Android Timer

姚臻
2023-12-01

Timer 跟线程的安全有关,所以我们要用Handler来处理:

代码如下:(此Demo主要是演示camera的self Timer 的功能)

package com.example.mytimer;

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.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class myTimer extends Activity implements OnClickListener{
    /** Called when the activity is first created. */
    private static final int NOTIFY = 1111;
    private Button mBtnStart;
    private Timer mTimer;
    private TimerTask mTTask;
    int mCount = 0;

    public Handler mHandler = new Handler(){  
        public void handleMessage(Message msg) {  
            switch (msg.what) {      
            case NOTIFY:      
                if (mCount > 3)
                {
                    mTimer.cancel();
                    mTTask.cancel();
                    mCount = 0;
                }
                else {
                    Toast.makeText(getApplicationContext(), String.valueOf(mCount), Toast.LENGTH_SHORT).show();   
                }
                break;      
            }      
            super.handleMessage(msg);  
        }  
    };
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mBtnStart = (Button)findViewById(R.id.start);       
        mBtnStart.setOnClickListener(this);
    }
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.start:
                mTimer = new Timer();
                mTTask = new myTaskTimer();
                mTimer.schedule(mTTask, 0, 1000);
                break;
        }
    }
    class myTaskTimer extends TimerTask{      
        @Override
        public void run(){
            Message message = new Message();      
            message.what = NOTIFY; 
            mCount++;
            mHandler.sendMessage(message);    
        }
    }
}

Note: 如果你已取消了当前的Timer, 要再次调用的话,你需要重新New一个,因为只有在Timer的构造函数才会调线程的start方法。

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