拋出問題：

1. kotlin 構(gòu)造函數(shù)干啥用的
2. init和構(gòu)造函數(shù)有啥區(qū)別
3. 生命成員變量private var testString 鲸郊？= null 啥時候分配空間
4. companion object 加載時序

Q：kotlin 構(gòu)造函數(shù)干啥用的
A：kotlin 的空參構(gòu)造就是init方法， 結(jié)論:空參構(gòu)造就是init方法

class testClass() {
    private var zdf:String?=null
    private var zdf01:String?=null
    init {
        zdf01 = "123"
        copy()
    }
    private fun copy(){
        zdf ="hei hei"
    }
}
---------------------------------------
public final class testClass {
   private String zdf;
   private String zdf01 = "123";
   private final void copy() {
      this.zdf = "hei hei";
   }
   public testClass() {
      this.copy();
   }
}

Q：kotlin 構(gòu)造函數(shù)干啥用的
A: init和構(gòu)造函數(shù)有啥區(qū)別团搞。 結(jié)論：如果使用了多個構(gòu)造方法严望，init為空參構(gòu)造，剩下的構(gòu)造方法該怎么實現(xiàn)怎么實現(xiàn)

class testClass() {
    private var zdf:String?=null
    private var zdf01:String?=null
    constructor(s: String,int: Int) : this() {

    }
    constructor(s:String) : this() {}

    init {
        zdf01 = "123"
        copy()
    }
    private fun copy(){
        zdf ="hei hei"
    }
}
-------------------------------
public final class testClass {
   private String zdf;
   private String zdf01;

   private final void copy() {
      this.zdf = "hei hei";
   }

   public testClass() {
      this.zdf01 = "123";
      this.copy();
   }

   public testClass(@NotNull String s, int var2) {
      Intrinsics.checkParameterIsNotNull(s, "s");
      this();
   }

   public testClass(@NotNull String s) {
      Intrinsics.checkParameterIsNotNull(s, "s");
      this();
   }
}

Q：聲明成員變量private var testString 逻恐？= null 啥時候分配空間
A：成員變量在new的時候像吻，使用new關(guān)鍵字構(gòu)造對象時分配。優(yōu)先于構(gòu)造塊和構(gòu)造方法執(zhí)行之前复隆。

Q：companion object 加載時序
A: companion object 伴生對象拨匆，類似于靜態(tài)方法
結(jié)論 : 修飾為伴生對象,伴生對象在類中只能存在一個，類似于java中的靜態(tài)方法 Java 中使用類訪問靜態(tài)成員挽拂，靜態(tài)方法惭每。

class MainActivity : AppCompatActivity() {
    private var testString : String?=null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }
    init {
        testString = "zdf"
        println(testString)
        println(testInt)
    }
    companion object{
        const val testInt:Int = 1
    }
}
--------------------------------
public final class MainActivity extends AppCompatActivity {
   private String testString = "zdf";
   public static final int testInt = 1;
   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(-1300009);
   }

   public MainActivity() {
      String var1 = this.testString;
      boolean var2 = false;
      System.out.println(var1);
      byte var3 = 1;
      var2 = false;
      System.out.println(var3);
   }

   public View _$_findCachedViewById(int var1) {
      if (this._$_findViewCache == null) {
         this._$_findViewCache = new HashMap();
      }

      View var2 = (View)this._$_findViewCache.get(var1);
      if (var2 == null) {
         var2 = this.findViewById(var1);
         this._$_findViewCache.put(var1, var2);
      }

      return var2;
   }

   public void _$_clearFindViewByIdCache() {
      if (this._$_findViewCache != null) {
         this._$_findViewCache.clear();
      }

   }