Android 使用Thread+Handler实现非UI线程更新UI界面

摘要:每个Android应用程序都运行在一个dalvik虚拟机进程中,进程开始的时候会启动一个主线程(MainThread),主线程负责处理和ui相关的事件,因此主线程通常又叫UI线程。而由于Android采用UI单线程模型,所以只能在主线程中对UI元素进行操作。如果在非UI线程直接对UI进行了操作,则会报错:CalledFromWrongThreadException:only the original thread that created a view hierarchy can touch its views。

Android为我们提供了消息循环的机制,我们可以利用这个机制来实现线程间的通信。那么,我们就可以在非UI线程发送消息到UI线程,最终让Ui线程来进行ui的操作。

对于运算量较大的操作和IO操作,我们需要新开线程来处理这些繁重的工作,以免阻塞ui线程。在发送http等网络请求时,会经常使用!


实例讲解

下面承接前几篇文章中对天气情况(Weather)的一些详细说明,继续完善,实现在Android客户端的一个天气预报功能的开发:

WeatherActivity主程序代码:

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package com.dm.weather;

import android.annotation.TargetApi;
import android.app.Activity;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.widget.SwipeRefreshLayout;
import android.util.Log;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.dm.CommonData.RetData;
import com.dm.CommonData.Weather;
import com.google.gson.Gson;

import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

/**
* Thread + Handler 实例
*/
public class WeatherActivity extends Activity {
private SwipeRefreshLayout swipeRefreshLayout;
private TextView refreshTv;

private static final String LOG_TAG = "WeatherActivity";
private static final int MSG_SUCCESS = 1; // 成功标识
private static final int MSG_FAILURE = 0; // 失败标识
private static final String REQUEST_URL = "http://apistore.baidu.com/microservice/weather?cityname=郑州";
private static final String REQUEST_BASE_URL = "http://apistore.baidu.com/microservice/weather";

private ImageView weatherIcon;
private TextView weatherDateTv;
private TextView weatherTimeTv;
private TextView weatherStatusTv;
private TextView windDirectionTv;
private TextView windSpeedTv;
private TextView weatherCurrentTmpTv;
private TextView weatherLowTmpTv;
private TextView weatherHighTmpTv;
private TextView sunRiseTimeTv;
private TextView sunSetTimeTv;

private Thread mThread = null;

private Handler weatherHander = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_SUCCESS:
// 使用Gson对Json数据的解析,请翻看之前的文章:[Java中使用Gson解析json数据](http://blog.csdn.net/mduanfire/article/details/44703059%20+ "Java中使用Gson解析json数据")
Gson weatherGson = new Gson();
Log.i(LOG_TAG, msg.obj.toString());

Weather weather = weatherGson.fromJson(msg.obj.toString(), Weather.class);
RetData retData = weather.getRetData();

weatherDateTv.setText(retData.getDate() + " ");
weatherTimeTv.setText(retData.getTime());
windDirectionTv.setText(retData.getWD());
windSpeedTv.setText(retData.getWS());
weatherStatusTv.setText(retData.getWeather());
weatherCurrentTmpTv.setText(retData.getTemp());
weatherLowTmpTv.setText(retData.getL_tmp());
weatherHighTmpTv.setText(retData.getH_tmp());
sunRiseTimeTv.setText(retData.getSunrise());
sunSetTimeTv.setText(retData.getSunset());

switch (retData.getWeather()) {
case "晴":
weatherIcon.setImageResource(R.drawable.qing);
break;
case "多云":
weatherIcon.setImageResource(R.drawable.duoyun);
break;
case "阴":
weatherIcon.setImageResource(R.drawable.yin);
break;
case "阵雨":
weatherIcon.setImageResource(R.drawable.zhengyu);
break;
case "雷阵雨":
weatherIcon.setImageResource(R.drawable.leizhengyu);
break;
case "雷阵雨伴有冰雹":
weatherIcon.setImageResource(R.drawable.leizhengyubanyoubingbao);
break;
case "雨夹雪":
weatherIcon.setImageResource(R.drawable.yujiaxue);
break;
case "小雨":
weatherIcon.setImageResource(R.drawable.xiaoyu);
break;
case "中雨":
weatherIcon.setImageResource(R.drawable.zhongyu);
break;
case "大雨":
weatherIcon.setImageResource(R.drawable.dayu);
break;
case "暴雨":
weatherIcon.setImageResource(R.drawable.baoyu);
break;
case "大暴雨":
weatherIcon.setImageResource(R.drawable.dabaoyu);
break;
case "特大暴雨":
weatherIcon.setImageResource(R.drawable.tedabaoyu);
break;
case "阵雪":
weatherIcon.setImageResource(R.drawable.zhengxue);
break;
case "小雪":
weatherIcon.setImageResource(R.drawable.xiaoxue);
break;
case "中雪":
weatherIcon.setImageResource(R.drawable.zhongxue);
break;
case "大雪":
weatherIcon.setImageResource(R.drawable.daxue);
break;
case "暴雪":
weatherIcon.setImageResource(R.drawable.baoxue);
break;
case "雾":
weatherIcon.setImageResource(R.drawable.wu);
break;
case "冻雨":
weatherIcon.setImageResource(R.drawable.dongyu);
break;
case "沙尘暴":
weatherIcon.setImageResource(R.drawable.shachenbao);
break;
case "浮尘":
weatherIcon.setImageResource(R.drawable.fuchen);
break;
case "扬沙":
weatherIcon.setImageResource(R.drawable.yangsha);
break;
case "强沙尘暴":
weatherIcon.setImageResource(R.drawable.qiangshachenbao);
break;
case "霾":
weatherIcon.setImageResource(R.drawable.mai);
break;
case "小到中雨":
weatherIcon.setImageResource(R.drawable.zhongyu);
break;
case "中到大雨":
weatherIcon.setImageResource(R.drawable.dayu);
break;
case "大到暴雨":
weatherIcon.setImageResource(R.drawable.baoyu);
break;
case "暴雨到大暴雨":
weatherIcon.setImageResource(R.drawable.dabaoyu);
break;
case "大暴雨到特大暴雨":
weatherIcon.setImageResource(R.drawable.tedabaoyu);
break;
case "小到中雪":
weatherIcon.setImageResource(R.drawable.zhongxue);
break;
case "中到大雪":
weatherIcon.setImageResource(R.drawable.daxue);
break;
case "大到暴雪":
weatherIcon.setImageResource(R.drawable.baoxue);
break;
default:
weatherIcon.setImageResource(R.drawable.qita);
break;
}

refreshTv.setText("刷新成功");
swipeRefreshLayout.setRefreshing(false);
break;
case MSG_FAILURE:
Toast.makeText(getApplicationContext(), "FAILURE, 网络繁忙!", Toast.LENGTH_LONG).show();
break;
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.weather_activity);

initTitleView();
initWeatherView();
initBaseView();
}

@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
private void initBaseView() {
refreshTv = (TextView) findViewById(R.id.refresh_tv);
swipeRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe_container);
swipeRefreshLayout.setColorSchemeResources(android.R.color.holo_blue_light, android.R.color.holo_red_light, android.R.color.holo_orange_light, android.R.color.holo_green_light);
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
refreshTv.setText("正在刷新");
// 开启新的线程,请求网络数据,返回json数据
mThread = new Thread(runnable);
mThread.start();
}
});
}

Runnable runnable = new Runnable() {
@Override
public void run() {

// Http get
// String requestUrl = REQUEST_URL;
//
// HttpGet httpGet = new HttpGet(requestUrl);
//
// try {
// HttpResponse httpResponse = new DefaultHttpClient().execute(httpGet);
//
// if (httpResponse.getStatusLine().getStatusCode() == 200) {
// String requestResult = EntityUtils.toString(httpResponse.getEntity());
//
// Log.i(LOG_TAG, "requestResult = " + requestResult);
//
// 使用定义的weatherHander的obtainMessage()方法将成功标志和请求成功得到的json字符串传递过去,之后在Hander中进行解析
weatherHander.obtainMessage(MSG_SUCCESS, requestResult).sendToTarget();
// } else {
// Log.i(LOG_TAG, "requestError = " + httpResponse.getStatusLine());
// Toast.makeText(getApplicationContext(), "Response Error!!" + httpResponse.getStatusLine(), Toast.LENGTH_SHORT).show();
// }
// } catch (IOException e) {
// Log.i(LOG_TAG, e.getMessage());
// e.printStackTrace();
// }

// Http post
String url = REQUEST_URL;
HttpPost httpPost = new HttpPost(url);
try {
HttpResponse httpResponse = new DefaultHttpClient().execute(httpPost);

if (httpResponse.getStatusLine().getStatusCode() == 200) {
String requestResult = EntityUtils.toString(httpResponse.getEntity());

Log.i(LOG_TAG, "requestResult = " + requestResult);
weatherHander.obtainMessage(MSG_SUCCESS, requestResult).sendToTarget();
} else {
Log.i(LOG_TAG, "requestError = " + httpResponse.getStatusLine());
Toast.makeText(getApplicationContext(), "Response Error!!" + httpResponse.getStatusLine(), Toast.LENGTH_SHORT).show();
}
} catch (IOException e) {
Log.i(LOG_TAG, "+++++: " + e.getMessage());
e.printStackTrace();
}
}
};

private void initTitleView() {
ImageView titleBackImv = (ImageView) findViewById(R.id.titleBack_iv);
TextView titleTextTv = (TextView) findViewById(R.id.titleText_tv);

titleTextTv.setText("天气状况");
titleBackImv.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
}

private void initWeatherView() {
weatherIcon = (ImageView) findViewById(R.id.weather_icon);
weatherDateTv = (TextView) findViewById(R.id.weather_date);
weatherTimeTv = (TextView) findViewById(R.id.weather_time);
windDirectionTv = (TextView) findViewById(R.id.weather_windstatus);
windSpeedTv = (TextView) findViewById(R.id.weather_windspeed);
weatherStatusTv = (TextView) findViewById(R.id.weather_status);
weatherCurrentTmpTv = (TextView) findViewById(R.id.weather_curent_tmp);
weatherLowTmpTv = (TextView) findViewById(R.id.weather_low_tmp);
weatherHighTmpTv = (TextView) findViewById(R.id.weather_high_tmp);
sunRiseTimeTv = (TextView) findViewById(R.id.weather_sunrise_time);
sunSetTimeTv = (TextView) findViewById(R.id.weather_sunset_time);
}
}

weather_activity界面布局代码

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<?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"
android:background="@color/seashell">

<include
android:id="@+id/weather_include"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
layout="@layout/title_layout" />

<android.support.v4.widget.SwipeRefreshLayout
android:id="@+id/swipe_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignTop="@+id/weather_icon">

<TextView
android:id="@+id/refresh_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Refresh?"
android:padding="5dp"
android:gravity="center_horizontal" />

</android.support.v4.widget.SwipeRefreshLayout>

<ImageView
android:id="@+id/weather_icon"
android:layout_width="120dp"
android:layout_height="120dp"
android:background="@color/powderblue"
android:padding="10dp"
android:layout_marginTop="15dp"
android:layout_marginLeft="15dp"
android:layout_below="@+id/weather_include"
android:src="@drawable/qita" />

<TextView
android:id="@+id/weather_city"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="郑州"
android:textSize="24sp"
android:textColor="@color/black"
android:layout_alignParentRight="true"
android:layout_marginTop="15dp"
android:layout_marginRight="15dp"
android:layout_below="@+id/weather_include"
android:layout_alignRight="@+id/weather_icon" />

<TextView
android:id="@+id/weather_status"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~~~~"
android:textSize="22sp"
android:textColor="@color/black"
android:layout_alignBottom="@+id/weather_icon"
android:layout_centerHorizontal="true" />

<TextView
android:id="@+id/weather_windspeed"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~ "
android:textSize="18sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_windstatus"
android:layout_alignRight="@+id/weather_city"
android:layout_alignEnd="@+id/weather_city" />

<TextView
android:id="@+id/weather_windstatus"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~~~~"
android:textSize="18sp"
android:textColor="@color/black"
android:layout_above="@+id/weather_status"
android:layout_alignRight="@+id/weather_windspeed"
android:layout_alignEnd="@+id/weather_windspeed" />

<TextView
android:id="@+id/weather_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~~~~ "
android:textSize="18sp"
android:textColor="@color/black"
android:layout_toLeftOf="@+id/weather_time"
android:layout_below="@+id/weather_city" />

<TextView
android:id="@+id/weather_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~ "
android:textSize="18sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_city"
android:layout_alignLeft="@+id/weather_city"
android:layout_alignStart="@+id/weather_city" />


<TextView
android:id="@+id/weather_curent_tmp_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="当前气温: "
android:textSize="20sp"
android:textColor="@color/black"
android:layout_marginTop="15dp"
android:layout_below="@+id/weather_icon"
android:layout_alignLeft="@+id/weather_icon"
android:layout_alignStart="@+id/weather_icon" />

<TextView
android:id="@+id/weather_curent_tmp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~"
android:textSize="20sp"
android:textColor="@color/black"
android:layout_alignTop="@+id/weather_curent_tmp_hint"
android:layout_toRightOf="@+id/weather_curent_tmp_hint"
android:layout_toEndOf="@+id/weather_curent_tmp_hint" />

<TextView
android:id="@+id/weather_low_tmp_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="最低气温: "
android:textSize="20sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_curent_tmp_hint"
android:layout_toLeftOf="@+id/weather_curent_tmp"
android:layout_toStartOf="@+id/weather_curent_tmp" />

<TextView
android:id="@+id/weather_low_tmp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~"
android:textSize="20sp"
android:textColor="@color/black"
android:layout_alignTop="@+id/weather_low_tmp_hint"
android:layout_toRightOf="@+id/weather_low_tmp_hint"
android:layout_toEndOf="@+id/weather_low_tmp_hint" />

<TextView
android:id="@+id/weather_high_tmp_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="最高气温: "
android:textSize="20sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_low_tmp_hint"
android:layout_toLeftOf="@+id/weather_high_tmp"
android:layout_toStartOf="@+id/weather_high_tmp" />

<TextView
android:id="@+id/weather_high_tmp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~"
android:textSize="20sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_low_tmp"
android:layout_toRightOf="@+id/weather_low_tmp_hint"
android:layout_toEndOf="@+id/weather_low_tmp_hint" />

<TextView
android:id="@+id/weather_sunrise_time_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="日出时间: "
android:textSize="20sp"
android:textColor="@color/black"
android:layout_alignTop="@+id/weather_low_tmp"
android:layout_alignRight="@+id/weather_date"
android:layout_alignEnd="@+id/weather_date" />

<TextView
android:id="@+id/weather_sunrise_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~"
android:textSize="20sp"
android:textColor="@color/black"
android:layout_alignTop="@+id/weather_sunrise_time_hint"
android:layout_alignLeft="@+id/weather_time"
android:layout_alignStart="@+id/weather_time" />

<TextView
android:id="@+id/weather_sunset_time_hint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="日落时间: "
android:textSize="20sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_sunrise_time_hint"
android:layout_alignLeft="@+id/weather_sunrise_time_hint"
android:layout_alignStart="@+id/weather_sunrise_time_hint" />

<TextView
android:id="@+id/weather_sunset_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="~~~"
android:textSize="20sp"
android:textColor="@color/black"
android:layout_below="@+id/weather_sunrise_time"
android:layout_alignLeft="@+id/weather_sunrise_time"
android:layout_alignStart="@+id/weather_sunrise_time" />
</RelativeLayout>

{ 布局代码中使用到的SwipeRefreshLayout Google官方下拉刷新控件将在下篇文章中介绍 }


在AndroidManifest.xml中添加获取网络的权限

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<uses-permission android:name="android.permission.INTERNET"></uses-permission><!--不要忘记设置网络访问权限-->
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

最终效果预览:

未刷新时
刷新成功时的数据显示

总结:

非UI线程发送消息到UI线程分为两个步骤

1 发送消息到UI线程的消息队列:

1
Message obtainMessage(int what,Object object)

通过使用Handler, 构造一个Message对象,这个对象存储了是否成功标识what和json字符串,然后通过message.sendToTarget()方法把这条message放到消息队列中去。


2 处理发送到UI线程的消息:

ui线程中,我们覆盖了handleMessage

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public void handleMessage (Message msg)

这个方法是处理分发给ui线程的消息,判断msg.what的值可以知道mThread是否成功获取数据,如果json字符串数据成功获取,那么可以通过msg.obj获取到这个对象,之后开始解析。


最后在使用布局中相应的TextView将数据填充,实现更新。

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