android 自定义view的构造

      at java.lang.reflect.Constructor.newInstance0(Native Method)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
      at android.view.LayoutInflater.createView(LayoutInflater.java:852)
      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1008)
      at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959)
      at android.view.LayoutInflater.rInflate(LayoutInflater.java:1138)
      at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1099)
      at android.view.LayoutInflater.rInflate(LayoutInflater.java:1141)
      at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1099)
      at android.view.LayoutInflater.inflate(LayoutInflater.java:680)
      at android.view.LayoutInflater.inflate(LayoutInflater.java:532)
      at android.view.LayoutInflater.inflate(LayoutInflater.java:479)
      at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:710)
      at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:195)
      //自定义view时，调用trace如上。

       try {
          //通过已注册的 Factory或 Factory2接口创建视图
          //典型的AppCompatActivity通过此接口将 TextView替换为 AppCompatTextView
          //内部通过new的方式创建view
          View view = tryCreateView(parent, name, context, attrs);
          if (view == null) {
              final Object lastContext = mConstructorArgs[0];
              mConstructorArgs[0] = context;
              try {
                  if (-1 == name.indexOf('.')) {
                      //不含. 不是自定义view
                      view = onCreateView(context, parent, name, attrs);
                  } else {
                      //自定义view
                      view = createView(context, name, null, attrs);
                  }
              } finally {
                  mConstructorArgs[0] = lastContext;
              }
          }

          return view;
      } catch (InflateException e) {
          throw e;
      }
      //层层调用
      view = createView(context, name, null, attrs);
      final View view = constructor.newInstance(args);
      Object[] args = mConstructorArgs;
      //mConstructorArgs是LayoutInflater的普通属性。被定义为长度为2的数组
      //final Object[] mConstructorArgs = new Object[2];
      //通过反射方式创建view
      final View view = constructor.newInstance(args);
      return view;
      //所以，无论xml怎么写，自定义view只会走双参构造。