安卓Chronometer计时器的使用

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


public class Test extends Activity implements OnClickListener {
    private int startTime = 0;
    private boolean PAUSE = false;
    //从开始到暂停的时间差
    private long rangeTime;
    private Chronometer chronometer;
    private Button btnPC;
    private Button btnStart;
    private Button btnStop;
    private Button btnRest;
    private EditText edtSetTime;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_aa);
        initView();
        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) {
                    chronometer.stop();
                    // 给用户提示
                    showDialog();
                }
            }
        });
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btnStart:
                rangeTime = 0;
                String ss = edtSetTime.getText().toString();
                if (!(ss.equals("") && ss != null)) {
                    startTime = Integer.parseInt(edtSetTime.getText().toString());
                }
                // 设置开始计时时间
                chronometer.setBase(SystemClock.elapsedRealtime());
                // 开始记时
                chronometer.start();
                //开始按钮不可用
                btnStart.setEnabled(false);
                btnPC.setEnabled(true);
                btnStop.setEnabled(true);
                btnRest.setEnabled(true);
                PAUSE=false;
                btnPC.setText("暂停");
                break;
            case R.id.btnPC:
                //暂停计时
                if (!PAUSE) {
                    btnPC.setText("继续");
                    //从开始计时计时器运行的时间差。。。。。关键
                    rangeTime = SystemClock.elapsedRealtime() - chronometer.getBase();
                    chronometer.stop();
                } else {
                    //继续计时
                    btnPC.setText("暂停");
                    //设置计时器的基时间。。。。。关键
                    chronometer.setBase(SystemClock.elapsedRealtime() - rangeTime);
                    chronometer.start();
                }
                PAUSE = !PAUSE;
                break;
            case R.id.btnStop:
                chronometer.stop();
                btnStart.setEnabled(true);
                PAUSE=false;
                btnPC.setText("暂停");
                btnPC.setEnabled(false);
                break;
            case R.id.btnReset:
                chronometer.stop();
                chronometer.setBase(SystemClock.elapsedRealtime());
                btnStart.setEnabled(true);
                PAUSE=false;
                btnPC.setText("暂停");
                btnPC.setEnabled(false);
                break;
        }
    }

    protected void showDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.mipmap.ic_launcher);
        builder.setTitle("警告").setMessage("时间到")
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                    }
                });
        AlertDialog dialog = builder.create();
        dialog.show();
    }
    private void initView() {
        chronometer = (Chronometer) findViewById(R.id.chronometer1);
        btnStart = (Button) findViewById(R.id.btnStart);
        btnPC = (Button) findViewById(R.id.btnPC);
        btnStop = (Button) findViewById(R.id.btnStop);
        btnRest = (Button) findViewById(R.id.btnReset);
        edtSetTime = (EditText) findViewById(R.id.setTimeEdit);
        btnStart.setOnClickListener(this);
        btnPC.setOnClickListener(this);
        btnStop.setOnClickListener(this);
        btnRest.setOnClickListener(this);
        btnPC.setEnabled(false);
        btnStop.setEnabled(false);
        btnRest.setEnabled(false);
    }

}