Android插件化（三）：加载插件apk中的Resource资源

最新推荐文章于 2024-07-11 10:31:41 发布

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最新推荐文章于 2024-07-11 10:31:41 发布

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转自：http://blog.youkuaiyun.com/nupt123456789/article/details/50411581

简介

如何加载未安装apk中的资源文件呢？我们从android.content.res.AssetManager.java的源码中发现，它有一个私有方法addAssetPath，只需要将apk的路径作为参数传入，我们就可以获得对应的AssetsManager对象，然后我们就可以使用AssetsManager对象，创建一个Resources对象，然后就可以从Resource对象中访问apk中的资源了。总结如下：

1.新建一个AssetManager对象
2.通过反射调用addAssetPath方法
3.以AssetsManager对象为参数，创建Resources对象即可。

代码如下：

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">package</span> net.mobctrl.hostapk;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> java.io.File;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.content.Context;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.content.res.AssetManager;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">import</span> android.content.res.Resources;

<span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @Author</span> Zheng Haibo
 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @PersonalWebsite</span> http://www.mobctrl.net
 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @version</span> $Id: LoaderResManager.java, v 0.1 2015年12月11日 下午7:58:59 mochuan.zhb
 *          Exp $
 *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @Description</span> 动态加载资源的管理器
 */</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">BundlerResourceLoader</span> {</span>

    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> AssetManager <span class="hljs-title" style="box-sizing: border-box;">createAssetManager</span>(String apkPath) {
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
            AssetManager assetManager = AssetManager.class.newInstance();
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
                AssetManager.class.getDeclaredMethod(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"addAssetPath"</span>, String.class).invoke(
                        assetManager, apkPath);
            } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (Throwable th) {
                System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:createAssetManager :"</span>+th.getMessage());
                th.printStackTrace();
            }
            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> assetManager;
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (Throwable th) {
            System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:createAssetManager :"</span>+th.getMessage());
            th.printStackTrace();
        }
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;
    }

    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
     * 获取Bundle中的资源
     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context
     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> apkPath
     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @return</span>
     */</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> Resources <span class="hljs-title" style="box-sizing: border-box;">getBundleResource</span>(Context context){
        AssetsManager.copyAllAssetsApk(context);
        File dir = context.getDir(AssetsManager.APK_DIR, Context.MODE_PRIVATE);
        String apkPath = dir.getAbsolutePath()+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"/BundleApk.apk"</span>;
        System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:apkPath = "</span>+apkPath+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">",exists="</span>+(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> File(apkPath).exists()));
        AssetManager assetManager = createAssetManager(apkPath);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Resources(assetManager, context.getResources().getDisplayMetrics(), context.getResources().getConfiguration());
    }

}
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li></ul>

DEMO

注意：我们使用Resources对象，获取资源时，传递的ID必须是离线apk中R文件对应的资源的ID。如果使用getIdentifier方法，第一个参数是资源名称，第二个参数是资源类型，第三个参数是离线apk的包名，切记第三个参数。

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">Resources resources = BundlerResourceLoader.getBundleResource(getApplicationContext());
        imageView = (ImageView)findViewById(R.id.image_view_iv);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(resources != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>){
            String str = resources.getString(resources.getIdentifier(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"test_str"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"string"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"net.mobctrl.normal.apk"</span>));
            String strById = resources.getString(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0x7f050001</span>);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//注意，id参照Bundle apk中的R文件</span>
            System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:"</span>+str);
            Toast.makeText(getApplicationContext(),strById, Toast.LENGTH_SHORT).show();

            Drawable drawable = resources.getDrawable(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0x7f020000</span>);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//注意，id参照Bundle apk中的R文件</span>
            imageView.setImageDrawable(drawable);
        }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

上述代码是加载离线apk中的字符串和Drawable资源，那么layout资源呢？

问题引入

我们使用LayoutInflate对象，一般使用方法如下：

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">View view = LayoutInflater.from(context).inflate(R.layout.main_fragment, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

其中，R.layout.main_fragment我们可以通过上述方法获取其ID，那么关键的一步就是如何生成一个context？直接传入当前的context是不行的。
解决方案有2个：
- 1.创建一个自己的ContextImpl，Override其方法。
- 2.通过反射，直接替换当前context的mResources私有成员变量。<>br
当然，我们是使用第二种方案：

<code class="language-java hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">    <span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">attachBaseContext</span>(Context context) {
        replaceContextResources(context);
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.attachBaseContext(context);
    }

    <span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
     * 使用反射的方式，使用Bundle的Resource对象，替换Context的mResources对象
     *<span class="hljs-javadoctag" style="color: rgb(102, 0, 102); box-sizing: border-box;"> @param</span> context
     */</span>
    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">replaceContextResources</span>(Context context){
        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {
            Field field = context.getClass().getDeclaredField(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mResources"</span>);
            field.setAccessible(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);
            field.set(context, mBundleResources);
            System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:repalceResources succ"</span>);
        } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (Exception e) {
            System.out.println(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"debug:repalceResources error"</span>);
            e.printStackTrace();
        }
    }
</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li></ul>

我们在Activity的attachBaseContext方法中，对Context的mResources进行替换，这样，我们就可以加载离线apk中的布局了。

资源文件的打包过程

如果想要做到插件化，需要了解Android资源文件的打包过程，这样可以为每一个插件进行编号，然后按照规则生成R文件。例如，以携程DynamicAPK为例，它将插件的R文件按照如下规则：

1.R文件为int型，前8位代表插件的Id，其中两个特殊的Id：Host是0x7f，android系统自带的是以0x01开头.
2.紧跟着的8位是区分资源类型的，比如layout，id,string,dimen等
3.后面16位是资源的编号

按照上述规则生成对应的插件apk。然后在运行时，我们可以写一个ResourceManager类，它继承自Resource对象，然后所有的Activity，都将其context的mResource成员变量修改为ResourceManager类，然后Override其方法，然后在加载资源时，根据不同的id的前缀，查找对应插件的Resource即可。也就是说，用一个类做分发。