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：

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/**          * 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 ;

直接上代码：

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package com.android.clearmemory;      import android.app.Activity;  import android.app.ActivityManager;  import android.app.ActivityManager.MemoryInfo;  import android.app.ActivityManager.RunningAppProcessInfo;  import android.content.Context;  import android.os.Bundle;  import android.util.Log;  import android.view.View;  import android.widget.Button;  import android.widget.Toast;      import java.util.List;      public class ClearMemoryActivity extends Activity {       private static final String TAG = "ClearMemoryActivity" ;           /**       * Called when the activity is first created.       */       @Override       public void onCreate(Bundle savedInstanceState) {           super .onCreate(savedInstanceState);           setContentView(R.layout.main);               Button clear = (Button) findViewById(R.id.clear);           clear.setOnClickListener( new View.OnClickListener() {               @Override               public void onClick(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(ClearMemoryActivity. this );                   Log.d(TAG, "-----------before memory info : " + beforeMem);                   int count = 0 ;                   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                                   Log.d(TAG, "It will be killed, package name : " + pkgList[j]);                                   am.killBackgroundProcesses(pkgList[j]);                                   count++;                               }                           }                           }                   }                       long afterMem = getAvailMemory(ClearMemoryActivity. this );                   Log.d(TAG, "----------- after memory info : " + afterMem);                   Toast.makeText(ClearMemoryActivity. this , "clear " + count + " process, "                               + (afterMem - beforeMem) + "M" , Toast.LENGTH_LONG).show();               }           });               ClearMemoryFloatView.instance(getApplicationContext()).createView();       }           //获取可用内存大小       private long getAvailMemory(Context context) {           // 获取android当前可用内存大小           ActivityManager am = (ActivityManager) context.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