Android 主线程子线程执行关系

Android 切换线程的方式[我常用的]

 

    1. Handler.post[切换至主线程]

    2. new Thread().start()[切换至子线程]

    3. 线程池 ThreadPoolExecutor.execute()[切换至子线程]

    4. runOnUiThread[切换至主线程]

 

然后写代码看一下他们之间的执行关系[代码中一看就清晰了]

package calldead.redwolf.threaddemo;

import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

/**
 * 思考各种切线程方式之间的主从关系
 */
public class MainActivity extends AppCompatActivity {
    private String TAG = "RedWolfChao";
    //  线程池 1
    private ThreadPoolExecutor mThreadPoolExecutor =
            new ThreadPoolExecutor(3, 5, 1,
                    TimeUnit.SECONDS, new LinkedBlockingDeque<Runnable>(100));
    //  Handler
    private Handler mHandler = new Handler();

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

    private void execThread() {
        //  直接执行[主线程]
        Log.i(TAG, "[Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
        //  new Thread[子线程]
        new Thread(new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "newThread [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        //  子线程中runOnUiThread [主线程]
                        Log.i(TAG, "newThread_runOnUi [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
                    }
                });
            }
        }).start();
        //  线程池执行 [子线程]
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "ThreadPoolExecutor [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
                //  线程池runOnUi [主线程]
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Log.i(TAG, "ThreadPoolExecutor_runOnUi [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
                    }
                });
            }
        };
        mThreadPoolExecutor.execute(runnable);
        //  直接runOnUi 没啥意义 读源码就知道了 [主线程]
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "runOnUi [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
            }
        });
        //
        mHandler.post(new Runnable() {
            @Override
            public void run() {
                Log.i(TAG, "mHandler.post [Name] = " + Thread.currentThread().getName() + " [ID] = " + Thread.currentThread().getId());
            }
        });
    }
}

 

日志打印如下 ; 

01-11 14:04:10.826 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: [Name] = main [ID] = 1

01-11 14:04:10.826 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: runOnUi [Name] = main [ID] = 1

01-11 14:04:10.830 12804-12829/calldead.redwolf.threaddemo I/RedWolfChao: ThreadPoolExecutor [Name] = pool-1-thread-1 [ID] = 208

01-11 14:04:10.833 12804-12828/calldead.redwolf.threaddemo I/RedWolfChao: newThread [Name] = Thread-207 [ID] = 207

01-11 14:04:10.850 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: mHandler.post [Name] = main [ID] = 1

01-11 14:04:10.850 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: ThreadPoolExecutor_runOnUi [Name] = main [ID] = 1

01-11 14:04:10.850 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: newThread_runOnUi [Name] = main [ID] = 1

结论 : 

• 主线程[UI]只有一个

• 其它子线程可以有任意个

如图 :

 

 

附带runOnUiThread源码 : 

 

注释翻译 :

在UI线程上运行指定的操作。如果当前线程是ui-hread，则立即执行该操作。如果当前线程不是UI线程，则该操作将发布到UI线程的事件队列。