Android 使用Thread+Handler实现非UI线程更新UI界面

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**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：

Handler-no-fresh
Handler-fresh-show

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:

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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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