我们的认识

我们都知道, 在Android中我们获取一个资源只需要使用Context.getResource().getXXXX()就可以获取到对应的资源文件. 那么如果我们想要加载其他应用的res内容, 那么就应该构造出他们环境的Resource. 有了Resource还不行, 我们还需要获取资源文件的ID, 其中ID我们可以通过R.java文件通过反射获取.

所以我们的目标就是(分别对于已安装的应用和未安装的应用):

构造出Resource
获取资源的ID

ResourceBundle就是我们的资源包, 其中只有两张图片

android_resource_bundle_load.gif android_resource_bundle_struct.png android_resource_bundle_content.png

已经安装的应用

获取Resource

对于已经安装的应用, 获取Resource的方法很简单, 只要获取到Context就可以获取对应环境下的Resource了, 其中有一个方法Context.createPackageContext(String packageName, int flags)可以根据包名获取已经安装应用的Context.

首先我们建一个Bean来存储已经加载的资源

public class LoadedResource {    public Resources resources;    public String packageName;    public ClassLoader classLoader;}

然后我们就可以写加载的方法

/** * 获取已安装应用资源 *  * @param packageName */public LoadedResource getInstalledResource(String packageName) {    LoadedResource resource = mResources.get(packageName);  // 先从缓存中取, 没有就去加载    if (resource == null) {        try {            Context context = mContext.createPackageContext(packageName,                    Context.CONTEXT_INCLUDE_CODE | Context.CONTEXT_IGNORE_SECURITY);            resource = new LoadedResource();            resource.packageName = packageName;            resource.resources = context.getResources();            resource.classLoader = context.getClassLoader();            mResources.put(packageName, resource);  // 得到结果缓存起来        } catch (Exception e) {            e.printStackTrace();        }    }    return resource;}

至此, 我们就能获取到了Resource

获取资源ID

根据上面的思路, 我们使用反射区获取. 大概看一下R文件的结构

package com.example.resourcebundle;public final class R {    public static final class attr {    }    public static final class drawable {        public static final int image=0x7f020000;        public static final int image1=0x7f020001;    }    public static final class mipmap {        public static final int ic_launcher=0x7f030000;    }    public static final class string {        public static final int app_name=0x7f040000;    }    ...}

对应的资源类型都有一个静态内部类, 那么我们就可以使用反射无获取对应的数值

/** * 获取资源ID *  * @param packageName   包名 * @param type          对应的资源类型, drawable mipmap等 * @param fieldName * @return */public int getResourceID(String packageName, String type, String fieldName) {    int resID = 0;    LoadedResource installedResource = getInstalledResource(packageName);   // 获取已安装APK的资源    if (installedResource != null) {        String rClassName = packageName + ".R$" + type; // 根据匿名内部类的命名, 拼写出R文件的包名+类名        try {            Class cls = installedResource.classLoader.loadClass(rClassName);    //  加载R文件            resID = (Integer) cls.getField(fieldName).get(null);    //  反射获取R文件对应资源名的ID        } catch (Exception e) {            e.printStackTrace();        }    } else {        Log.w(TAG, "resource is null:" + packageName);    }    return resID;}

现在我们加载已经安装APK的资源的编码就已经完成.

调用

getDrawable("com.example.resourcebundle", "image1")

未安装的应用

我们先看一下getDrawable方法是怎么去获取资源的

public Drawable getDrawable(@DrawableRes int id, @Nullable Theme theme)        throws NotFoundException {    final TypedValue value = obtainTempTypedValue();    try {        final ResourcesImpl impl = mResourcesImpl;        impl.getValue(id, value, true);        return impl.loadDrawable(this, value, id, theme, true);    } finally {        releaseTempTypedValue(value);    }}

上面代码我们可以看到, 资源其实是通过impl代理去拿到的, 继续...

void getValue(@AnyRes int id, TypedValue outValue, boolean resolveRefs)        throws NotFoundException {    boolean found = mAssets.getResourceValue(id, 0, outValue, resolveRefs);    if (found) {        return;    }    throw new NotFoundException("Resource ID #0x" + Integer.toHexString(id));}

然后再通过assets去代理获取, 继续看看assets从哪里设置的

public ResourcesImpl(@NonNull AssetManager assets, @Nullable DisplayMetrics metrics,        @Nullable Configuration config, @NonNull DisplayAdjustments displayAdjustments) {    mAssets = assets;    mMetrics.setToDefaults();    mDisplayAdjustments = displayAdjustments;    updateConfiguration(config, metrics, displayAdjustments.getCompatibilityInfo());    mAssets.ensureStringBlocks();}

再寻找ResourcesImpl的构造函数从哪里调用

public Resources(AssetManager assets, DisplayMetrics metrics, Configuration config) {    this(null);    mResourcesImpl = new ResourcesImpl(assets, metrics, config, new DisplayAdjustments());}

最后, 我们回到Resource的构造函数中, 也就是说正确调用Resources的构造函数, 那么我们就能构造出正确的Resource

但是, 如何得到一个AssetManager呢? 大家请参考文章Android应用程序资源管理器（Asset Manager）的创建过程分析
, 里面说明了AssetManager的加载原理和过程. 我们按部就班反射调用public final int addAssetPath(String path)方法去添加资源文件路径.

那么我们现在就可以编码了

/** * 加载未安装应用资源包 *  * @param resourcePath * @return */public LoadedResource loadResource(String resourcePath) {    LoadedResource loadResource = null;    PackageInfo info = queryPackageInfo(resourcePath);  //  获取未安装APK的PackageInfo    if (info != null) { //  获取成功        loadResource = mRescources.get(info.packageName);   // 先从缓存中取, 存在则直接返回, 不重复添加. 否则就搜索添加        if (loadResource == null) {            try {                AssetManager assetManager = AssetManager.class.newInstance();   // 创建AssetManager实例                Class cls = AssetManager.class;                Method method = cls.getMethod("addAssetPath", String.class);                method.invoke(assetManager, resourcePath);  // 反射设置资源加载路径                Resources resources = new Resources(assetManager, mContext.getResources().getDisplayMetrics(),                        mContext.getResources().getConfiguration());    // 构造出正确的Resource                loadResource = new LoadedResource();                loadResource.resources = resources;                loadResource.packageName = info.packageName;                loadResource.classLoader = new DexClassLoader(resourcePath, mDexDir, null,                        mContext.getClassLoader()); //  设置正确的类加载器, 因为需要去加载R文件                mRescources.put(info.packageName, loadResource);    // 缓存                Log.w(TAG, "build resource:" + resourcePath);            } catch (Exception e) {                e.printStackTrace();            }        }    }    Log.w(TAG, "load resource:" + resourcePath);    return loadResource;}/** * 获取未安装应用PackageInfo *  * @param resourcePath * @return */private PackageInfo queryPackageInfo(String resourcePath) {    return mContext.getPackageManager().getPackageArchiveInfo(resourcePath, PackageManager.GET_ACTIVITIES);}

既然我们现在已经获取了Resource, 那么下面获取资源文件就与上面是一样的

LoadedResource loadResource = loadResource("/storage/sdcard0/bundle.apk");Drawable drawable = getDrawable(loadResource.packageName, "image");

最后代码

LoadedResource.java

package com.example.host.res;import android.content.res.Resources;public class LoadedResource {    public Resources resources;    public String packageName; public ClassLoader classLoader;}

ResourceManager.java

package com.example.host.res;import java.io.File;import java.lang.reflect.Method;import java.util.HashMap;import java.util.Map;import android.content.Context;import android.content.pm.PackageInfo;import android.content.pm.PackageManager;import android.content.res.AssetManager;import android.content.res.Resources;import android.graphics.drawable.Drawable;import android.util.Log;import dalvik.system.DexClassLoader;public class ResourceManager {    private static final String TAG = "ResourceManager";    private ResourceManager() {    }    public static void init(Context context) {        UnInstalled.sManager.init(context);        Installed.sManager.init(context);    }    public static UnInstalled unInstalled() {        return UnInstalled.sManager;    }    public static Installed installed() {        return Installed.sManager;    }    /**     * 针对于未安装应用     */    public static class UnInstalled {        static final UnInstalled sManager = new UnInstalled();        private Context mContext;        private Map mRescources = new HashMap();        private String mDexDir;        private UnInstalled() {        }        /**         * 初始化         *         * @param context         */        public void init(Context context) {            mContext = context.getApplicationContext();            File dexDir = mContext.getDir("dex", Context.MODE_PRIVATE);            if (!dexDir.exists()) {                dexDir.mkdir();            }            mDexDir = dexDir.getAbsolutePath();        }        /**         * 获取未安装应用资源的ID         *         * @param packageName         * @param fieldName         * @return         */        public int getResourceID(String packageName, String type, String fieldName) {            int resID = 0;            LoadedResource recource = getUnInstalledRecource(packageName);            String rClassName = packageName + ".R$" + type;            Log.w(TAG, "resource class:" + rClassName + ",fieldName:" + fieldName);            try {                Class cls = recource.classLoader.loadClass(rClassName);                resID = (Integer) cls.getField(fieldName).get(null);            } catch (Exception e) {                e.printStackTrace();            }            return resID;        }        /**         * 获取未安装应用Drawable         *         * @param packageName         * @param fieldName         * @return         */        public Drawable getDrawable(String packageName, String fieldName) {            Drawable drawable = null;            int resourceID = getResourceID(packageName, "drawable", fieldName);            LoadedResource recource = getUnInstalledRecource(packageName);            if (recource != null) {                drawable = recource.resources.getDrawable(resourceID);            }            return drawable;        }        /**         * 加载未安装应用资源包         *         * @param resourcePath         * @return         */        public LoadedResource loadResource(String resourcePath) {            LoadedResource loadResource = null;            PackageInfo info = queryPackageInfo(resourcePath);    //    获取未安装APK的PackageInfo            if (info != null) {    //   获取成功                loadResource = mRescources.get(info.packageName);    // 先从缓存中取, 存在则直接返回, 不重复添加. 否则就搜索添加                if (loadResource == null) {                    try {                        AssetManager assetManager = AssetManager.class.newInstance();    // 创建AssetManager实例                        Class cls = AssetManager.class;                        Method method = cls.getMethod("addAssetPath", String.class);                        method.invoke(assetManager, resourcePath);    // 反射设置资源加载路径                        Resources resources = new Resources(assetManager, mContext.getResources().getDisplayMetrics(),                                mContext.getResources().getConfiguration());    // 构造出正确的Resource                        loadResource = new LoadedResource();                        loadResource.resources = resources;                        loadResource.packageName = info.packageName;                        loadResource.classLoader = new DexClassLoader(resourcePath, mDexDir, null,                                mContext.getClassLoader());    //   设置正确的类加载器, 因为需要去加载R文件                        mRescources.put(info.packageName, loadResource);    // 缓存                        Log.w(TAG, "build resource:" + resourcePath);                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }            Log.w(TAG, "load resource:" + resourcePath);            return loadResource;        }        /**         * 获取未安装应用PackageInfo         *         * @param resourcePath         * @return         */        private PackageInfo queryPackageInfo(String resourcePath) {            return mContext.getPackageManager().getPackageArchiveInfo(resourcePath, PackageManager.GET_ACTIVITIES);        }        /**         * 获取未安装应用LoadResource         *         * @param packageName         * @return         */        public LoadedResource getUnInstalledRecource(String packageName) {            LoadedResource loadResource = mRescources.get(packageName);            if (loadResource == null) {                Log.w(TAG, "resource " + packageName + " not founded");            }            return loadResource;        }    }    /**     * 针对于已安装应用     */    public static class Installed {        static final Installed sManager = new Installed();        private Context mContext;        private Map mResources = new HashMap();        private Installed() {        }        /**         * 初始化         *         * @param context         */        public void init(Context context) {            mContext = context.getApplicationContext();        }        /**         * 获取已安装应用资源         *         * @param packageName         */        public LoadedResource getInstalledResource(String packageName) {            LoadedResource resource = mResources.get(packageName);    // 先从缓存中取, 没有就去加载            if (resource == null) {                try {                    Context context = mContext.createPackageContext(packageName,                            Context.CONTEXT_INCLUDE_CODE | Context.CONTEXT_IGNORE_SECURITY);                    resource = new LoadedResource();                    resource.packageName = packageName;                    resource.resources = context.getResources();                    resource.classLoader = context.getClassLoader();                    mResources.put(packageName, resource);    // 得到结果缓存起来                } catch (Exception e) {                    e.printStackTrace();                }            }            return resource;        }        /**         * 获取资源ID         *         * @param packageName         * @param type         * @param fieldName         * @return         */        public int getResourceID(String packageName, String type, String fieldName) {            int resID = 0;            LoadedResource installedResource = getInstalledResource(packageName);    // 获取已安装APK的资源            if (installedResource != null) {                String rClassName = packageName + ".R$" + type;    // 根据匿名内部类的命名, 拼写出R文件的包名+类名                try {                    Class cls = installedResource.classLoader.loadClass(rClassName);    //  加载R文件                    resID = (Integer) cls.getField(fieldName).get(null);    //  反射获取R文件对应资源名的ID                } catch (Exception e) {                    e.printStackTrace();                }            } else {                Log.w(TAG, "resource is null:" + packageName);            }            return resID;        }        /**         * 获取已加载应用Drawable         *         * @param packageName         * @param fieldName         * @return         */        public Drawable getDrawable(String packageName, String fieldName) {            Drawable drawable = null;            int resourceID = getResourceID(packageName, "drawable", fieldName);            LoadedResource installedResource = getInstalledResource(packageName);            if (installedResource != null) {                drawable = installedResource.resources.getDrawable(resourceID);            }            return drawable;        }    }}

activity_main.xml

MainActivity.java

package com.example.host;import android.app.Activity;import android.graphics.drawable.Drawable;import android.os.Bundle;import android.view.View;import android.widget.ImageView;import com.example.host.act.ActivityManager;import com.example.host.res.LoadedResource;import com.example.host.res.ResourceManager;public class MainActivity extends Activity {    ImageView imageView;    ActivityManager mPluginManager = ActivityManager.getInstance();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        ResourceManager.init(this);        mPluginManager.init(this);        imageView = (ImageView) findViewById(R.id.imageView);    }    /**     * 加载已安装APK资源     *     * @param v     */    public void loadInstalledBundle(View v) {        Drawable drawable = ResourceManager.installed().getDrawable("com.example.resourcebundle", "image1");        if (drawable != null) {            imageView.setImageDrawable(drawable);        }    }    /**     * 加载未安装APK资源     *     * @param v     */    public void loadUninstalledBundle(View v) {        LoadedResource loadResource = ResourceManager.unInstalled().loadResource("/storage/sdcard0/bundle.apk");        Drawable drawable = ResourceManager.unInstalled().getDrawable(loadResource.packageName, "image");        if (drawable != null) {            imageView.setImageDrawable(drawable);        }    }}

测试加载安装APK资源就安装ResourceBundle应用, 测试加载未安装APK资源就把ResourceBundle应用放到指定位置

其中ResourceBundle只要包含image和image1的两个drawable就可以了

Android黑科技动态加载(三)之动态加载资源

目录