机器人计时器？怎么做？
机器人计时器？怎么做？
提问于 2018-08-15 01:00:45
有人可以给出一个每秒钟更新文本字段的简单示例吗？
我想做一个飞球，需要每秒计算、更新球的坐标，我需要计时器。
（http://android-developers.blogspot.com/2007/11/stitch-in-time.html）
回答 2
Stack Overflow用户
发布于 2018-08-15 09:21:20
很简单！创造新的定时器。
Timer timer = new Timer();然后扩展计时器任务。
class UpdateBallTask extends TimerTask {
Ball myBall;
public void run() {
//calculate the new position of myBall
}
}然后以一些更新间隔将新任务添加到Timer
final int FPS = 40;
TimerTask updateBall = new UpdateBallTask();
timer.scheduleAtFixedRate(updateBall, 0, 1000/FPS);Stack Overflow用户
发布于 2018-08-15 10:21:27
有3种简单的方法来处理这个问题。下面是一个显示3个示例，底部是一个示例，显示了我认为更可取的方法。记得在onPause中清理你的任务，必要时保存状态。
import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.Handler.Callback;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class main extends Activity {
TextView text, text2, text3;
long starttime = 0;
//this posts a message to the main thread from our timertask
//and updates the textfield
final Handler h = new Handler(new Callback() {
@Override
public boolean handleMessage(Message msg) {
long millis = System.currentTimeMillis() - starttime;
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
text.setText(String.format("%d:%02d", minutes, seconds));
return false;
}
});
//runs without timer be reposting self
Handler h2 = new Handler();
Runnable run = new Runnable() {
@Override
public void run() {
long millis = System.currentTimeMillis() - starttime;
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
text3.setText(String.format("%d:%02d", minutes, seconds));
h2.postDelayed(this, 500);
}
};
//tells handler to send a message
class firstTask extends TimerTask {
@Override
public void run() {
h.sendEmptyMessage(0);
}
};
//tells activity to run on ui thread
class secondTask extends TimerTask {
@Override
public void run() {
main.this.runOnUiThread(new Runnable() {
@Override
public void run() {
long millis = System.currentTimeMillis() - starttime;
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
text2.setText(String.format("%d:%02d", minutes, seconds));
}
});
}
};
Timer timer = new Timer();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
text = (TextView)findViewById(R.id.text);
text2 = (TextView)findViewById(R.id.text2);
text3 = (TextView)findViewById(R.id.text3);
Button b = (Button)findViewById(R.id.button);
b.setText("start");
b.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Button b = (Button)v;
if(b.getText().equals("stop")){
timer.cancel();
timer.purge();
h2.removeCallbacks(run);
b.setText("start");
}else{
starttime = System.currentTimeMillis();
timer = new Timer();
timer.schedule(new firstTask(), 0,500);
timer.schedule(new secondTask(), 0,500);
h2.postDelayed(run, 0);
b.setText("stop");
}
}
});
}
@Override
public void onPause() {
super.onPause();
timer.cancel();
timer.purge();
h2.removeCallbacks(run);
Button b = (Button)findViewById(R.id.button);
b.setText("start");
}
}要记住的主要事情是UI只能从主ui线程修改，所以使用处理程序或activity.runOnUIThread（Runnable r）;
这是我认为首选的方法。
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class TestActivity extends Activity {
TextView timerTextView;
long startTime = 0;
//runs without a timer by reposting this handler at the end of the runnable
Handler timerHandler = new Handler();
Runnable timerRunnable = new Runnable() {
@Override
public void run() {
long millis = System.currentTimeMillis() - startTime;
int seconds = (int) (millis / 1000);
int minutes = seconds / 60;
seconds = seconds % 60;
timerTextView.setText(String.format("%d:%02d", minutes, seconds));
timerHandler.postDelayed(this, 500);
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.test_activity);
timerTextView = (TextView) findViewById(R.id.timerTextView);
Button b = (Button) findViewById(R.id.button);
b.setText("start");
b.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Button b = (Button) v;
if (b.getText().equals("stop")) {
timerHandler.removeCallbacks(timerRunnable);
b.setText("start");
} else {
startTime = System.currentTimeMillis();
timerHandler.postDelayed(timerRunnable, 0);
b.setText("stop");
}
}
});
}
@Override
public void onPause() {
super.onPause();
timerHandler.removeCallbacks(timerRunnable);
Button b = (Button)findViewById(R.id.button);
b.setText("start");
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100002167
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