Java反射機制

由於反射比較抽象，這也是反射的基操，所以沒效果圖，直接上代碼：

package com.example.a51044.fanshe;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.example.a51044.fanshe.bean.Student;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button Field_Btn;
    private Button Method_Btn;
    private Button Concur_Btn;
    private Student student;
    private Class aClass;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        student=new Student();
        //通過創建對象得到該類的字節碼對象
        aClass = student.getClass();

    }

    private void initView() {
        Field_Btn = (Button) findViewById(R.id.Field_Btn);
        Method_Btn = (Button) findViewById(R.id.Method_Btn);
        Concur_Btn = (Button) findViewById(R.id.Concur_Btn);

        Field_Btn.setOnClickListener(this);
        Method_Btn.setOnClickListener(this);
        Concur_Btn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.Field_Btn:
                getField();
                setField();
                break;
            case R.id.Method_Btn:
                getMotheds();
                break;
            case R.id.Concur_Btn:
                getConstructors();
                break;
        }
    }

    
    private void getConstructors() {
        //得到該類中所有的構造方法，不加Declared只能得到公共的構造方法
        Constructor[] constructors = aClass.getDeclaredConstructors();
        for(Constructor c:constructors)
        {
            //循環獲取構造方法的名字
            Log.e("構造方法",c.getName());
        }

        try {
            //通過參數得知是哪個構造方法
            Constructor constructor = aClass.getDeclaredConstructor(String.class, String.class, int.class);
            Object o = constructor.newInstance("memeda", "heheh", 20);
            Log.e("獲取構造",o.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void getMotheds() {
        //獲取到該類的所有的方法
        Method[] methods = aClass.getDeclaredMethods();
        for(Method m:methods)
        {
            Log.e("查看方法",m.getName());
        }

        try {
            //得到方法名爲getInfo的方法，後面參數對應的是基本類裏的參數
            Method info = aClass.getDeclaredMethod("getInfo", String.class, String.class, int.class);
            info.setAccessible(true);
            //通過反射得到該類的實例
            Object instance = aClass.newInstance();
            info.invoke(instance,"李小強","男",18);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    private void getField()
    {
        //獲取所有的成員變量
        Field[] fields = aClass.getDeclaredFields();
        for(Field f:fields)
        {
            //獲取到所有的成員變量名字
            Log.e("變量",f.getName());
        }
        try {
            //指定獲取到某個變量
            Field lick = aClass.getDeclaredField("lick");
            //暴力反射後可以獲取到私有的
            lick.setAccessible(true);
            //個人理解爲得到這個變量的值（僅供參考）
            Object o = lick.get(student);
            if(o instanceof String)
           {
                Log.e("通過反射獲取到的屬性值",o.toString());
           }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    private void setField()
    {
        try {
            Field name = aClass.getDeclaredField("name");
            name.setAccessible(true);
            //通過反射創建一個該類的實例
            Student instance = (Student) aClass.newInstance();
            //給name屬性賦值
            name.set(instance,"李廣強");
            Log.e("給屬性賦值",instance.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }




}

我的基本類：

package com.example.a51044.fanshe.bean;

import android.util.Log;

public class Student {
    private String name;
    private String sex;
    private int age;
    private String lick = "lvxx 帥";

    public Student(String name, String sex, int age) {
        this.name = name;
        this.sex = sex;
        this.age = age;
    }

    public Student() {

    }




    public void getInfo(String name) {
        this.name = name;
    }

    private void getInfo(String name, String sex,int age) {
        Log.e("name和sex", name + ",sex=" + sex+",age="+age);

    }


    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age=" + age +
                ", lick='" + lick + '\'' +
                '}';
    }
}