Android BaseAdapter

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BaseAdapter是Android应用程序中经常用到的基础数据适配器，其主要用途为将一组数据传递到ListView，Spinner，GridView等UI组件。BaseAdapter对于前面提到的三个UI组件来说是万能的，ListView、Spinner、GridView各自都有自己的适配器，但是BaseAdapter对于它们是通用的。比如我们经常使用的ListView的SimpleAdapter是继承自BaseAdapter的。

下面就来看一看BaseAdapter的用法：
使用BaseAdapter时，我们常写一个类来继承它。因为BaseAdapter是一个抽象类，所以要在类中实现它的方法。

public class MyAdapter extends BaseAdapter{        private Context context;        private List<String> listBase;        public MyAdapter(Context context,ArrayList<String> listBase){            this.context = context;            this.listBase = listBase;        }        @Override        public int getCount() {            return listBase.size();        }        @Override        public Object getItem(int i) {            return listBase.get(i);        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(int i, View view, ViewGroup viewGroup) {            ViewHolder viewHolder;            if (view == null){                view = View.inflate(context,R.layout.list_item_view,null);                viewHolder = new ViewHolder();                viewHolder.textView = (TextView) view.findViewById(R.id.textView1);                view.setTag(viewHolder);            }else {                viewHolder = (ViewHolder) view.getTag();            }            viewHolder.textView.setText(listBase.get(i));            return view;        }        public class ViewHolder{            public TextView textView;        }    }

子项布局文件：
list_item_view.xml

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical" android:layout_width="match_parent"    android:layout_height="match_parent">    <LinearLayout        android:orientation="horizontal"        android:layout_width="match_parent"        android:layout_height="wrap_content">        <TextView            android:id="@+id/textView1"            android:layout_width="wrap_content"            android:layout_height="wrap_content" />    </LinearLayout></LinearLayout>

下面是整体代码：
MainActivity.java

public class MainActivity extends Activity {    ListView listView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        listView = (ListView) findViewById(R.id.list_view);        List<String> listData = new ArrayList<String>();        for (int i =0;i<100;i++){            listData.add("Item"+i);        }        listView.setAdapter(new MyAdapter(this, (ArrayList<String>) listData));    }    public class MyAdapter extends BaseAdapter{        private Context context;        private List<String> listBase;        public MyAdapter(Context context,ArrayList<String> listBase){            this.context = context;            this.listBase = listBase;        }        @Override        public int getCount() {            return listBase.size();        }        @Override        public Object getItem(int i) {            return listBase.get(i);        }        @Override        public long getItemId(int i) {            return i;        }        @Override        public View getView(int i, View view, ViewGroup viewGroup) {            ViewHolder viewHolder;            if (view == null){                view = View.inflate(context,R.layout.list_item_view,null);                viewHolder = new ViewHolder();                viewHolder.textView = (TextView) view.findViewById(R.id.textView1);                view.setTag(viewHolder);            }else {                viewHolder = (ViewHolder) view.getTag();            }            viewHolder.textView.setText(listBase.get(i));            return view;        }        public class ViewHolder{            public TextView textView;        }    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.menu_main, menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        //noinspection SimplifiableIfStatement        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }}

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