android View.measure

本文介绍在构建View前如何获取其宽度。需要先进行测量,使用三种模式:UNSPECIFIED(不限定)、EXACTLY(固定)和AT_MOST(最多)。通过调用measure()方法,并使用getMeasuredWidth()和getMeasuredHeight()来获取测量后的尺寸。

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在还没有构建View 之前无法取得View的度宽。
在此之前我们必须选 measure 一下.


测量的三种模式:
UNSPECIFIED: 不限定
EXACTLY: 固定
AT_MOST:最多

view.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED);
measure()后调用getMeasuredWidth()和getMeasuredHeight()得到测量后的值。
E FATAL EXCEPTION: main Process: com.example.kucun2, PID: 20791 java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:454) at android.widget.ArrayAdapter.getView(ArrayAdapter.java:416) at com.example.kucun2.function.Adapter$5.getView(Adapter.java:158) at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:206) at android.widget.Spinner.onMeasure(Spinner.java:622) at androidx.appcompat.widget.AppCompatSpinner.onMeasure(AppCompatSpinner.java:444) at android.view.View.measure(View.java:29007) at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1226) at android.widget.LinearLayout.onMeasure(LinearLayout.java:728) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1613) at android.widget.LinearLayout.measureVertical(LinearLayout.java:883) at android.widget.LinearLayout.onMeasure(LinearLayout.java:726) at android.view.View.measure(View.java:29007) at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1641) at android.widget.FrameLayout.onMeasure(FrameLayout.java:205) at android.widget.ScrollView.onMeasure(ScrollView.java:559) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.FrameLayout.onMeasure(FrameLayout.java:205) at android.view.View.measure(View.java:29007) at androidx.constraintlayout.widget.ConstraintLayout$Measurer.measure(ConstraintLayout.java:811) at androidx.constraintlayout.core.widgets.analyzer.BasicMeasure.measure(BasicMeasure.java:466) at androidx.constraintlayout.core.widgets.analyzer.BasicMeasure.measureChildren(BasicMeasure.java:134) at androidx.constraintlayout.core.widgets.analyzer.BasicMeasure.solverMeasure(BasicMeasure.java:278) at androidx.constraintlayout.core.widgets.ConstraintWidgetContainer.measure(ConstraintWidgetContainer.java:120) at androidx.constraintlayout.widget.ConstraintLayout.resolveSystem(ConstraintLayout.java:1594) at androidx.constraintlayout.widget.ConstraintLayout.onMeasure(ConstraintLayout.java:1708) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at androidx.coordinatorlayout.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:760) at com.google.android.material.appbar.HeaderScrollingViewBehavior.onMeasureChild(HeaderScrollingViewBehavior.java:100) at com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior.onMeasureChild(AppBarLayout.java:2381) at androidx.coordinatorlayout.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:831) at android.view.View.measure(View.java:29007) at androidx.drawerlayout.widget.DrawerLayout.onMeasure(DrawerLayout.java:1156) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.FrameLayout.onMeasure(FrameLayout.java:205) at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:145) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1613) at android.widget.LinearLayout.measureVertical(LinearLayout.java:883) at android.widget.LinearLayout.onMeasure(LinearLayout.java:726) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.FrameLayout.onMeasure(FrameLayout.java:205) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1613) 2025-06-11 09:10:16.360 20791-20791 AndroidRuntime com.example.kucun2 E at android.widget.LinearLayout.measureVertical(LinearLayout.java:883) at android.widget.LinearLayout.onMeasure(LinearLayout.java:726) at android.view.View.measure(View.java:29007) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:7132) at com.android.internal.policy.DecorView.measureChildWithMargins(DecorView.java:3010) at android.widget.FrameLayout.onMeasure(FrameLayout.java:205) at com.android.internal.policy.DecorView.onMeasure(DecorView.java:911) at android.view.View.measure(View.java:29007) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:5801) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:3999) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:4393) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:3667) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:12113) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:2459) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:2468) at android.view.Choreographer.doCallbacks(Choreographer.java:1693) at android.view.Choreographer.doFrame(Choreographer.java:1448) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:2284) at android.os.Handler.handleCallback(Handler.java:1014) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loopOnce(Looper.java:250) at android.os.Looper.loop(Looper.java:340) at android.app.ActivityThread.main(ActivityThread.java:9913) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:621) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:957)
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06-12
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