如何在Android中设置计时器? [英] How to set timer in android?
问题描述
有人可以举一个简单的例子来说明每秒更新文本字段吗?
Can someone give a simple example of updating a textfield every second or so?
我想做一个飞行球,并且需要每秒计算/更新球坐标,这就是为什么我需要某种计时器的原因.
I want to make a flying ball and need to calculate/update the ball coordinates every second, that's why I need some sort of a timer.
我没有从此处获得任何信息
推荐答案
好,因为尚未清除,但有3种简单的方法可以解决此问题. 下面是显示所有3个示例的示例,底部是仅显示我认为更可取的方法的示例.还记得在onPause上清理任务,必要时保存状态.
ok since this isn't cleared up yet there are 3 simple ways to handle this. Below is an example showing all 3 and at the bottom is an example showing just the method I believe is preferable. Also remember to clean up your tasks in onPause, saving state if necessary.
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,只能从主ui线程修改UI,因此请使用处理程序或activity.runOnUIThread(Runnable r);
the main thing to remember is that the UI can only be modified from the main ui thread so use a handler or activity.runOnUIThread(Runnable r);
这是我认为是首选的方法.
Here is what I consider to be the preferred method.
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");
}
}
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