[Android学习系列13]关于Gridview的一些事

用mvc的思想去理解 数据源，adapter，xxxView的关系，写代码就轻松多了

先写一个简单的gridview

第一版:只有图片

xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:paddingTop="10dp"
    tools:context=".ActivityMain" >

    <GridView
        android:id="@+id/gridView1"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:numColumns="3"
        android:columnWidth="90dp"
        android:horizontalSpacing="10dp"
        android:verticalSpacing="10dp"
        android:stretchMode="spacingWidth"
         >
    </GridView>

</LinearLayout>

java代码

public class ActivityMain extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        
        GridView gridView = (GridView)findViewById(R.id.gridView1);
        gridView.setAdapter( new MyGridviewAdapter(this) );
        
        
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    
    
    
    class MyGridviewAdapter extends BaseAdapter {
        
        Context context;  //传入ActivityMain给adapter，创建imageview的时候要用到
        
        //做一个数组存图表的id
        int []imagesId = {R.drawable.icon1,R.drawable.icon2,R.drawable.icon3,
                          R.drawable.icon4,R.drawable.icon5,R.drawable.icon6,
                          R.drawable.icon7,R.drawable.icon8,R.drawable.icon9};
        
        MyGridviewAdapter(Context con) {
            this.context = con;
        }
        
        @Override
        public int getCount() {
            return imagesId.length;
        }

        @Override
        public Object getItem(int arg0) {
            return arg0;
        }

        @Override
        public long getItemId(int arg0) {
            return arg0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            //这里重头戏，既然要getview，就返回一个图标的imageview给它
            
            ImageView imgview = new ImageView(context);
            imgview.setImageResource( imagesId[position] );
            
            return imgview; 
            
            
        }

        
    }
    
    

}

第二版:只有图片

上面的有点问题，看其他人的代码，会对convertView做一个null判断，避免重复创建，节约资源

改进

修改getview方法:

        public View getView(int position, View convertView, ViewGroup parent) {
            //这里重头戏，既然要getview，就返回一个图标的imageview给它
            
            //ImageView imgview = new ImageView(context);
            //imgview.setImageResource( imagesId[position] );
            
            ImageView imgview;
            if( convertView == null )
            {
                imgview = new ImageView(context);
                imgview.setImageResource( imagesId[position] );
            }
            else
            {
                imgview = (ImageView)convertView;
            }
            
            
            return imgview; 
            
            
        }

 长这样:

第三版:  图片 + 文字

首先自定义一个grid_one_item.xml，里面混和了图片和文字

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
    
    <ImageView 
        android:id="@+id/grid_item_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    
    <TextView 
        android:id="@+id/grid_item_text"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"/>
    

</LinearLayout>

java代码 重点理解适配器部分

public class ActivityMain extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        
        GridView gridView = (GridView)findViewById(R.id.gridView1);
        gridView.setAdapter( new MyGridviewAdapter(this) );
        
        
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    
    
    //拥有textview的string内容  和imageview的资源id
    class IconInfo {
        String text;
        int imageid;
    }
    
    //一个混合了textview和imageview的类
    class MixedView {
        ImageView imgview;
        TextView textview;
    }
    
    
    class MyGridviewAdapter extends BaseAdapter {
        
        Context context;  //传入ActivityMain给adapter，创建view的时候要用到
        LayoutInflater inflater;  
        List<IconInfo> iconInfoList;
        
        
        //做一个数组存图表的id
        int []imagesId = {R.drawable.icon1,R.drawable.icon2,R.drawable.icon3,
                          R.drawable.icon4,R.drawable.icon5,R.drawable.icon6,
                          R.drawable.icon7,R.drawable.icon8,R.drawable.icon9};
        String []titles = {"标题1","标题2","标题3","标题4","标题5","标题6","标题7","标题8","标题9"};
        
        
        MyGridviewAdapter(Context con) {
            
            this.context = con;
            inflater = LayoutInflater.from(context);
            
            iconInfoList = new ArrayList<IconInfo>();
            for(int i=0; i<imagesId.length; i++)
            {
                IconInfo iconInfo = new IconInfo();
                iconInfo.imageid = imagesId[i];
                iconInfo.text = titles[i];
                iconInfoList.add(iconInfo);
            }
            
        }
        
        @Override
        public int getCount() {
            return imagesId.length;
        }

        @Override
        public Object getItem(int arg0) {
            return arg0;
        }

        @Override
        public long getItemId(int arg0) {
            return arg0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            MixedView mixedView;
            //用setTag() getTag()  来节约findViewById所消耗的性能  
            if( convertView == null )
            {
                convertView = inflater.inflate(R.layout.grid_one_item, null);
                mixedView = new MixedView();
                mixedView.imgview  = (ImageView)convertView.findViewById(R.id.grid_item_image);
                mixedView.textview = (TextView)convertView.findViewById(R.id.grid_item_text); 
                convertView.setTag(mixedView);
            }
            else
            {
                mixedView = (MixedView)convertView.getTag();
            }
            
            mixedView.imgview.setImageResource( iconInfoList.get(position).imageid );
            mixedView.textview.setText( iconInfoList.get(position).text );
            
            return convertView; 
            
            
        }

        
    }
    
    

}

个人粗俗地理解这两句(错了求指正):

convertView.setTag(mixedView);  //  为convertView设定一个   指向mixedView的引用

mixedView= (MixedView) convertView.getTag();  //  把convertView所引用的对象赋给mixedView，  也就是说，convertView和mixedView引用的是同一个内存里的东西

//所以getview时  我们做处理的是mixedView，还可以返回convertView，因为他们引用的是同一个东西啊

 最后长这样：

android:stretchMode 参考下图

更多参考:

http://liangruijun.blog.51cto.com/3061169/647355

http://www.cnblogs.com/topcoderliu/archive/2011/06/07/2074419.html