FrameWork内核解析之XMS内核管理（一）上篇

阿里P7Android高级架构进阶视频免费学习请点击：https://space.bilibili.com/474380680
本篇文章将继续从以下两个内容来介绍XMS内核管理之AMS:

• [Activity的管理]
• [ Android插件化开发之运行未安装apk的activity]

一、Activity的管理

1、ActivityRecord是Activity管理的最小单位，它对应着一个用户界面;
2、TaskRecord也是一个栈式管理结构，每一个TaskRecord都可能存在一个或多个ActivityRecord，栈顶的ActivityRecord表示当前可见的界面;
3、ActivityStack是一个栈式管理结构，每一个ActivityStack都可能存在一个或多个TaskRecord，栈顶的TaskRecord表示当前可见的任务;
4、ActivityStackSupervisor管理着多个ActivityStack，但当前只会有一个获取焦点(Focused)的ActivityStack;
5、ProcessRecord记录着属于一个进程的所有ActivityRecord，运行在不同TaskRecord中的ActivityRecord可能是属于同一个 ProcessRecord。

 

​

 

 

​

 

二、Android插件化开发之运行未安装apk的activity

2.1、介绍

我们知道PathClassLoader是一个应用的默认加载器(而且他只能加载data/app/xxx.apk的文件)，但是我们加载插件一般使用DexClassLoader加载器，所以这里就有问题了，其实如果对于开始的时候，每个人都会认为很简单，很容易想到使用DexClassLoader来加载Activity获取到class对象，在使用Intent启动

2.2、替换LoadApk里面的mClassLoader

我们知道我们可以将我们使用的DexClassLoader加载器绑定到系统加载Activity的类加载器上就可以了，这个是我们的思路。也是最重要的突破点。下面我们就来通过源码看看如何找到加载Activity的类加载器。加载Activity的时候，有一个很重要的类：LoadedApk.Java，这个类是负责加载一个Apk程序的，我们可以看一下他的源码：

 

​

 

我们知道内部有个mClassLoader成员变量，我们只需要获取它就可以了，因为它不是静态的，所以我们需要先获取LoadApk这个类的对象，我们再去看看ActivityThread.java这个类。

 

​

 

我们可以发现ActivityThread里面有个静态的成员变量sCurrentActivityThread,然后还有一个ArrayMap存放Apk包名和LoadedApk映射关系的数据结构，我们通过反射来获取mClassLoader对象。

如果对ActivityThread.java这个类不熟悉的可以看我这篇博客，http://blog.csdn.net/u011068702/article/details/53207039 （Android插件化开发之AMS与应用程序(客户端ActivityThread、Instrumentation、Activity)通信模型分析）非常重要，是app程序的入口处。

2.3、实现具体代码

1）我们先需要一个测试apk,然后把这个测试的test.apk,放到手机sdcard里面去，关键代码如下

package com.example.testapkdemo;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Toast;

public class MainActivity extends ActionBarActivity {

    public static View parentView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (parentView == null) {
            setContentView(R.layout.activity_main);
        } else {
            setContentView(parentView);
        }
        findViewById(R.id.button).setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "我是来自插件", Toast.LENGTH_SHORT).show();
            }
        });
    }

    public void setView(View view) {
        this.parentView = view;
    }
}

效果图如下：

 

​

image.png

接下来是我宿主代码：

ReflectHelper.java  这个是的我的反射帮助类

package com.example.dexclassloaderactivity;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Arrays;

/**
 * 反射辅助函数
 * @author
 *
 */
public class ReflectHelper {
    public static final Class<?>[] PARAM_TYPE_VOID = new Class<?>[]{};

    public static Object invokeStaticMethod(String className, String methodName, Class<?>[] paramTypes, Object...params) {
        try {
            Class<?> clazz = Class.forName(className);
            Method method = clazz.getMethod(methodName, paramTypes);
            method.setAccessible(true);
            return method.invoke(null, params);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static Object invokeMethod(String className, String methodName, Class<?>[] paramTypes, Object obj, Object...params) {
        try {
            Class<?> clazz = Class.forName(className);
            Method method = clazz.getMethod(methodName, paramTypes);
            method.setAccessible(true);
            return method.invoke(obj, params);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static Object getStaticField(String className, String fieldName) {
        try {
            Class<?> clazz = Class.forName(className);
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            return field.get(null);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static Object getField(String className, String fieldName, Object obj) {
        try {
            Class<?> clazz = Class.forName(className);
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            return field.get(obj);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void setStaticField(String className, String fieldName, Object value) {
        try {
            Class<?> clazz = Class.forName(className);
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            field.set(null, value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void setField(String className, String fieldName, Object obj, Object value) {
        try {
            Class<?> clazz = Class.forName(className);
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            field.set(obj, value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Object createInstance(String className, Class<?>[] paramTypes, Object...params) {
        Object object = null;
        try {
            Class<?> cls = Class.forName(className);
            Constructor<?> constructor = cls.getConstructor(paramTypes);
            constructor.setAccessible(true);
            object = constructor.newInstance(params);
        }catch (Exception e) {
            e.printStackTrace();
        }
        return object;
    }

    /**
     * Locates a given field anywhere in the class inheritance hierarchy.
     *
     * @param instance an object to search the field into.
     * @param name field name
     * @return a field object
     * @throws NoSuchFieldException if the field cannot be located
     */
    public static Field findField(Object instance, String name) throws NoSuchFieldException {
        for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
            try {
                Field field = clazz.getDeclaredField(name);

                if (!field.isAccessible()) {
                    field.setAccessible(true);
                }

                return field;
            } catch (NoSuchFieldException e) {
                // ignore and search next
            }
        }

        throw new NoSuchFieldException("Field " + name + " not found in " + instance.getClass());
    }

    /**
     * Locates a given field anywhere in the class inheritance hierarchy.
     *
     * @param  cls to search the field into.
     * @param name field name
     * @return a field object
     * @throws NoSuchFieldException if the field cannot be located
     */
    public static Field findField2(Class<?> cls, String name) throws NoSuchFieldException {
        Class<?> clazz = null;
        for (clazz = cls; clazz != null; clazz = clazz.getSuperclass()) {
            try {
                Field field = clazz.getDeclaredField(name);

                if (!field.isAccessible()) {
                    field.setAccessible(true);
                }

                return field;
            } catch (NoSuchFieldException e) {
                // ignore and search next
            }
        }

        throw new NoSuchFieldException("Field " + name + " not found in " + clazz);
    }

    /**
     * Locates a given method anywhere in the class inheritance hierarchy.
     *
     * @param instance an object to search the method into.
     * @param name method name
     * @param parameterTypes method parameter types
     * @return a method object
     * @throws NoSuchMethodException if the method cannot be located
     */
    public static Method findMethod(Object instance, String name, Class<?>... parameterTypes)
            throws NoSuchMethodException {
        for (Class<?> clazz = instance.getClass(); clazz != null; clazz = clazz.getSuperclass()) {
            try {
                Method method = clazz.getDeclaredMethod(name, parameterTypes);

                if (!method.isAccessible()) {
                    method.setAccessible(true);
                }

                return method;
            } catch (NoSuchMethodException e) {
                // ignore and search next
            }
        }

        throw new NoSuchMethodException("Method " + name + " with parameters " +
                Arrays.asList(parameterTypes) + " not found in " + instance.getClass());
    }
}

MyApplication.java 这个类用实现替换mClassLoader

package com.example.dexclassloaderactivity;

import java.io.File;
import java.lang.ref.WeakReference;

import dalvik.system.DexClassLoader;
import android.annotation.SuppressLint;
import android.app.Application;
import android.os.Environment;
import android.util.ArrayMap;
import android.util.Log;

public class MyApplication extends Application{

    public static final String TAG = "MyApplication";
    public static final String AppName = "test.apk";
    public static int i = 0;

    public static DexClassLoader mClassLoader;

    @Override
    public void onCreate() {
        Log.d(TAG, "替换之前系统的classLoader");
        showClassLoader();
        try {
            String cachePath = this.getCacheDir().getAbsolutePath();
            String apkPath = /*Environment.getExternalStorageState() + File.separator*/"/sdcard/"+ AppName;
            mClassLoader = new DexClassLoader(apkPath, cachePath,cachePath, getClassLoader());
            loadApkClassLoader(mClassLoader);
        } catch (Exception e) {
            e.printStackTrace();
        }
        Log.d(TAG, "替换之后系统的classLoader");
        showClassLoader();
    }

    @SuppressLint("NewApi")
    public void loadApkClassLoader(DexClassLoader loader) {
        try {
            Object currentActivityThread  = ReflectHelper.invokeMethod("android.app.ActivityThread", "currentActivityThread", new Class[] {},new Object[] {});
            String packageName = this.getPackageName();
            ArrayMap mpackages = (ArrayMap) ReflectHelper.getField("android.app.ActivityThread", "mPackages", currentActivityThread);
            WeakReference wr= (WeakReference)mpackages.get(packageName);
            Log.e(TAG, "mClassLoader:" + wr.get());
            ReflectHelper.setField("android.app.LoadedApk", "mClassLoader", wr.get(), loader);
            Log.e(TAG, "load:" + loader);
        } catch (Exception e) {
            Log.e(TAG, "load apk classloader error:" + Log.getStackTraceString(e));
        }
    }

    /**
     * 打印系统的classLoader
     */
    public void showClassLoader() {
        ClassLoader classLoader = getClassLoader();
        if (classLoader != null){
            Log.i(TAG, "[onCreate] classLoader " + i + " : " + classLoader.toString());
            while (classLoader.getParent()!=null){
                classLoader = classLoader.getParent();
                Log.i(TAG,"[onCreate] classLoader " + i + " : " + classLoader.toString());
                i++;
            }
        }
    }
}

然后就是MainActivity.java文件，里面包含了下面另外一种方式，打开activity，所以我把函数 inject(DexClassLoader loader)先注释掉。

package com.example.dexclassloaderactivity;

import java.io.File;
import java.lang.reflect.Array;
import java.lang.reflect.Field;

import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;
import dalvik.system.DexClassLoader;
import dalvik.system.PathClassLoader;

public class MainActivity extends ActionBarActivity{

    public static final String TAG = "MainActivity";
    public static final String AppName = "test.apk";
    public static DexClassLoader mDexClassLoader = null;
    public static final String APPName = "test.apk";
    public TextView mText;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.text2).setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View v) {
                try {
//                   inject(MyApplication.mClassLoader);
                     String apkPath = Environment.getExternalStorageDirectory().toString() + File.separator + APPName;
                     Class clazz = MyApplication.mClassLoader.loadClass("com.example.testapkdemo.MainActivity");
                     Intent intent = new Intent(MainActivity.this, clazz);
                     startActivity(intent);
                     finish();
                } catch (Exception e) {
                    Log.e(TAG, "name:" + Log.getStackTraceString(e));
                }
            }
        });
    }

    private void inject(DexClassLoader loader){  

        PathClassLoader pathLoader = (PathClassLoader) getClassLoader();
        try {
            Object dexElements = combineArray(
                    getDexElements(getPathList(pathLoader)),
                    getDexElements(getPathList(loader)));
            Object pathList = getPathList(pathLoader);
            setField(pathList, pathList.getClass(), "dexElements", dexElements);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }  

    private static Object getPathList(Object baseDexClassLoader)
            throws IllegalArgumentException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException {
        ClassLoader bc = (ClassLoader)baseDexClassLoader;
        return getField(baseDexClassLoader, Class.forName("dalvik.system.BaseDexClassLoader"), "pathList");
    }  

    private static Object getField(Object obj, Class<?> cl, String field)
            throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
        Field localField = cl.getDeclaredField(field);
        localField.setAccessible(true);
        return localField.get(obj);
    }  

    private static Object getDexElements(Object paramObject)
            throws IllegalArgumentException, NoSuchFieldException, IllegalAccessException {
        return getField(paramObject, paramObject.getClass(), "dexElements");
    }
    private static void setField(Object obj, Class<?> cl, String field,
            Object value) throws NoSuchFieldException,
            IllegalArgumentException, IllegalAccessException {  

        Field localField = cl.getDeclaredField(field);
        localField.setAccessible(true);
        localField.set(obj, value);
    }  

    private static Object combineArray(Object arrayLhs, Object arrayRhs) {
        Class<?> localClass = arrayLhs.getClass().getComponentType();
        int i = Array.getLength(arrayLhs);
        int j = i + Array.getLength(arrayRhs);
        Object result = Array.newInstance(localClass, j);
        for (int k = 0; k < j; ++k) {
            if (k < i) {
                Array.set(result, k, Array.get(arrayLhs, k));
            } else {
                Array.set(result, k, Array.get(arrayRhs, k - i));
            }
        }
        return result;
    }
}

这里一定要注意，我们犯了3个错，

1、test.apk的路径写错了，下次写文件路径的时候，我们应该需要加上File file = new File(path); 用file.exist()函数来判断是否存在

2、从sdcard卡里面读取test.apk，没加上权限， <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

3、写了Application,忘了在AndroidManifest.xml文件里面声明。

我们还需要注意要加上开启activity 在AndroidManifest.xml里面注册，切记，希望下次不要再次犯错。

AndroidManifest.xml文件如下：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.dexclassloaderactivity"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="11"
        android:targetSdkVersion="21" />

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

    <application
        android:name="com.example.dexclassloaderactivity.MyApplication"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
                android:name="com.example.testapkdemo.MainActivity">
        </activity>
    </application>

</manifest>

运行结果如下：

 

​

 

然后这里又出现了插件资源和宿主资源冲突问题，我们后面再来研究。

4、合并PathClassLoader和DexClassLoader中的dexElements数组
我们首先来看一下PathClassLoader和DexClassLoader类加载器的父类BaseDexClassloader的源码：

(这里需要注意的是PathClassLoader和DexClassLoader类的父加载器是BaseClassLoader,他们的父类是BaseDexClassLoader)

 

​

 

这里有一个DexPathList对象，在来看一下DexPathList.java源码：

 

​

 

Elements数组，我们看到这个变量他是专门存放加载的dex文件的路径的，系统默认的类加载器是PathClassLoader，本身一个程序加载之后会释放一个dex出来，这时候会将dex路径放到里面，当然DexClassLoader也是一样的，那么我们会想到，我们是否可以将DexClassLoader中的dexElements和PathClassLoader中的dexElements进行合并，然后在设置给PathClassLoader中呢？这也是一个思路。我们来看代码：

/**
 * 以下是一种方式实现的
 * @param loader
 */
private void inject(DexClassLoader loader){
    PathClassLoader pathLoader = (PathClassLoader) getClassLoader();

    try {
        Object dexElements = combineArray(
                getDexElements(getPathList(pathLoader)),
                getDexElements(getPathList(loader)));
        Object pathList = getPathList(pathLoader);
        setField(pathList, pathList.getClass(), "dexElements", dexElements);
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (NoSuchFieldException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
}

private static Object getPathList(Object baseDexClassLoader)
        throws IllegalArgumentException, NoSuchFieldException, IllegalAccessException, ClassNotFoundException {
    ClassLoader bc = (ClassLoader)baseDexClassLoader;
    return getField(baseDexClassLoader, Class.forName("dalvik.system.BaseDexClassLoader"), "pathList");
}

private static Object getField(Object obj, Class<?> cl, String field)
        throws NoSuchFieldException, IllegalArgumentException, IllegalAccessException {
    Field localField = cl.getDeclaredField(field);
    localField.setAccessible(true);
    return localField.get(obj);
}

private static Object getDexElements(Object paramObject)
        throws IllegalArgumentException, NoSuchFieldException, IllegalAccessException {
    return getField(paramObject, paramObject.getClass(), "dexElements");
}
private static void setField(Object obj, Class<?> cl, String field,
        Object value) throws NoSuchFieldException,
        IllegalArgumentException, IllegalAccessException {

    Field localField = cl.getDeclaredField(field);
    localField.setAccessible(true);
    localField.set(obj, value);
}

private static Object combineArray(Object arrayLhs, Object arrayRhs) {
    Class<?> localClass = arrayLhs.getClass().getComponentType();
    int i = Array.getLength(arrayLhs);
    int j = i + Array.getLength(arrayRhs);
    Object result = Array.newInstance(localClass, j);
    for (int k = 0; k < j; ++k) {
        if (k < i) {
            Array.set(result, k, Array.get(arrayLhs, k));
        } else {
            Array.set(result, k, Array.get(arrayRhs, k - i));
        }
    }
    return result;
}

然后运行的时候把MyApplication.java文件里面的函数loadApkClassLoader(mClassLoader);注释掉，然后把MainActivity.java文件里面的inject(MyApplication.mClassLoader)不要注释，运行效果一样。
阿里P7Android高级架构进阶视频免费学习请点击：https://space.bilibili.com/474380680
参考https://blog.csdn.net/u011068702/article/details/53523609
https://www.jianshu.com/p/0bbcffbc7796