1.首先必须新建一个apk，类似的插件，然后在该apk的AndroidManifest.xml文件的application加上一个meta-data。这个是下一步查找是否是自己的插件的apk做一个标记。
<meta-data android:name="skin_demo2_plugin" android:value="com.example.skindemo2.icon"/>
2.在该apk添加一些图片，也可以用其他（包括style等）这里主要是为了演示。在该apk的MainActivity定义一个方法。这里主要为了方便主apk快速调用这个方法。
static int allDrawableId[] = {R.drawable.img_apparel_accessories,R.drawable.img_computers_software
,R.drawable.img_electro,R.drawable.img_electronics,R.drawable.img_entertaiment
,R.drawable.img_food_beverage,R.drawable.img_kids_baby,R.drawable.img_sport,R.drawable.img_toys_games};
public int getDrawableIdForOtherApp(int position){
if(position < allDrawableId.length){
return allDrawableId[position];
}
return 0;
}
3.在主apk中通过读取所有安装的应用，通过分析applicationInfo的meta-data，然后判断是否是自己的插件apk。
然后通过context.createPackageContext(packageName,int flag)得到相应插件的context。然后通过类加载器得到MainActivity的class类，然后通过反射得到方法返回的值。然后就可以得到drawable对象。
package com.example.skindemo2;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.graphics.drawable.Drawable;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends Activity {
private Button mSwtichImgBgBtn;
private ImageView mShowImg;
private Context context;
private ArrayList<String> mPluginPackageNameList = new ArrayList<String>();
private int position = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
context = this;
mSwtichImgBgBtn = (Button) this.findViewById(R.id.swtichImgBgBtn);
mSwtichImgBgBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
swtichImgUsePlugin();
}
});
mShowImg = (ImageView) this.findViewById(R.id.myShowImg);
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params) {
findPluginPackageName();
return null;
}
@Override
protected void onPostExecute(Void result) {
swtichImgUsePlugin();
super.onPostExecute(result);
}
}.execute();
}
private void findPluginPackageName() {
PackageManager pm = context.getPackageManager();
List<PackageInfo> list = pm.getInstalledPackages(0);//得到所有安装的apk的PackageInfo
String meta = null;
ApplicationInfo aInfo = null;
for (PackageInfo pi : list) {
String pkgName = pi.packageName;
try {
aInfo = pm.getApplicationInfo(pkgName,
PackageManager.GET_META_DATA);
} catch (NameNotFoundException e) {
e.printStackTrace();
}
if (aInfo == null || aInfo.metaData == null)
continue;
meta = aInfo.metaData.getString("skin_demo2_plugin");
if (meta == null || "".equals(meta))
continue;
if ("com.example.skindemo2.icon".equals(meta)) {
//通过meta的值判断是否是自己的插件apk
mPluginPackageNameList.add(aInfo.packageName);
}
}
}
//必须在主线程中操作
private void swtichImgUsePlugin() {
//我这里为了方便直接就取了第一个插件apk数据，实际中是通过用户选择的apk来切换
if (mPluginPackageNameList.size() != 0) {
try {
//通过createPackageContext方法得到插件apk的context
Context otherplusContext = context.createPackageContext(
mPluginPackageNameList.get(0),
Context.CONTEXT_INCLUDE_CODE
| Context.CONTEXT_IGNORE_SECURITY);
//通过得到插件apk的context类加载器，然后得到MainActvity的类对象
Class<?> mainClass = otherplusContext
.getClassLoader()
.loadClass(mPluginPackageNameList.get(0) + ".MainActivity");
//通过反射得到相应位置的drawable
Method m = mainClass.getMethod("getDrawableIdForOtherApp",
int.class);
int imgBgId = (Integer) m.invoke(mainClass.newInstance(), position);
//为了可以循环切换img
if(imgBgId == 0){
position = 0;
}else{
position += 1;
}
//得到drawable对象
Drawable drawable = otherplusContext.getResources()
.getDrawable(imgBgId);
mShowImg.setImageDrawable(drawable);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}