Android_自定义适配器

目录

一、自定义Adapter

二、在布局文件中添加ListView标签

三、编写行布局文件

四、在Activity中编写代码

五、ListView Item点击长按事件

六、ListView 优化

七、页面跳转传值

一、在java/com.ryan.test下创建MyAdapter类，继承类BaseAdapter类

public class MyAdapter extends BaseAdapter{

    //数据集合
    List<Map<String,Object>> list;
    //反射器
    LayoutInflater inflater;

    //构造器
    public MyAdapter(Context context) {
        this.inflater = LayoutInflater.from(context);
    }

    public void setList(List<Map<String, Object>> list) {
        this.list = list;
    }

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

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

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


    //实现getView方法
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        //反射行布局
        View view = inflater.inflate(R.layout.item,null);

        //获取各个控件
        ImageView logo = (ImageView) convertView.findViewById(R.id.logo);
        TextView title = (TextView) convertView.findViewById(R.id.title);
        TextView version = (TextView) convertView.findViewById(R.id.version);
        TextView size = (TextView) convertView.findViewById(R.id.size);

        //给控件赋值
        Map map = list.get(position);
        logo.setImageResource((Integer) map.get("logo"));
        title.setText((String) map.get("title"));
        version.setText((String) map.get("version"));
        size.setText((String) map.get("size"));

        return view;
    }
}

 

二、在布局文件中添加ListView标签(main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.ryan.test.MainActivity">

    <ListView
        android:listSelector="@drawable/item_selector"
        android:id="@+id/list_main"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

注：用Selector背景选择器实现Item项选中后的背景颜色改变

res/drawable下item_selector.xml文件设置选中和未选中的颜色 透明色为#00000000

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@color/transparent" android:state_pressed="false"/>
    <item android:drawable="@color/choose" android:state_pressed="true"/>
</selector>

 

 

三、编写行布局文件(item.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:descendantFocusability="blocksDescendants"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:padding="5dp"
        android:layout_margin="5dp"
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_vertical">
        <ImageView
            android:id="@+id/logo"
            android:layout_width="70dp"
            android:layout_height="70dp"
            android:src="@drawable/danger"
            />
        <LinearLayout
            android:layout_weight="1"
            android:orientation="vertical"
            android:layout_marginLeft="5dp"
            android:padding="5dp"
            android:layout_width="0dp"
            android:layout_height="wrap_content">
            <TextView
                android:id="@+id/title"
                android:layout_marginTop="3dp"
                android:textSize="18sp"
                android:text="危险品"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
            <TextView
                android:id="@+id/version"
                android:layout_marginTop="3dp"
                android:textSize="12sp"
                android:text="版本：1.0"
                android:textColor="#999"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
            <TextView
                android:id="@+id/size"
                android:layout_marginTop="3dp"
                android:textSize="12sp"
                android:text="占用空间：20M"
                android:textColor="#999"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>
            <Button
            android:text="卸载"
            android:layout_width="100dp"
            android:layout_height="50dp"
            android:background="@drawable/btn_selector"
            android:textColor="#fff"
            android:textSize="18sp"
            />
    </LinearLayout>
</LinearLayout>

注：

问题: 当点击某一行的时候, 没有背景色的变化
原因: 行中包含了按钮, 按钮抢夺了焦点
解决方案: 夺回焦点，在行布局中设置descendantFocusability属性

四、在Activity中编写代码

//1.获取ListView对象
ListView list_main = (ListView) findViewById(R.id.list_main);


//2.数据源
List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();
Map<String, Object> map = new HashMap<String, Object>();
map.put("logo", R.drawable.danger);
map.put("title", "千千静听");
map.put("version", "版本: 8.4.0");
map.put("size", "大小: 32.81M");
list.add(map);



//3. 准备适配器Adapter
MyAdapter adapter = new MyAdapter(this);
adapter.setList(list);

//4. 将适配器关联到ListView
list_main.setAdapter(adapter);

 

五、ListView Item点击长按事件

//5.监听item事件
list_main.setOnItemClickListener(this);
list_main.setOnItemLongClickListener(this);

   @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Toast.makeText(this,"点击"+position,Toast.LENGTH_SHORT).show();
       
    }

    @Override
    public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
        Toast.makeText(this,"长按"+position,Toast.LENGTH_SHORT).show();
        return true;
    }

注：长按事件onItemLongClick需要返回值

如果希望长按事件后，不再触发点击事件，则应将返回值设为true

六、ListView 优化

    public class ViewHolder{
        ImageView logo;
        TextView title;
        TextView version;
        TextView size;
    }
    
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;

        if(convertView == null){
            convertView = inflater.inflate(R.layout.item,null);
            holder = new ViewHolder();
            holder.logo = (ImageView) convertView.findViewById(R.id.logo);
            holder.title = (TextView) convertView.findViewById(R.id.title);
            holder.version = (TextView) convertView.findViewById(R.id.version);
            holder.size = (TextView) convertView.findViewById(R.id.size);
            convertView.setTag(holder);
        }else{
            holder = (ViewHolder)convertView.getTag();
        }
        
        Map map = list.get(position);

        holder.logo.setImageResource((Integer) map.get("logo"));
        holder.title.setText((String) map.get("title"));
        holder.version.setText((String) map.get("version"));
        holder.size.setText((String) map.get("size"));

        return convertView;
    }

七、页面跳转传值

1.创建一个独立的Activity

public class DetailActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.detail);

        String index = getIntent().getStringExtra("index");
        String title = getIntent().getStringExtra("title");
        TextView info = (TextView) findViewById(R.id.info);
        info.setText("编号："+index+"   标题："+title);
    }
}

2.编写item点击事件，实现跳转操作

public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        //1.创建Intent对象
        Intent intent = new Intent();
        //2.设置跳转界面
        intent.setClass(this,DetailActivity.class);
        //传值
        HashMap<String,Object> itemMap = (HashMap<String,Object>)parent.getItemAtPosition(position);

        intent.putExtra("index",""+position);
        intent.putExtra("title",""+itemMap.get("title"));
        //3.跳转
        startActivity(intent);
    }