参考自Google官方文档Traning/Getting Started/Building a simple user interface, Startinganother activity，http://developer.android.com/training/basics/firstapp/building-ui.html

1、创建主Activity

使用Eclipse新建项目MyFirstApp,UI布局如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:paddingBottom="@dimen/activity_vertical_margin"android:paddingLeft="@dimen/activity_horizontal_margin"android:paddingRight="@dimen/activity_horizontal_margin"android:paddingTop="@dimen/activity_vertical_margin"android:orientation="horizontal"tools:context=".MainActivity"><EditTextandroid:id="@+id/et_message"android:layout_height="wrap_content"android:layout_width="0dp"android:layout_weight="1"android:hint="@string/input_here"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@string/click"android:onClick="sendMessage"/></LinearLayout>

注意通过权重来分配尺寸的方式

组件1：

android:layout_width="0dp"
android:layout_weight="1"

组件2：

android:layout_width="wrap_content"

2、在主类中指定onclick所对应的sendMessage方法

package com.lujinhong.androidtraningmyfirstapp;import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;public class MainActivity extends Activity{public final static String EXTRA_MESSAGE="com.lujinhong.myfirstapp.MESSAGE";@Overrideprotected void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);}@Overridepublic boolean onCreateOptionsMenu(Menu menu){// Inflate themenu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}public void sendMessage(View v){EditText et_message=(EditText)this.findViewById(R.id.et_message);String message= et_message.getText().toString().trim();Intent intent= new Intent(this,DisplayMessageActivity.class);intent.putExtra(EXTRA_MESSAGE, message);this.startActivity(intent);}}

（1）关于intent

An Intent isan object that provides runtime binding between separate components (such astwo activities). TheIntent representsan app’s "intent to do something." You can use intents for a widevariety of tasks, but most often they’re used to startanother activity.

（2）调用另一个activity的步骤：

l  首先取得editText中的文字

EditText et_message = (EditText) this.findViewById(R.id.et_message);
String message = et_message.getText().toString().trim();

l  然后创建一下intent，并把文字作为K-V形式保存到intent中

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

创建intent时，通过一个类名，指定调用哪个类文件。

l  最后启动一个新的activity.

this.startActivity(intent);

3、显示另一个Activity

package com.lujinhong.androidtraningmyfirstapp;import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.widget.TextView;public class DisplayMessageActivityextends Activity{@Overrideprotected void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_display_message);// Get the messagefrom the intentIntent intent= getIntent();String message= intent.getStringExtra(MainActivity.EXTRA_MESSAGE);// Create the textviewTextView textView=new TextView(this);textView.setTextSize(40);textView.setText(message);// Set the textview as the activity layoutsetContentView(textView);}@Overridepublic boolean onCreateOptionsMenu(Menu menu){// Inflate themenu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.display_message, menu);return true;}}