线程使用简介

1、耗时操作都需要使用到线程。

2、开启线程的活动结束后线程未被关闭的话依旧在运行

1）线程的常规操作

代码如下：

	@Override
	protected void onCreate(@Nullable Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		ButterKnife.bind(this);
		Log.e("MainActivity", "页面1创建");
		next.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				startActivity(new Intent(MainActivity.this, SecondActivity.class));
			}
		});
		start.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				//传建一个计数线程，每个1S 计数
				new Thread(new Runnable() {
					@Override
					public void run() {
						int num = 0;
						Log.e("MainActivity", "线程开始");
						while (true) {
							try {
								Thread.sleep(1000);
								Log.e("MainActivity", "记数开始:" + num);
								num++;
							} catch (InterruptedException e) {
								e.printStackTrace();
							}
						}
//						Log.e("MainActivity", "线程结束");		//循环条件为true 死循环时 后面代码会报错
					}
				}).start();
			}
		});
	}

	@Override
	protected void onStop() {
		super.onStop();
		Log.e("MainActivity", "页面1onStop");
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		Log.e("MainActivity", "页面1结束");
	}

打印log如下：

01-11 14:17:27.588 26204-26204/com.leixiansheng.test E/MainActivity: 页面1创建
01-11 14:17:34.120 26204-26229/com.leixiansheng.test E/MainActivity: 线程开始
01-11 14:17:35.121 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:0
01-11 14:17:36.122 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:1
01-11 14:17:37.123 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:2
01-11 14:17:37.465 26204-26204/com.leixiansheng.test E/MainActivity: 页面2创建
01-11 14:17:37.819 26204-26204/com.leixiansheng.test E/MainActivity: 页面1onStop
01-11 14:17:38.124 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:3
01-11 14:17:39.124 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:4
01-11 14:17:40.125 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:5
01-11 14:17:40.505 26204-26204/com.leixiansheng.test E/MainActivity: 页面2结束
01-11 14:17:41.126 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:6
01-11 14:17:42.127 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:7
01-11 14:17:43.079 26204-26204/com.leixiansheng.test E/MainActivity: 页面1onStop
01-11 14:17:43.079 26204-26204/com.leixiansheng.test E/MainActivity: 页面1结束
01-11 14:17:43.128 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:8
01-11 14:17:44.128 26204-26229/com.leixiansheng.test E/MainActivity: 记数开始:9

从操作可以看出，开启线程后，进入其他页面线程依旧可以运行。并且有个问题，退出程序后线程还在运行，必须手动杀死程序进程，线程才会停止。（这样就会造成线程泄漏）

2）为了保证程序结束时也停止线程，我们可以引入 volatile 线程标识符

代码如下：

private volatile boolean isStop = false;		//线程停止标识符

	@Override
	protected void onCreate(@Nullable Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		ButterKnife.bind(this);
		Log.e("MainActivity", "页面1创建");
		next.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				startActivity(new Intent(MainActivity.this, SecondActivity.class));
			}
		});
		start.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				//传建一个计数线程，每个1S 计数
				new Thread(new Runnable() {
					@Override
					public void run() {
						int num = 0;
						Log.e("MainActivity", "线程开始");
						while (!isStop) {
							try {
								Thread.sleep(1000);
								Log.e("MainActivity", "记数开始:" + num);
								num++;
							} catch (InterruptedException e) {
								e.printStackTrace();
							}
						}
						Log.e("MainActivity", "线程结束");		//循环条件为true 死循环时 后面代码会报错
					}
				}).start();
			}
		});
	}

	@Override
	protected void onStop() {
		super.onStop();
		Log.e("MainActivity", "页面1onStop");
	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		isStop = true;
		Log.e("MainActivity", "页面1结束");
	}

打印log如下： 

01-11 14:41:10.755 27113-27113/com.leixiansheng.test E/MainActivity: 页面1创建
01-11 14:41:22.010 27113-27149/com.leixiansheng.test E/MainActivity: 线程开始
01-11 14:41:23.012 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:0
01-11 14:41:24.012 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:1
01-11 14:41:24.816 27113-27113/com.leixiansheng.test E/MainActivity: 页面2创建
01-11 14:41:25.013 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:2
01-11 14:41:25.168 27113-27113/com.leixiansheng.test E/MainActivity: 页面1onStop
01-11 14:41:26.014 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:3
01-11 14:41:27.014 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:4
01-11 14:41:28.015 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:5
01-11 14:41:28.022 27113-27113/com.leixiansheng.test E/MainActivity: 页面2结束
01-11 14:41:29.016 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:6
01-11 14:41:30.016 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:7
01-11 14:41:31.017 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:8
01-11 14:41:31.135 27113-27113/com.leixiansheng.test E/MainActivity: 页面1onStop
01-11 14:41:31.136 27113-27113/com.leixiansheng.test E/MainActivity: 页面1结束
01-11 14:41:32.018 27113-27149/com.leixiansheng.test E/MainActivity: 记数开始:9
01-11 14:41:32.018 27113-27149/com.leixiansheng.test E/MainActivity: 线程结束

从日志可以看出。开始线程后，进入其他页面线程依旧在运行，程序退出后线程也随程序结束。