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";
@Override
protected 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 block
e.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。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。
