[Android]BaseAdapter-ListView实现

1. MainActivity.java

public class MainActivity extends Activity {
//声明UI组件和资源变量等
private ListView lv2;
private MyListViewAdapter listViewAdapter;;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//基于BaseAdapter
//setContentView(R.layout.gallery);
//setGalleryView();
//基于ListView、GridView及Spinner和BaseAdapter实现
setContentView(R.layout.main);
setLGSView();
}

private void setLGSView() {
lv2 = (ListView)findViewById(R.id.listview2);
listViewAdapter = new MyListViewAdapter(this);
lv2.setAdapter(listViewAdapter);
}

2. MyListViewAdapter.java

package home.lee.listviewadapterdemo;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyListViewAdapter extends BaseAdapter {

private Context context;//为myInflater而采用context
private LayoutInflater myInflater;

public MyListViewAdapter(Context context) {
super();
this.context = context;
}

@Override
public int getCount() {//用来说明需要绘制的条目数
return 8;//数组的长度，即个数，可以根据实际调整
}

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

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {//用来说明需要绘制的条目数个条目就调用一次这个方法
ViewHolder holder = new ViewHolder();
if (convertView == null)
{
/**
* 这个方法getView()，是用来逐一绘制每一条item
*
* setTag()会把View与ViewHolder绑定，形成一一对应的关系，拖动listview的时候会重新绘制每一条item
* 但是那些已经取得绑定的View，会调用getTag()方法，就不会重新绘制，而是拿到内存中已经取得的资源，提高了效率
*
* @param position position就是位置从0开始
* @param convertView convertView是Spinner,ListView中每一项要显示的view
* @param parent parent就是父窗体了，也就是Spinner,ListView,GridView了
* @return 通常return 的view也就是convertView
*
* 在程序中动态加载以上布局:
* LayoutInflater flater = LayoutInflater.from(this);
* View view = flater.inflate(R.layout.example, null);
*/
myInflater = LayoutInflater.from(context);
convertView = myInflater.inflate(R.layout.item_list, null);

holder.icon = (ImageView)convertView.findViewById(R.id.itemimageview2);
holder.text = (TextView)convertView.findViewById(R.id.itemtextview2);

convertView.setTag(holder);
}
else
{
holder = (ViewHolder) convertView.getTag();
}

if (position <= 1)
{
holder.icon.setImageResource(android.R.drawable.btn_dropdown);
holder.text.setText("你好");
}
else if (position <= 3 && position >= 2)
{
holder.icon.setImageResource(android.R.drawable.edit_text);
holder.text.setText("Hello");
}
else
{
holder.icon.setImageResource(android.R.drawable.spinner_dropdown_background);
holder.text.setText("안녕하세요");
}
return convertView;
}

private class ViewHolder
{
TextView text;
ImageView icon;
}

}

 

3. main.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:id="@+id/linearlayout2"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="ListView" />
<ListView
android:id="@+id/listview2"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</ListView>
</LinearLayout>

4. item_list.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:orientation="horizontal" >
<TextView
android:id="@+id/itemtextview2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text=""
android:layout_weight="1"/>
<ImageView
android:id="@+id/itemimageview2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:contentDescription="@string/app_name"
android:src="@drawable/ic_launcher"
android:layout_weight="10"/>
</LinearLayout>

运行结果：

其改进应用可参考： GridView及SpinnerView