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;  

     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。