[从XML渲染设计器时出现NullPointerException

Question

我是android新手。

我从XML更改了设计器，现在它显示了异常。我只是想拥有一张3x5的狭窄桌子，但我不知道为什么它会显示异常。

请帮助我解决它。

这里是错误：

java.lang.NullPointerException
at android.widget.LinearLayout.forceUniformHeight(LinearLayout.java:1380)
at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1368)
at android.widget.TableRow.onMeasure(TableRow.java:114)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.TableLayout.measureChildBeforeLayout(TableLayout.java:464)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.TableLayout.measureVertical(TableLayout.java:476)
at android.widget.TableLayout.onMeasure(TableLayout.java:439)
at android.view.View.measure(View.java:17547)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:444)
at android.view.View.measure(View.java:17547)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:875)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17547)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.measureView(RenderSessionImpl.java:640)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.render(RenderSessionImpl.java:540)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:323)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:350)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:497)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:485)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:894)
at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:485)
at com.android.tools.idea.rendering.RenderTask.render(RenderTask.java:590)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.doRender(AndroidLayoutPreviewToolWindowManager.java:644)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager.access$1700(AndroidLayoutPreviewToolWindowManager.java:79)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7$1.run(AndroidLayoutPreviewToolWindowManager.java:586)
at com.intellij.openapi.progress.impl.CoreProgressManager$2.run(CoreProgressManager.java:152)
at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:452)
at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:402)
at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:54)
at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:137)
at org.jetbrains.android.uipreview.AndroidLayoutPreviewToolWindowManager$7.run(AndroidLayoutPreviewToolWindowManager.java:581)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:320)
at com.intellij.util.ui.update.MergingUpdateQueue.execute(MergingUpdateQueue.java:310)
at com.intellij.util.ui.update.MergingUpdateQueue$2.run(MergingUpdateQueue.java:254)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:269)
at com.intellij.util.ui.update.MergingUpdateQueue.flush(MergingUpdateQueue.java:227)
at com.intellij.util.ui.update.MergingUpdateQueue.run(MergingUpdateQueue.java:217)
at com.intellij.util.concurrency.QueueProcessor.runSafely(QueueProcessor.java:238)
at com.intellij.util.Alarm$Request$1.run(Alarm.java:351)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

这是我的代码：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

<TableLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:stretchColumns="*" >

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <Button
            android:text="Accelerate"
            android:id="@+id/button"
            android:layout_column="1"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Left"
            android:id="@+id/button4"
            android:layout_column="0" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Stop"
            android:id="@+id/button5"
            android:layout_column="1" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Right"
            android:id="@+id/button6"
            android:layout_column="2" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Break"
            android:id="@+id/button8"
            android:layout_column="1" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1">

        <SeekBar
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_span="3"
            android:id="@+id/seekBar"
            android:layout_column="0" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <SeekBar
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_span="3"
            android:id="@+id/seekBar2"
            android:layout_column="0" />
    </TableRow>

</TableLayout>

Answer 1

您正在获取异常，因为将android:layout_column="1"属性与android:layout_height="match_parent"一起使用是无效的情况。

尝试删除它应该起作用的android:layout_column="1"属性。

喜欢以下内容：

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

<TableLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
     android:stretchColumns="*">

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <Button
            android:text="Accelerate"
            android:id="@+id/button"
            android:layout_span="3"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Left"
            android:id="@+id/button4"
            android:layout_column="0" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Stop"
            android:id="@+id/button5"
            android:layout_column="1" />

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Right"
            android:id="@+id/button6"
            android:layout_column="2" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <Button
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Break"
            android:id="@+id/button8"/>
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1">

        <SeekBar
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_span="3"
            android:id="@+id/seekBar"
            android:layout_column="0" />
    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="1" >

        <SeekBar
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_span="3"
            android:id="@+id/seekBar2"
            android:layout_column="0" />
    </TableRow>

</TableLayout>
</RelativeLayout>

Answer 2

另一个解决方案是删除android:layout_column。还要选中this答案。