Android第二周（第二部分）－listview

ListView

1.基础

listview一般都是撑满屏幕match_parent
页面一定要在AndroidManifest中进行注册
Adapter
setAdapter进行listview和adapter绑定

1.修改AndroidManifest.xml注册ListViewDemoActivity类<?xml version="1.0" encoding="utf-8"?><manifest    package="com.geekband.Test01"    xmlns:android="http://schemas.android.com/apk/res/android"    android:versionName="1.0.0">    <application        android:allowBackup="true"        android:icon="@mipmap/geekband"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme">        <activity android:name=".SplashActivity">            <intent-filter>                <action android:name="android.intent.action.MAIN"/>                <category android:name="android.intent.category.LAUNCHER"/>            </intent-filter>        </activity>        <activity            android:name=".MainActivity"            android:icon="@drawable/abc_ic_ab_back_mtrl_am_alpha">        </activity>        <activity            android:name=".ListViewDemoActivity"            android:icon="@drawable/abc_ic_ab_back_mtrl_am_alpha">        </activity>    </application></manifest>2.创建PhoneBookAdapter，为页面类提供数据来源public class PhoneBookAdapter extends BaseAdapter {    private Context mContext;    private LayoutInflater mLayoutInflater;    private String[] mNames = {"小明", "小花"};    public PhoneBookAdapter(Context context) {         mContext = context;         mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);    }    @Override    public int getCount() {        // 有多少条数据        return mNames.length;    }    @Override    public Object getItem(int position) {        // 返回某一条数据对象        return mNames[position];    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        // 返回一个视图         convertView = mLayoutInflater.inflate(R.layout.item_phone_book_friend, null);        TextView nameTextView = (TextView) convertView.findViewById(R.id.name_text_view);        nameTextView.setText(mNames[position]);        return convertView;    }}3.创建页面布局activity_listview_demo.xml<?xml version="1.0" encoding="utf-8"?><LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/phone_book"/>    <ListView        android:id="@+id/list_view"        android:layout_width="match_parent"        android:layout_height="match_parent">    </ListView></LinearLayout>4.创建页面类，页面类中使用ListView并绑定前面创建的Adapterpublic class ListViewDemoActivity extends Activity {    private ListView mPhoneBookListView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_listview_demo);        mPhoneBookListView = (ListView) findViewById(R.id.list_view);        PhoneBookAdapter phoneBookAdapter = new PhoneBookAdapter(ListViewDemoActivity.this);        mPhoneBookListView.setAdapter(phoneBookAdapter);    }}5.创建item_phone_book_friend.xml<?xml version="1.0" encoding="utf-8"?><LinearLayout    xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <TextView        android:id="@+id/name_text_view"        android:layout_width="fill_parent"        android:layout_height="wrap_content"/></LinearLayout>

关键元素
1.修改AndroidManifest.xml文件，注册Activity类
2.创建Adapter类，为页面类提供数据来源
3.创建布局文件
4.创建Activity类，按照生命周期写7大方法，其中在onCreate()方法中至少要完成绑定布局的工作；另外为ListView控件绑定Adapter
5.创建子视图布局item_phone_book_friend.xml
6.Adapter类中通过重写getView()方法来将子视图添加到ListView内，

LayoutInflater mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);convertView = mLayoutInflater.inflate(R.layout.item_phone_book_friend, null);

7.Adapter类中通过重写getCount()方法确定在ListView中显示多少个子视图。

2.进阶

为listview整体或者具体项目绑定点击或者长按事件
更新listview中数据，修改adapter中数据；调用notifyDataSetChanged()方法

3.优化

public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder viewHolder;        if (convertView == null) {            convertView = mLayoutInflater.inflate(R.layout.item_phone_book_friend, null);            viewHolder = new ViewHolder();            // 获取控件            viewHolder.nameTextView = (TextView) convertView.findViewById(R.id.name_text_view);            viewHolder.ageTextView = (TextView) convertView.findViewById(R.id.age_text_view);            viewHolder.avatarImageView = (ImageView) convertView.findViewById(R.id.avatar_image_view);            convertView.setTag(viewHolder);        } else {            viewHolder = (ViewHolder) convertView.getTag();        }        // 和数据之间进行绑定        viewHolder.nameTextView.setText(mUserInfos.get(position).getUserName());        viewHolder.ageTextView.setText(String.valueOf(mUserInfos.get(position).getAge()));        viewHolder.avatarImageView.setImageResource(R.drawable.ic_launcher);        return convertView;    }    class ViewHolder {        TextView nameTextView;        TextView ageTextView;        ImageView avatarImageView;    }

1. 只加载一次子视图即mLayoutInflater.inflate(R.layout.item_phone_book_friend, null);只执行一次
2. 由于每次看到页面都要执行getView，因此需要缓存子视图中的控件，以免重复findViewByID