Android(安卓)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(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] = 101-11 14:04:10.826 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: runOnUi [Name] = main [ID] = 101-11 14:04:10.830 12804-12829/calldead.redwolf.threaddemo I/RedWolfChao: ThreadPoolExecutor [Name] = pool-1-thread-1 [ID] = 20801-11 14:04:10.833 12804-12828/calldead.redwolf.threaddemo I/RedWolfChao: newThread [Name] = Thread-207 [ID] = 20701-11 14:04:10.850 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: mHandler.post [Name] = main [ID] = 101-11 14:04:10.850 12804-12804/calldead.redwolf.threaddemo I/RedWolfChao: ThreadPoolExecutor_runOnUi [Name] = main [ID] = 101-11 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。

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