MyBaseAdapter

最新推荐文章于 2022-06-07 21:38:57 发布

shenshencode

最新推荐文章于 2022-06-07 21:38:57 发布

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分类专栏：学习源码文章标签： android BaseAdapter

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本文介绍如何在Android应用中使用ListView展示动态加载的数据，并通过自定义BaseAdapter实现高效的数据绑定，包括创建主布局与item布局文件。

MainActivity

public class MainActivity extends Activity {

	private List<ItemBean> mListData;
	private ListView mListView;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		//准备数据源
		mListData = new ArrayList<ItemBean>();
		for (int i = 0; i < 20; i++) {
			mListData.add(new ItemBean(R.drawable.ic_launcher, "标题"+i, "我是一个内容文字"+i));
		}
		
		//准备适配器
		MyAdapter adapter = new MyAdapter(MainActivity.this, mListData);
		
		//找到控件并绑定适配器
		mListView = (ListView) findViewById(R.id.listview);
		mListView.setAdapter(adapter);
	}
}

两个Xml，一个是主布局，一个是item布局

主布局

<LinearLayout 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"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

item布局

<?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"
    android:padding="8dp"
 >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="12dp"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/imageView1"
        android:layout_toRightOf="@+id/imageView1"
        android:text="Large Text"
        android:layout_marginLeft="12dp"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/imageView1"
        android:layout_toRightOf="@+id/imageView1"
        android:layout_marginLeft="12dp"
        android:text="TextView" />

</RelativeLayout>

自定义一个BaseAdapter

public class MyAdapter extends BaseAdapter {

	private List<ItemBean> mLists;
	private LayoutInflater mInflater;

	public MyAdapter(Context context, List<ItemBean> lists) {
		this.mLists = lists;
		mInflater = LayoutInflater.from(context);
	}

	@Override
	public int getCount() {
		// TODO 自动生成的方法存根
		return mLists.size();
	}

	@Override
	public Object getItem(int position) {
		// TODO 自动生成的方法存根
		return mLists.get(position);
	}

	@Override
	public long getItemId(int position) {
		// TODO 自动生成的方法存根
		return position;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		/*
		 * 方法1 没做缓存处理 View view = mInflater.inflate(R.layout.item, null);
		 * ImageView imageView = (ImageView) view.findViewById(R.id.imageView1);
		 * TextView title = (TextView) view.findViewById(R.id.textView1);
		 * TextView content = (TextView) view.findViewById(R.id.textView2);
		 * 
		 * ItemBean bean = mLists.get(position);
		 * imageView.setImageResource(bean.getImageicon());
		 * title.setText(bean.getTitle()); content.setText(bean.getContent());
		 * return view;
		 */
		/*
		 * 方法1 有缓存但是每次都要findViewById还是浪费了资源 if (convertView == null) {
		 * convertView = mInflater.inflate(R.layout.item, null); } ImageView
		 * imageView = (ImageView) convertView.findViewById(R.id.imageView1);
		 * TextView title = (TextView) convertView.findViewById(R.id.textView1);
		 * TextView content = (TextView)
		 * convertView.findViewById(R.id.textView2);
		 * 
		 * ItemBean bean = mLists.get(position);
		 * imageView.setImageResource(bean.getImageicon());
		 * title.setText(bean.getTitle()); content.setText(bean.getContent());
		 * return convertView;
		 */
		ViewHolder viewHolder;
		if (convertView == null) {
			viewHolder = new ViewHolder();
			convertView = mInflater.inflate(R.layout.item, null);
			viewHolder.imageView = (ImageView) convertView
					.findViewById(R.id.imageView1);
			viewHolder.title = (TextView) convertView
					.findViewById(R.id.textView1);
			viewHolder.content = (TextView) convertView
					.findViewById(R.id.textView2);
			convertView.setTag(viewHolder);
		}else{
			viewHolder = (ViewHolder) convertView.getTag();
		}
		ItemBean bean = mLists.get(position);
		viewHolder.imageView.setImageResource(bean.getImageicon());
		viewHolder.title.setText(bean.getTitle());
		viewHolder.content.setText(bean.getContent());
		return convertView;
	}

	class ViewHolder {
		public ImageView imageView;
		public TextView title;
		public TextView content;
	}
}