有人能给出一个简单的例子，每秒钟更新一个文本框左右?
我想要制作一个飞行的球，并需要每秒计算/更新球的坐标，这就是为什么我需要某种计时器。
我从这里什么也得不到。
当前回答
好的，因为这还没有清除，有3个简单的方法来处理这个。 下面的示例显示了所有3种方法，底部的示例显示了我认为更可取的方法。还记得在onPause中清理你的任务，如有必要保存状态。
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活动。
以下是我认为最好的方法。
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");
}
}
其他回答
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.TextView;
import android.app.Activity;
public class MainActivity extends Activity {
CheckBox optSingleShot;
Button btnStart, btnCancel;
TextView textCounter;
Timer timer;
MyTimerTask myTimerTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
optSingleShot = (CheckBox)findViewById(R.id.singleshot);
btnStart = (Button)findViewById(R.id.start);
btnCancel = (Button)findViewById(R.id.cancel);
textCounter = (TextView)findViewById(R.id.counter);
btnStart.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0) {
if(timer != null){
timer.cancel();
}
//re-schedule timer here
//otherwise, IllegalStateException of
//"TimerTask is scheduled already"
//will be thrown
timer = new Timer();
myTimerTask = new MyTimerTask();
if(optSingleShot.isChecked()){
//singleshot delay 1000 ms
timer.schedule(myTimerTask, 1000);
}else{
//delay 1000ms, repeat in 5000ms
timer.schedule(myTimerTask, 1000, 5000);
}
}});
btnCancel.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
if (timer!=null){
timer.cancel();
timer = null;
}
}
});
}
class MyTimerTask extends TimerTask {
@Override
public void run() {
Calendar calendar = Calendar.getInstance();
SimpleDateFormat simpleDateFormat =
new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
final String strDate = simpleDateFormat.format(calendar.getTime());
runOnUiThread(new Runnable(){
@Override
public void run() {
textCounter.setText(strDate);
}});
}
}
}
. xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold" />
<CheckBox
android:id="@+id/singleshot"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Single Shot"/>
您希望UI更新发生在已经存在的UI线程中。
最好的方法是使用一个Handler，它使用postDelayed在延迟后运行一个Runnable(每次运行都安排下一次运行);使用removeCallbacks清除回调。
您已经找到了正确的地方，所以再看一遍，也许可以弄清楚为什么代码示例不是您想要的。(请参见从计时器更新UI的同一篇文章)。
这里是解决方案，您需要在代码中添加以下类。您可以直接向XML文件添加视图。
import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.widget.TextView;
import java.util.Locale;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.TimeUnit;
public class TimerTextView extends TextView {
private static final int DEFAULT_INTERVAL = 1000;
private Timer timer = new Timer();
private long endTime = 0;
private long interval = DEFAULT_INTERVAL;
private boolean isCanceled = false;
public TimerTextView(Context context) {
super(context);
}
public TimerTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public TimerTextView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public TimerTextView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
@Override protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
stopTimer();
}
@Override protected void onVisibilityChanged(View changedView, int visibility) {
super.onVisibilityChanged(changedView, visibility);
if (VISIBLE == visibility) {
startTimer();
} else {
stopTimer();
}
}
public void setInterval(long interval) {
if (interval >= 0) {
this.interval = interval;
stopTimer();
startTimer();
}
}
public void setEndTime(long endTime) {
if (endTime >= 0) {
this.endTime = endTime;
stopTimer();
startTimer();
}
}
private void startTimer() {
if (endTime == 0) {
return;
}
if (isCanceled) {
timer = new Timer();
isCanceled = false;
}
timer.scheduleAtFixedRate(new TimerTask() {
@Override public void run() {
if (null == getHandler()) {
return;
}
getHandler().post(new Runnable() {
@Override public void run() {
setText(getDurationBreakdown(endTime - System.currentTimeMillis()));
}
});
}
}, 0, interval);
}
private void stopTimer() {
timer.cancel();
isCanceled = true;
}
private String getDurationBreakdown(long diff) {
long millis = diff;
if (millis < 0) {
return "00:00:00";
}
long hours = TimeUnit.MILLISECONDS.toHours(millis);
millis -= TimeUnit.HOURS.toMillis(hours);
long minutes = TimeUnit.MILLISECONDS.toMinutes(millis);
millis -= TimeUnit.MINUTES.toMillis(minutes);
long seconds = TimeUnit.MILLISECONDS.toSeconds(millis);
return String.format(Locale.ENGLISH, "%02d:%02d:%02d", hours, minutes, seconds);
//return "${getWithLeadZero(hours)}:${getWithLeadZero(minutes)}:${getWithLeadZero(seconds)}"
}
}
如果你已经有了时间。
public class Timer {
private float lastFrameChanged;
private float frameDuration;
private Runnable r;
public Timer(float frameDuration, Runnable r) {
this.frameDuration = frameDuration;
this.lastFrameChanged = 0;
this.r = r;
}
public void update(float dt) {
lastFrameChanged += dt;
if (lastFrameChanged > frameDuration) {
lastFrameChanged = 0;
r.run();
}
}
}
我认为你可以用Rx方法来做:
timerSubscribe = Observable.interval(1, TimeUnit.SECONDS)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<Long>() {
@Override
public void call(Long aLong) {
//TODO do your stuff
}
});
然后取消这个:
timerSubscribe.unsubscribe();
接收定时器 http://reactivex.io/documentation/operators/timer.html
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