Intent
use to
request an action from another app component
like
evolve, can put same information in it
Two type of Intent
Explicit intents:spefiiced to which activity
Implicit intents: don’tspefiiced to which activity,but declare a general action to perform comparing the contents of the intent to the intent filters declared in the manifest file of other apps on the device.
to find what app can be call.
Explain:
Illustration of how an
implicit intent is delivered through the system to start another activity: [1] Activity
creates an Intent with an action
description and passes it to
startActivity(). [2] The Android System searches all apps
for an intent filter that matches the intent. When a match is found, [3] the system starts the matching
activity (Activity B)
by invoking its onCreate() method and passing it
the Intent.
Android system will check all the intent filter in manifest in different app,to find the right apps,
to start another Activity by Explicit intents
if i am in Activity A, I want to start the Activity B
1 2 3 | Intent intent = new Intent(this,B.class); intent.putExtra("name","vlue");// put other information on to the intent startActivity(intent); |
Send informatiom to other Activity
At Activity B, I want to get back the information that i put into the intent
1 2 | Intent intent = getIntent(); String s=intent.getStringExtra("name"); |
Bundle
bundle is like a box, we can put many thing in it.
1 2 3 4 5 6 7 8 9 10 | put bundle into the intent Bundle bundle=new Bundle(); bundle.putChar("key", 'v'); intent.putExtra("bundle", bundle); get value form the bundle Bundle bundle1=intent.getBundleExtra("bundle"); bundle1.getChar("key"); |
Some common intent use in
explain Component
name, Action, Data, Category
http://developer.android.com/guide/components/intents-filters.html
Intent and the Filter
ref:http://jasonandroid.blogspot.hk/2013/10/intents-and-intent-filters.html
Explicit intents vs Implicit intents and intent filter
A intent can hold Component name, Action, Data, Category,Extra and Flag
if not have Component name,the intent is a Implicit intents
Component name
Action
A string that specifies the generic action to perform (such as view or pick).
the defined action
Data
Category
kind of component that should handle the intent.
Extra
Flag
how to create a intent filter for a Activity?
we need to think abou whta action that the activity what to do,than set the app right data ,action and ategory
a intentFilter at last have on action
if a activity want to receive Implicit intents,must have
<category android:name="android.intent.category.DEFAULT"/>
example
How to compare the Intent and the rule of compare the Data?
https://developer.android.com/guide/components/intents-filters.html
action test,data test(type and data),Category test
Action test
in the filter,can have one or more action
How to pass?
if the intent want to pass the test,one action match is ok
if intent filter have no action,no intent can pass the test
if intent has no action,but the filter have one or more action,the intent pass the test
Data test(type and data)
data can
<scheme>://<host>:<port>/<path>
For example:
content://com.example.project:200/folder/subfolder/etc
example
<intent-filter>
<data android:mimeType="video/mpeg" android:scheme="http" ... />
<data android:mimeType="audio/mpeg" android:scheme="http" ... />
...
</intent-filter>
<intent-filter>
<data android:mimeType="image/*" />
...
</intent-filter>
important:
Each of these attributes is optional in a <data> element, but there are linear dependencies:
If a scheme is not specified, the host is ignored.
If a host is not specified, the port is ignored.
If both the scheme and host are not specified, the path is ignored.
Compare the dtat
compared only to the parts of the URI included in the filter. For example:
If a filter specifies only a scheme, all URIs with that scheme match the filter.
If a filter specifies a scheme and an authority but no path, all URIs with the same scheme and authority pass the filter, regardless of their paths.
If a filter specifies a scheme, an authority, and a path, only URIs with the same scheme, authority, and path pass the filter.
The data test compares both the URI and the MIME type in the intent to a URI and MIME type specified in the filter. The rules are as follows:
- An intent that contains neither a URI nor a MIME type passes the test only if the filter does not specify any URIs or MIME types.
- An intent that contains a URI but no MIME type (neither explicit nor inferable from the URI) passes the test only if its URI matches the filter's URI format and the filter likewise does not specify a MIME type.
- An intent that contains a MIME type but not a URI passes the test only if the filter lists the same MIME type and does not specify a URI format.
- An intent that contains both a URI and a MIME type (either explicit or inferable from the URI) passes the MIME type part of the test only if that type matches a type listed in the filter. It passes the URI part of the test either if its URI matches a URI in the filter or if it has a
content: or file: URI and the filter does not specify a URI. In other words, a component is presumed to support content: and file: data if its filter lists only a MIME type.
Category test
Filter can have 0 or more categorycontent: or file: URI and the filter does not specify a URI. In other words, a component is presumed to support content: and file: data if its filter lists only a MIME type.How to pass?
all the Category in the intent must match the Category in the filter,
the other Category in the filter no need to consider
intent have no Category ,must pass the test
important!!!!
if intent send by startActivity()
CATEGORY_DEFAUL will add,so the filter must have CATEGORY_DEFAULT
if filter already have CATEGORY.LAUNCGER and CATEGORY.DEFAULT,no need CATEGORY_DEFAULT
