View的getWidth/getHeight与getMeasuredWidth/getMeasuredHeight的区别
程序员文章站
2022-07-14 17:40:33
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某个View的显示流程是这样的:
Activity.onCreate–>Activity.onStart–>Activity.onResume–>image.onMeasure–>image.onLayout–>onGlobalLayoutListener–>Activity.onWindowFocusChanged–>….–>image.onDraw
onWindowFocusChanged是当activity可见时的调用的,在此之前的函数中调用View.getWidth/getHeight得到的是0,onWindowFocusChanged函数中获View.getWidth/getHeight是合适的。getWidth/getHeight一般是控件添加到Activity之后,显示到屏幕中的实际宽度。而View.getMeasureWidth/getMeasureHeight是配合view.measure使用的,如果未调用View.measure,那么调用view.getMeasureWidth的效果和View.getWidth一样。
如果我们要在onWindowFocusChanged之前的函数,如onCreate中获得View的宽度/高度,有如下三种方法:
方法一:
- int width =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
- int height =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
- view.measure(width,height);
- int height=view.getMeasuredHeight();
- int width=view.getMeasuredWidth();
int width =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
int height =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
view.measure(width,height);
int height=view.getMeasuredHeight();
int width=view.getMeasuredWidth();
方法二:
//增加组件绘制之前的监听
- ViewTreeObserver vto =view.getViewTreeObserver();
- vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
- @Override
- public boolean onPreDraw() {
- int height =view.getMeasuredHeight();
- int width =view.getMeasuredWidth();
- }
- });
ViewTreeObserver vto =view.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
int height =view.getMeasuredHeight();
int width =view.getMeasuredWidth();
}
});
方法三:
//增加整体布局监听
- ViewTreeObserver vto = view.getViewTreeObserver();
- vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener(){
- @Override
- public void onGlobalLayout() {
- view.getViewTreeObserver().removeGlobalOnLayoutListener(this);
- int height =view.getMeasuredHeight();
- int width =view.getMeasuredWidth();
- }
- });
ViewTreeObserver vto = view.getViewTreeObserver();
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener(){
@Override
public void onGlobalLayout() {
view.getViewTreeObserver().removeGlobalOnLayoutListener(this);
int height =view.getMeasuredHeight();
int width =view.getMeasuredWidth();
}
});
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