用心学Android之Handler续篇

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在上一篇的结尾处，总结出了Handler机制也可以用于主线程/UI线程向子线程/工作线程发送消息，但是没有给出实践的例程。

为了满足“童鞋们”的需要，在这一篇中给出一个例子，顺便纠正上一篇中的一个错误。Looper释放资源的方法是在Activity的onDestroy()方法中调用线程Looper的quit()方法，而不是release()方法。

activity_main.xml代码

<?xmlversion="1.0"encoding="utf-8"?>

<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"

xmlns:autonavi="http://schemas.android.com/apk/res/com.AMap"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical">

<ListView

android:id="@+id/providersList"

android:layout_width="fill_parent"

android:layout_height="0dp"

android:layout_weight="0.8">

</ListView>

<TextView

android:id="@+id/CurrnetLocation"

android:layout_width="fill_parent"

android:layout_height="wrap_content"/>

</LinearLayout>

MainActivity.java代码

import java.io.IOException;

import java.util.List;

import android.app.Activity;

import android.content.Context;

import android.location.Address;

import android.location.Geocoder;

import android.location.Location;

import android.location.LocationListener;

import android.location.LocationManager;

import android.location.LocationProvider;

import android.os.Bundle;

import android.os.Handler;

import android.os.Looper;

import android.os.Message;

import android.view.Menu;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ArrayAdapter;

import android.widget.ListView;

import android.widget.TextView;

import com.amap.mapapi.core.GeoPoint;

import com.amap.mapapi.map.MapController;

import com.amap.mapapi.map.MapView;

public class MainActivity extends Activity {

private LocationManagerm_locationManager;

private LocationProviderm_locationProvider;

private Handlerm_mainHandler = new Handler() {

@Override

public voidhandleMessage(Message msg) {

// TODO 自动生成的方法存根

super.handleMessage(msg);

switch (msg.what){

case 0:

((TextView)findViewById(R.id.CurrnetLocation))

.setText((String)msg.obj);

break;

}

};

private Handlerm_addressParseThreadHandler;

private Thread m_addressParseThread= new Thread() {

@Override

public void run() {

// TODO 自动生成的方法存根

super.run();

Looper.prepare();

m_addressParseThreadHandler= new Handler() {

@Override

public voidhandleMessage(Message msg) {

//TODO 自动生成的方法存根

super.handleMessage(msg);

switch(msg.what) {

case0:

Messagesend_msg = m_mainHandler.obtainMessage();

send_msg.what= 0;

Strings="位置提供者:"+msg.getData().getString("ProviderName")+"\n";

s+=addressParse((Location)msg.obj);

send_msg.obj= s;

m_mainHandler.sendMessage(send_msg);

break;

}

};

Looper.loop();

}

};

@Override

protected voidonCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

if (m_locationManager== null)

m_locationManager= (LocationManager) getSystemService(Context.LOCATION_SERVICE);

initProvidersList();

m_addressParseThread.start();

}

@Override

protected void onDestroy() {

// TODO 自动生成的方法存根

super.onDestroy();

m_addressParseThreadHandler.getLooper().quit();

}

// 初始化位置提供者列表

private voidinitProvidersList() {

// 列出可用的位置提供者

ListView providersList= (ListView) findViewById(R.id.providersList);

providersList.setAdapter(newArrayAdapter<String>(this,

android.R.layout.simple_list_item_1,

((LocationManager)getSystemService(Context.LOCATION_SERVICE))

.getProviders(true)));

providersList.setOnItemClickListener(newOnItemClickListener() {

@Override

public voidonItemClick(AdapterView<?> arg0, View arg1, int arg2,

longarg3) {

// TODO 自动生成的方法存根

if(m_locationManager != null) {

m_locationProvider= m_locationManager.getProvider(arg0

.getItemAtPosition(arg2).toString());

}

if(m_addressParseThreadHandler != null) {

Messagesend_msg = m_addressParseThreadHandler

.obtainMessage();

send_msg.what= 0;

send_msg.obj= getCurrentLocation(m_locationProvider);

//这里还用到了Bundle

Bundlebu=new Bundle();

bu.putString("ProviderName",m_locationProvider.getName());

send_msg.setData(bu);

m_addressParseThreadHandler.sendMessage(send_msg);

}

});

}

// 获得当前位置

private LocationgetCurrentLocation(LocationProvider lp) {

if (m_locationManager!= null && lp != null

&&m_locationManager.isProviderEnabled(lp.getName())) {

returnm_locationManager.getLastKnownLocation(lp.getName());

} else {

return null;

}

// 解析地址信息

private StringaddressParse(Location location) {

String latLongString ="";

if (location != null) {

latLongString +="当前位置提供者是:" + location.getProvider() + "\n";

double lat =location.getLatitude();

double lng =location.getLongitude();

latLongString ="纬度:" + lat + "\n" + "经度:" + lng +"\n";

List<Address>addList = null;

Geocoder ge = newGeocoder(this);

try {

addList =ge.getFromLocation(lat, lng, 1);

} catch(IOException e) {

// TODOAuto-generated catch block

e.printStackTrace();

}

if (addList !=null && addList.size() > 0) {

for (int i =0; i < addList.size(); i++) {

Addressad = addList.get(i);

latLongString+= ad.getCountryName() + ";"

+ad.getLocality();

if (i!= 0) {

latLongString+= "\n";

}

} else {

latLongString +="无法获取位置信息";

}

return latLongString;

}

@Override

public boolean onCreateOptionsMenu(Menumenu) {

// Inflate the menu;this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main,menu);

return true;

}

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