Service & Timer & Handler & leaked ServiceConnection

定义一个Service,每隔一秒钟，变量count增加1；

在Activity里bindService，然后利用new Timer() 和 Handler，每隔一秒利用IBinder实例mBinder的getNumber（）方法读取count的最新值，并显示在TextView.

首次运行，报错。

Debug模式，发现MainActivity.class 79行的HandleMessage()方法在onServiceConnected()（MainActivity.class 第68行）之前就执行了，mBinder对象还未初始化（该对像是回调onServiceConnected()方法时初始化 ）， 所以才会出现NullPointerException.

试着去解决问题：在83行增加判断语句

 83　if (mBinder != null) {   //**此处未加if判断语句就会出错，提示NullPointerException
 84     // 获取Service中的实时Count值，并在UI中显示
 85     mCount = mBinder.getNumber() + "";
 86     }

 87 
 88  // 在Toast中显示count
 89  textView1.setText(mCount);

然后在程序可以运行，但是刚开始TextView显示“default”（mCount的初始值） ， 一秒钟之后才开始显示累加的数字。

但是LogCat还是有抱错

问题1：为什么HandleMessage()方法在onServiceConnected()之前就执行了？

问题2：为什么有ServiceConnection 泄漏？

问题2的已解决：在MainActivity中，改写onDestroy()

@Override
    protected void onDestroy() {
        super.onDestroy();
        //在关闭Activity时取消与mService的绑定
        unbindService(conn);        
    }

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Service定义如下：

package com.rocky.myfirstserviceapp.service;

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;

public class MyService extends Service {

    private int count = 0;
    private boolean quit = false;
    private MyBinder binder = new MyBinder();
    
    public class MyBinder extends Binder{
        public int getNumber(){
            //获取即时数值
            return count;
        }
    }
    
    @Override
    public IBinder onBind(Intent intent) {
        System.out.println("Service is binded");
        return binder; //返回IBinder实例
    }
    
    @Override
    public void onCreate() {
        super.onCreate();
        System.out.println("Service is Created");
        
        //新建一 个线程,每隔1秒加1
        new Thread(){
            public void run() {
                while(!false){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    count++;
                }
            };
        }.start();
    }
    
    @Override
    public boolean onUnbind(Intent intent) {
        System.out.print("Service is Unbinded");
        return true;
    }
    
    @Override
    public void onDestroy() {
        super.onDestroy();
        this.quit = true;
        System.out.print("Service is destroyed");
    }

}

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Activity 定义如下：

package com.rocky.myfirstserviceapp;

import java.util.Timer;
import java.util.TimerTask;

import com.rocky.myfirstserviceapp.service.MyService;
import com.rocky.myfirstserviceapp.service.MyService.MyBinder;

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.app.Service;
import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import android.os.Build;

/**
 * 
 * @author LinXing 利后Service从1增加到100， 每秒加1。 多个Activity从Service中提取即时数值
 */

public class MainActivity extends Activity {

    // 保存所启动的Service的IBinder对象
    private MyService.MyBinder mBinder;
    private TextView textView1;

    private ServiceConnection conn;

    // 接收信息后更新UI
    private Handler mHandler;

    private String mCount = "default";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView1 = (TextView) findViewById(R.id.textView1);

        // 创建启动Service的Intent
        Intent intent = new Intent(this, MyService.class);
 57 
        // 定义一个ServiceConnection对象
        conn = new ServiceConnection() {

            @Override
            public void onServiceDisconnected(ComponentName name) {
                System.out.print("Service is disconnected");
            }

            @Override
            public void onServiceConnected(ComponentName name, IBinder service) {
                mBinder = (MyService.MyBinder) service;
                System.out.print("Service is connected");
            }
        };

        // 绑定service
        bindService(intent, conn, Service.BIND_AUTO_CREATE);

        // 实现Handler
        mHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                super.handleMessage(msg);

                if (msg.what == 0x33) {
                    if (mBinder != null) {   //**此处未加if判断语句就会出错，提示NullPointerException
                        // 获取Service中的实时Count值，并在UI中显示
                        mCount = mBinder.getNumber() + "";
                    }

                    // 在Toast中显示count
                    textView1.setText(mCount);
                }

            }
        };

        // 计时器,每隔一秒发送一个消息
        new Timer().schedule(new TimerTask() {

            @Override
            public void run() {
                Message msg = new Message();
                msg.what = 0x33;
                mHandler.sendMessage(msg);
            }
        }, 0, 1000);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

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