Android反编译 -- 错误代码还原

他叫自己MR.张

发布于 2019-07-01 17:25:12

1.1K0

发布于 2019-07-01 17:25:12

文章被收录于专栏：Android必知必会

PS：如果阅读体验不好，可以尝试Github版（<-点左边）

1. `setColor(-16777216)`

反编译的代码中会有很多setColor(int)的情况，比如setColor(-16777216)，这个值比较特别，能轻易的查到Android文档中对这个整数的定义：

public static final int BLACK. Added in API level 1 Constant Value: -16777216 ( 0xff000000).

也就是说setColor(-16777216)中-16777216对应的颜色是BLACK(0xff000000)，那么其他系统未定义成某个颜色名的值呢？

-16777216 对应 0xff000000
       -1 对应 0xffffffff
 0xffffff 的值 16777215

那么对任意的 setColor(int)中的int值，我们可以：
0xffffffff+(int)+1 或 0xffffffff-(-int+1) 

则对于 ：setColor(-16777216)
可写成 ：setColor(0xffffffff - 16777215)) 或 setColor(-16777216 + 1 + 0xffffffff))

这样，我们就不用查文档寻找特定的颜色值，也能解决任意颜色的设置。

Stackoverflow : How to set color using integer?

2.`MeasureSpec.makeMeasureSpec(xx, int)`

反编译的代码中MeasureSpec.makeMeasureSpec(xx, int)的第二个参数是个int类型的数，这个比较简单，直接看文档或者源码即可找到：

源码：

public static class MeasureSpec {
        public static final int UNSPECIFIED = 0;
        public static final int EXACTLY = 1073741824;
        public static final int AT_MOST = -2147483648;
        ...
        }

文档：

public static final int AT_MOST
Added in API level 1
Measure specification mode: The child can be as large as it wants up to the specified size.
Constant Value: -2147483648 (0x80000000)

public static final int EXACTLY
Added in API level 1
Measure specification mode: The parent has determined an exact size for the child. The child is going to be given those bounds regardless of how big it wants to be.
Constant Value: 1073741824 (0x40000000)

public static final int UNSPECIFIED
Added in API level 1
Measure specification mode: The parent has not imposed any constraint on the child. It can be whatever size it wants.
Constant Value: 0 (0x00000000)

则对于： MeasureSpec.makeMeasureSpec(xx, 0) 我们应该修改为 MeasureSpec.makeMeasureSpec(xx, View.MeasureSpec.UNSPECIFIED)

其他依次类推。

3.`setVisibility(int)`

这个同[2],看文档或者看源码：

public static final int VISIBLE = 0;
public static final int INVISIBLE = 4;
public static final int GONE = 8;

则对于：setVisibility(0) ==> setVisibility(View.VISIBLE)

其他依次类推。

4.`new Runnable()...`

反编译的代码中：

new Runnable() {
    final /* synthetic */ AbstractButton a;
        {
        this.a = r1;
       }

       public final void run() {
          this.a.xxxxx();
       }
};

可直接去掉成员变量：

new Runnable() {
       public final void run() {
          xxxxx();
       }
};

5.`new Handler()...`

同[4],直接去掉成员变量:

new Handler() {
            final /* synthetic */ ButtonSave a;

            {
                this.a = r1;
            }

            public final void handleMessage(Message message) {
                    this.a.xxx();
            }
        };
//修改为
new Handler() {
            public final void handleMessage(Message message) {
                xxx();
            }
        };

6.`context.getSystemService("layout_inflater")`

直接看源码即可：

public static final String POWER_SERVICE = "power";
public static final String WINDOW_SERVICE = "window";
public static final String LAYOUT_INFLATER_SERVICE = "layout_inflater";
public static final String ACCOUNT_SERVICE = "account";
public static final String ACTIVITY_SERVICE = "activity";
public static final String ALARM_SERVICE = "alarm";
public static final String NOTIFICATION_SERVICE = "notification";
public static final String ACCESSIBILITY_SERVICE = "accessibility";
...

则context.getSystemService("layout_inflater") ==> context.getSystemService(Context.LAYOUT_INFLATER_SERVICE)

其他依次类推。

7.`intent.setFlags(335544320)`

先看源码：

Intent implements Parcelable, Cloneable  {
    public static final int FLAG_GRANT_READ_URI_PERMISSION = 1;
    public static final int FLAG_GRANT_WRITE_URI_PERMISSION = 2;
    public static final int FLAG_FROM_BACKGROUND = 4;
    public static final int FLAG_DEBUG_LOG_RESOLUTION = 8;
    public static final int FLAG_EXCLUDE_STOPPED_PACKAGES = 16;
    public static final int FLAG_INCLUDE_STOPPED_PACKAGES = 32;
    public static final int FLAG_ACTIVITY_NO_HISTORY = 1073741824;
    public static final int FLAG_ACTIVITY_SINGLE_TOP = 536870912;
    public static final int FLAG_ACTIVITY_NEW_TASK = 268435456;
    public static final int FLAG_ACTIVITY_MULTIPLE_TASK = 134217728;
    public static final int FLAG_ACTIVITY_CLEAR_TOP = 67108864;
    public static final int FLAG_ACTIVITY_FORWARD_RESULT = 33554432;
    public static final int FLAG_ACTIVITY_PREVIOUS_IS_TOP = 16777216;
    public static final int FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS = 8388608;
    public static final int FLAG_ACTIVITY_BROUGHT_TO_FRONT = 4194304;
    public static final int FLAG_ACTIVITY_RESET_TASK_IF_NEEDED = 2097152;
    public static final int FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY = 1048576;
    public static final int FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET = 524288;
    public static final int FLAG_ACTIVITY_NO_USER_ACTION = 262144;
    public static final int FLAG_ACTIVITY_REORDER_TO_FRONT = 131072;
    public static final int FLAG_ACTIVITY_NO_ANIMATION = 65536;
    public static final int FLAG_ACTIVITY_CLEAR_TASK = 32768;
    public static final int FLAG_ACTIVITY_TASK_ON_HOME = 16384;
    public static final int FLAG_RECEIVER_REGISTERED_ONLY = 1073741824;
    public static final int FLAG_RECEIVER_REPLACE_PENDING = 536870912;
    public static final int FLAG_RECEIVER_FOREGROUND = 268435456;

那么对于intent.setFlags(int); 中 int值是上面四种之一的话就比较简单，例如：

intent.setFlags(536870912); ==> intent.setFlags(PendingIntent.FLAG_NO_CREATE);

但是遇到一个比较特别的：intent.setFlags(335544320);

源码里根本没有这样一个值啊，其实intent.setFlags( A | B )是可以使用|(或运算)的，那么：

10000000000000000000000000000 = 268435456
                    |               |
  100000000000000000000000000 =  67108864
10100000000000000000000000000 = 335544320

即 268435456 | 67108864 = 335544320

从而:

intent.setFlags(335544320);==>

intent.setFlags( FLAG_ACTIVITY_NEW_TASK | FLAG_ACTIVITY_CLEAR_TOP )

或者

intent.setFlags( FLAG_RECEIVER_FOREGROUND | FLAG_ACTIVITY_CLEAR_TOP )

从 Codota 中搜索intent.setFlags(335544320);看到的是第一种情况，结合intent.setFlags()的用法，应该也是第一种情况。