将Android打包成jar包供人使用，可利用java的反射技术，获取相应的id.方便使用者替换自己所需要的。
1.新建Android项目：ActivityLibrary，这就是需要我们打包成jar包的项目：
2.MResource这个类的作用，，就是利用J2SE反射技术获取相应的ID资源。Android SDK也提供了获取Id资源的方法：getResources().getIdentifier("main_activity", "layout", getPackageName());
看下MResource的代码：
package com.example.activitylibrary;import android.content.Context;/** * 根据资源的名字获取其ID值 * @author howlaa */ public class MResource {//根据名称获取IDpublic static int getIdByName(Context context, String className, String name) {String packageName = context.getPackageName();Class r = null;int id = 0;try{r = Class.forName(packageName + ".R");Class[] classes = r.getClasses();Class desireClass = null;for (int i = 0; i < classes.length; ++i) {if (classes[i].getName().split("\\$")[1].equals(className)) {desireClass = classes[i];break;}}if (desireClass != null)id = desireClass.getField(name).getInt(desireClass);} catch (ClassNotFoundException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (SecurityException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (NoSuchFieldException e) {e.printStackTrace();}return id;}//获取ID数组public static int[] getIdsByName(Context context, String className, String name) {String packageName = context.getPackageName();Class r = null;int[] ids = null;try {r = Class.forName(packageName + ".R");Class[] classes = r.getClasses();Class desireClass = null;for (int i = 0; i < classes.length; ++i) {if (classes[i].getName().split("\\$")[1].equals(className)) {desireClass = classes[i];break;}}if ((desireClass != null) && (desireClass.getField(name).get(desireClass) != null) && (desireClass.getField(name).get(desireClass).getClass().isArray()))ids = (int[])desireClass.getField(name).get(desireClass);}catch (ClassNotFoundException e) {e.printStackTrace();} catch (IllegalArgumentException e) {e.printStackTrace();} catch (SecurityException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (NoSuchFieldException e) {e.printStackTrace();}return ids;} }3.在layout下新建activity_main.xml:<RelativeLayout xmlns:android=""xmlns:tools=""android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity" ><Buttonandroid:id="@+id/button1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentLeft="true"android:layout_alignParentRight="true"android:layout_alignParentTop="true" /><TextViewandroid:id="@+id/textView1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentLeft="true"android:layout_alignParentRight="true"android:layout_below="@+id/button1" /><ImageViewandroid:id="@+id/imageView1"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_alignParentLeft="true"android:layout_alignParentRight="true"android:layout_below="@+id/textView1"android:layout_marginTop="28dp"android:src="@drawable/ic_launcher" /></RelativeLayout>4.看下mainactivity:package com.example.activitylibrary;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;import android.widget.Toast;import android.app.Activity;public class MainActivity extends Activity {String msg = "hello bitch"; @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(MResource.getIdByName(getApplication(), "layout", "activity_main"));TextView mTextView = (TextView) findViewById(MResource.getIdByName(getApplication(), "id", "textView1")); mTextView.setText(msg);Button mButton = (Button) findViewById(MResource.getIdByName(getApplication(), "id", "button1"));mButton.setText(msg);mButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {Toast.makeText(getApplication(), msg, Toast.LENGTH_SHORT).show();}}); }}5.我们将ActivityLibrary工程打成Jar包。右键项目—>Export—->Java—>JAR file—->Next如下图人创造奇迹常常是在瞬间，
