实现正方形布局SquareLayout的几种方法

下面介个方法都是复写 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
方法1

@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {setMeasuredDimension(getDefaultSize(0, widthMeasureSpec), getDefaultSize(0, heightMeasureSpec));  // Children are just made to fill our space.  int childWidthSize = getMeasuredWidth();  int childHeightSize = getMeasuredHeight();  //高度和宽度一样  heightMeasureSpec = widthMeasureSpec = MeasureSpec.makeMeasureSpec(childWidthSize, MeasureSpec.EXACTLY);  super.onMeasure(widthMeasureSpec, heightMeasureSpec);  
}

方法2

@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, widthMeasureSpec);/重写此方法后默认调用父类的onMeasure方法,分别将宽度测量空间与高度测量空间传入
super.onMeasure(widthMeasureSpec, heightMeasureSpec);/}

方法3

*/
public class SquareLayout extends FrameLayout {private int orientation = LinearLayout.HORIZONTAL;public SquareLayout(Context context) {super(context);}private void init(Context context, AttributeSet attrs, int defStyleAttr) {TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.SquareLayout, defStyleAttr, 0);int index = typedArray.getInt(R.styleable.SquareLayout_square_orientation, -1);
//        int index = MyInputConnectionWrapper.getInt(com.android.internal.R.styleable.LinearLayout_orientation, -1);if (index >= 0) {setOrientation(index);}typedArray.recycle();}public SquareLayout(Context context, AttributeSet attrs) {super(context, attrs);init(context, attrs, 0);}public SquareLayout(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init(context, attrs, defStyleAttr);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//        super.onMeasure(orientation == LinearLayout.HORIZONTAL ? widthMeasureSpec : heightMeasureSpec, orientation == LinearLayout.HORIZONTAL ? widthMeasureSpec : heightMeasureSpec);super.onMeasure(widthMeasureSpec, heightMeasureSpec);//核心就是下面这块代码块啦
//        int width = orientation == LinearLayout.HORIZONTAL ? getMeasuredWidth() : getMeasuredHeight();if (orientation == LinearLayout.HORIZONTAL) {setMeasuredDimension(widthMeasureSpec, widthMeasureSpec);} else {setMeasuredDimension(heightMeasureSpec, heightMeasureSpec);}int width = getMeasuredWidth();int height = getMeasuredHeight();ViewGroup.LayoutParams lp = getLayoutParams();lp.height = orientation == LinearLayout.HORIZONTAL ? width : width;lp.width = orientation == LinearLayout.HORIZONTAL ? width : height;setLayoutParams(lp);}public void setOrientation(int orientation) {this.orientation = orientation;}}

我本人用第一种和第三种方法，不过都发现在某些情况下会出现毛病，第二种方法没用过

官方的方式

*/
public class SquareFrameLayout extends FrameLayout {public SquareFrameLayout(Context context) {super(context);}public SquareFrameLayout(Context context, AttributeSet attrs) {super(context, attrs);}public SquareFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}public SquareFrameLayout(Context context, AttributeSet attrs,int defStyleAttr, int defStyleRes) {super(context, attrs, defStyleAttr, defStyleRes);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {final int widthSize = MeasureSpec.getSize(widthMeasureSpec);final int heightSize = MeasureSpec.getSize(heightMeasureSpec);if (widthSize == 0 && heightSize == 0) {// If there are no constraints on size, let FrameLayout measuresuper.onMeasure(widthMeasureSpec, heightMeasureSpec);// Now use the smallest of the measured dimensions for both dimensionsfinal int minSize = Math.min(getMeasuredWidth(), getMeasuredHeight());setMeasuredDimension(minSize, minSize);return;}final int size;if (widthSize == 0 || heightSize == 0) {// If one of the dimensions has no restriction on size, set both dimensions to be the// on that doessize = Math.max(widthSize, heightSize);} else {// Both dimensions have restrictions on size, set both dimensions to be the// smallest of the twosize = Math.min(widthSize, heightSize);}final int newMeasureSpec = MeasureSpec.makeMeasureSpec(size, MeasureSpec.EXACTLY);super.onMeasure(newMeasureSpec, newMeasureSpec);}
}