public class CustomLinearLayout extends LinearLayout {
  public CustomLinearLayout(Context context) {
    super(context);
  }

  public CustomLinearLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public CustomLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public CustomLinearLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
  }
}

<declare-styleable name="CustomLinearLayout_Layout">
  <!-- 定义比例 -->
  <attr name="inner_percent" format="float"/>
</declare-styleable>

public void addView(View child, int index, LayoutParams params)

public class CustomLinearLayout extends LinearLayout {
  public CustomLinearLayout(Context context) {
    super(context);
  }

  public CustomLinearLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  public CustomLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
  }

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public CustomLinearLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
  }
  public static class LayoutParams extends LinearLayout.LayoutParams {

    private float innerPercent;

    private static final int DEFAULT_WIDTH = WRAP_CONTENT;
    private static final int DEFAULT_HEIGHT = WRAP_CONTENT;

    public LayoutParams() {
      super(DEFAULT_WIDTH, DEFAULT_HEIGHT);
      innerPercent = -1.0f;
    }

    public LayoutParams(float innerPercent) {
      super(DEFAULT_WIDTH, DEFAULT_HEIGHT);
      this.innerPercent = innerPercent;
    }

    public LayoutParams(ViewGroup.LayoutParams p) {
      super(p);
    }

    @TargetApi(Build.VERSION_CODES.KITKAT)
    public LayoutParams(LinearLayout.LayoutParams source) {
      super(source);
    }

    @TargetApi(Build.VERSION_CODES.KITKAT)
    public LayoutParams(LayoutParams source) {
      super(source);
      this.innerPercent = source.innerPercent;
    }

    public LayoutParams(Context c, AttributeSet attrs) {
      super(c, attrs);
      init(c, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
      TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomLinearLayout_Layout);
      innerPercent = a.getFloat(R.styleable.CustomLinearLayout_Layout_inner_percent, -1.0f);
      a.recycle();
    }
  }
}

<?xml version="1.0" encoding="utf-8"?>
<com.egos.samples.custom_layout.CustomLinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="200dp"
  android:layout_height="200dp"
  android:id="@+id/test_layout"
  android:background="#ffff0000"
  android:gravity="center"
  android:orientation="vertical">
  <ImageView
    android:text="Egos"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:onClick="add"
    android:background="#ff00ff00"
    app:inner_percent="0.8"/>
</com.egos.samples.custom_layout.CustomLinearLayout>

requestLayout();
invalidate(true);

@Override 
protected void measureChildWithMargins(View child, int parentWidthMeasureSpec,
                    int widthUsed, int parentHeightMeasureSpec, int heightUsed) {
  // 在xml强制写成match_parent，然后在这里强制设置成
  if (child != null && child.getLayoutParams() instanceof LayoutParams &&
      ((LayoutParams) child.getLayoutParams()).innerPercent != -1.0f) {
    parentWidthMeasureSpec = MeasureSpec.makeMeasureSpec((int) (MeasureSpec.getSize(parentWidthMeasureSpec) *
        ((LayoutParams) child.getLayoutParams()).innerPercent), MeasureSpec.getMode(parentWidthMeasureSpec));
    parentHeightMeasureSpec = MeasureSpec.makeMeasureSpec((int) (MeasureSpec.getSize(parentHeightMeasureSpec) *
        ((LayoutParams) child.getLayoutParams()).innerPercent), MeasureSpec.getMode(parentHeightMeasureSpec));
    super.measureChildWithMargins(child, parentWidthMeasureSpec, widthUsed,
      parentHeightMeasureSpec, heightUsed);
  } else {
    super.measureChildWithMargins(child, parentWidthMeasureSpec, widthUsed,
        parentHeightMeasureSpec, heightUsed);
  }
}

/**
 * 当checkLayoutParams返回false的时候就会执行到这里的generateLayoutParams
 */
 @Override
protected LinearLayout.LayoutParams generateLayoutParams(ViewGroup.LayoutParams lp) {
  return super.generateLayoutParams(lp);
}

/**
 * 当addView的时候没有设置LayoutParams的话就会默认执行这里的generateDefaultLayoutParams
 */
@Override
protected LayoutParams generateDefaultLayoutParams() {
  return new LayoutParams();
}

/**
 * 写在xml中属性的时候就会执行这里的generateLayoutParams
 */
@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
  return new LayoutParams(getContext(), attrs);
}