一手遮天 Android

Posted 2021-06-02 webabcd - 专注于 android, ios, uw

一手遮天 android - 锁和并发处理: Lock 基础

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd

一手遮天 Android - 锁和并发处理: Lock 基础

示例如下:

/concurrent/LockDemo1.java

/**
 * Lock 基础
 *
 * Lock 是一个接口，ReentrantLock 实现了这个接口
 *     lock(), tryLock(), unlock()
 *     推荐 lock() 写在 try 外，unlock() 写在 finally 内
 */

package com.webabcd.androiddemo.concurrent;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import com.webabcd.androiddemo.R;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class LockDemo1 extends AppCompatActivity {

    private int _number = 0;
    private TextView _textView1;

    private Lock _lock = new ReentrantLock();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_concurrent_lockdemo1);

        _textView1 = (TextView) findViewById(R.id.textView1);

        sample();
    }

    // 启 2 个线程对 _number 不停的做 +1 的操作，有锁则结果正确，无锁则结果错误
    private void sample() {
        ExecutorService pool = Executors.newFixedThreadPool(2);
        pool.execute(new MyRunnable());
        pool.execute(new MyRunnable());
        pool.shutdown();

        while (true) {
            try {
                boolean terminated = pool.awaitTermination(10, TimeUnit.MILLISECONDS);
                // 线程池中的线程都执行完毕后则退出此循环
                if (terminated) {
                    break;
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        _textView1.setText(String.valueOf(_number));
    }

    private class MyRunnable implements Runnable {
        @Override
        public void run() {
            for (int i = 0; i < 10000; i++) {
                // 获取锁
                _lock.lock();

                // 尝试获取锁，并立即返回结果（获取到锁了则返回 true，没获取到锁则返回 false）
                // boolean ok = _lock.tryLock();

                // 尝试获取锁，并指定超时时间（获取到锁了则返回 true，没获取到锁则返回 false，）
                // boolean ok = _lock.tryLock(1000, TimeUnit.MILLISECONDS);

                try {
                    _number++;
                } catch (Exception ex) {

                } finally {
                    _lock.unlock();
                }
            }
        }
    }
}

/layout/activity_concurrent_lockdemo1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

项目地址 https://github.com/webabcd/AndroidDemo
作者 webabcd