LinearLayout.java

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// -*- mode: java; c-basic-offset: 2; -*-
// Copyright 2009-2011 Google, All Rights reserved
// Copyright 2011-2012 MIT, All rights reserved
// Released under the Apache License, Version 2.0
// http://www.apache.org/licenses/LICENSE-2.0
 
package com.google.appinventor.components.runtime;
 
import com.google.appinventor.components.annotations.SimpleObject;
import com.google.appinventor.components.common.ComponentConstants;
 
import android.content.Context;
import android.view.ViewGroup;
 
@SimpleObject
public final class LinearLayout implements Layout {
 
  private final android.widget.LinearLayout layoutManager;
 
  LinearLayout(Context context, int orientation) {
    this(context, orientation, null, null);
  }
 
  LinearLayout(Context context, int orientation, final Integer preferredEmptyWidth,
      final Integer preferredEmptyHeight) {
    if (preferredEmptyWidth == null && preferredEmptyHeight != null ||
        preferredEmptyWidth != null && preferredEmptyHeight == null) {
      throw new IllegalArgumentException("LinearLayout - preferredEmptyWidth and " +
          "preferredEmptyHeight must be either both null or both not null");
    }
 
    // Create an Android LinearLayout, but override onMeasure so that we can use our preferred
    // empty width/height.
    layoutManager = new android.widget.LinearLayout(context) {
      @Override
      protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // If there was no preferred empty width/height specified (see constructors above), just
        // call super. (This is the case for the Form component.)
        if (preferredEmptyWidth == null || preferredEmptyHeight == null) {
          super.onMeasure(widthMeasureSpec, heightMeasureSpec);
          return;
        }
 
        // If the layout has any children, just call super.
        if (getChildCount() != 0) {
          super.onMeasure(widthMeasureSpec, heightMeasureSpec);
          return;
        }
 
        setMeasuredDimension(getSize(widthMeasureSpec, preferredEmptyWidth),
                             getSize(heightMeasureSpec, preferredEmptyHeight));
      }
 
      private int getSize(int measureSpec, int preferredSize) {
        int result;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
 
        if (specMode == MeasureSpec.EXACTLY) {
        // We were told how big to be
          result = specSize;
        } else {
        // Use the preferred size.
          result = preferredSize;
          if (specMode == MeasureSpec.AT_MOST) {
          // Respect AT_MOST value if that was what is called for by measureSpec
            result = Math.min(result, specSize);
          }
        }
 
        return result;
      }
    };
 
    layoutManager.setOrientation(
        orientation == ComponentConstants.LAYOUT_ORIENTATION_HORIZONTAL ?
        android.widget.LinearLayout.HORIZONTAL : android.widget.LinearLayout.VERTICAL);
  }
 
  // Layout implementation
 
  public ViewGroup getLayoutManager() {
    return layoutManager;
  }
 
  public void add(AndroidViewComponent component) {
    layoutManager.addView(component.getView(), new android.widget.LinearLayout.LayoutParams(
        ViewGroup.LayoutParams.WRAP_CONTENT,  // width
        ViewGroup.LayoutParams.WRAP_CONTENT,  // height
        0f));                                 // weight
  }
 
  public void setHorizontalGravity(int gravity) {
    layoutManager.setHorizontalGravity(gravity);
  }
 
  public void setVerticalGravity(int gravity) {
    layoutManager.setVerticalGravity(gravity);
  }
 
  public void setBaselineAligned(boolean baselineAligned) { layoutManager.setBaselineAligned(baselineAligned); }
 
}