在實際開發(fā)項目中,本實例經(jīng)常被用到,GridView的最后項顯示一個增加圖片的按鈕,點擊該按鈕可以動態(tài)增加Item。
1.main.xml:
<RelativeLayout 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" >
<GridView
android:id="@+id/gv_test"
android:numColumns="3"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</RelativeLayout>
布局文件很簡單,在相對布局中引入了一個gridview控件,numColumns屬性指定了一行顯示3項。
2.grid_item.xml:
<?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" >
<ImageView
android:id="@+id/item"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
gridview的子布局就一個imageview控件,用于顯示圖片。
3.GridViewAdapter.java:
package com.yayun.gridviewdemo;
//省略導(dǎo)入
public class GridViewAdapter extends BaseAdapter {
private Context context;
private List<Integer> list;
LayoutInflater layoutInflater;
private ImageView mImageView;
public GridViewAdapter(Context context, List<Integer> list) {
this.context = context;
this.list = list;
layoutInflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
return list.size()+1;//注意此處
}
@Override
public Object getItem(int position) {
return list.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
convertView = layoutInflater.inflate(R.layout.grid_item, null);
mImageView = (ImageView) convertView.findViewById(R.id.item);
if (position < list.size()) {
mImageView.setBackgroundResource(list.get(position));
}else{
mImageView.setBackgroundResource(R.drawable.pic3);//最后一個顯示加號圖片
}
return convertView;
}
}
創(chuàng)建適配器類,繼承自BaseAdapter適配器,適配器類構(gòu)造方法傳入上下文對象context和數(shù)據(jù)集合List。要注意的地方,getCount方法返回的數(shù)量要加1,這個就是存放“+”的地方。在getView方法中,進(jìn)行判斷,最后一個位置設(shè)置加號圖片。
4.MainActivity.java:
package com.yayun.gridviewdemo;
//省略導(dǎo)入的包
public class MainActivity extends ActionBarActivity {
private List<Integer> mDatas;
private GridView mGridView;
private GridViewAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mGridView=(GridView) findViewById(R.id.gv_test);
initDatas(); //初始化數(shù)據(jù)
adapter=new GridViewAdapter(MainActivity.this,mDatas);
mGridView.setAdapter(adapter);
mGridView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
if(position==parent.getChildCount()-1){
mDatas.add(R.drawable.pic1);
Toast.makeText(MainActivity.this, "您點擊了添加", 1).show();
adapter=new GridViewAdapter(MainActivity.this, mDatas);
mGridView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
}
});
}
private void initDatas() {
mDatas=new ArrayList<>();
mDatas.add(R.drawable.pic1);
mDatas.add(R.drawable.pic1);
mDatas.add(R.drawable.pic1);
mDatas.add(R.drawable.pic1);
mDatas.add(R.drawable.pic1);
}
}
設(shè)置了GridView的setOnItemClickListener監(jiān)聽事件,由條件:position==parent.getChildCount()-1判斷是否點擊了最后一個帶有加號圖片的項目,若單擊了則重新生成一項加入到mDatas中去,并調(diào)用notifyDataSetChanged方法重繪GridView控件。
運行項目:
點擊最后一個+圖片,可以動態(tài)增加item。