Android反射机制技术的使用示例

 转:http://blog.csdn.net/lfdfhl/article/details/10311505

  1 package com.nthm.androidtestActivity;

  2 

  3 import java.io.File;

  4 import java.lang.reflect.Constructor;

  5 import java.lang.reflect.Field;

  6 import java.lang.reflect.Method;

  7 import com.nthm.androidtest.R;

  8 import android.os.Bundle;

  9 import android.app.Activity;

 10 import android.content.ContextWrapper;

 11 /**

 12  * Demo描述:

 13  * Android中Java反射技术的使用示例

 14  * 在Java中描述字节码文件(xxx.class)的类叫Class

 15  * 反射的过程可视为剖析Class的过程

 16  */

 17 public class MainActivity extends Activity {

 18     @Override

 19     protected void onCreate(Bundle savedInstanceState) {

 20         super.onCreate(savedInstanceState);

 21         setContentView(R.layout.main);

 22         init();

 23     }

 24     private void init(){

 25         try {

 26             /**

 27              * 1 反射出无参的构造方法并得到对象

 28              * 注意:

 29              *      1 在Class.forName()中应该传入含有包名的类全名

 30              *      2 newInstance()方法的本质是调用类的无参Public构造方法

 31              */

 32             String className1="com.nthm.androidtestBean.Worker";

 33             Class clazz1=Class.forName(className1);

 34             Object object1=clazz1.newInstance();

 35             System.out.println("object1.toString()="+object1.toString());

 36             /**

 37              * 2 反射出带参数的构造方法并得到对象

 38              */

 39             String className2="com.nthm.androidtestBean.Worker";

 40             Class clazz2=Class.forName(className2);

 41             Constructor constructor1=clazz2.getConstructor(int.class,String.class);

 42             Object object2=constructor1.newInstance(18,"小明");

 43             System.out.println("object2.toString()="+object2.toString());

 44             

 45             /**

 46              * 3 获取类的私有(private)字段

 47              * 注意:

 48              *      获取共有(public)字段应调用clazz3.getField(name)方法

 49              */

 50             String className3="com.nthm.androidtestBean.Worker";

 51             Class clazz3=Class.forName(className3);

 52             Field ageField1=clazz3.getDeclaredField("age");

 53             System.out.println("ageField1="+ageField1);

 54             

 55             /**

 56              * 4 获取和更改某个对象的私有字段

 57              *   即模拟get()和set()方法

 58              */

 59             String className4="com.nthm.androidtestBean.Worker";

 60             Class clazz4=Class.forName(className4);

 61             Field ageField2=clazz4.getDeclaredField("age");

 62             Object object4=constructor1.newInstance(18,"小明");

 63             //取消访问私有字段的合法性检查

 64             ageField2.setAccessible(true);

 65             //获取对象的私有字段

 66             Object ageObject4=ageField2.get(object4);

 67             System.out.println("ageObject4="+ageObject4.getClass().getName());

 68             System.out.println("ageObject4="+ageObject4);

 69             

 70             //再更改对象的私有字段的值

 71             ageField2.set(object4, 9527);

 72             //重新获得

 73             Object ageObject5=ageField2.get(object4);

 74             System.out.println("ageObject5="+ageObject5);

 75             

 76             /**

 77              * 5 调用对象的带参数的方法

 78              */

 79             String className5="com.nthm.androidtestBean.Worker";

 80             Class clazz5=Class.forName(className5);

 81             Method method=clazz5.getMethod("printMessage", String.class,int.class,int.class);

 82             Object object5=clazz5.newInstance();

 83             method.invoke(object5, "周星星",50,9527);

 84             

 85             //获取ContextWrapper对象中的mBase对象，该变量保存了ContextImpl对象

 86             Field field=ContextWrapper.class.getDeclaredField("mBase");

 87             //跳过属性的修饰(public private protect)检查

 88             field.setAccessible(true);

 89             //获取对象的指定属性的值

 90             Object obj=field.get(this);

 91             //根据获取的值所属的类来获取该类中的其他属性

 92             field=obj.getClass().getDeclaredField("mPreferencesDir");

 93             //跳过属性的修饰(public private protect)检查

 94             field.setAccessible(true);

 95             File file=new File("/sacard");

 96             //对该属性重新赋值

 97             field.set(obj, file);

 98         } catch (Exception e) {

 99             System.out.println(e.toString());

100         }

101     

102     }

103 

104 }

 1 package com.nthm.androidtestBean;

 2 

 3 public class Worker {

 4     private int age;

 5     private String name;

 6     public Worker() {

 7         super();

 8         System.out.println("---> public Worker(){ }");

 9     }

10     public Worker(int age, String name) {

11         super();

12         this.age = age;

13         this.name = name;

14         System.out.println("---> public Worker(int age, String name){ }");

15     }

16     public int getAge() {

17         return age;

18     }

19     public void setAge(int age) {

20         this.age = age;

21     }

22     public String getName() {

23         return name;

24     }

25     public void setName(String name) {

26         this.name = name;

27     }

28     @Override

29     public String toString() {

30         return "Worker [age=" + age + ", name=" + name + "]";

31     }

32     

33     public void printMessage(String name,int age,int salary){

34         System.out.println("name="+name+",age="+age+",salary="+salary);

35     }

36     

37 }

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

 2     xmlns:tools="http://schemas.android.com/tools"

 3     android:layout_width="match_parent"

 4     android:layout_height="match_parent"

 5     >

 6 

 7     <TextView

 8         android:layout_width="wrap_content"

 9         android:layout_height="wrap_content"

10         android:text="Android中Java反射技术的使用" 

11         android:layout_centerInParent="true"/>

12 

13 </RelativeLayout>