Thread

讓主線程等待子線程的運行

方法一：join,理解成等待子線程終止，可用於等待一個或多個子線程的結果，而後主線程再繼續執行。

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.e("Thread", "主線程開始運行");
        new Thread1().start();
        Log.e("Thread", "主線程結束運行");
    }
}

public class Thread1 extends Thread{
    @Override
    public void run() {
        Log.e("Thread", "Thread1開始運行");
        Thread2 thread2 = new Thread2();
        thread2.start();
        try {
            thread2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.e("Thread","Thread1結束運行");
    }
}

public class Thread2 extends Thread{
    @Override
    public void run() {
        Log.e("Thread", "Thread2開始運行");
        try {
            Thread2.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.e("Thread","Thread2結束運行");
    }
}

 咱們在主線程中添加了一個thread1，在thread1中運行並加入thread2，在thread2中讓他延時1S。

咱們來看看結果，（主線程可能在Thread1開始前結束，可能在在開始後結束，這不是重點），Thread1在Thread2運行結束後才結束

說明咱們作到了讓父線程（Thread1）等待子線程(Thread2)

 

 

 2.使用FLAG標誌位，就是設一個全局變量，子線程沒結束就一直while（）

public class MainActivity extends AppCompatActivity {
    public static int FLAG = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        new Thread1().start();
    }
}

public class Thread1 extends Thread{
    @Override
    public void run() {
        Log.e("Thread", "Thread1開始運行");
        Thread2 thread2 = new Thread2();
        thread2.start();
        while(MainActivity.FLAG != 1){
            //這裏能夠作點其餘的事情哦
        }
        MainActivity.FLAG = 0;
        Log.e("Thread","Thread1結束運行");
    }
}

public class Thread2 extends Thread{
    @Override
    public void run() {
        Log.e("Thread", "Thread2開始運行");
        try {
            Thread2.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.e("Thread","Thread2結束運行");
        MainActivity.FLAG = 1;
    }
}

 

運行結果，能夠看到咱們成功了，可是我不喜歡這種方法，感受很卑鄙

 

3.CountDownLatch 經過檢查子線程的個數來實現的

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        new Thread1().start();
    }
}


public class Thread1 extends Thread{
    public static CountDownLatch countDownLatch = new CountDownLatch(1);//設置數量
    @Override
    public void run() {
        Log.e("Thread", "Thread1開始運行");
        Thread2 thread2 = new Thread2();
        thread2.start();
        try {
            countDownLatch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.e("Thread","Thread1結束運行");
    }
}


public class Thread2 extends Thread{
    @Override
    public void run() {
        Log.e("Thread", "Thread2開始運行");
        try {
            Thread2.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        Log.e("Thread","Thread2結束運行");
        Thread1.countDownLatch.countDown();//運行結束，數量減小
    }
}

 

 

不用說太多