Android 开发问题：View 的 getWidth、getHeight 方法返回的值都为 0
ImageViewivTest=findViewById(R.id.iv_test);intwidth=ivTest.getWidth();intheight=ivTest.getHeight();Log.i(TAG,"width: "+width);Log.i(TAG,"height: "+height);# 输出结果 width: 0 height: 0- 在 Android 开发中，上述代码中，getWidth、getHeight 方法返回的值都为 0
问题原因
当一个 Activity 启动时，视图的创建和显示需要经过几个关键阶段：视图创建阶段 -> 测量阶段 -> 布局阶段 -> 绘制阶段
在 onCreate 或过早的阶段调用这些方法时，视图尚未完成测量和布局流程，因此坐标值尚未计算，默认返回 0
处理策略
- 使用
View.post方法，确保视图已完成布局
ImageViewivTest=findViewById(R.id.iv_test);ivTest.post(()->{intwidth=ivTest.getWidth();intheight=ivTest.getHeight();Log.i(TAG,"width: "+width);Log.i(TAG,"height: "+height);});补充学习
- 在 onCreate 方法中，任何需要等待测量和布局阶段完成后才能确定的信息都无法获取，例如
- 尺寸相关方法：getWidth、getHeight、getMeasuredWidth、getMeasuredHeight
ImageViewivTest=findViewById(R.id.iv_test);intwidth=ivTest.getWidth();intheight=ivTest.getHeight();intmeasuredWidth=ivTest.getMeasuredWidth();intmeasuredHeight=ivTest.getMeasuredHeight();Log.i(TAG,"width: "+width);Log.i(TAG,"height: "+height);Log.i(TAG,"measuredWidth: "+measuredWidth);Log.i(TAG,"measuredHeight: "+measuredHeight);# 输出结果 width: 0 height: 0 measuredWidth: 0 measuredHeight: 0// 使用 View.post 方法处理后ImageViewivTest=findViewById(R.id.iv_test);ivTest.post(()->{intwidth=ivTest.getWidth();intheight=ivTest.getHeight();intmeasuredWidth=ivTest.getMeasuredWidth();intmeasuredHeight=ivTest.getMeasuredHeight();Log.i(TAG,"width: "+width);Log.i(TAG,"height: "+height);Log.i(TAG,"measuredWidth: "+measuredWidth);Log.i(TAG,"measuredHeight: "+measuredHeight);});# 输出结果 width: 200 height: 200 measuredWidth: 200 measuredHeight: 200- 相对位置相关方法：getLeft、getRight、getTop、getBottom、getX、getY
ImageViewivTest=findViewById(R.id.iv_test);intleft=ivTest.getLeft();intright=ivTest.getRight();inttop=ivTest.getTop();intbottom=ivTest.getBottom();floatx=ivTest.getX();floaty=ivTest.getY();Log.i(TAG,"left: "+left);Log.i(TAG,"right: "+right);Log.i(TAG,"top: "+top);Log.i(TAG,"bottom: "+bottom);Log.i(TAG,"x: "+x);Log.i(TAG,"y: "+y);# 输出结果 left: 0 right: 0 top: 0 bottom: 0 x: 0.0 y: 0.0// 使用 View.post 方法处理后ImageViewivTest=findViewById(R.id.iv_test);ivTest.post(()->{intleft=ivTest.getLeft();intright=ivTest.getRight();inttop=ivTest.getTop();intbottom=ivTest.getBottom();floatx=ivTest.getX();floaty=ivTest.getY();Log.i(TAG,"left: "+left);Log.i(TAG,"right: "+right);Log.i(TAG,"top: "+top);Log.i(TAG,"bottom: "+bottom);Log.i(TAG,"x: "+x);Log.i(TAG,"y: "+y);});# 输出结果 left: 0 right: 200 top: 161 bottom: 361 x: 0.0 y: 161.0- 绝对位置相关方法：getLocationOnScreen、getLocationInWindow、getGlobalVisibleRect
ImageViewivTest=findViewById(R.id.iv_test);int[]locationOnScreen=newint[2];ivTest.getLocationOnScreen(locationOnScreen);int[]locationInWindow=newint[2];ivTest.getLocationInWindow(locationInWindow);Rectrect=newRect();ivTest.getGlobalVisibleRect(rect);Log.i(TAG,"locationOnScreen: "+Arrays.toString(locationOnScreen));Log.i(TAG,"locationInWindow: "+Arrays.toString(locationInWindow));Log.i(TAG,"rect: "+rect);# 输出结果 locationOnScreen: [0, 0] locationInWindow: [0, 0] rect: Rect(0, 0 - 0, 0)// 使用 View.post 方法处理后ImageViewivTest=findViewById(R.id.iv_test);ivTest.post(()->{int[]locationOnScreen=newint[2];ivTest.getLocationOnScreen(locationOnScreen);int[]locationInWindow=newint[2];ivTest.getLocationInWindow(locationInWindow);Rectrect=newRect();ivTest.getGlobalVisibleRect(rect);Log.i(TAG,"locationOnScreen: "+Arrays.toString(locationOnScreen));Log.i(TAG,"locationInWindow: "+Arrays.toString(locationInWindow));Log.i(TAG,"rect: "+rect);});# 输出结果 locationOnScreen: [0, 161] locationInWindow: [0, 161] rect: Rect(0, 161 - 200, 361)