Question

我想在无限循环中打开/关闭闪光灯，所以当它打开时它应该等待5秒然后关闭然后等待5秒再次打开，依此类推...... 我怎么能这样做？

这是我的代码：

b2.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {
                        // TODO Auto-generated method stub

                    //  num = Integer.parseInt(n.getText().toString());

                        while(bl){

                             if(camera == null){

                                 new Thread(new Runnable() {
                                        @Override
                                        public void run() {
                                            try {
                                                Thread.sleep(5000);
                                            } catch (InterruptedException e) {
                                                e.printStackTrace();
                                            }
                                            runOnUiThread(new Runnable() {
                                                @Override
                                                public void run() {
                                                    turnOn();
                                                }
                                            });
                                        }
                                    }).start();
                                }

                             else{

                                 new Thread(new Runnable() {
                                        @Override
                                        public void run() {
                                            try {
                                                Thread.sleep(5000);
                                            } catch (InterruptedException e) {
                                                e.printStackTrace();
                                            }
                                            runOnUiThread(new Runnable() {
                                                @Override
                                                public void run() {
                                                    turnOff();
                                                }
                                            });
                                        }
                                    }).start();
                                }
                        }

                    }
                });

Answer 1

我建议不要使用Thread来实现这一目标。为什么不使用Runnable课程并通过Handler延迟发布？例如：

Handler handler = new Handler(); // make this a member variable of your class
boolean isOn = false; // make this a member variable of your class

final Runnable flashRunnable = new Runnable() {
    @Override
    public void run() {
        if (isOn) {
            turnOff();
            isOn = false;
        } else {
            turnOn();
            isOn = true;
        }
        handler.postDelayed(flashRunnable, 5000);
    }
};

handler.postDelayed(flashRunnable, 5000);

如果您需要在UI线程的Runnable内运行代码，您甚至可以在postDelayed上致电View而不是创建Handler

Answer 2

尝试使用Executors代替（丑陋）Thread.sleep（）：

boolean cameraOn = true

final Runnable runnable = new Runnable() {
    @Override
    public void run() {
        // your logic here:
        // if (cameraOn) ...
        // else ...
        // cameraOn = !cameraOn
    }
};

Executors.newScheduledThreadPool(1).schedule(new Runnable() {

    @Override
    public void run() {
        runnable.run();
    }

}, 5, TimeUnit.SECONDS);

为什么线程创建失败？

2 个答案: