多线程——分线程通过Handler操作界面

我就是我 2023-09-28 16:32 120阅读 0赞

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布局：

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代码：

package com.example.myapplication;
    
    import android.annotation.SuppressLint;
    import android.os.Bundle;
    import android.os.Handler;
    import android.os.Looper;
    import android.os.Message;
    import android.view.View;
    import android.widget.TextView;
    import androidx.appcompat.app.AppCompatActivity;
    import java.util.Random;
    
    @SuppressLint("HandlerLeak")
    public class MainActivity extends AppCompatActivity implements View.OnClickListener
    {
        private TextView tv_message; // 声明一个文本视图对象
        
        private boolean isPlaying = false; // 是否正在播放新闻
        
        private int BEGIN = 0, SCROLL = 1, END = 2; // 0为开始，1为滚动，2为结束
        
        private String[] mNewsArray = { "北斗导航系统正式开通，定位精度媲美GPS",
                "黑人之死引发美国各地反种族主义运动", "印度运营商禁止华为中兴反遭诺基亚催债",
                "贝鲁特发生大爆炸全球紧急救援黎巴嫩", "日本货轮触礁毛里求斯造成严重漏油污染"
        };
    
        @Override
        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            
            setContentView(R.layout.activity_main);
            tv_message = findViewById(R.id.tv_message);
            
            findViewById(R.id.btn_start).setOnClickListener(this);
            findViewById(R.id.btn_stop).setOnClickListener(this);
        }
    
        @Override
        public void onClick(View v) 
        {
            if (v.getId() == R.id.btn_start)   // 点击了开始播放新闻的按钮
            { 
                if (!isPlaying)      // 如果不在播放就开始播放
                {
                    isPlaying = true;
                    new PlayThread().start(); // 创建并启动新闻播放线程
                }
            }
            else if (v.getId() == R.id.btn_stop)   // 点击了结束播放新闻的按钮
            {
                isPlaying = false;
            }
        }
    
        // 定义一个新闻播放线程
        private class PlayThread extends Thread 
        {
            @Override
            public void run() 
            {
                mHandler.sendEmptyMessage(BEGIN); // 向处理器发送播放开始的空消息
                
                while (isPlaying)          // 正在播放新闻
                { 
                    try 
                    {
                        sleep(2000); // 睡眠两秒(2000毫秒)
                    } 
                    catch (InterruptedException e) 
                    {
                        e.printStackTrace();
                    }
                    
                    Message message = Message.obtain(); // 获得默认的消息对象
                    
                    //Message message = mHandler.obtainMessage(); // 获得处理器的消息对象
                    
                    message.what = SCROLL; // 消息类型
                    
                    message.obj = mNewsArray[new Random().nextInt(5)]; // 消息描述
                    
                    mHandler.sendMessage(message); // 向处理器发送消息
                }
                
                mHandler.sendEmptyMessage(END); // 向处理器发送播放结束的空消息
                
                // 如果只要简单处理，也可绕过Handler，直接调用runOnUiThread方法操作界面
    //            runOnUiThread(new Runnable() {
    //                @Override
    //                public void run() {
    //                    String desc = String.format("%s\n%s %s", tv_message.getText().toString(), DateUtil.getNowTime(), "新闻播放结束，谢谢观看");
    //                    tv_message.setText(desc);
    //                }
    //            });
                
                isPlaying = false;
            }
        }
    
        // 创建一个处理器对象
        private Handler mHandler = new Handler(Looper.myLooper()) 
        {
            // 在收到消息时触发
            public void handleMessage(Message msg) 
            {
                
                String desc = tv_message.getText().toString();
                
                if (msg.what == BEGIN)    // 开始播放
                { 
                    desc = String.format("%s\n%s %s", desc, DateUtil.getNowTime(), "开始播放新闻");
                }
                else if (msg.what == SCROLL)     // 滚动播放
                { 
                    desc = String.format("%s\n%s %s", desc, DateUtil.getNowTime(), msg.obj);
                } 
                else if (msg.what == END)        // 结束播放
                { 
                    desc = String.format("%s\n%s %s", desc, DateUtil.getNowTime(), "新闻播放结束");
                }
                
                tv_message.setText(desc);
            }
            
        };
    
    }

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DateUtil

package com.example.myapplication;
    
    import android.annotation.SuppressLint;
    import android.text.TextUtils;
    
    import java.text.SimpleDateFormat;
    import java.util.Calendar;
    import java.util.Date;
    
    @SuppressLint("SimpleDateFormat")
    public class DateUtil 
    {
        // 获取当前的日期时间
        public static String getNowDateTime(String formatStr)
        {
            String format = formatStr;
            if (TextUtils.isEmpty(format))
            {
                format = "yyyyMMddHHmmss";
            }
            SimpleDateFormat sdf = new SimpleDateFormat(format);
            return sdf.format(new Date());
        }
    
        // 获取当前的时间
        public static String getNowTime()
        {
            SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
            return sdf.format(new Date());
        }
    
        // 获取当前的时间(精确到毫秒)
        public static String getNowTimeDetail()
        {
            SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS");
            return sdf.format(new Date());
        }
    
        public static String getNowDate()
        {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
            return sdf.format(new Date());
        }
    
        public static String getDate(Calendar calendar)
        {
            Date date = calendar.getTime();
            // 创建一个日期格式化的工具
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            // 将当前日期时间按照指定格式输出格式化后的日期时间字符串
            return sdf.format(date);
        }
    
        public static String getMonth(Calendar calendar)
        {
            Date date = calendar.getTime();
            // 创建一个日期格式化的工具
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");
            // 将当前日期时间按照指定格式输出格式化后的日期时间字符串
            return sdf.format(date);
        }
    
        public static Date formatString(String strTime)
        {
            Date date = new Date();
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            try
            {
                date = sdf.parse(strTime);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
    
            return date;
        }
    
    }

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