android - 在线程android中使用处理程序

Question

我正在尝试在线程内运行处理程序，但出现错误“无法在未调用 Looper.prepare() 的线程内创建处理程序”我花了数小时寻找解决方案，但找不到所以我决定发布这个。我试过调用“Looper.prepare();”，它修复了强制关闭问题，但阻止了处理程序中的代码工作。

    public void ten(View view) {
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            private Vibrator mVibrator;
            private Runnable runnable;
            private Handler handler;

            public void run() {
                mVibrator = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
                mVibrator.vibrate(1000 * 10);// 10 sec sprint

                // HANDLER
                handler = new Handler();
                runnable = new Runnable() {
                    public void run() {
                        // calculate result1
                        TextView theFact = (TextView) findViewById(R.id.txtCurrentSpeed);
                        String shareFact = theFact.getText().toString();
                        TextView theFact1 = (TextView) findViewById(R.id.result1);
                        theFact1.setText(String.valueOf(shareFact));
                        // calculate result1
                    }
                };
                handler.postDelayed(runnable, 3000);
                // HANDLER END //
            }
        }, 5000, 60 * 1000 * 3);// 3 minute break (+5s first run delay)
    }
}



08-10 21:37:59.187: E/AndroidRuntime(26129): FATAL EXCEPTION: Timer-0
08-10 21:37:59.187: E/AndroidRuntime(26129): Process: com.example.speedometer, PID: 26129
08-10 21:37:59.187: E/AndroidRuntime(26129): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
08-10 21:37:59.187: E/AndroidRuntime(26129):    at android.os.Handler.<init>(Handler.java:200)
08-10 21:37:59.187: E/AndroidRuntime(26129):    at android.os.Handler.<init>(Handler.java:114)
08-10 21:37:59.187: E/AndroidRuntime(26129):    at com.example.speedometer.MainActivity$2.run(MainActivity.java:141)
08-10 21:37:59.187: E/AndroidRuntime(26129):    at java.util.Timer$TimerImpl.run(Timer.java:284)

我用 Thread 替换了 Handler，线程内的代码有效，但是它强制关闭并给出以下异常:

08-10 21:57:35.477: E/AndroidRuntime(31261): FATAL EXCEPTION: Thread-4399
08-10 21:57:35.477: E/AndroidRuntime(31261): Process: com.example.speedometer, PID: 31261
08-10 21:57:35.477: E/AndroidRuntime(31261): android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:7147)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:998)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.View.requestLayout(View.java:18491)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.View.requestLayout(View.java:18491)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.View.requestLayout(View.java:18491)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.View.requestLayout(View.java:18491)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:361)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.view.View.requestLayout(View.java:18491)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.widget.TextView.checkForRelayout(TextView.java:8060)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.widget.TextView.setText(TextView.java:4836)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.widget.TextView.setText(TextView.java:4660)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at android.widget.TextView.setText(TextView.java:4635)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at com.example.speedometer.MainActivity$2$1.run(MainActivity.java:154)
08-10 21:57:35.477: E/AndroidRuntime(31261):    at java.lang.Thread.run(Thread.java:818)

Answer 1

android的Main/UI线程默认有一个looper。因此，如果您在方法在 UI 线程上运行的 Activity/Fragment/View 中的任何位置创建 Handler 的实例，它将使用默认的 Looper 并且永远不会抛出异常。

因此，最好在主/UI 线程上创建 Handler 来更新 UI。

话虽如此，解决您的解决方案的最简单方法是像这样将默认 Looper 作为参数传递

 handler = new Handler(Looper.getMainLooper());

这将解决您尝试更新 UI 时遇到的问题。