【我的Android进阶之旅】Android Studio 使用 ASM Bytecode Outline 插件来研究Java字节码

其他 2020-02-23 10:45:14 阅读次数: 0

一、需求描述

最近在研究滴滴公司开源的booster框架的源码，地址：https://github.com/didi/booster

但是会有些以为，里面的代码是怎么写出来的？ 有些代码确实有点看不懂，比如下面的

it.desc == "()V"

到底是怎么写出来的？

L$SHADOW_TOAST;)V

为什么要这么拼成 Landroid/widget/Toast？？？

这些人写代码的时候，难道是一个一个手动敲的？不会敲错吗？

我想这些这些使用asm操作java字节码的操作，肯定是能够看到java字节码，才把部分逻辑写完的。那么如何查看java字节码呢？？

通过网上查询了几篇博客，大概了解了可以使用ASM Bytecode Outline插件来查看java字节码。

在这里插入图片描述

二、如何使用ASM Bytecode Outline插件？

2.1 先下载ASM Bytecode Outline插件

在这里插入图片描述
在这里插入图片描述
点击【Get】 进入下载版本页面 https://plugins.jetbrains.com/plugin/5918-asm-bytecode-outline/versions

在这里插入图片描述
选择最新的0.3.5版本，点击【Download】下载下来
在这里插入图片描述

2.2 安装ASM Bytecode Outline插件

【Settings】–>【Plugins】
在这里插入图片描述
点击右上角图标，选择【Install Plugn from Disk】
在这里插入图片描述
选择刚下好的 asm-bo-0.3.5.zip 点击 【OK】 即可安装
在这里插入图片描述
安装好了，点击【Restart IDE】 生效
在这里插入图片描述

三、如何使用ASM Bytecode Outline插件

重启Android Studio之后，就会有ASM的标志，如下所示
在这里插入图片描述

点击即可展开
在这里插入图片描述

选择一个java文件，查看其java字节码 ，如下所示

进入java文件编辑区域，鼠标右键弹出菜单项，选择【Show Bytecode outline】
在这里插入图片描述
然后后面的ASM框就会显示内容，如下所示

在这里插入图片描述
SizeConvertUtil.java 源代码如下所示

package com.xtc.common.util;

import android.content.Context;

/**
 * 尺寸转换工具
 * <p>
 * Created by ouyangpeng on 2015/9/21.
 */
public class SizeConvertUtil {
    /**
     * 根据手机的分辨率从 dp 的单位 转成为 px(像素)
     *
     * @param context 上下文
     * @param dp      dp的值
     * @return px的值
     */
    public static int dpToPx(Context context, float dp) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dp * scale + 0.5f);
    }

    /**
     * 根据手机的分辨率从 px(像素) 的单位 转成为 dp
     *
     * @param context 上下文
     * @param px      px的值
     * @return dp的值
     */
    public static int pxToDp(Context context, float px) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (px / scale + 0.5f);
    }

    /**
     * 将px值转换为sp值，保证文字大小不变
     *
     * @param context 上下文
     * @param px      px的值
     * @return sp的值
     */
    public static int pxToSp(Context context, float px) {
        //DisplayMetrics类中属性scaledDensity
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (px / fontScale + 0.5f);
    }

    /**
     * 将sp值转换为px值，保证文字大小不变
     *
     * @param context 上下文
     * @param sp      sp的值
     * @return px的值
     */
    public static int spToPx(Context context, float sp) {
        //DisplayMetrics类中属性scaledDensity
        final float fontScale = context.getResources().getDisplayMetrics().scaledDensity;
        return (int) (sp * fontScale + 0.5f);
    }
}
  • 对应的字节码如下所示【Bytecode面板内容】
// class version 51.0 (51)
// access flags 0x21
public class com/xtc/common/util/SizeConvertUtil {

  // compiled from: SizeConvertUtil.java

  // access flags 0x1
  public <init>()V
   L0
    LINENUMBER 10 L0
    ALOAD 0
    INVOKESPECIAL java/lang/Object.<init> ()V
    RETURN
   L1
    LOCALVARIABLE this Lcom/xtc/common/util/SizeConvertUtil; L0 L1 0
    MAXSTACK = 1
    MAXLOCALS = 1

  // access flags 0x9
  public static dpToPx(Landroid/content/Context;F)I
   L0
    LINENUMBER 19 L0
    ALOAD 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    GETFIELD android/util/DisplayMetrics.density : F
    FSTORE 2
   L1
    LINENUMBER 20 L1
    FLOAD 1
    FLOAD 2
    FMUL
    LDC 0.5
    FADD
    F2I
    IRETURN
   L2
    LOCALVARIABLE context Landroid/content/Context; L0 L2 0
    LOCALVARIABLE dp F L0 L2 1
    LOCALVARIABLE scale F L1 L2 2
    MAXSTACK = 2
    MAXLOCALS = 3

  // access flags 0x9
  public static pxToDp(Landroid/content/Context;F)I
   L0
    LINENUMBER 31 L0
    ALOAD 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    GETFIELD android/util/DisplayMetrics.density : F
    FSTORE 2
   L1
    LINENUMBER 32 L1
    FLOAD 1
    FLOAD 2
    FDIV
    LDC 0.5
    FADD
    F2I
    IRETURN
   L2
    LOCALVARIABLE context Landroid/content/Context; L0 L2 0
    LOCALVARIABLE px F L0 L2 1
    LOCALVARIABLE scale F L1 L2 2
    MAXSTACK = 2
    MAXLOCALS = 3

  // access flags 0x9
  public static pxToSp(Landroid/content/Context;F)I
   L0
    LINENUMBER 44 L0
    ALOAD 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    GETFIELD android/util/DisplayMetrics.scaledDensity : F
    FSTORE 2
   L1
    LINENUMBER 45 L1
    FLOAD 1
    FLOAD 2
    FDIV
    LDC 0.5
    FADD
    F2I
    IRETURN
   L2
    LOCALVARIABLE context Landroid/content/Context; L0 L2 0
    LOCALVARIABLE px F L0 L2 1
    LOCALVARIABLE fontScale F L1 L2 2
    MAXSTACK = 2
    MAXLOCALS = 3

  // access flags 0x9
  public static spToPx(Landroid/content/Context;F)I
   L0
    LINENUMBER 57 L0
    ALOAD 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    GETFIELD android/util/DisplayMetrics.scaledDensity : F
    FSTORE 2
   L1
    LINENUMBER 58 L1
    FLOAD 1
    FLOAD 2
    FMUL
    LDC 0.5
    FADD
    F2I
    IRETURN
   L2
    LOCALVARIABLE context Landroid/content/Context; L0 L2 0
    LOCALVARIABLE sp F L0 L2 1
    LOCALVARIABLE fontScale F L1 L2 2
    MAXSTACK = 2
    MAXLOCALS = 3
}
  • 【ASMified面板内容】
    在这里插入图片描述
package asm.com.xtc.common.util;

import java.util.*;

import org.objectweb.asm.*;

public class SizeConvertUtilDump implements Opcodes {

    public static byte[] dump() throws Exception {

        ClassWriter cw = new ClassWriter(0);
        FieldVisitor fv;
        MethodVisitor mv;
        AnnotationVisitor av0;

        cw.visit(V1_7, ACC_PUBLIC + ACC_SUPER, "com/xtc/common/util/SizeConvertUtil", null, "java/lang/Object", null);

        cw.visitSource("SizeConvertUtil.java", null);

        {
            mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
            mv.visitCode();
            Label l0 = new Label();
            mv.visitLabel(l0);
            mv.visitLineNumber(10, l0);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
            mv.visitInsn(RETURN);
            Label l1 = new Label();
            mv.visitLabel(l1);
            mv.visitLocalVariable("this", "Lcom/xtc/common/util/SizeConvertUtil;", null, l0, l1, 0);
            mv.visitMaxs(1, 1);
            mv.visitEnd();
        }
        {
            mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "dpToPx", "(Landroid/content/Context;F)I", null, null);
            mv.visitCode();
            Label l0 = new Label();
            mv.visitLabel(l0);
            mv.visitLineNumber(19, l0);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/Context", "getResources", "()Landroid/content/res/Resources;", false);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/res/Resources", "getDisplayMetrics", "()Landroid/util/DisplayMetrics;", false);
            mv.visitFieldInsn(GETFIELD, "android/util/DisplayMetrics", "density", "F");
            mv.visitVarInsn(FSTORE, 2);
            Label l1 = new Label();
            mv.visitLabel(l1);
            mv.visitLineNumber(20, l1);
            mv.visitVarInsn(FLOAD, 1);
            mv.visitVarInsn(FLOAD, 2);
            mv.visitInsn(FMUL);
            mv.visitLdcInsn(new Float("0.5"));
            mv.visitInsn(FADD);
            mv.visitInsn(F2I);
            mv.visitInsn(IRETURN);
            Label l2 = new Label();
            mv.visitLabel(l2);
            mv.visitLocalVariable("context", "Landroid/content/Context;", null, l0, l2, 0);
            mv.visitLocalVariable("dp", "F", null, l0, l2, 1);
            mv.visitLocalVariable("scale", "F", null, l1, l2, 2);
            mv.visitMaxs(2, 3);
            mv.visitEnd();
        }
        {
            mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "pxToDp", "(Landroid/content/Context;F)I", null, null);
            mv.visitCode();
            Label l0 = new Label();
            mv.visitLabel(l0);
            mv.visitLineNumber(31, l0);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/Context", "getResources", "()Landroid/content/res/Resources;", false);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/res/Resources", "getDisplayMetrics", "()Landroid/util/DisplayMetrics;", false);
            mv.visitFieldInsn(GETFIELD, "android/util/DisplayMetrics", "density", "F");
            mv.visitVarInsn(FSTORE, 2);
            Label l1 = new Label();
            mv.visitLabel(l1);
            mv.visitLineNumber(32, l1);
            mv.visitVarInsn(FLOAD, 1);
            mv.visitVarInsn(FLOAD, 2);
            mv.visitInsn(FDIV);
            mv.visitLdcInsn(new Float("0.5"));
            mv.visitInsn(FADD);
            mv.visitInsn(F2I);
            mv.visitInsn(IRETURN);
            Label l2 = new Label();
            mv.visitLabel(l2);
            mv.visitLocalVariable("context", "Landroid/content/Context;", null, l0, l2, 0);
            mv.visitLocalVariable("px", "F", null, l0, l2, 1);
            mv.visitLocalVariable("scale", "F", null, l1, l2, 2);
            mv.visitMaxs(2, 3);
            mv.visitEnd();
        }
        {
            mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "pxToSp", "(Landroid/content/Context;F)I", null, null);
            mv.visitCode();
            Label l0 = new Label();
            mv.visitLabel(l0);
            mv.visitLineNumber(44, l0);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/Context", "getResources", "()Landroid/content/res/Resources;", false);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/res/Resources", "getDisplayMetrics", "()Landroid/util/DisplayMetrics;", false);
            mv.visitFieldInsn(GETFIELD, "android/util/DisplayMetrics", "scaledDensity", "F");
            mv.visitVarInsn(FSTORE, 2);
            Label l1 = new Label();
            mv.visitLabel(l1);
            mv.visitLineNumber(45, l1);
            mv.visitVarInsn(FLOAD, 1);
            mv.visitVarInsn(FLOAD, 2);
            mv.visitInsn(FDIV);
            mv.visitLdcInsn(new Float("0.5"));
            mv.visitInsn(FADD);
            mv.visitInsn(F2I);
            mv.visitInsn(IRETURN);
            Label l2 = new Label();
            mv.visitLabel(l2);
            mv.visitLocalVariable("context", "Landroid/content/Context;", null, l0, l2, 0);
            mv.visitLocalVariable("px", "F", null, l0, l2, 1);
            mv.visitLocalVariable("fontScale", "F", null, l1, l2, 2);
            mv.visitMaxs(2, 3);
            mv.visitEnd();
        }
        {
            mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "spToPx", "(Landroid/content/Context;F)I", null, null);
            mv.visitCode();
            Label l0 = new Label();
            mv.visitLabel(l0);
            mv.visitLineNumber(57, l0);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/Context", "getResources", "()Landroid/content/res/Resources;", false);
            mv.visitMethodInsn(INVOKEVIRTUAL, "android/content/res/Resources", "getDisplayMetrics", "()Landroid/util/DisplayMetrics;", false);
            mv.visitFieldInsn(GETFIELD, "android/util/DisplayMetrics", "scaledDensity", "F");
            mv.visitVarInsn(FSTORE, 2);
            Label l1 = new Label();
            mv.visitLabel(l1);
            mv.visitLineNumber(58, l1);
            mv.visitVarInsn(FLOAD, 1);
            mv.visitVarInsn(FLOAD, 2);
            mv.visitInsn(FMUL);
            mv.visitLdcInsn(new Float("0.5"));
            mv.visitInsn(FADD);
            mv.visitInsn(F2I);
            mv.visitInsn(IRETURN);
            Label l2 = new Label();
            mv.visitLabel(l2);
            mv.visitLocalVariable("context", "Landroid/content/Context;", null, l0, l2, 0);
            mv.visitLocalVariable("sp", "F", null, l0, l2, 1);
            mv.visitLocalVariable("fontScale", "F", null, l1, l2, 2);
            mv.visitMaxs(2, 3);
            mv.visitEnd();
        }
        cw.visitEnd();

        return cw.toByteArray();
    }
}
  • 【Groovified面板内容】

在这里插入图片描述

// class version 51.0 (51)
// access flags 0x21
public class com/xtc/common/util/SizeConvertUtil {


  @groovyx.ast.bytecode.Bytecode
  public void <init>() {
    aload 0
    INVOKESPECIAL java/lang/Object.<init> ()V
    return
  }

  @groovyx.ast.bytecode.Bytecode
  public static int dpToPx(android.content.Context a,float b) {
    aload 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    getfield 'android/util/DisplayMetrics.density','F'
    fstore 2
    fload 1
    fload 2
    fmul
    ldc 0.5f
    fadd
    f2i
    ireturn
  }

  @groovyx.ast.bytecode.Bytecode
  public static int pxToDp(android.content.Context a,float b) {
    aload 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    getfield 'android/util/DisplayMetrics.density','F'
    fstore 2
    fload 1
    fload 2
    fdiv
    ldc 0.5f
    fadd
    f2i
    ireturn
  }

  @groovyx.ast.bytecode.Bytecode
  public static int pxToSp(android.content.Context a,float b) {
    aload 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    getfield 'android/util/DisplayMetrics.scaledDensity','F'
    fstore 2
    fload 1
    fload 2
    fdiv
    ldc 0.5f
    fadd
    f2i
    ireturn
  }

  @groovyx.ast.bytecode.Bytecode
  public static int spToPx(android.content.Context a,float b) {
    aload 0
    INVOKEVIRTUAL android/content/Context.getResources ()Landroid/content/res/Resources;
    INVOKEVIRTUAL android/content/res/Resources.getDisplayMetrics ()Landroid/util/DisplayMetrics;
    getfield 'android/util/DisplayMetrics.scaledDensity','F'
    fstore 2
    fload 1
    fload 2
    fmul
    ldc 0.5f
    fadd
    f2i
    ireturn
  }
}

从上面的ASM Bytecode Outline 插件我们就可以看到对应的字节码了，对比源文件，大概能够看懂一些些了。

在这里插入图片描述

四、参考资料

具体关于字节码的相关知识点，请参考下面的链接

作者：欧阳鹏 欢迎转载，与人分享是进步的源泉！
转载请保留原文地址：https://blog.csdn.net/qq446282412/article/details/100566678
☞ 本人QQ: 3024665621
☞ QQ交流群: 123133153
☞ github.com/ouyangpeng
☞ [email protected]

欧阳鹏 博客专家
发布了469 篇原创文章 · 获赞 1467 · 访问量 359万+
他的留言板 关注

猜你喜欢

转载自blog.csdn.net/qq446282412/article/details/100566678
今日推荐
火速冲上 GitHub 热榜 —— 开源编程语言、框架哪有这么可爱？
北京人形机器人创新中心发布全球首个纯电驱拟人奔跑的全尺寸人形机器人“天工”
LFOSSA 源来如此公开课 | 掌握云原生未来：CNCF 认证全面攻略与备考秘籍
国产云输入法——仅华为无云端数据上传安全问题
开源日报 | 工业开源项目OGG 1.0；姐姐，你要和我一起配置火狐吗；苹果AI遥遥落后？Fedora 40
开放签电子签章：停止新增，优化体验，前进更进（五一假期前工作）
开源日报 | 中学生开源前端动画引擎；全球首个Llama3 8B中文版开源模型；联想电脑恐出局；Linus讽刺AI炒作
周排行
浏览器对同一域名进行请求的最大并发连接数
React Hook之自定义Hook
【转】MyBatis缓存机制
-Java-泛型
自动化测试常用脚本-发送邮件
LeetCode#859: Buddy Strings
java、Python处理字符串
第二篇の博客
Hadoop伪分布式环境安装
SQL Server进阶（十一）临时表、表变量
每日归档
更多
2024-04-27(56)
2024-04-26(39)
2024-04-25(22)
2024-04-24(36)
2024-04-23(26)
2024-04-22(39)
2024-04-21(0)
2024-04-20(6)
2024-04-19(5)
2024-04-18(0)

代码天地 © 2018 codetd.com

境外服务器   最新电视剧2022