智者创造机会，强者把握机会，弱者等待机会。

本讲内容：定时器

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.text1.MainActivity$PlaceholderFragment" >

   <Chronometer 
       android:id="@+id/chronometer"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_marginTop="15dp"
       android:format="%s"
       android:gravity="center"
       android:textColor="#542039"
       android:textSize="25sp"/>
   <LinearLayout 
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_marginTop="10dp">
       <TextView 
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="2"
           android:gravity="center"
           android:text="设置时间:"
           android:textSize="25sp"/>
       <EditText 
           android:id="@+id/settime"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="3"
           android:inputType="number"/>
   </LinearLayout>
   
   <LinearLayout 
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:layout_margin="10dp">
       <Button 
           android:id="@+id/start"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="开始记时"/>
       <Button 
           android:id="@+id/stop"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="停止记时" />
       <Button 
           android:id="@+id/reset"
           android:layout_width="0dp"
           android:layout_height="wrap_content"
           android:layout_weight="1"
           android:text="重置"/>
   </LinearLayout>
   
</LinearLayout>

public class MainActivity extends Activity implements OnClickListener{
	private Button star;
	private Button stop;
	private Button reset;
	private EditText settime;
	private Chronometer chronometer;
	private int startTime=0;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		findViews();
		// 设置开始讲时时间
		chronometer.setBase(SystemClock.elapsedRealtime());
		// 开始记时  
        chronometer.start(); 
        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()>10*1000){
					 chronometer.stop();
					 //给用户提示  
                     showDialog(); 
				}
			}
		});
	}
	
	private void findViews() {
		star=(Button) findViewById(R.id.start);
		stop=(Button) findViewById(R.id.stop);
		reset=(Button) findViewById(R.id.reset);
		settime=(EditText) findViewById(R.id.settime);
		chronometer=(Chronometer) findViewById(R.id.chronometer);
		
		star.setOnClickListener(this);
		stop.setOnClickListener(this);
		reset.setOnClickListener(this);
	}
	
	private void showDialog() {
		AlertDialog.Builder builder=new Builder(this);
		builder.setIcon(R.drawable.ic_launcher).setTitle("警告").setMessage("时间到");
		builder.setPositiveButton("确定", null).setNegativeButton("取消", null).show();
	}

	@Override
	public void onClick(View v) {
		switch (v.getId()) {
		case R.id.start:
			String ss=settime.getText().toString();
			if(!(ss.equals("")&&ss!=null)){
				startTime=Integer.parseInt(ss);
			}
			// 设置开始讲时时间  
            chronometer.setBase(SystemClock.elapsedRealtime());  
            // 开始记时  
            chronometer.start();
			break;
		case R.id.stop:
			chronometer.stop();
			break;
		case R.id.reset:
			chronometer.setBase(SystemClock.elapsedRealtime());
			break;
		}
	}
}

本讲就到这里，Take your time and enjoy it

第七十二讲：Chronometer定时器（二）