Android反射机制技术的使用示例

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

package com.nthm.androidtestActivity;

import java.io.File;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import com.nthm.androidtest.R;
import android.os.Bundle;
import android.app.Activity;
import android.content.ContextWrapper;
/**
 * Demo描述:
 * Android中Java反射技术的使用示例
 * 在Java中描述字节码文件(xxx.class)的类叫Class
 * 反射的过程可视为剖析Class的过程
 */
public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        init();
    }
    private void init(){
        try {
            /**
             * 1 反射出无参的构造方法并得到对象
             * 注意:
             *      1 在Class.forName()中应该传入含有包名的类全名
             *      2 newInstance()方法的本质是调用类的无参Public构造方法
             */
            String className1="com.nthm.androidtestBean.Worker";
            Class clazz1=Class.forName(className1);
            Object object1=clazz1.newInstance();
            System.out.println("object1.toString()="+object1.toString());
            /**
             * 2 反射出带参数的构造方法并得到对象
             */
            String className2="com.nthm.androidtestBean.Worker";
            Class clazz2=Class.forName(className2);
            Constructor constructor1=clazz2.getConstructor(int.class,String.class);
            Object object2=constructor1.newInstance(18,"小明");
            System.out.println("object2.toString()="+object2.toString());
            
            /**
             * 3 获取类的私有(private)字段
             * 注意:
             *      获取共有(public)字段应调用clazz3.getField(name)方法
             */
            String className3="com.nthm.androidtestBean.Worker";
            Class clazz3=Class.forName(className3);
            Field ageField1=clazz3.getDeclaredField("age");
            System.out.println("ageField1="+ageField1);
            
            /**
             * 4 获取和更改某个对象的私有字段
             *   即模拟get()和set()方法
             */
            String className4="com.nthm.androidtestBean.Worker";
            Class clazz4=Class.forName(className4);
            Field ageField2=clazz4.getDeclaredField("age");
            Object object4=constructor1.newInstance(18,"小明");
            //取消访问私有字段的合法性检查
            ageField2.setAccessible(true);
            //获取对象的私有字段
            Object ageObject4=ageField2.get(object4);
            System.out.println("ageObject4="+ageObject4.getClass().getName());
            System.out.println("ageObject4="+ageObject4);
            
            //再更改对象的私有字段的值
            ageField2.set(object4, 9527);
            //重新获得
            Object ageObject5=ageField2.get(object4);
            System.out.println("ageObject5="+ageObject5);
            
            /**
             * 5 调用对象的带参数的方法
             */
            String className5="com.nthm.androidtestBean.Worker";
            Class clazz5=Class.forName(className5);
            Method method=clazz5.getMethod("printMessage", String.class,int.class,int.class);
            Object object5=clazz5.newInstance();
            method.invoke(object5, "周星星",50,9527);
            
            //获取ContextWrapper对象中的mBase对象，该变量保存了ContextImpl对象
            Field field=ContextWrapper.class.getDeclaredField("mBase");
            //跳过属性的修饰(public private protect)检查
            field.setAccessible(true);
            //获取对象的指定属性的值
            Object obj=field.get(this);
            //根据获取的值所属的类来获取该类中的其他属性
            field=obj.getClass().getDeclaredField("mPreferencesDir");
            //跳过属性的修饰(public private protect)检查
            field.setAccessible(true);
            File file=new File("/sacard");
            //对该属性重新赋值
            field.set(obj, file);
        } catch (Exception e) {
            System.out.println(e.toString());
        }
    
    }

}

package com.nthm.androidtestBean;

public class Worker {
    private int age;
    private String name;
    public Worker() {
        super();
        System.out.println("---> public Worker(){ }");
    }
    public Worker(int age, String name) {
        super();
        this.age = age;
        this.name = name;
        System.out.println("---> public Worker(int age, String name){ }");
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Worker [age=" + age + ", name=" + name + "]";
    }
    
    public void printMessage(String name,int age,int salary){
        System.out.println("name="+name+",age="+age+",salary="+salary);
    }
    
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Android中Java反射技术的使用" 
        android:layout_centerInParent="true"/>

</RelativeLayout>