如何在 View class 中设置定时器？

Question

我正在尝试设置一个用作计时器的文本。如果我扩展 Activity class，我将很容易地创建计时器。但是我在这个视图中面临很多问题 class。在这里，我编写了一个代码，其中圆的半径将减小，并且每次触摸屏幕时圆的半径都会增加。同时我需要一个计时器运行在顶部。因为我需要每 10 秒增加一次减速。

所以定时器在这里扮演着重要的角色。我尝试使用线程，它应该每 1 秒更新一次文本。但它显示了这个异常IllegalThreadStateException。

还有其他方法可以在此屏幕中实现计时器吗？或者我在代码中犯了什么错误..

感谢朋友们的帮助..

package com.kbt.testcircle;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Handler;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

public class MyView extends View {
    int radius = 100,i=0;

    boolean freeTouched = false;
    Path freePath;
    Handler handler = new Handler();

    public MyView(Context context) {
        super(context);
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MyView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public void calThread() {

        /*
         * Thread th=new Thread(){ public void run(){ try { sleep(2000); } catch
         * (InterruptedException e) { // TODO Auto-generated catch block
         * e.printStackTrace(); } finally{ radius-=1;
         * Log.i("kbt","inside thread 800 seconds"); } } }; th.start();
         */
        handler.postDelayed(new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub
                radius -= 1;
                Log.i("kbt", "inside thread 800 seconds");
                invalidate();
            }
        }, 500);


        Log.i("kbt", "Inside thread");
    }
Thread th=new Thread()
{
    public void run(){

        handler.postDelayed(new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub
                i++;
            }
        },1000);
    }
};
    @Override
    protected void onDraw(Canvas canvas) throws IllegalThreadStateException 
    {
        // TODO Auto-generated method stub

        th.start();
        Log.i("kbt","starting");
        super.onDraw(canvas);// th.start();

        Paint paint = new Paint();
        paint.setStyle(Paint.Style.STROKE);
        paint.setColor(Color.WHITE);
        paint.setStrokeWidth(3);
        canvas.drawCircle(getWidth() / 2, getHeight() / 2, radius, paint);
        paint.setColor(Color.WHITE);
        paint.setStrokeWidth(0);
        paint.setTextSize(25);
        canvas.drawText("Timer : "+i, getWidth()/4, getHeight()/4, paint);
        calThread();

        Log.i("kbt", "Inside clled");

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        switch (event.getAction()) {
        case MotionEvent.ACTION_UP:

            break;
        case MotionEvent.ACTION_DOWN:

            radius+=5;
            invalidate();
            /* freeTouched = true;
            freePath = new Path();
            freePath.moveTo(event.getX(), event.getY()); */
            break;
        case MotionEvent.ACTION_MOVE:
            /* freePath.lineTo(event.getX(), event.getY());
            invalidate(); */
            break;
        }

        return true;
    }

}

Answer 1

如果你真的要使用一个线程，你只能启动线程一次。如果要多次启动线程，请改用Runnable。

Answer 2

But it is showing this exception IllegalThreadStateException.

它是由不可运行或非线程引起的class。扩展 View 的 class 没有后台线程，因此您得到 IllegalThreadStateException.

Is there any other way to implement timer in this screen?

Java 提供了一个 Timer class 用于所有 class 类型：

Timer timer = new Timer();
TimerTask task = new TimerTask(){
    @Override
    public void run() {
    // do your thing here
    }
};
timer.schedule(task,
1, // delay the task 1ms before executed
10000); // repeating your task every 10000ms, i.e. 10 seconds

如何在 View class 中设置定时器？

How to set timer in View class?

multithreading

android

timer

draw