android显示意图激活另一个Activity的方法

package com.yy.twoactivity;

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

public class MainActivity extends Activity {

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
  
  /**
   * 点击事件，当用户点击的时候跳转到第二个界面
   * @param view
   */
  public void click(View view){
    //意图
    Intent intent=new Intent();
    //设置包和界面
    intent.setClassName(this, "com.yy.twoactivity.SecondActivity");
    //跳转到新的设定好的界面
    startActivity(intent);
  }
  
  /**
   * 点击事件，激活系统的应用 程序界面
   * @param view
   */
  public void click2(View view){
    //意图
    Intent intent=new Intent();
    //设置预打开系统应用的包和界面
    // cmp=com.android.gallery/com.android.camera.GalleryPicker 
    intent.setClassName("com.android.gallery", "com.android.camera.GalleryPicker");
    //跳转到新的设定好的界面
    startActivity(intent);
  }
}

package com.yy.twoactivity;

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

public class SecondActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity2);
  }
}

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

        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
    <activity
      android:name=".SecondActivity"
      android:label="@string/app_second_name" >
    </activity>
  </application>