android闹钟（三）：实现时钟功能

TimeView.java

package com.mytest.myclock;import java.util.Calendar;import android.content.Context;import android.opengl.Visibility;import android.os.Handler;import android.util.AttributeSet;import android.view.View;import android.widget.LinearLayout;import android.widget.TextView;public class TimeView extends LinearLayout {    private TextView timeText;    public TimeView(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        // TODO Auto-generated constructor stub    }    public TimeView(Context context, AttributeSet attrs) {        super(context, attrs);        // TODO Auto-generated constructor stub    }    public TimeView(Context context) {        super(context);        // TODO Auto-generated constructor stub    }    @Override    protected void onFinishInflate() {        // TODO Auto-generated method stub        super.onFinishInflate();        timeText = (TextView) findViewById(R.id.tv_time);        timeHandler.sendEmptyMessage(0);    }    private void refreshTime() {        Calendar cal = Calendar.getInstance();        String timeStr = String.format("%d:%d:%d", cal.get(Calendar.HOUR_OF_DAY), cal.get(Calendar.MINUTE),                cal.get(Calendar.SECOND));        timeText.setText(timeStr);        //System.out.println("timeStr============>" + timeStr);    }    @Override    protected void onVisibilityChanged(View changedView, int visibility) {        // TODO Auto-generated method stub        super.onVisibilityChanged(changedView, visibility);        if (getVisibility() == View.VISIBLE) {            timeHandler.sendEmptyMessageDelayed(0, 1000);        } else {            timeHandler.removeMessages(0);        }    }    private Handler timeHandler = new Handler() {        public void handleMessage(android.os.Message msg) {            refreshTime();            if (getVisibility() == View.VISIBLE) {                // 每隔一秒给自己发送消息                timeHandler.sendEmptyMessageDelayed(0, 1000);            }        };    };}

View Code

小结：

1、在onFinishInflate中发送消息，实现时间的第一次显示。后来又在handler的handleMessage方法中发送消息，有点相当于调用死循环来刷新时间。

2、当用户切换后，时钟tab不可见时，记得onVisibilityChanged中停止发送消息，不再刷新时间。

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