其实我原本是只想说一个线程之间的通讯 handler,但是觉得内容有点少，就直接写了个demo。我之前是做过仿手机管家这种软件的（当然只是自己做着好玩的），所以 就提取了一点内容结合线程通讯写了个小的demo.

不说废话了，直接上代码：

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/ll_main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.ehsure.handlerdemo.MainActivity">
      <TextView
          android:id="@+id/main_change_tv"
          android:gravity="center"
          android:textSize="16sp"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          />
      <TextView
          android:id="@+id/main_scan_tv"
          android:layout_width="match_parent"
          android:gravity="center"
          android:textSize="16sp"
          android:layout_height="wrap_content"
          />

</LinearLayout>

MianActivity.class

public class MainActivity extends Activity {
    private List<String> appNameList = new ArrayList<String>();
    public int backAppSize = 0;
    TextView main_scan_tv;
    TextView main_change_tv;
    LinearLayout ll_main_layout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initWidget();
        new MyThread().start();
    }

    public void initWidget(){
        main_change_tv = (TextView)findViewById(R.id.main_change_tv);
        main_scan_tv = (TextView)findViewById(R.id.main_scan_tv);
        ll_main_layout = (LinearLayout)findViewById(R.id.ll_main_layout);
    }

    /*
 * 线程扫描所有后台软件
 */
    class MyThread extends Thread{
        @Override
        public void run() {
            // TODO Auto-generated method stub
            try {
                PackageManager pm = MainActivity.this.getPackageManager();
                ActivityManager activityManager = (ActivityManager) MainActivity.this
                        .getSystemService(MainActivity.this.ACTIVITY_SERVICE);
                List<ActivityManager.RunningServiceInfo> runningApp = activityManager
                        .getRunningServices(100);//这个数字是设置的最大程序数
                Iterator<ActivityManager.RunningServiceInfo> iterator = runningApp.iterator();
                int allCount = 0;//这个是所有后台软件的总大小
                while (iterator.hasNext()) {
                    ActivityManager.RunningServiceInfo backApp = iterator.next();
                    ComponentName name = backApp.service;
                    String pkgName = name.getPackageName();
                    ApplicationInfo apps = pm.getApplicationInfo(pkgName, 0);
                    String appName = (String) apps.loadLabel(pm);// 拿到名字
                    Drawable appIcon = apps.loadIcon(pm);// 拿到图标
                    String appPath = apps.publicSourceDir;// 拿到app的路径
                    int length = (int) new File(appPath).length();
                    allCount+=length;
                    SystemClock.sleep(100);
                    String out = appName+"~"+getFileSize(allCount);//这个方法是将字节转换成kb或mb，自己写的一个小算法
                    //这里之所以这么写 是因为一款软件可能会有好几个进程，如果不根据名字来判断，会有很多重复的。
                    boolean flag = true;
                    for (String ss : appNameList) {
                        if(ss.equals(appName)){
                            flag = false;
                        }
                    }
                    if(flag==true){
                        appNameList.add(appName);
                    }
                    handler.obtainMessage(0x001, out).sendToTarget();
                }
                backAppSize = allCount;
                SystemClock.sleep(2000);
                handler.sendEmptyMessage(0x002);
            } catch (PackageManager.NameNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    /*
     * 将字节转换成kb或mb
     */
    public String getFileSize(long size){
        String mySize = "";
        if(size>(1024*1024)){
            BigDecimal bd = new BigDecimal((double)size/(1024*1024));
            BigDecimal bd2 =bd.setScale(2, BigDecimal.ROUND_DOWN);
            mySize = (Double.parseDouble(bd2+""))+"M";
        }else{
            mySize = (size/1024)+"k";
        }
        return mySize;
    }




    Handler handler = new Handler(){
        public void handleMessage(Message msg) {
            int code = msg.what;
            switch (code) {
                case 0x001:
                    String str = (String) msg.obj;
                    String [] ss = str.split("~");
                    main_scan_tv.setText(ss[0]);
                    main_change_tv.setText(ss[1]);
                    break;
                case 0x002:
                    main_scan_tv.setText("一共发现" + appNameList.size() + "款后台软件");
                    ll_main_layout.setBackgroundColor(Color.rgb(10, 163, 245));
                    break;
            }
        }
    };

}
我这里用到的handler发送消息用了两种方式，当然也是推荐的
1.

handler.sendEmptyMessage(0x002);这个就是不传递消息或者数据的

2.

handler.obtainMessage(0x001, out).sendToTarget();这个也就是最常用的一种，是传递Object对象过去

其实还有一种：

Message msg = new Message();

msg.what =0x001;
msg.obj = out;
handler.sendMessage(msg);

但是这种方式 handler传递多少次消息 Message就会实例化多少个，所以不太推荐，因为会造成内存损耗。

通过线程通讯获取手机正在运行中的软件及大小（仿手机管家 扫描软件）