android 计时器

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dip"
        android:orientation="horizontal" >

        <TextView
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="4"
            android:gravity="center"
            android:text="设置时间:" />

        <EditText
            android:id="@+id/edt_settime"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:inputType="number" />
    </LinearLayout>

    <Chronometer
        android:id="@+id/chronometer"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:textColor="#ff0000"
        android:textSize="60dip" />

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_margin="10dip"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btntimeopp"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="开始记时" />



        <Button
            android:id="@+id/btnReset"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="重置" />
    </LinearLayout>

</LinearLayout>

package com.example.yanlei.yl;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.SystemClock;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Chronometer;
import android.widget.EditText;


public class MainActivity extends AppCompatActivity {

    // 设置初始时间
    private int startTime = 0;
    // 声明计时器Chronomete对象
    private Chronometer chronometer;
    // 定义计时器操作按钮
    private Button btnOperate;
    // 定义计时器重置按钮
    private Button btnRest;
    // 定义到达时间的edittext
    private EditText edtSetTime;
    // 开始boolOperate=true,停止boolOperate=false
    private Boolean boolOperate = true;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 得到布局中的所有对象
        findView();
        // 设置对象的监听器
        setListener();
    }

    // 得到布局中的所有对象
    private void findView() {
        // TODO Auto-generated method stub
        chronometer = (Chronometer) findViewById(R.id.chronometer);
        btnOperate = (Button) findViewById(R.id.btntimeopp);
        btnRest = (Button) findViewById(R.id.btnReset);
        edtSetTime = (EditText) findViewById(R.id.edt_settime);
    }

    // 得到布局中的所有对象
    private void setListener() {
        // TODO Auto-generated method stub
        btnRest.setOnClickListener(listener);
        btnOperate.setOnClickListener(listener);
        chronometer
                .setOnChronometerTickListener(new Chronometer.OnChronometerTickListener() {
                    @Override
                    public void onChronometerTick(Chronometer chronometer) {
                        // 如果开始计时到现在超过了startime秒
                        if (SystemClock.elapsedRealtime()
                                - chronometer.getBase() > startTime * 1000) {
                            // 计时器停止
                            chronometer.stop();
                            // 给用户提示
                            showDialog();
                        }
                    }
                });
    }

    OnClickListener listener = new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            switch (v.getId()) {
                // 开始按钮
                case R.id.btntimeopp:
                    // 如果boolOperate==true,说明计时开始
                    if (boolOperate) {
                        String ss = edtSetTime.getText().toString();
                        // 把到达时间转化为Int类型
                        if (!(ss.equals("") && ss != null)) {
                            startTime = Integer.parseInt(edtSetTime.getText()
                                    .toString());
                        }
                        // 设置开始时间
                        chronometer.setBase(SystemClock.elapsedRealtime());
                        // 开始记时
                        chronometer.start();
                        boolOperate = false;
                        // eidttext不可点
                        edtSetTime.setClickable(false);
                        btnOperate.setText("点击停止");
                    }
                    // 如果boolOperate==false,说明计时结束
                    else {
                        // 计时停止
                        chronometer.stop();
                        boolOperate = true;
                        // eidttex可点
                        edtSetTime.setClickable(true);
                        btnOperate.setText("点击开始");
                    }

                    break;
                // 重置按钮
                case R.id.btnReset:
                    chronometer.setBase(SystemClock.elapsedRealtime());
                    break;
                default:
                    break;
            }
        }
    };

    protected void showDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.drawable.ic_launcher);
        builder.setTitle("闫磊温馨提醒你").setMessage("设置："+startTime+"秒，时间到了")
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    }
                });

        AlertDialog dialog = builder.create();
        dialog.show();
    }
}