<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" tools:layout_editor_absoluteY="0dp"
tools:layout_editor_absoluteX="0dp">
<TextView
android:text="00:00:00"
android:textSize="60sp"
android:gravity="center"
android:layout_width="match_parent"
android:layout_height="wrap_content" android:id="@ id/timeView"/>
<Button
android:text="start"
android:onClick="onClickStart"
android:layout_width="match_parent"
android:layout_height="wrap_content" android:id="@ id/start"/>
<Button
android:text="stop"
android:onClick="onClickStop"
android:layout_width="match_parent"
android:layout_height="wrap_content" android:id="@ id/stop"/>
<Button
android:text="reset"
android:onClick="onClickReset"
android:layout_width="match_parent"
android:layout_height="wrap_content" android:id="@ id/reset"/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>MainActivity
代码语言：javascript复制package com.test;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private int seconds = 0;
private boolean running = false; //计时状态
private boolean wasRunning = false; //保存running的状态
//app进入后台，暂停计时
@Override
protected void onStop() {
super.onStop();
wasRunning = running;
running = false;
}
//重新进入app，开始计时
@Override
protected void onStart() {
super.onStart();
if(wasRunning) running = true;
}
//失去焦点(如分屏)，暂停计时
@Override
protected void onPause() {
super.onPause();
wasRunning = running;
running = false;
}
//获得焦点,重新开始计时
@Override
protected void onResume() {
super.onResume();
if(wasRunning) running = true;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//获取保存的状态
if(savedInstanceState!=null){
seconds = savedInstanceState.getInt("seconds");
running = savedInstanceState.getBoolean("running");
wasRunning = savedInstanceState.getBoolean("wasRunning");
}
runTime();
}
/**
*保存状态
*/
@Override
public void onSaveInstanceState(Bundle saveInstanceState) {
super.onSaveInstanceState(saveInstanceState);
saveInstanceState.putInt("seconds",seconds);
saveInstanceState.putBoolean("running",running);
saveInstanceState.putBoolean("wasRunning",wasRunning);
}
/**
* 响应button的onClick事件
* 方法名和onClick的值一致
*/
public void onClickStart(View button){
running = true;
}
public void onClickStop(View button){
running = false;
}
public void onClickReset(View button){
running = false;
seconds = 0;
}
/**
* 注意 ui线程不能被堵塞，因此不能在ui线程中调用sleep方法
* 只允许ui线程更新界面，不能在后台线程更新界面
*
* ** 使用ui线程的Handler定时更新 **
* 将任务封装到 Runnable的run方法中 ，通过Handler的
* post(立即提交任务)或postDelayed(实现定时调度)方法提交到ui线程
*/
private void runTime(){
final Handler handler = new Handler();
handler.post(new Runnable() {
@Override
public void run() {
final TextView textView = findViewById(R.id.timeView);
int hour = seconds /3600$;
int minute = seconds600/60;
String time = String.format("d:d:d",hour,minute,seconds`);
textView.setText(time);
if(running) seconds ;
handler.postDelayed(this,1000);
}
}
);
}
}
