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This article will explain in detail how to use Intent in Android. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

1. What is implicit Intent?

Intent is an important component of Android, which is often used to launch a new Activity or Service, broadcast an event, and pass data between Android components. There are usually two ways to start a new Activity or Service through Intent, one is to show the startup, and the other is to start implicitly.

Displaying startup is a clear indication of the class or package name of the Activity or Service to be launched. For example:

Intent intent = newIntent (this,PlayerActivity.class); startActivity (intent); Intent intent = newIntent (); intent.setClass (this,PlayerActivity.class); startActivity (intent); Intent intent = newIntent (); intent.setClassName ("com.jhuster.videoplayer", "com.jhuster.videoplayer.PlayerActivity"); startActivity (intent)

Implicit startup does not specify which Activity or Service to start, but allows the system to filter out the appropriate targets by setting Action, Data, and Category.

For example, make a phone call:

Intent intent = new Intent (Intent.ACTION_DIAL,Uri.parse ("tel:021-80961111")); startActivity (intent)

After receiving the implicit startup request, the system will compare and determine whether it matches the current Activity request according to what each Intent in the system declares in the AndroidManifest.xml file.

Therefore, if we want PlayerActivity to be started implicitly by the system, we first need to add it to the AndroidManifest.xml file for the Activity.

two。 Add for PlayerActivity

There are many tags, here only introduce and add the most basic and most commonly used three tags, respectively, and.

2.1 add

This tag must be added, can be defined by yourself, can also use the system predefined variables, the Android system defines a lot of action by default, you can check the SDK document, or Google "android.intent.action."

Here, because our class is used to "play video", we can use the system predefined: android.intent.action.VIEW, which means that you need to launch an Activity to display the specified data (including pictures, videos, documents, etc.).

After it is added, it looks like this:

2.2 add

Category stands for category and defines the category of Activity. Activity can set one or more category tags. There are generally three commonly used: DEFAULT,HOME,LAUNCHER

DEFAULT default action HOME is set to the startup Activity of the local desktop application LAUNCHER this APP

We can use the DEFAULT category in this application, and DEFAULT is also the most commonly used option for category.

With the addition of category, it looks like this:

2.3 add

Data represents the data source and is the most complex tag in, because different Activity supports a variety of data sources and types, so it needs to be indicated by detailed data tag information.

The data tag has many attributes, including:

Android:host: specify the hostname, for example: google.comandroid:port: specify the host port, for example: 80android:path: specify a valid path value for URL, for example: / index/examplesandroid:mimeType: specify the data type that the component can execute, for example: proomwicpicpathcine jpeid80android:path scheme: specify a specific mode, for example: content,http

Here, suppose our video player supports multiple data sources, including local video files, local media URL, and network video streams (HTTP, RTMP, RTSP protocols). In addition, assume that our video player only supports mp4 and 3gpp file formats.

So, let's add the two most commonly used tags, scheme and mimeType, and explain what kind of data source or data format each tag corresponds to.

(1)

The xxx here can be: file,content, network protocols (HTTP,RTMP, RTSP, etc.)

In this application, we added the following to PlayerActivity:

After adding these data tag entries, our PlayerActivity will be implicitly launched if the data source URL in the implicit Intent is a URL resource that starts with "file://","content://", "http://","rtsp://".

For example, other Activity can implicitly launch our PlayerActivity.

Intent intent = new Intent (Intent.ACTION_VIEW); intent.setData (Uri.fromFile (new File ("/ sdcard/test.3gp")); startActivity (intent)

The statement Uri.fromFile converts the specified file location to a Uri object that starts with "file://", as in the example above, the resulting URL is:" file:///sdcard/test.3gp".

Similarly, we can use Uri.parse to convert our common network address strings into Uri objects, such as:

Intent intent = new Intent (Intent.ACTION_VIEW); intent.setData (Uri.parse ("http://ticktick.blog.51cto.com/test.mp4"));startActivity(intent);)

(2)

MimeType is used to set the data type, such as image data (p_w_picpath/png or paired picture picture *), video data (video/mp4 or video/*), if you use * to represent all the subtypes that match.

MIME TYPE is a standard for tagging data types on the Internet, and now it already supports a lot of types. I won't enumerate them here, but you can search on Google.

In this application, we assume that we need to support mp4 and 3gpp, so we can add two mimeType:

In that case, other Activity can implicitly launch our PlayerActivity. Note that when mimeType has been added, the implicit Intent must set the Type parameter to match the Activity, so it is recommended to use the setDataAndType method instead of a single setData method.

Intent intent = new Intent (Intent.ACTION_VIEW); intent.setDataAndType (Uri.fromFile (new File ("/ sdcard/test.3gp")), "video/3gpp"); startActivity (intent)

Of course, the "video/3gpp" here can also be written as "video/*", but this may match some players that do not support 3gpp.

(3) Summary

With the tag added, it looks like this:

3. Get parameters in PlayerActivity

Now that we know how to add and call our PlayerActivity through the implicit Intent, let's learn how to parse the parameters from the implicit Intent in PlayerActivity.

In fact, Intent provides many ways to Get relevant parameter information, such as:

Public String getAction (); public Uri getData (); public String getScheme (); public String getType ()

The above method can obtain the Action,Data Uri,Scheme and MimeType values of Intent, respectively.

For the Uri object that starts with "file://", we can get the specific file address with the file://" prefix removed by the Uri.getPath method." For example: "file:///sdcard/test.mp4" can be converted to the actual" / sdcard/test.mp4 ".

For network code streams, such as Uri that begins with "http://","rtsp://", etc., it can be directly converted to a string of actual addresses through the toString () method.

For the URI object at the beginning of "content://", it is usually the result retrieved from the system's media database, so you need to find the actual file address in reverse, and a function is provided here for conversion.

Public static String getVideoPath (Context context, Uri uri) {Uri videopathURI = uri; if (uri.getScheme (). ToString (). CompareTo ("content") = 0) {Cursor cursor = context.getContentResolver (). Query (uri, null, null); if (cursor.moveToFirst ()) {int column_index = cursor.getColumnIndexOrThrow (MediaStore.Video.Media.DATA) VideopathURI = Uri.parse (cursor.getString (column_index)); return videopathURI.getPath ();} else if (uri.getScheme (). CompareTo ("file") = = 0) {return videopathURI.getPath ();} return videopathURI.toString () } this is the end of the article on "how to use Intent in Android". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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