Android ListView 列表视图 Ⅲ ListView的优化

 

一级优化示例:
public class MyAdapter extends BaseAdapter {

    List<Map<String, Object>> list;
    LayoutInflater inflater;

    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;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if(convertView == null){
        convertView = inflater.inflate(R.layout.item, null);
    }
        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);

        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 convertView;
    }
}

储存n(4)+1个item视图缓存对象

二级优化示例:
public class MyAdapter extends BaseAdapter {

    List<Map<String, Object>> list;
    LayoutInflater inflater;

    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;
    }

    @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(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;
    }

    public class ViewHolder{
        ImageView logo;
        TextView title;
        TextView version;
        TextView size;
    }
}

setTag携带任何类型的对象 getTag取出对象

界面的跳转  界面与界面的传值

准备:

Activity

public class DetailActivity extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //设置全局
        setContentView(R.layout.main8);
        //初始化控件
        
        
    }
}

layout

<?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"
    >


    <TextView
        android:id="@+id/info"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="28sp"
        android:text="信息"
        />

</RelativeLayout>

Activity注册: Android -- manifests -- AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.srq.appch5">

    <!-- To auto-complete the email text field in the login form with the user's emails -->
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.READ_PROFILE" />
    <uses-permission android:name="android.permission.READ_CONTACTS" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>     //意图过滤器
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".DetailActivity"/>    //<activity android:name="com.srq.appch5.DetailActivity"/>

    </application>

</manifest>

java代码(不全)

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Toast.makeText(this, "点击"+position,Toast.LENGTH_SHORT).show();
    Intent intent = new Intent();  //被动的包裹
    intent.setClass(this,DetailActivity.class);
    startActivity(intent);    //发送intent
}

示例:

Java代码(不全)

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Toast.makeText(this, "点击"+position,Toast.LENGTH_SHORT).show();
    Intent intent = new Intent();
    intent.setClass(this,DetailActivity.class);
    intent.putExtra("index",""+position);
    startActivity(intent);
}

DetailActivity.xml

public class DetailActivity extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //设置全局
        setContentView(R.layout.main8);
        //初始化控件

        String index = getIntent().getStringExtra("index");

        TextView info = (TextView) findViewById(R.id.info);
        info.setText("编号:"+index);

    }
}

Java代码

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    Toast.makeText(this, "点击"+position,Toast.LENGTH_SHORT).show();
    Intent intent = new Intent();
    intent.setClass(this,DetailActivity.class);

    //1.获取所点击行的数据(Map)
    HashMap<String, Object> itemMap
            = (HashMap<String, Object>) parent.getItemAtPosition(position);
    intent.putExtra("index",""+position);
    intent.putExtra("title",""+itemMap.get("title"));
    startActivity(intent);

DetailActivity.xml

public class DetailActivity extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //设置全局
        setContentView(R.layout.main8);
        //初始化控件

        String index = getIntent().getStringExtra("index");
        String title = getIntent().getStringExtra("title");

        TextView info = (TextView) findViewById(R.id.info);
        info.setText("编号:"+index + " "+ title);

    }
}

Java完整代码

public class MainActivity extends Activity implements AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main7);

        //1.拿到listview对象
        ListView lv = (ListView) this.findViewById(R.id.lv_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.ic_10);
        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);

        map = new HashMap<String, Object>();
        map.put("logo", R.drawable.ic_2);
        map.put("title", "时空猎人");
        map.put("version", "版本: 2.4.1");
        map.put("size", "大小: 84.24M");
        list.add(map);

        map = new HashMap<String, Object>();
        map.put("logo", R.drawable.ic_4);
        map.put("title", "360新闻");
        map.put("version", "版本: 6.2.0");
        map.put("size", "大小: 11.74M");
        list.add(map);

        map = new HashMap<String, Object>();
        map.put("logo", R.drawable.ic_15);
        map.put("title", "捕鱼达人2");
        map.put("version", "版本: 2.3.0");
        map.put("size", "大小: 45.53M");
        list.add(map);



        //3.设置适配器
        MyAdapter adapter = new MyAdapter(this);
        adapter.setList(list);


        //4.关联适配器
         lv.setAdapter(adapter);

        //5
        lv.setOnItemClickListener(this);
        lv.setOnItemLongClickListener(this);


    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Toast.makeText(this, "点击"+position,Toast.LENGTH_SHORT).show();
        Intent intent = new Intent();
        intent.setClass(this,DetailActivity.class);

        //1.获取所点击行的数据(Map)
        HashMap<String, Object> itemMap
                = (HashMap<String, Object>) parent.getItemAtPosition(position);
        intent.putExtra("index",""+position);
        intent.putExtra("title",""+itemMap.get("title"));
        startActivity(intent);
    }

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