Service-1-Start service

服務「啟動」表示應用程式元件 (例如 Activity) 透過呼叫 startService() 來啟動服務。一旦啟動，服務可以無限次數地在背景中執行，就算啟動服務的元件已終結也不會影響。 通常，已啟動的服務會執行單一操作且不會將結果傳回呼叫端。例如，服務可能會透過網路下載或上傳檔案。

服務會在其託管程序的主執行緒中執行 —
 服務不會建立自己的執行緒且不會在另外的程序中執行 (除非您另行指定)。 如果您的服務即將從事任何 CPU 密集的作業或封鎖操作 (如播放 MP3 或連線網路)，您應該在服務中建立新的執行緒來執行這些工作。 透過使用另外的執行緒，您會降低應用程式不回應 (ANR) 錯誤的風險，且應用程式的主執行緒仍可以專務於使用者與您的 Activity 互動。

1. Create a Service

public class EchoService extends Service {
    public EchoService() {
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return super.onStartCommand(intent, flags, startId);
    }


    @Override
    public void onCreate() {
        super.onCreate();
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }
}

2.At activity A start A service

Intent intent = new Intent(this,EchoService.class);
  startService(intent);

when you call startService(intent);, will execute onCreate and onStartCommand method. However, will you call again startService, only onStartCommand  will execute again.

when onStartCommand  finish ,the Service object still here

3.Stop the service

In the service :

stopSelf() 

outside the Service:

 stopService()

after call these method, OnDestroy() will call

當不再使用服務且正在終結服務時，系統會呼叫此方法。您的服務應該實作此方法來清除任何如執行緒、註冊的接聽器，接收器等資源。 這會是服務接收到的最後呼叫。

Start another Activity and Get Back the Result

If:
A start B,B give back the information to A

A start B

At A activity

A start B

Intent intent = new Intent(this,actB.class);
startActivityForResult(intent,0);

Reecive the information from B, onActivityResult

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

    }

At B activity

B send back the information and close

Intent i =new Intent();
i.putExtra("name","Roy");
setResult(0,i);
 finish();

Send Object to other Activity

Method1(low efficiency)

use Serializable

implement Serializable the class that you want to sent

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class Car implements Serializable{} intent.putExtra("car",car);

Get back the Object from intent

1	Car c2= (Car) intent.getSerializableExtra("car");

Method2

use Parcelable

if i want to send a car object
First, implement Parcelable to car ,and override  some method

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class Car implements Parcelable{ public Car() { } protected Car(Parcel in) { //what the code here to create the Car from a Parcel } public static final Creator<Car> CREATOR = new Creator<Car>() { @Override public Car createFromParcel(Parcel in) { return new Car(in); } @Override public Car[] newArray(int size) { return new Car[size]; } }; @Override public int describeContents() { return 0; } @Override public void writeToParcel(Parcel dest, int flags) { dest.writeString("information"); dest.writeInt(1); } }

Put into the intent

1	intent.putExtra("key",new Car());

Get back the object

1	intent.getParcelableExtra("key");

Activity and Intent

Intent

use to request an action from another app component

like evolve, can put same information in it

Two type of Intent

Use the intenExplicit intents vs Implicit intents

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

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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.

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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 Implicit intents

http://developer.android.com/guide/components/intents-common.html

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

combine https://www.blogger.com/blogger.g?blogID=1723759563624018420#editor/target=post;postID=4564683925715541141;onPublishedMenu=allposts;onClosedMenu=allposts;postNum=14;src=postname

https://www.blogger.com/blogger.g?blogID=1723759563624018420#editor/target=post;postID=3160921220889333677;onPublishedMenu=allposts;onClosedMenu=allposts;postNum=7;src=postname

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

https://developer.android.com/reference/android/content/Intent.html

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:

1. 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.
2. 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.
3. 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.
4. 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 category

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