Android中的多线程示例

同时处理多个任务是“多任务处理” 。以同样的方式，在一台计算机中同时运行的多个线程称为“多线程” 。从技术上讲，线程是进程的单元。多个这样的线程组合形成一个进程。这意味着当一个进程中断时，等效数量的线程可用。
例如，“自动更正”是指软件在键入的当前单词中查找错误的过程。无休止地检查错误并同时提供建议是多线程过程的一个示例。

示例Android应用：

让我们尝试在Android应用程序的帮助下可视化多线程。在下面的示例中，单击按钮时同时启动3个线程并同时工作。

方法：
步骤1：在activity_main.xml中添加以下代码。在这里，我们添加了三个TextViews和一个按钮。

步骤2：在MainActivity中添加以下代码。在这里，创建了三个线程，每个线程在单击按钮时都会每秒更新一次相应的TextView(在代码中声明)。这些线程将继续运行，直到再次单击该按钮(即“停止”)为止。

Java

class MainActivity : AppCompatActivity() {
    @SuppressLint("SetTextI18n")
    override fun onCreate(savedInstanceState: Bundle?)
    {
        super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
  
            // Assigning Layout elements
            val tv1
            = findViewById(R.id.tv1)
                val tv2
            = findViewById(R.id.tv2)
                val tv3
            = findViewById(R.id.tv3)
                val btn
            = findViewById(R.id.btnStart)
  
            // Boolean for Button (initially False)
            var boolbtn
            = false
              // Button onClick action
              btn.setOnClickListener
        {
            // Button (True)
            boolbtn = !boolbtn
                      // Case where Button is False
                      if (!boolbtn)
            {
                tv1.text = "Stopped1"
                tv2.text = "Stopped2"
                tv3.text = "Stopped3"
                btn.text = "Start"
            }
            // Case where Threads are running
            else
            {
                // Setting the button text as "Stop"
                btn.text = "Stop"
  
                           // Thread 1
                           Thread(Runnable {
  
                               // Runs only when Button is True
                               while (boolbtn) {
  
                                   runOnUiThread
                                   {
                                       tv1.text = "Started1"
                                   }
                                   Thread.sleep(1000)
                                       runOnUiThread
                                   {
                                       tv1.text = "Activity1"
                                   }
                                   Thread.sleep(1000)
                               }
                           }).start()
  
                           // Thread 2
                           Thread(Runnable {
  
                                 // Runs only when Button is
                                 // True
                                 while (boolbtn) {
                                     runOnUiThread
                                     {
                                         tv2.text = "Started2"
                                     }
                                     Thread.sleep(1000)
                                         runOnUiThread
                                     {
                                         tv2.text = "Activity2"
                                     }
                                     Thread.sleep(1000)
                                 }
                             }).start()
  
                           // Thread 3
                           Thread(Runnable {
  
                                   // Runs only when Button is
                                   // True
                                   while (boolbtn) {
                                       runOnUiThread
                                       {
                                           tv3.text = "Started3"
                                       }
                                       Thread.sleep(1000)
                                           runOnUiThread
                                       {
                                           tv3.text = "Activity3"
                                       }
                                       Thread.sleep(1000)
                                   }
                               })
                               .start()
            }
        }
    }
}

输出：

多线程概念适用于各种机器上的大量日常应用程序。然而，同样存在缺点。在初学者级别，人们只能想到机器上的负载或增加的复杂性。但是，从更高的角度来看，预计会出现多种情况，例如复杂的测试，不可预测的结果，死锁，饥饿等。

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