onMeasure与onSizeChanged获取尺寸区别

自定义view如下&＃xff1a;


public class MyView extends View {private static final int DEFAULT_WIDTH &＃61; 100;private static final int DEFAULT_HEIGHT &＃61; 100;private Paint paint;private Rect rect;public MyView(Context context) {super(context);init();}public MyView(Context context, &＃64;Nullable AttributeSet attrs) {super(context, attrs);init();}public MyView(Context context, &＃64;Nullable AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init();}private void init() {paint &＃61; new Paint();paint.setColor(Color.parseColor("#ff0000"));rect &＃61; new Rect(getPaddingLeft(), getPaddingTop(), 200, 200);}&＃64;Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {int width &＃61; getProperSize(DEFAULT_WIDTH, widthMeasureSpec);int height &＃61; getProperSize(DEFAULT_HEIGHT, heightMeasureSpec);setMeasuredDimension(width, height);}private int getProperSize(int defaultSize, int measureSpec) {int result;int mode &＃61; MeasureSpec.getMode(measureSpec);int size &＃61; MeasureSpec.getSize(measureSpec);if (mode &＃61;&＃61; MeasureSpec.EXACTLY) {result &＃61; size;} else {result &＃61; defaultSize;if (mode &＃61;&＃61; MeasureSpec.AT_MOST) {result &＃61; Math.min(result, size);}}return result;}&＃64;Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);//可省略}&＃64;Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);canvas.drawRect(rect, paint);}}


onMeasure与onSizeChanged获取尺寸区别&＃xff1a;

获取的尺寸单位均为px

&＃64;Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);//int width &＃61; getWidth();int height &＃61; getHeight();int measuredHeight &＃61; getMeasuredHeight();int measuredWidth &＃61; getMeasuredWidth();//onMeasure中&＃xff1a;//Width &＃61; Height &＃61; 0 //当具体数据或match_parent时&＃xff1a;//measuredHeight的最后数值 &＃61; onSizeChanged中h &＃61; height &＃61; measuredHeight//measuredWidth的最后数值 &＃61; onSizeChanged中w &＃61; width &＃61; measuredWidthint suggestedMinimumWidth &＃61; getSuggestedMinimumWidth();int suggestedMinimumHeight &＃61; getSuggestedMinimumHeight();//等于xml中指定的min尺寸与背景图的min尺寸中较大值&＃xff0c;否则为零
}&＃64;Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);//空方法&＃xff0c;可删int width &＃61; getWidth();int height &＃61; getHeight();int measuredHeight &＃61; getMeasuredHeight();int measuredWidth &＃61; getMeasuredWidth();//onSizeChanged中//w &＃61; width &＃61; measuredWidth//h &＃61; height &＃61; measuredHeight//oldw &＃61; onMeasure方法中getWidth()的最后数值//oldh &＃61; onMeasure方法中getHeight()的最后数值int suggestedMinimumWidth &＃61; getSuggestedMinimumWidth();int suggestedMinimumHeight &＃61; getSuggestedMinimumHeight();//等于xml中指定的min尺寸与背景图的min尺寸中较大值&＃xff0c;否则为零
}

super.onMeasure(widthMeasureSpec, heightMeasureSpec);源码&＃xff1a;

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));
}

public static int getDefaultSize(int size, int measureSpec) {int result &＃61; size;int specMode &＃61; MeasureSpec.getMode(measureSpec);int specSize &＃61; MeasureSpec.getSize(measureSpec);switch (specMode) {case MeasureSpec.UNSPECIFIED:result &＃61; size;break;case MeasureSpec.AT_MOST:case MeasureSpec.EXACTLY:result &＃61; specSize;break;}return result;
}

可看出&＃xff1a;
wrap_content和match_parent具有相同的效果&＃xff0c;即填充父容器

getSuggestedMinimumWidth方法源码&＃xff1a;

private int mMinWidth;
private int mMinHeight;private Drawable mBackground;protected int getSuggestedMinimumWidth() {return (mBackground &＃61;&＃61; null) ? mMinWidth : max(mMinWidth, mBackground.getMinimumWidth());
}protected int getSuggestedMinimumHeight() {return (mBackground &＃61;&＃61; null) ? mMinHeight : max(mMinHeight, mBackground.getMinimumHeight());}