Android 显示意图激活另外一个Actitity

package com.wuyudong.twoactivity;

import android.app.Activity;
import android.os.Bundle;

//activity是系统的重要组件
//OS要想找到activity 就必须在清单文件中配置
public class OtherScreenActivity extends Activity {
    
    //重写activity的onCreate方法 方法里面设置初始化程序的界面
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_two);
    }

}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button" />

    <ProgressBar
        android:id="@+id/progressBar1"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

package com.wuyudong.twoactivity;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    
    //当用户点击按钮的时候跳转到第二个页面
    public void click(View view) {
        Intent intent = new Intent();
        intent.setClassName(this, "com.wuyudong.twoactivity.OtherScreenActivity");
        startActivity(intent);
    }
}

    //当用户点击按钮的时候跳转到第二个页面
    public void click(View view) {
        //Intent intent = new Intent();
        //intent.setClassName(this, "com.wuyudong.twoactivity.OtherScreenActivity");
        Intent intent = new Intent(this, OtherScreenActivity.class);
        startActivity(intent);
    }

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.wuyudong.twoactivity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:icon="@drawable/icon1"
            android:name="com.wuyudong.twoactivity.MainActivity"
            android:label="@string/activity01" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
         <activity
             android:icon="@drawable/icon2"
            android:name="com.wuyudong.twoactivity.OtherScreenActivity"
            android:label="@string/activity02" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<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:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="我是第一个界面" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="click"
        android:text="跳转到第二个界面" />

</LinearLayout>

    
    //当用户点击按钮的时候激活图库的应用
    //com.android.gallery/com.android.camera.GalleryPicker
    public void click2(View view) {
         Intent intent = new Intent();
         intent.setClassName("com.android.gallery", "com.android.camera.GalleryPicker");
         startActivity(intent);
     }

package com.wuyudong.testnetwork;

import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.widget.Toast;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // 检查用户的网络情况
        ConnectivityManager cm = (ConnectivityManager) this
                .getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = cm.getActiveNetworkInfo();

        if (info != null && info.isConnected()) {
            Toast.makeText(this, "网络可用", 0).show();
        } else {
            Toast.makeText(this, "网络不可用", 0).show();
            //定向用户到系统网络的界面
            Intent intent = new Intent();
            //07-11 15:11:47.488: I/ActivityManager(859): 
            //Starting: Intent { act=android.intent.action.MAIN cmp=com.android.settings/.WirelessSettings } from pid 1293
            intent.setClassName("com.android.settings", "com.android.settings.WirelessSettings");
            startActivity(intent);
        }

    }

}