第八十五讲：GridView和ActivityGroup实现的Tab分页

逆境是成长必经的过程，能勇于接受逆境的人，生命就会日渐的茁壮。

本讲内容：GridView和ActivityGroup实现的Tab分页

一、ActivityGroup相关--getLocalActivityManager() 以及intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)用法

1、ActivityGroup中可以调用getLocalActivityManager（）方法获取LocalActityManager来管理Activity。

2、LocalActivityManager通过startActivity(String
id, Intent intent)方法,可以与指定的Actiivty绑定，并且返回一个Window。LocalActivityManager可以同时管理多个Activity

3、Window可以通过getDecorView()方法，返回一个View,然后通过与指定容器的addView(View)方法,实现不同的效果

intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)如果在当前任务中，有要启动的Activity，那么把该Acitivity之前的所有Activity都关掉，并把此Activity置前以避免创建Activity的实例

示例一效果图：

下面是res/layout/activity_main.xml 布局文件：

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

    <!-- 动态显示界面 -->
    <LinearLayout
        android:id="@+id/body"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_above="@+id/gridView"
        android:layout_alignParentTop="true"
        android:orientation="vertical" >
    </LinearLayout>

    <!-- 底部功能菜单栏 -->
    <GridView
        android:id="@+id/gridView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:background="@drawable/navigationbardown"
        android:cacheColorHint="#00000000"
        android:gravity="center"
        android:listSelector="@android:color/transparent"
        android:verticalSpacing="0dp" />

</RelativeLayout>

技巧 ：制作背景色：用PS 画条黑线（navigationbardown.png）
即为黑色了

下面是ImageAdaper.java文件：

public class ImageAdapter extends BaseAdapter{
	//普通图片数组
	private int[] imgs={R.drawable.home, R.drawable.addrbook, R.drawable.longnormal};
	//高亮图片数组
        protected int[] imgsLight={R.drawable.home1, R.drawable.addrbook1, R.drawable.longhightlight};;

	private int selectItem;
	private Context context;  

	//图片适配器，里面有一个设置高亮的方法比较重要
	protected void setImageLih(int selectItem) {
		this.selectItem=selectItem;
		//界面刷新
		notifyDataSetChanged();
	}

	public ImageAdapter(Context context) {
		this.context = context;
	}

	@Override
	public int getCount() {
		return imgs.length;
	}

	@Override
	public Object getItem(int position) {
		return imgs[position];
	}

	@Override
	public long getItemId(int position) {
		return position;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		if(convertView==null){//产生ImageView 对象
			convertView = new ImageView(context);
		}
		if(position==selectItem){
			convertView.setBackgroundResource(imgsLight[position]);
		}else{
			convertView.setBackgroundResource(imgs[position]);
		}
		return convertView;
	}

}

下面是MainActivity.java主界面文件：

public class MainActivity extends ActivityGroup {
	// Tab标签
	private GridView gridView;
	// GridView 适配器
	private ImageAdapter adapter;

	// 装载Activity的容器
	private LinearLayout layout;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initUI();
	}

	private void initUI() {
		adapter = new ImageAdapter(this);
		layout = (LinearLayout) findViewById(R.id.body);
		gridView = (GridView) findViewById(R.id.gridView);
		// 因为我们显示一行，列数等于数组的长度
		gridView.setNumColumns(adapter.getCount());
		gridView.setAdapter(adapter);
		startActivity(0);
		gridView.setOnItemClickListener(new OnItemClickListener() {
			@Override
			public void onItemClick(AdapterView<?> Parent, View view,
					int position, long id) {
				// 点击设置高亮显示
				adapter.setImageLih(position);
				startActivity(position);
			}
		});

	}

	// 根据position跳转到不同的Activity
	private void startActivity(int position) {
		// 先清除容器里面的View
		layout.removeAllViews();
		Intent intent = null;
		if (position == 0) {
			intent = new Intent(MainActivity.this, OneView.class);
		} else if (position == 1) {
			intent = new Intent(MainActivity.this, TwoView.class);
		} else if (position == 2) {
			intent = new Intent(MainActivity.this, ThreeView.class);
		}
		intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);

		// 将Activity转换成View
		View view = getLocalActivityManager().startActivity("intent", intent)
				.getDecorView();
		LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
				LinearLayout.LayoutParams.MATCH_PARENT,
				LinearLayout.LayoutParams.MATCH_PARENT);
		// 将Activity转换成的View添加到容器
		layout.addView(view, layoutParams);
	}

}

使用view的removeAllViews()方法清除不需要的view，使用addView(View
v)方法添加需要的view。

下面是OneView.java界面文件：

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

下面是TwoView.java界面文件：

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

下面是ThreeView.java界面文件：

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

Take your time and enjoy it