Starting Another Activity

  次阅读 作者:智能小宝 来源:互联网 2016-01-14 10:42 我要评论(0)

Respond to the Send Button

To respond to the button's on-click event, open the main.xml layout file and add the android:onClick attribute to the <Button> element:

<Button

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="@string/button_send"

android:onClick="sendMessage" />

The android:onClick attribute’s value, "sendMessage", is the name of a method in your activity that the system calls when the user clicks the button.

Open the MainActivity class and add the corresponding method:

/** Called when the user clicks the Send button */

public void sendMessage(View view) {

// Do something in response to button

}

Tip: In Eclipse, press Ctrl + Shift + O to import missing classes (Cmd + Shift + O on Mac).

In order for the system to match this method to the method name given to android:onClick, the signature must be exactly as shown. Specifically, the method must:

Be public

Have a void return value

Have a View as the only parameter (this will be the View that was clicked)

Next, you’ll fill in this method to read the contents of the text field and deliver that text to another activity.

Build an Intent

An Intent is an object that provides runtime binding between separate components (such as two activities). The Intent represents an app’s "intent to do something." You can use intents for a wide variety of tasks, but most often they’re used to start another activity.

Inside the sendMessage() method, create an Intent to start an activity called DisplayMessageActivity:

Intent intent = new Intent(this, DisplayMessageActivity.class);

The constructor used here takes two parameters:

A Context as its first parameter (this is used because the Activity class is a subclass of Context)

The Class of the app component to which the system should deliver the Intent (in this case, the activity that should be started)

Sending an intent to other apps

The intent created in this lesson is what's considered an explicit intent, because the Intent specifies the exact app component to which the intent should be given. However, intents can also be implicit, in which case the Intent does not specify the desired component, but allows any app installed on the device to respond to the intent as long as it satisfies the meta-data specifications for the action that's specified in various Intent parameters. For more information, see the class about Interacting with Other Apps.

Note: The reference to DisplayMessageActivity will raise an error if you’re using an IDE such as Eclipse because the class doesn’t exist yet. Ignore the error for now; you’ll create the class soon.

An intent not only allows you to start another activity, but it can carry a bundle of data to the activity as well. So, use findViewById() to get the EditText element and add its text value to the intent:

Intent intent = new Intent(this, DisplayMessageActivity.class);

EditText editText = (EditText) findViewById(R.id.edit_message);

String message = editText.getText().toString();

intent.putExtra(EXTRA_MESSAGE, message);

An Intent can carry a collection of various data types as key-value pairs called extras. The putExtra() method takes the key name in the first parameter and the value in the second parameter.

本站文章信息来源于网络以及网友投稿,本站只负责对文章进行整理、排版、编辑,是出于传递更多信息之目的,并不意味着赞同其观点或证实其内容的真实性。如果您有什么意见或建议,请联系QQ28-1688-302!

人工智能实验室
相关文章相关文章
  • 韩春雨称已能重复实验结果 近期将有消息公布

    韩春雨称已能重复实验结果 近期将有消息公布

  • 无人驾驶汽车如何改变城市生活?听听他们怎么说

    无人驾驶汽车如何改变城市生活?听听他们怎么说

  • 未来两年人工智能要怎么走?看这篇就够了

    未来两年人工智能要怎么走?看这篇就够了

  • 英国研发“杀生”机器人 通过生命体获取能量

    英国研发“杀生”机器人 通过生命体获取能量

网友点评网友点评
阅读推荐阅读推荐

据国外媒体报道,在过去两年内,聊天机器人(chatbot)、人工智能以及机器学习的研发和采用取得了巨大进展。许多初创公司正利用人工智能和...

霍金 视觉中国 图 英国著名物理学家霍金(Stephen Hawking)再次就人工智能(AI)发声,他认为:对于人类来说,强大AI的出现可能是最美妙的...

文|郑娟娟 今年,人工智能(AI) 60岁了。在AI60岁的时候,笔者想要介绍一下AI100,一个刚刚2岁的研究项目,但它的预设寿命是100年,甚至更长...

AlphaGo与李世石的人机大战,为大众迅速普及了人工智能的概念。 但对谷歌而言,除了下围棋,现在的人工智能进展到哪一步了?未来,人工智能...