`handler.postDelayed`无法正常工作

huangapple
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英文:

handler.postDelayed not working correctly

问题

我有一个简单的秒表代码片段。线程在自定义类中运行，它通过接口连接到主活动

  1. public class MainActivity extends AppCompatActivity implements MainActivityInteractionInterface{
  3. public static boolean isRunning = false;
  4. Stopwatch stopWatch;
  5. private TextView textViewMilliSeconds;
  6. private TextView textViewSeconds;
  8. @Override
  9. protected void onCreate(Bundle savedInstanceState) {
  10.     super.onCreate(savedInstanceState);
  11.     setContentView(R.layout.activity_main);
  13.     textViewMilliSeconds = findViewById(R.id.textViewStopwatchMilliseconds);
  14.     textViewSeconds = findViewById(R.id.textViewStopwatchSeconds);
  16.     stopWatch = new Stopwatch(this, getApplicationContext());
  17.     stopWatch.runThread();
  18. }
  20. @Override
  21. public void updateUI() {
  22.     String time = String.format(Locale.getDefault(), "%03d", stopWatch.getMilliseconds());
  23.     textViewMilliSeconds.setText(time);
  25.     String timeSeconds = String.format(Locale.getDefault(), "%02d", stopWatch.getSeconds());
  26.     textViewSeconds.setText(timeSeconds);
  27. }
  29. public void startTimer(View view) {
  30.     isRunning = !isRunning;
  31. }
  32. }
  1. public class Stopwatch {
  2. private int milliseconds = 0;
  3. private int seconds = 0;
  5. public int getMilliseconds() {
  6.     return milliseconds;
  7. }
  9. public int getSeconds() {
  10.     return seconds;
  11. }
  13. private MainActivityInteractionInterface interactionInterface;
  14. private Context applicationContext;
  16. public Stopwatch(MainActivityInteractionInterface interactionInterface, Context applicationContext){
  17.     this.interactionInterface = interactionInterface;
  18.     this.applicationContext = applicationContext;
  19. }
  21. public void runThread(){
  22.     final Handler handler = new Handler();
  23.     handler.post(new Runnable(){
  24.         @Override
  25.         public void run(){
  26.             if(isRunning) {
  27.                 milliseconds++;
  28.                 if (milliseconds == 1000) {
  29.                     milliseconds = 0;
  30.                     seconds++;
  31.                     if(seconds == 60){
  32.                         seconds = 0;
  33.                     }
  34.                 }
  35.             }
  36.             interactionInterface.updateUI();
  37.             handler.postDelayed(this, 1);
  38.         }
  39.     });
  40. }
  41. }

处理程序应该每1毫秒更新一次，在达到1000毫秒时，经过1秒。如果我设置handler.postDelayed延迟低于15，达到1000毫秒将需要确切的18秒，为什么？

英文:

I have a simple stopwatch code piece. Thread is running in custom class, it connects to the main activity via Interface

  1. public class MainActivity extends AppCompatActivity implements MainActivityInteractionInterface{
  3. public static boolean isRunning = false;
  4. Stopwatch stopWatch;
  5. private TextView textViewMilliSeconds;
  6. private TextView textViewSeconds;
  8. @Override
  9. protected void onCreate(Bundle savedInstanceState) {
  10.     super.onCreate(savedInstanceState);
  11.     setContentView(R.layout.activity_main);
  13.     textViewMilliSeconds = findViewById(R.id.textViewStopwatchMilliseconds);
  14.     textViewSeconds = findViewById(R.id.textViewStopwatchSeconds);
  16.     stopWatch = new Stopwatch(this, getApplicationContext());
  17.     stopWatch.runThread();
  18. }
  20. @Override
  21. public void updateUI() {
  22.     String time = String.format(Locale.getDefault(), "%03d", stopWatch.getMilliseconds());
  23.     textViewMilliSeconds.setText(time);
  25.     String timeSeconds = String.format(Locale.getDefault(), "%02d", stopWatch.getSeconds());
  26.     textViewSeconds.setText(timeSeconds);
  27. }
  29. public void startTimer(View view) {
  30.     isRunning = !isRunning;
  31. }
  1. public class Stopwatch {
  2. private int milliseconds = 0;
  3. private int seconds = 0;
  5. public int getMilliseconds() {
  6.     return milliseconds;
  7. }
  9. public int getSeconds() {
  10.     return seconds;
  11. }
  13. private MainActivityInteractionInterface interactionInterface;
  14. private Context applicationContext;
  16. public Stopwatch(MainActivityInteractionInterface interactionInterface, Context applicationContext){
  17.     this.interactionInterface = interactionInterface;
  18.     this.applicationContext = applicationContext;
  19. }
  21. public void runThread(){
  22.     final Handler handler = new Handler();
  23.     handler.post(new Runnable(){
  24.         @Override
  25.         public void run(){
  26.             if(isRunning) {
  27.                 milliseconds++;
  28.                 if (milliseconds == 1000) {
  29.                     milliseconds = 0;
  30.                     seconds++;
  31.                     if(seconds == 60){
  32.                         seconds = 0;
  33.                     }
  34.                 }
  35.             }
  36.             interactionInterface.updateUI();
  37.             handler.postDelayed(this, 1);
  38.         }
  39.     });
  40. }

handler should update every 1 millisec, when there is 1000 milliseconds, 1 second passes by
If I set handler.postDelayed delay anything below 15 reaching 1000 milliseconds would take exactly 18 seconds, why?

答案1

得分: 1

我不知道为什么需要长达18秒的时间，但我可以告诉你这个：Android每16毫秒刷新一次UI（以达到60fps的速率），所以在更短的时间内将处理程序设置为updateUI没有意义，而且可能还会干扰它。

依我拙见，将其更新间隔设置为20毫秒，并相应地更改计数器的值，如下所示：

  1. handler.post(new Runnable(){
  2.     @Override
  3.     public void run(){
  4.         if(isRunning) {
  5.             milliseconds++;
  6.             if (milliseconds == 50) {
  7.                 milliseconds = 0;
  8.                 seconds++;
  9.                 if(seconds == 60){
  10.                     seconds = 0;
  11.                 }
  12.             }
  13.         }
  14.         interactionInterface.updateUI();
  15.         handler.postDelayed(this, 20);
  16.     }
  17. });
英文:

I don't know why it would take up to 18seconds, but I can tell you this: Android refresh the UI every 16msec (to have a rate of 60fps), so setting the handler to updateUI in a lesser time would make no sense and maybe also interfier with it.

In my humble opinion, make it to update in 20msec and change the counter values according, like this:

  1. handler.post(new Runnable(){
  2.     @Override
  3.     public void run(){
  4.         if(isRunning) {
  5.             milliseconds++;
  6.             if (milliseconds == 50) {
  7.                 milliseconds = 0;
  8.                 seconds++;
  9.                 if(seconds == 60){
  10.                     seconds = 0;
  11.                 }
  12.             }
  13.         }
  14.         interactionInterface.updateUI();
  15.         handler.postDelayed(this, 20);
  16.     }
  17. });

答案2

得分: 0

看看 handler.postDelayed(this, 1); 的第二个参数。

根据你增加毫秒的方式进行修改。

英文:

Look at the second argument of handler.postDelayed(this, 1);

Change it according to the way you increment your milliseconds.

huangapple
  • 本文由 发表于 2020年4月5日 20:10:47
  • 转载请务必保留本文链接：https://java.coder-hub.com/61042358.html
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