Intent.setData vs Intent.putExtra

问题:

I'm trying to follow this tutorial:

http://www.vogella.com/articles/AndroidCalendar/article.html

I understand what putExtra does

but I fail to understand what setData() means?

Android Docs, wasn't much helpful:

Set the data this intent is operating on.

what does this mean for the constant

intent.setData(CalendarContract.Events.CONTENT_URI); ?

There doesn't seem to be any affect when I comment out this line.

回答1:

setData() is used to point to the location of a data object (like a file for example), while putExtra() adds simple data types (such as an SMS text string for example).

Here are two examples to clarify:

setData() used here to set the location of a file that you want to share.

File fileToShare = new File("/sdcard/somefile.dat");
Intent i = new Intent();
i.setAction(Intent.ACTION_SEND);
i.setData(Uri.fromFile(fileToShare));
startActivity(i);

putExtra() is used here to set the text content that you want to share.

Intent i = new Intent();
i.setAction(Intent.ACTION_SEND);
String textBodyString = "some text";
i.putExtra(Intent.EXTRA_TEXT, textBodyString);
i.setType(HTTP.PLAIN_TEXT_TYPE);

For more information I suggest some readings about Intents and the setData(), setType() and setDataAndType()

回答2:

setData() is used for the Android System to find an application component that matches the data attribute in implicit intent.

---

putExtra() is mainly used to pass some information to the selected application component,by the Android system.

回答3:

I think that .putExtra is to transfer a string or something. like Aramex :P

while .setData is to set the intent's data type.

see in the intent it's Intent.ACTION_INSERT. So it's waiting for something to be inserted. That's why you set the data. .setData(CalendarContract.Events.CONTENT_URI); You inserted the calendar events.

回答4:

I've found a good answer here: https://google-developer-training.gitbooks.io/android-developer-fundamentals-course-concepts/content/en/Unit%201/21_c_understanding_activities_and_intents.html

Use the intent data field (Intent.setData): - When you only have one piece of information you need to send to the started activity. - When that information is a data location that can be represented by a URI.

Use the intent extras (Intent.putExtra): - If you want to pass more than one piece of information to the started activity. - If any of the information you want to pass is not expressible by a URI.

Intent data and extras are not exclusive; you can use data for a URI and extras for any additional information the started activity needs to process the data in that URI.