Android实现定时器App(线程的使用,跨线程更新UI)

一.运行效果

在这里插入图片描述

点击启动计时
在这里插入图片描述
点击停止计时

二.项目情况

本项目主要学习二点:

线程的使用
跨线程更新UI

1.项目源代码

activity_main.xml 前端代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/constraintLayout"
        android:layout_width="0dp"
        android:layout_height="181dp"
        android:layout_marginStart="1dp"
        android:layout_marginTop="1dp"
        android:layout_marginEnd="1dp"
        android:background="#FFEB3B"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/text_shownum"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="156dp"
            android:layout_marginTop="28dp"
            android:text="0"
            android:textColor="#F44336"
            android:textSize="50sp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="56dp"
            android:layout_marginTop="28dp"
            android:text="秒"
            android:textColor="#000000"
            android:textSize="50sp"
            app:layout_constraintStart_toEndOf="@+id/text_shownum"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/btn_end"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginEnd="92dp"
            android:layout_marginBottom="11dp"
            android:onClick="btn_end"
            android:text="停止计时"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent" />

        <Button
            android:id="@+id/btn_start"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="45dp"
            android:layout_marginBottom="11dp"
            android:onClick="btn_start"
            android:text="启动计时"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity 后端代码:

package com.example.project6;

import static android.view.View.INVISIBLE;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    
    
    private TextView txt_shownum;
    private Button btn_start,btn_end;
    private Thread currentThread=null;
    private int showNum = 0;
    private boolean tage = false;
    Handler handler = new Handler() {
    
    

        public void handleMessage(Message msg) {
    
    
            // 获取数据
            if (msg.what == 1){
    
    
                txt_shownum.setText(String.valueOf(msg.arg1));
            }

        }

    };

    Runnable runnable=new Runnable() {
    
    
        @Override
        public void run() {
    
    
            try {
    
    
                while (tage) {
    
    
                    // 延时1s更新数据
                    Thread.sleep(1000);
                    // 跨线程传递数据
                    ++showNum;
                    Message msg = new Message();
                    msg.what = 1;
                    msg.arg1 = showNum;
                    handler.sendMessage(msg);
                }

            } catch (InterruptedException e) {
    
    
                e.printStackTrace();
            }
        }
    };

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

    private void initView() {
    
    
        txt_shownum = findViewById(R.id.text_shownum);
        btn_start = findViewById(R.id.btn_start);
        btn_end = findViewById(R.id.btn_end);
        // 默认情况下停止按钮无法启动
        btn_end.setEnabled(false);
    }

    public void btn_end(View view) throws InterruptedException {
    
    
        btn_start.setEnabled(true);
        btn_end.setEnabled(false);
        tage = false;
        currentThread.interrupt();
    }

    public void btn_start(View view) {
    
    
        tage = true;
        // 停止按钮有效
        btn_end.setEnabled(true);
        btn_start.setEnabled(false);
        // 开始计时
        currentThread = new Thread(runnable);
        currentThread.start();

    }



}