android学习笔记——计时器实现

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<?xml version="1.0"
encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

              android:orientation="vertical"

              android:layout_width="fill_parent"

              android:layout_height="fill_parent"

              android:gravity="center_horizontal"

        >

    <Chronometer

            android:id="@+id/test"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:textSize="12pt"

            android:textColor="#ffff0000"

            />

    <Button

            android:id="@+id/start"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="启动"

            />

</LinearLayout>

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package
com.example.test3_3_12;

import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.Chronometer;

import android.os.SystemClock;

public
class MyActivity extends
Activity {

    Button start;

    Chronometer ch;

    /**

     * Called when the activity is first created.

     */

    @Override

    public
void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        ch=(Chronometer)findViewById(R.id.test);

        start=(Button) findViewById(R.id.start);

        start.setOnClickListener(new
View.OnClickListener() {

            @Override

            public
void onClick(View view) {

                //设置开始时间

                ch.setBase(SystemClock.elapsedRealtime());

                //启动计时器

                ch.start();

                start.setEnabled(false);

            }

        });

        //为Chronometer绑定事件监听器

        ch.setOnChronometerTickListener(new
Chronometer.OnChronometerTickListener() {

            @Override

            public
void onChronometerTick(Chronometer chronometer) {

                //如果从开始计时到现在超过了20s

                if(SystemClock.elapsedRealtime()-ch.getBase()>20*1000)

                {

                    ch.stop();

                    start.setEnabled(true);

                }

            }

        });

    }

}