转载：ActivityGroup 实现TabHost

转载：ActivityGroup 实现TabHost

原文地址：[url]http://blog.youkuaiyun.com/hellogv/article/details/6057174[/url]


很多客户端软件和浏览器软件都喜欢用Tab分页标签来搭建界面框架。读者也许会马上想到使用TabHost 与 TabActivity的组合，其实最常用的不是它们，而是由GridView与ActivityGroup的组合。每当用户在GridView选中一项，ActivityGroup就把该项对应的Activity的Window作为View添加到ActivityGroup所指定的容器(LinearLayout)中。

效果图：

[img]http://dl.iteye.com/upload/attachment/0066/6395/c56cc54f-346d-3e73-b0e5-cf25f7051a94.jpg[/img]


ImageAdapter是本实例的关键之一，它继承于BaseAdapter，并加入一些自定义的方法。ImageAdapter的源码如下：

package org.hwq.activitygroup.main;

import android.content.Context;
import android.graphics.Color;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.GridView;
import android.widget.ImageView;

public class ImageAdapter extends BaseAdapter {
	private Context context;
	private ImageView[] img;

	ImageAdapter(Context context,int weight,int height,int[] img){
		this.context = context;
		this.img = new ImageView[img.length];
		for(int i=0;i<img.length;i++){
			this.img[i] = new ImageView(context);
			this.img[i].setLayoutParams(new GridView.LayoutParams(weight,height));
			this.img[i].setAdjustViewBounds(false);
			this.img[i].setPadding(2, 2, 2, 2);
			this.img[i].setImageResource(img[i]);
		}
	}

	public void focus(int id){
		for(int i=0;i<img.length;i++){
			if(i == id){
				img[i].setBackgroundColor(Color.YELLOW);
			}else{
				img[i].setBackgroundColor(Color.TRANSPARENT);
			}
		}
	}

	public int getCount() {
		return img.length;
	}

	public Object getItem(int position) {
		return position;
	}

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

	public View getView(int position, View convertView, ViewGroup parent) {
		ImageView imageview;
		if(convertView == null){
			imageview = img[position];
		}else{
			imageview = (ImageView) convertView;
		}
		return imageview;
	}

}

SetFocus(int)这个方法是个关键点，即实现选中的效果。例如有ABCD4个Item，其中C被选中了，那么除C以外的Item都被设置为未被选中的样式，而C则设置为选中的样式。

接下来就开始写主Activity，主Activity包含GridView控件，有2点是需要注意一下的。

SetNumColumns()：必须要使用setNumColumns来设置列数，因为这个GridView只有一行，即所有的Item都在同一行，Item数量即为列数。
setSelector(new ColorDrawable(Color.TRANSPARENT))：把系统默认选中的背景色透明化，因为我们已经在BaseAdapter中加入了SetFocus()来改变选中的样式。
ActivityGroupActivity.java

package org.hwq.activitygroup.main;

import android.app.ActivityGroup;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.GridView;
import android.widget.LinearLayout;

public class ActivityGroupActivity extends ActivityGroup {
	private GridView gridview;
	private LinearLayout layout;
	private int[] img;
	private ImageAdapter adapter;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        img = new int[]{R.drawable.img1,R.drawable.img2,R.drawable.img3,R.drawable.img4};
        gridview = (GridView) findViewById(R.id.gridView1);
        layout = (LinearLayout) findViewById(R.id.linearlayout);
        gridview.setNumColumns(img.length);
        gridview.setSelector(new ColorDrawable(Color.TRANSPARENT));
        gridview.setGravity(Gravity.CENTER);
        gridview.setVerticalSpacing(0);
        int weight = getWindowManager().getDefaultDisplay().getWidth()/img.length;
        adapter = new ImageAdapter(this,weight,48,img);
        switchActivity(0);
        gridview.setAdapter(adapter);
        gridview.setOnItemClickListener(new GridviewItemListener());
    }
    class GridviewItemListener implements GridView.OnItemClickListener{
		public void onItemClick(AdapterView<?> parent, View view, int position,
				long id) {
			switchActivity(position);
		}
    }
    public void switchActivity(int id){
    	adapter.focus(id);
    	layout.removeAllViews();
    	Intent intent = null;
    	if(id == 0){
    		intent = new Intent(this,ActivityA.class);
    	}else if(id == 1){
    		intent = new Intent(this,ActivityB.class);
    	}else if(id == 2){
    		intent = new Intent(this,ActivityC.class);
    	}else if(id == 3){
    		intent = new Intent(this,ActivityD.class);
    	}
    	intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    	Window group = getLocalActivityManager().startActivity("", intent);
    	layout.addView(group.getDecorView(),LayoutParams.FILL_PARENT,LayoutParams.FILL_PARENT);
    }
}

main.xml

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

    <GridView
        android:id="@+id/gridView1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:numColumns="3" >
    </GridView>
    <LinearLayout
        android:id="@+id/linearlayout"
        android:layout_width="fill_parent"
        android:layout_height="match_parent"
        >
	</LinearLayout>
</LinearLayout>

demo源码：