

 

 

 参考资料:

 Android 开发文档