自定义Adpter使用方法以及注意点

写一个ListView,里面的Item样式自定义，如下界面：



activity_white_pkg.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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:weightSum="1"
tools:context="com.meitu.travelapk.activity.WhitePkgActivity">

<ListView
android:layout_weight="1"
android:id="@+id/whitePkg_lsv"
android:layout_width="fill_parent"
android:layout_height="fill_parent"></ListView>

<Button
android:id="@+id/whitePkg_ok_btn"
android:layout_width="fill_parent"
android:layout_height="50dp"
android:background="@color/colorPrimary"
android:text="保  存"
android:textColor="@android:color/white"
android:textSize="@dimen/textSizeNormal" />
</LinearLayout>

编写item对应的界面item_white_pkg.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"
android:showDividers="end">

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:paddingBottom="5dp"
android:paddingTop="5dp">

<ImageView
android:id="@+id/appIcon"
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_gravity="center"
android:src="@drawable/ic_info_black_24dp" />

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="50dp"
android:layout_weight="1"
android:orientation="vertical">

<TextView
android:id="@+id/appName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="appName"
android:textSize="@dimen/textSizeNormal" />

<TextView
android:id="@+id/pkgName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="appName"
android:textSize="@dimen/textSizeSmall" />
</LinearLayout>

<CheckBox
android:id="@+id/state_cbox"
android:layout_width="40dp"
android:layout_height="20dp"
android:layout_gravity="center"
android:clickable="false"
android:focusable="false"
android:focusableInTouchMode="false" />
</LinearLayout>

<ImageView
android:layout_width="fill_parent"
android:layout_height="1dp"
android:background="@color/lightGray"
android:paddingTop="5dp" />

</LinearLayout>

对应的Activity，里面的ConfigData用于数据存储，AppInfo用于获取应用信息，此处不给出

import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;

import com.meitu.travelapk.R;
import com.meitu.travelapk.data.AppInfo;
import com.meitu.travelapk.data.ConfigData;
import com.meitu.travelapk.views.WhitePkgAdapter;

import java.util.ArrayList;

public class WhitePkgActivity extends AppCompatActivity  implements View.OnClickListener,AdapterView.OnItemClickListener{
public static final int LOAD_LIST = 1;
ListView whitePkg_lsv;
Button ok_btn;
ViewHandler viewHandler = new ViewHandler();
//获取应用信息
ArrayList<AppInfo> appList = AppInfo.getAllAppsInfo();

@Override
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_white_pkg);
findViews();
addEvents();
initData();
}

void initData(){

//        开启另一个线程加载应用数据，防止ANR
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
viewHandler.sendEmptyMessage(LOAD_LIST);
}
});
thread.start();
}

void findViews() {
whitePkg_lsv = (ListView) findViewById(R.id.whitePkg_lsv);
ok_btn = (Button) findViewById(R.id.whitePkg_ok_btn);

}

void addEvents() {
ok_btn.setOnClickListener(this);
whitePkg_lsv.setOnItemClickListener(this);
}

@Override
public void onClick(View v) {
switch (v.getId()){
case  R.id.whitePkg_ok_btn:

Intent intent=new Intent();
intent.setClass(WhitePkgActivity.this,MainActivity.class);
startActivity(intent);
break;
}
}

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
WhitePkgAdapter.ViewHolder vHolder = (WhitePkgAdapter.ViewHolder) view.getTag();
AppInfo appInfo = appList.get(position);
ArrayList<String> whiteList= ConfigData.getWhitePkgList();
vHolder.checked.toggle();
if (vHolder.checked.isChecked()&&!whiteList.contains(appInfo.packageName)){
whiteList.add(appInfo.packageName);
}else{
whiteList.remove(appInfo.packageName);
}

}

class ViewHandler extends Handler {
public ViewHandler() {
}

// TODO Auto-generated constructor stub

@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case LOAD_LIST:

//适配器
WhitePkgAdapter adapter = new WhitePkgAdapter(WhitePkgActivity.this, appList);
//加载适配器
whitePkg_lsv.setAdapter(adapter);

break;

}
}

}
}

适配器

public class WhitePkgAdapter extends BaseAdapter {
private Context mContext;
private List<AppInfo> mList;

public WhitePkgAdapter(Context context, List<AppInfo> list) {
this.mContext = context;
this.mList = list;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return mList.size();
}

@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return mList.get(position);
}

@Override
public long getItemId(int index) {
// TODO Auto-generated method stub
return index;
}

public class ViewHolder {
public ImageView icon;
public TextView appName;
public TextView pkgName;
public CheckBox checked;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
LayoutInflater _LayoutInflater = LayoutInflater.from(mContext);
ViewHolder holder = new ViewHolder();
if (convertView == null) {
convertView = _LayoutInflater.inflate(R.layout.item_white_pkg, null);
holder.icon = (ImageView) convertView
.findViewById(R.id.appIcon);
holder.appName = (TextView) convertView
.findViewById(R.id.appName);
holder.pkgName = (TextView) convertView
.findViewById(R.id.pkgName);
holder.checked = (CheckBox) convertView.findViewById(R.id.state_cbox);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.icon.setImageDrawable(mList.get(position).appIcon);
holder.appName.setText(mList.get(position).appName);
holder.pkgName.setText(mList.get(position).packageName);
return convertView;
}
}

《《《《注意》》》》》》

这里的getView方法的书写应遵循以下顺序：

1、如果拿到的convertView是空，则为holder赋上对应的值，并且将setTag, 以供后期holder的获取，

2、如果convertView已经有内容了，则直接使用getTag方法，

3、在确保holder内容非空了之后，统一为holder赋值，初始化item界面。