自己实现ArrayAdapter

今天看了下Android 的ArrayAdapter源代码，它继承了BaseAdapter，代码加上注释有500多行。

于是，我精简了下，自己写个了最简单的供大家理解。

 public class MyArrayAdapter<T> extends BaseAdapter  {
    private List<T> mObjects;
    private int mResource;
    private LayoutInflater mInflater;

    public MyArrayAdapter(Context context, int layoutId, List<T> objects) {
        mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        mResource = layoutId;
        mObjects = objects;
    }

    @Override
    public int getCount() {
        return mObjects.size();
    }

    @Override
    public T getItem(int position) {
        return mObjects.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
         View view;
         TextView text;

         if (convertView == null) {
             view = mInflater.inflate(mResource, null);
         } else {
             view = convertView;
         }
         text = (TextView) view;
         T item = getItem(position);
         if (item instanceof CharSequence) {
             text.setText((CharSequence)item);
         } else {
             text.setText(item.toString());
         }
         return view;
    }
}

布局文件可以直接用android系统自带的android.R.layout.simple_list_item_1，里面只有一个TextView。

为了方便理解，我们还是自己动手写一个吧！

<?xml version="1.0" encoding="utf-8"?>

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textSize="24sp"
/>

然后我们的main.xml,内容如下

<?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" >
    <ListView 
        android:id="@+id/listview"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        />
</LinearLayout>

最后，Activity

    private ListView listview;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        listview = (ListView)findViewById(R.id.listview);
        ArrayList<String> data = new ArrayList<String>();
        data.add("hello");
        data.add("bupt");
        
        MyArrayAdapter<String> adapter = new MyArrayAdapter<String>(this, 
                R.layout.item, data);
        listview.setAdapter(adapter);
    }

真实的ArrayAdapter比这复杂多了，大家可以自己查看下源代码。