【Android学习】壳的前置知识

bootstrap classloader
extensions classloader
application classloader
系统中加载顺序也是如上

加载时机
隐式加载
	创建类的实例
	访问类的静态变量或者为静态变量赋值
	调用类的静态方法
	使用反射方式强制创建某个类或接口对应的java.lang.Class对象
	初始化某个类的子类
显示加载
	使用LoadClass
	使用forname加载
	

加载
	查找和导入这个class文件
链接
	检查 检查导入的class文件的正确性
	准备 给类的静态变量分配存储空间
	解析 把符号引用转成直接引用
初始化
	调用 clinit 函数 将静态变量 静态代码块做初始化操作

package com.example.kanxue12;

import android.os.Bundle;
import android.util.Log;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });
        testClassLoader();
    }
    public void testClassLoader(){
        ClassLoader thisClassLoader = MainActivity.class.getClassLoader();
        Log.i("kanxue","thisClassLoader"+thisClassLoader);
        ClassLoader tmpClassLoader=null;
        ClassLoader parentClassLoader=thisClassLoader.getParent();
        while(parentClassLoader!=null){
            Log.i("kanxue","this:"+thisClassLoader+"-----"+parentClassLoader);
            thisClassLoader = parentClassLoader;
            parentClassLoader = tmpClassLoader;
        }
        Log.i("kanxue","root"+thisClassLoader);
    }
}

kanxue                  com.example.kanxue12                 I  thisClassLoaderdalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.example.kanxue12-SIKDTDOcNa_tqDC7e59_RA==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.kanxue12-SIKDTDOcNa_tqDC7e59_RA==/lib/arm64, /system/lib64, /vendor/lib64]]]
1970-02-28 14:36:28.646 20586-20586 kanxue                  com.example.kanxue12                 I  this:dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.example.kanxue12-SIKDTDOcNa_tqDC7e59_RA==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.kanxue12-SIKDTDOcNa_tqDC7e59_RA==/lib/arm64, /system/lib64, /vendor/lib64]]]-----java.lang.BootClassLoader@eece960
1970-02-28 14:36:28.646 20586-20586 kanxue                  com.example.kanxue12                 I  rootjava.lang.BootClassLoader@eece960

package com.example.kanxue122;

import android.content.Context;
import android.os.Bundle;
import java.lang.Object;
import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import java.io.File;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;


import dalvik.system.DexClassLoader;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });
        Context appContext = this.getApplicationContext();
        try {
            testDexClassLoader(appContext,"/sdcard/classes3.dex");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }
    public void testDexClassLoader(Context context,String dexfilepath) throws ClassNotFoundException {
        File optfile = context.getDir("opt_dex",0);
        File libfile = context.getDir("lib_path",0);
        ClassLoader parentClassLoader = MainActivity.class.getClassLoader();
        DexClassLoader dexClassLoader = new DexClassLoader(dexfilepath,optfile.getAbsolutePath(), libfile.getAbsolutePath(), MainActivity.class.getClassLoader());
        Class<?> clazz=null;
        try {
            clazz=dexClassLoader.loadClass("com.example.kanxue12.test");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        if(clazz!=null){
            try {
                Method testFunctionMethod = clazz.getDeclaredMethod("test1");
                Object obj = clazz.newInstance();
                testFunctionMethod.invoke(obj);
            } catch (NoSuchMethodException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }

        }

    }
}