標籤:就是 bsp direct try 它的 return method out 代理
No1:
外掛程式化技術的好處:
1)減輕應用的記憶體和CPU佔用
2)實現熱插拔,即在不發布新版本的情況下更新某些模組
No2:
外掛程式化方案必須要解決三個基礎性問題:資源訪問、Activity生命週期的管理和ClassLoader的管理
No3:
宿主是指普通的apk,外掛程式一般指經過處理的dex或者apk。外掛程式化架構大多採用apk作為外掛程式,很多需要用到代理Activity,外掛程式Activity的啟動大多數是藉助一個代理Activity來實現的。
No4:
Activity的工作主要是通過ContextImpl來完成的,Activity中有一個交mBase的成員變數,它的類型就是ContextImpl。Context中有兩個抽象方法getAssets和getResources,通過它們來擷取資源的,真正實現在ContextImpl中。
No5:
資源訪問
載入apk中的資源
protected void loadResources(){ try{ AssetManager assetManager = AssetManager.class.newInstance(); Method addAssetPath = assetManager.getClass().getMethod("addAssetPath",String.class); addAssetPath.invoke(assetManager,mDexPath); mAssetManager = assetManager; }catch(Exception e){ e.printStackTrace(); } Resources superRes = super.getResources(); mResources = new Resources(mAssetManager,superRes.getDisplayMetrics(),superRes.getConfiguration()); mTheme = mResources.newTheme(); mTheme.setTo(super.getTheme());}
通過反射,調用AssetManager中addAssetPath方法,將一個apk中的資源載入到Resources對象中。然後通過AssetManager來建立一個新的Resources對象
public final int addAssetPath(String path){ synchronized(this){ int res = addAssetPathNative(path); makeStringBlocks(mStringBlocks); return res; }}
接著在代理Activity中實現getAssets和getResources
@Overridepublic AssetManager getAssets(){ return mAssetManager == null?super.getAssets():mAssetManager;}@Overridepublic Resources getResources(){ return mResources == null?super.getResources():mResources;}
No6:
Activity生命週期的管理
反射方式
@Overrideprotected void onResume(){ super.onResume(); Method onResume = mActivityLifecircleMethods.get("onResume"); if(onResume!=null){ try{ onResume.invoke(mRemoteActivity,new Object[]{ }) }catch(Exception e){ e.printStackTrace(); } }}@Overrideprotected void onPause(){ Method onPause = mActivityLifecircleMethods.get("onPause"); if(onPause!=null){ try{ onPause.invoke(mRemoteActivity,new Object[]{ }) }catch(Exception e){ e.printStackTrace(); } } super.onPause();}
介面方式
public interface DLPlugin{ public void onStart(); public void onRestart(); public void onResume(); public void onPause(); public void onStop(); public void onDestroy(); ...}
代理Actvitiy中調用
...@Overrideprotected void onStart(){ mRemoteActivity.onStart(); super.onStart();}@Overrideprotected void onRestart(){ mRemoteActivity.onRestart(); super.onRestart();}@Overrideprotected void onResume(){ mRemoteActivity.onResume(); super.onResume();}
mRemoteActivity就是DLPlugin的實現
No7:
外掛程式ClassLoader的管理
public class DLClassLoader extends DexClassLoader{ private static final String TAG ="DLClassLoader"; private static final HashMap<String,DLClassLoader> mPluginClassLoaders = new HashMap<String,DLClassLoader>(); protected DLClassLoader(String dexPath,String optimizedDirectory,String libraryPath,Classloader parent){ super(dexPath,optimizedDirectory,libraryPath,parent); } public static DLClassLoader getClassLoader(String dexPath,Context context,Classloader parentLoader){ DLClassLoader dLassLoader = mPluginClassLoaders.get(dexPath); if(dLassLoader != null){ return DLClassLoader; } File dexOutputDir = context.getDir("dex",Context.MODE_PRIVATE); final String dexOutputPath = dexOutputDir.getAbsolutePath(); dLClassLoader = new DLClassLoader(dexPath,dexOutputPath,null,parentLoader); mPluginClassLoaders.put(dexPath,dLClassLoader); return dLClassLoader; }}
通過將不同外掛程式的ClassLoader儲存在一個HashMap中,這樣就可以保證不同外掛程式中的類彼此互不干擾。
Android動態載入技術(外掛程式化技術)