Android 一键清理、内存清理功能实现

360桌面、金山清理大师等都提供了一键清理、一键加速等功能，其实就是杀一些后台进程来达到释放内存的目的。

   基本思路就是列出所有运行的进程，查看其重要值（RunningAppProcessInfo.importance，值越大说明进程重要程度越低），可以设定一个阈值，

如果该进程的重要值大于该阈值，就可以杀掉该进程。

进程的重要值有以下几个等级：

/**              * Constant for {@link #importance}: this is a persistent process.              * Only used when reporting to process observers.              * @hide              */              public static final int IMPORTANCE_PERSISTENT = 50;                    /**              * Constant for {@link #importance}: this process is running the              * foreground UI.              */              public static final int IMPORTANCE_FOREGROUND = 100;                            /**              * Constant for {@link #importance}: this process is running something              * that is actively visible to the user, though not in the immediate              * foreground.              */              public static final int IMPORTANCE_VISIBLE = 200;                            /**              * Constant for {@link #importance}: this process is running something              * that is considered to be actively perceptible to the user.  An              * example would be an application performing background music playback.              */              public static final int IMPORTANCE_PERCEPTIBLE = 130;                            /**              * Constant for {@link #importance}: this process is running an              * application that can not save its state, and thus can't be killed              * while in the background.              * @hide              */              public static final int IMPORTANCE_CANT_SAVE_STATE = 170;                            /**              * Constant for {@link #importance}: this process is contains services              * that should remain running.              */              public static final int IMPORTANCE_SERVICE = 300;                            /**              * Constant for {@link #importance}: this process process contains              * background code that is expendable.              */              public static final int IMPORTANCE_BACKGROUND = 400;                            /**              * Constant for {@link #importance}: this process is empty of any              * actively running code.              */              public static final int IMPORTANCE_EMPTY = 500;  

需要权限：

<uses-permission android:name="android.permission.KILL_BACKGROUND_PROCESSES"/>

具体操作代码如下：

package com.example.demo;import java.util.List;import android.app.Activity;import android.app.ActivityManager;import android.app.ActivityManager.MemoryInfo;import android.app.ActivityManager.RunningAppProcessInfo;import android.content.Context;import android.content.pm.PackageManager;import android.content.pm.PackageManager.NameNotFoundException;import android.os.Bundle;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.widget.Toast;public class CleanProcessActivity extends Activity {private static final String TAG = "Clean";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_clean_process);}    public void clean(View v){    //To change body of implemented methods use File | Settings | File Templates.          ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);          List<RunningAppProcessInfo> infoList = am.getRunningAppProcesses();          List<ActivityManager.RunningServiceInfo> serviceInfos = am.getRunningServices(100);          long beforeMem = getAvailMemory(this);          Log.d(TAG, "-----------before memory info : " + beforeMem);          int count = 0;          PackageManager pm = getPackageManager();                if (infoList != null) {              for (int i = 0; i < infoList.size(); ++i) {                  RunningAppProcessInfo appProcessInfo = infoList.get(i);                  Log.d(TAG, "process name : " + appProcessInfo.processName);                  //importance 该进程的重要程度  分为几个级别，数值越低就越重要。                  Log.d(TAG, "importance : " + appProcessInfo.importance);                                                   // 一般数值大于RunningAppProcessInfo.IMPORTANCE_SERVICE的进程都长时间没用或者空进程了                  // 一般数值大于RunningAppProcessInfo.IMPORTANCE_VISIBLE的进程都是非可见进程，也就是在后台运行着                  if (appProcessInfo.importance > RunningAppProcessInfo.IMPORTANCE_VISIBLE) {                      String[] pkgList = appProcessInfo.pkgList;                      for (int j = 0; j < pkgList.length; ++j) {//pkgList 得到该进程下运行的包名                          String appName = null;try {appName = (String) pm.getApplicationLabel(pm.getApplicationInfo(pkgList[j], 0)); } catch (NameNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}Log.d(TAG, "It will be killed, package name : " + pkgList[j]+" -- "+appName );                          am.killBackgroundProcesses(pkgList[j]);                          count++;                      }                  }              }          }          long afterMem = getAvailMemory(this);          Log.d(TAG, "----------- after memory info : " + afterMem);          Toast.makeText(this, "clear " + count + " process, "                      + (afterMem - beforeMem) + "M", Toast.LENGTH_LONG).show();      }private long getAvailMemory(CleanProcessActivity cleanProcessActivity) {// 获取android当前可用内存大小          ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);          MemoryInfo mi = new MemoryInfo();          am.getMemoryInfo(mi);          //mi.availMem; 当前系统的可用内存          //return Formatter.formatFileSize(context, mi.availMem);// 将获取的内存大小规格化          Log.d(TAG, "可用内存---->>>" + mi.availMem / (1024 * 1024));          return mi.availMem / (1024 * 1024);  } }

注意：

我这里选择阈值是IMPORTANCE_VISIBLE级别的，也就是非可见的后台进程和服务会被杀掉（一些系统进程肯定除外）。

清理的效果跟金山清理大师和360桌面的一键清理效果差不多。

如果不想杀的太凶，可以选择IMPORTANCE_SERVICE级别，杀掉那些长时间没用或者空进程了，

这个级别的清理力度不够大，达不到金山清理大师的效果。

转自：http://www.open-open.com/lib/view/open1415889849742.html