android应用Theme(二)

另外一种实现android应用Theme的方式是通过apk来实现的。

以下是一个demo。

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加入一些图片，也能够用其它（包含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高速调用这种方法。

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中通过读取全部安装的应用，通过分析applicationInfo的meta-data。然后推断是否是自己的插件apk。

然后通过context.createPackageContext(packageName,int flag)得到对应插件的context。然后通过类载入器得到MainActivity的class类。然后通过反射得到方法返回的值。然后就能够得到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);//得到全部安装的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的值推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类载入器，然后得到MainActvity的类对象
				Class<?> mainClass = otherplusContext
						.getClassLoader()
						.loadClass(mPluginPackageNameList.get(0) + ".MainActivity");
				//通过反射得到对应位置的drawable
				Method m = mainClass.getMethod("getDrawableIdForOtherApp",
						int.class);
				int imgBgId = (Integer) m.invoke(mainClass.newInstance(), position);
				//为了能够循环切换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();
			}
		}

	}
}

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