Kotlin基础 4.companion object(伴生对象),更新中

Posted 2022-03-16 彬sir哥

第一步，写kotlin代码：

class MainActivity : AppCompatActivity() 
    companion object 
        const val REQUEST_CODE_TAKE_PHOTO = 101
        const val REQUEST_CODE_PICK_PHOTO = 102
    
    ...

第二步，转成Java代码：
tools->Kotlin->show Kotlin Bytecode可以查看kotlin代码的字节码

然后点击字节码右上角的Decompile可以将字节码转为java代码，如图：

第三步，查看java代码：

public final class MainActivity extends AppCompatActivity 
   private List pictures;
   private BaseQuickAdapter pictureAdapter;
   private Uri currentPictureUri;
   private File currentPictureFile;
   private final Set pictureAddressSet;
   public static final int REQUEST_CODE_TAKE_PHOTO = 101;
   public static final int REQUEST_CODE_PICK_PHOTO = 102;
   @NotNull
   public static final MainActivity.Companion Companion = new MainActivity.Companion((DefaultConstructorMarker)null);
   private HashMap _$_findViewCache;

   protected void onCreate(@Nullable Bundle savedInstanceState) 
      super.onCreate(savedInstanceState);
      this.setContentView(1300075);
      this.initListener();
      ...

第四步，得出结论
1.companion object的作用
使用companion object会在原类中生成一个内部类：public static final class Companion，同时在原类中创建这个内部类的对象(这么看，伴生对象是不是就理解了)