ListView用法详解

ListView作为一个经常被用来显示一组信息的控件,熟练掌握其用法显得尤为重要。这篇文章我们将从两个方面,介绍 ListView的用法

ListView无非也就是多个控件的多次重复显示,ListView将Android中MVC模式很好的展示出来。MVC模式中最重要的就是控制器,Adapter很好的担任了这个角色。所以本片文章主要从Adapter的角度来讲解ListView的用法。本篇文章将从两个方面介绍Adapter,SimpleAdapter和自定义Adapter。

Ⅰ、SimpleAdapter。SimpleAdapter已经可以加载较为丰富的内容,知识内容形式比较单一罢了。

①、准备数据源。这里我随便列了一组数据

<span style="white-space:pre">	</span>private String[] mtitle = {"姓名","性别","年龄","居住地","邮箱"};
	private String[] mdetailinfo = {"总有些草民想害朕","男","23","广东深圳","1178065943@qq.com"};
我们还需要一个集合来存放这些数据
		List<Map<String,Object>> mdata = new ArrayList<Map<String,Object>>();
		for(int i=0; i<mtitle.length; i++){
			Map<String,Object> map = new HashMap<String,Object>();
			map.put("titletv",mtitle[i]);
			map.put("detailtv",mdetailinfo[i]);
			mdata.add(map);
		}

②、准备总的一个布局,布局很简单就一个ListView

<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" >

    <ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >
    </ListView>

</LinearLayout>
③、总的布局有了,要显示当然缺不了每个item的布局

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

    <ImageView
        android:id="@+id/iconiv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/icon_img" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#B3EC64"
        android:orientation="vertical" >

        <TextView
            android:id="@+id/titletv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#E51A23"
            android:textSize="18sp" />

        <TextView
            android:id="@+id/detailtv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textColor="#E51A23"
            android:textSize="14sp" />
    </LinearLayout>

</LinearLayout>
④、好了,准备工作做好了,我们只需要使用SimpleAdapter准备的数据关联起来即可。下面是SimpleAdapter
		SimpleAdapter simpleAdapter = new SimpleAdapter(this,mdata,R.layout.list_item_layout,new String[]{
				"titletv","detailtv"
				},new int[]{
				R.id.titletv,R.id.detailtv});
		listView.setAdapter(simpleAdapter);

大功告成,看看效果

嘿嘿,看着还不错,ListView的使用是不是很简单呢,当然不是的,在开发过程中,我们经常需要自定义Adapter来加载我们多需要的数据,让我们的界面什么的看起来更好一些,下面我们就来介绍一下自定义Adapter。


II、我选取的例子是用ListView加载搜索到的蓝牙设备,并将设备的名字与地址都展示出来。

这个小Demo主要用到了四个类。BluetoothDeviceDB.java,DeviceInfo.java,DeviceInfoAdaper.java以及MainActivity.java.下面我将一一介绍各个类的用途。

①、BluetoothDeviceDB.主要是数据库的创建,表格的创建,以及增删查改几个方法,目的是用来存放匹配的蓝牙设备信息。代码如下:

import java.util.ArrayList;
import java.util.List;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteDatabase.CursorFactory;
import android.database.sqlite.sqliteOpenHelper;
import android.util.Log;

public class BluetoothDeviceDB extends sqliteOpenHelper {

	public static final String 	DATABASE_NAME = "BluetoothDB";

	public static final String TABLE_NAME = "bluetoothrecord";
	public static final String TITLE = "title";
	public static final String ADDRESS = "address";
	public static final String STATUS = "statue";
	public static final int STATUE_CONNECTED = 1;
	public static final int STATUE_NOCONNECT = 0;
	public static String _id = "_id"; 
	public static final String TABLE_CREATE = "create table " + TABLE_NAME
			+ "(" + _id + " INTEGER PRIMARY KEY AUTOINCREMENT," + TITLE
			+ " TEXT," + ADDRESS + " TEXT," + STATUS + " INTEGER" + ");";
	
	private static final String TAG = "BluetoothDeviceDB";

	private static final int DATABASE_VERSION = 2;
 
	
	public BluetoothDeviceDB(Context context){
		super(context,DATABASE_NAME,null,DATABASE_VERSION);
	}
	public BluetoothDeviceDB(Context context,String name,CursorFactory factory,int version) {
		super(context,name,factory,version);
	}

	//当数据库首次被创建时
	@Override
	public void onCreate(sqliteDatabase db) {
		db.execsql(TABLE_CREATE);
	}

	@Override
	public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
		String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;
		db.execsql(sql);
	}
	
	public long insert(sqliteDatabase db,String title,String address,int statue){
		Log.d(TAG,"BluetoothDeviceDB-----insert()");
		if(checkIsExist(db,address)){
			Log.d(DATABASE_NAME,address+ " the device is exist");
		}
		ContentValues cv = new ContentValues();
		long row;
		cv.put(TITLE,title);
		cv.put(ADDRESS,address);
		cv.put(STATUS,statue);
		row = db.insert(TABLE_NAME,cv);
		return row;
	}
	
	public long update(sqliteDatabase db,int statue,int position){
		ContentValues cv = new ContentValues();
		long row;
		cv.put(TITLE,statue);
		row = db.update(TABLE_NAME,cv,_id + "=" + position,null);
		return row;
	}
	//查询记录的总数
	public int getCount(sqliteDatabase db){
		String sql = "select count(*) from " + TABLE_NAME;
		Cursor c = db.rawQuery(sql,null);
		c.movetoFirst();
		int length = c.getInt(0);
		c.close();
		return length;
	}

	private boolean checkIsExist(sqliteDatabase db,String address) {
		ArrayList<CompanionData> list = selectAll(db);
		for(int i=0; i<list.size(); i++){
			if(list.get(i).compare(address)){
				return true;
			}
		}
		return false;
	}
	
	public CompanionData getCompanionData(sqliteDatabase db,String address){
		ArrayList<CompanionData> list = selectAll(db);
		for(int i=0; i<list.size(); i++){
			if(list.get(i).compare(address)){
				return list.get(i);
			}
		}
		return null;
	}
	
	private ArrayList<CompanionData> selectAll(sqliteDatabase db) {
		ArrayList<CompanionData> arrayList = new ArrayList<CompanionData>();
		Cursor cursor = db.query(TABLE_NAME,null);
		if(cursor != null && cursor.getCount() > 0){
			cursor.movetoFirst();
		}
		for(cursor.movetoFirst(); !cursor.isAfterLast();cursor.movetoNext()){
			CompanionData data = new CompanionData();
			data.setmId(cursor.getInt(0));
			data.setmTitle(cursor.getString(1));
			data.setmAddress(cursor.getString(2));
			data.setmStatue(cursor.getInt(3));
			arrayList.add(data);
		}
		cursor.close();
		return arrayList;
	}

	public class CompanionData{
		
		private int mId;
		private String mAddress;
		private String mTitle;
		private int mStatue;
		
		public int getmId() {
			return mId;
		}
	
		public void setmId(int mId) {
			this.mId = mId;
		}
		
		public String getmAddress() {
			return mAddress;
		}
		
		public void setmAddress(String mAddress) {
			this.mAddress = mAddress;
		}
		
		public String getmTitle() {
			return mTitle;
		}
		
		public void setmTitle(String mTitle) {
			this.mTitle = mTitle;
		}
		
		public int getmStatue() {
			return mStatue;
		}
		
		public void setmStatue(int mStatue) {
			this.mStatue = mStatue;
		}
		
		public boolean compare(String address){
			if(mAddress.equals(address)){
				return true;
			}else
			{
				return false;
			}
		}
	}
}
②、DeviceInfo.java顾名思义就是用来存放设备各种信息的分装类。代码如下:
public class DeviceInfo {
	private int imageId;
	private String deviceName;
	private String deviceAddress;
	
	public DeviceInfo(){
		imageId = R.drawable.ic_bluetooth;
	}
	
	public int getimageId() {
		return imageId;
	}
	
	public void setimageId(int imageId) {
		this.imageId = imageId;
	}
	
	public String getDeviceName() {
		return deviceName;
	}
	
	public void setDeviceName(String deviceName) {
		this.deviceName = deviceName;
	}
	
	public String getDeviceAddress() {
		return deviceAddress;
	}
	
	public void setDeviceAddress(String deviceAddress) {
		this.deviceAddress = deviceAddress;
	}

}
③、好了,数据准备工作做好了,我们这篇文章的重头戏来了,DeviceInfoAdapter.java,他是用来把DeviceInfo加载到ListView中的。自定义Adapter,其实就是继承BaseAdapter,然后重写它其中的四个方法,getCount(),getItem(),getItemId(),和getView();各个方法具体是干什么的,代码中都有注释了,我就不在这里重复描述了。自定义Adapter的关键就在此,只要把这四个方法理顺了,你就可以定制任何自己想要的Adapter了。ok,让我们来观摩观摩代码
package com.gajsh.bluetoothcommunication;

import java.util.List;

import com.gajsh.mybluetooth.R;

import android.annotation.SuppressLint;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

@SuppressLint("ViewHolder")
public class DeviceInfoAdapter extends BaseAdapter {
	private static final String TAG = "DeviceInfoAdapter";
	private Context context;

	List<DeviceInfo> devices;

	public DeviceInfoAdapter(Context context,List<DeviceInfo> mPairedList) {
		super();
		this.context = context;
		this.devices = mPairedList;
	}

	@Override
	public int getCount() {// 获取数据长度
		Log.d(TAG,"size:"+devices.size());
		return devices.size();
	}

	@Override
	public Object getItem(int position) {// 获取Item中的数据源组
		return devices.get(position);
	}

	@Override
	public long getItemId(int position) {// 用于item的定位--系统内部调用
		return position;
	}

	@Override
	public View getView(int position,View contentView,ViewGroup group) {
		if (devices != null)
			// 实例获取item控件
			// 为该控件管理布局并填充数据
			if (contentView == null) {
				LayoutInflater inflater = LayoutInflater.from(context);
				contentView = inflater.inflate(R.layout.list_item_layout,null);
				TextView devicename = (TextView) contentView
						.findViewById(R.id.titletv);
				TextView address = (TextView) contentView
						.findViewById(R.id.addresstv);
				devicename.setText(devices.get(position).getDeviceName());
				address.setText(devices.get(position).getDeviceAddress());

			}
		return contentView;
	}

}

④、最后一个类当然是让我们写的这些东西组织起来,让我们能够达到最终的目的—ListView显示所有匹配蓝牙设备的信息。

有几个要强调的地方。

1、蓝牙核心类BlueAdapter,它是通过getDefaultAdapter()来得到,而不是New出来,通过它可以进行蓝牙的搜索、匹配等。

2、addSystemPairedDevicesToDB(),这个类是将匹配的设备添加数据库中,其中涉及蓝牙设备是否存在于数据库的检查类ExistOnSystemDB();

3、将数据库中的设备信息取出来存放到List中,addPairedDevicetoList()

4、最终我们是在OnResume()这个生命周期的方法中完成数据的适配的。

下面是MainActivity.java的代码

import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import com.gajsh.mybluetooth.R;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.broadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.ListView;

public class MainActivity extends Activity {

	private static final String TAG = "MainActivity";
	private BluetoothAdapter mBtAdapter;
	BluetoothDeviceDB dbhelper;
	DeviceInfoAdapter mPairedAdapter;
	sqliteDatabase sql;
	Cursor cursor;
	List<DeviceInfo> mPairedList;
	ListView mPairedListView;
	Set<BluetoothDevice> pairedDevices;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		mPairedList = new ArrayList<DeviceInfo>();
		mPairedListView = (ListView) findViewById(R.id.pairedlv);
		dbhelper = new BluetoothDeviceDB(this);
		sql = dbhelper.getWritableDatabase();
		mBtAdapter = BluetoothAdapter.getDefaultAdapter();
		// 向数据库中提交匹配的蓝牙设备
		addSystemPairedDevicesToDB();

	};

	@Override
	protected void onResume() {
		super.onResume();
		Log.d(TAG,"-------------");
		addPairedDevicetoList();
		mPairedAdapter = new DeviceInfoAdapter(this,mPairedList);
		mPairedListView.setAdapter(mPairedAdapter);
		for (DeviceInfo device : mPairedList) {
			String devicename = device.getDeviceName();
			String address = device.getDeviceAddress();
			Log.d(TAG,"list的内容" + devicename + address);
		}

	}

	private void addPairedDevicetoList() {
		Cursor cursor = sql.rawQuery("select * from "
				+ BluetoothDeviceDB.TABLE_NAME + " order by "
				+ BluetoothDeviceDB._id,null);
		mPairedList.clear();
		if (cursor != null && cursor.movetoFirst()) {
			for (int i = 0; i < cursor.getCount(); i++) {
				Log.d(TAG,"这是添加第---" + i + "---个元素");
				DeviceInfo deviceInfo = new DeviceInfo();
				deviceInfo.setDeviceAddress(cursor.getString(cursor
						.getColumnIndex(BluetoothDeviceDB.ADDRESS)));
				deviceInfo.setDeviceName(cursor.getString(cursor
						.getColumnIndex(BluetoothDeviceDB.TITLE)));
				mPairedList.add(deviceInfo);
				cursor.movetoNext();
			}
		}
		if (cursor != null) {
			cursor.close();
			cursor = null;
		}
		Log.d(TAG,"---添加完成---");
	}

	private void addSystemPairedDevicesToDB() {
		pairedDevices = mBtAdapter.getBondedDevices();
		if (pairedDevices.size() > 0 && !ExistOnSystemDB(pairedDevices)) {
			for (BluetoothDevice device : pairedDevices) {
				String address = device.getAddress();
				String devicename = device.getName();
				if (address != null && devicename != null) {
					dbhelper.insert(sql,device.getName(),device.getAddress(),0);
				}
			}
		}
		Log.d(TAG,"数据库元素添加完成");
	}

	private boolean ExistOnSystemDB(Set<BluetoothDevice> pairedDevices) {
		Cursor cursor = sql.rawQuery("select address from "
				+ BluetoothDeviceDB.TABLE_NAME,null);
		if (cursor != null && cursor.movetoFirst()) {
			for (int j = 0; j < cursor.getCount(); j++) {
				String dbaddress = cursor.getString(cursor
						.getColumnIndex(BluetoothDeviceDB.ADDRESS));
				for (BluetoothDevice device : pairedDevices) {
					String pairedaddress = device.getAddress();
					if (pairedaddress.equalsIgnoreCase(dbaddress)) {
						return true;
					}
				}
			}
		}

		return false;
	}

}
基本代码都有了,下面我把布局文件也列来,相当简单,首先是主布局
<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" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@color/grey"
        android:text="@string/bondeddevices" />

    <ListView
        android:id="@+id/pairedlv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>
由于布局相对简单,我就不给大家介绍布局的实现思路了,下面是list_item_layout
<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" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:background="@color/grey"
        android:text="@string/bondeddevices" />

    <ListView
        android:id="@+id/pairedlv"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>
由于我都是练习Demo,所以采用的都是线性布局,建议大家多用用相对布局,在开发中相对布局应用相对来说比较多些。

不知不觉,自定义Adapter也讲完了,其中也涉及到了sqlite数据库,有兴趣的朋友可以多研究一下。当然我加载的信息比较简单,大家有兴趣可以弄得复杂些,最后把效果图给大家看下:

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