Android Open Source - org.numixproject.iconsubmit Square Grid Layout

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License

The source code is released under:

GNU General Public License

Java Source Code

package org.numixproject.iconsubmit.helpers;
/*  ww  w  .  j av  a2  s .c  o  m*/
import org.numixproject.iconsubmit.R;
import org.numixproject.iconsubmit.R.styleable;
import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

/**
 * A layout that arranges views into a grid of same-sized squares.
 * 
 * This source code contained in this file is in the Public Domain.
 * 
 * @author Tom Gibara
 *
 */

public class SquareGridLayout extends ViewGroup {

  // fields
  
  /**
   * Records the number of views on each side of the square (ie. the number of rows and columns)
   */
  
  private int mSize = 1;
  
  /**
   * Records the size of the square in pixels (excluding padding).
   * This is set during {@link #onMeasure(int, int)} 
   */
  
  private int mSquareDimensions;
  
  // constructors

  /**
   * Constructor used to create layout programatically.
   */
  
  public SquareGridLayout(Context context) {
    super(context);
  }

  /**
   * Constructor used to inflate layout from XML. It extracts the size from
   * the attributes and sets it.
   */
  
  /* This requires a resource to be defined like this:
   * 
   * <resources>
   *   <declare-styleable name="SquareGridLayout">
   *     <attr name="size" format="integer"/>
   *   </declare-styleable>
   * </resources>
   * 
   * So that the attribute can be set like this:
   * 
   * <com.tomgibara.android.util.SquareGridLayout
   *   xmlns:android="http://schemas.android.com/apk/res/android"
   *   xmlns:util="http://schemas.android.com/apk/res/com.tomgibara.android.background"
   *   util:size="3"
   *   />
   */
  
  public SquareGridLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.SquareGridLayout);
    setSize(a.getInt(R.styleable.SquareGridLayout_size, 1));
    a.recycle();
  }

  // accessors
  
  /**
   * Sets the number of views on each side of the square.
   * 
   * @param size the size of grid (at least 1)
   */
  
  public void setSize(int size) {
    if (size < 1) throw new IllegalArgumentException("size must be positive");
    if (mSize != size) {
      mSize = size;
      requestLayout();
    }
  }
  
  // View methods
  
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

    // breakdown specs
    final int mw = MeasureSpec.getMode(widthMeasureSpec);
    final int mh = MeasureSpec.getMode(heightMeasureSpec);
    final int sw = MeasureSpec.getSize(widthMeasureSpec);
    final int sh = MeasureSpec.getSize(heightMeasureSpec);
    
    // compute padding
    final int pw = getPaddingLeft() + getPaddingRight();
    final int ph = getPaddingTop() + getPaddingBottom();
    
    // compute largest size of square (both with and without padding)
    final int s;
    final int sp;
    if (mw == MeasureSpec.UNSPECIFIED && mh == MeasureSpec.UNSPECIFIED) {
      throw new IllegalArgumentException("Layout must be constrained on at least one axis");
    } else if (mw == MeasureSpec.UNSPECIFIED) {
      s = sh;
      sp = s - ph;
    } else if (mh == MeasureSpec.UNSPECIFIED) {
      s = sw;
      sp = s - pw;
    } else {
      if (sw - pw < sh - ph) {
        s = sw;
        sp = s - pw;
      } else {
        s = sh;
        sp = s - ph;
      }
    }

    // guard against giving the children a -ve measure spec due to excessive padding
    final int spp = Math.max(sp, 0);
    
    // pass on our rigid dimensions to our children
    final int size = mSize;
    for (int y = 0; y < size; y++) {
      for (int x = 0; x < size; x++) {
        final View child = getChildAt(y * size + x);
        if (child == null) continue;
        // measure each child
        // we could try to accommodate oversized children, but we don't
        measureChildWithMargins(child,
          MeasureSpec.makeMeasureSpec((spp + x) / size, MeasureSpec.EXACTLY), 0,
          MeasureSpec.makeMeasureSpec((spp + y) / size, MeasureSpec.EXACTLY), 0
        );
      }
    }
    
    //record our dimensions
    setMeasuredDimension(
      mw == MeasureSpec.EXACTLY ? sw : sp + pw,
      mh == MeasureSpec.EXACTLY ? sh : sp + ph
    );
    mSquareDimensions = sp;
  }
  
  // ViewGroup methods
  
  @Override
  protected LayoutParams generateDefaultLayoutParams() {
    return new MarginLayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
  }
  
  @Override
  protected LayoutParams generateLayoutParams(LayoutParams p) {
    return new MarginLayoutParams(p);
  }

  @Override
  public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new MarginLayoutParams(getContext(), attrs);
  }
  
  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    
    // recover the previously computed square dimensions for efficiency
    final int s = mSquareDimensions;
    
    {
      // adjust for our padding
      final int pl = getPaddingLeft();
      final int pt = getPaddingTop();
      final int pr = getPaddingRight();
      final int pb = getPaddingBottom();
      
      // allocate any extra spare space evenly
      l = pl + (r - pr - l - pl - s) / 2;
      t = pt + (b - pb - t - pb - s) / 2;
    }
    
    final int size = mSize;
    for (int y = 0; y < size; y++) {
      for (int x = 0; x < size; x++) {
        View child = getChildAt(y * mSize + x);
        // optimization: we are moving through the children in order
        // when we hit null, there are no more children to layout so return
        if (child == null) return;
        // get the child's layout parameters so that we can honour their margins
        MarginLayoutParams lps = (MarginLayoutParams) child.getLayoutParams();
        // we don't support gravity, so the arithmetic is simplified
        child.layout(
          l + (s *  x   ) / size + lps.leftMargin,
          t + (s *  y   ) / size + lps.topMargin,
          l + (s * (x+1)) / size - lps.rightMargin,
          t + (s * (y+1)) / size - lps.bottomMargin
        );
      }
    }
  }

}

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