扩展 SwitchMaterial 和 NPE 发生

问题描述 投票：0回答：2

我正在尝试在Android中自定义

SwitchMaterial
类，就像这样

class TipSwitchMaterial @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = android.R.attr.switchStyle
) : SwitchMaterial(context, attrs, defStyleAttr) {

}

我在活动 xml 中使用 

TipSwitchMaterial
，如下所示：

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:isScrollContainer="true"
    tools:context=".SidActivity">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

...

        <com.omnieyes.omnilite.view.TipSwitchMaterial
            android:id="@+id/event_record_sort_switch"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="8dp"
            android:text="@string/sort"
            android:tooltipText="@string/tooltip_sort"
            app:layout_constraintBottom_toBottomOf="@+id/predict_button"
            app:layout_constraintEnd_toStartOf="@id/predict_button"
            app:layout_constraintHorizontal_chainStyle="packed"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@+id/predict_button" />
...

然而，在进入该活动后，就会发生

NPE
：

2023-03-23 15:21:36.630 17706-17706/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.omnieyes.omnilite, PID: 17706
    java.lang.NullPointerException: Attempt to invoke interface method 'int java.lang.CharSequence.length()' on a null object reference
        at android.text.StaticLayout.<init>(StaticLayout.java:455)
        at androidx.appcompat.widget.SwitchCompat.makeLayout(SwitchCompat.java:982)
        at androidx.appcompat.widget.SwitchCompat.onMeasure(SwitchCompat.java:905)
        at android.view.View.measure(View.java:25466)
        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:25466)
        at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1412)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.widget.ScrollView.onMeasure(ScrollView.java:452)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:145)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:721)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6957)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at com.android.internal.policy.DecorView.onMeasure(DecorView.java:747)
        at android.view.View.measure(View.java:25466)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:3397)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:2228)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2486)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1952)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:8171)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:972)
        at android.view.Choreographer.doCallbacks(Choreographer.java:796)
        at android.view.Choreographer.doFrame(Choreographer.java:731)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:957)
        at android.os.Handler.handleCallback(Handler.java:938)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

我这样做是因为我想在 this post 中应用类似点击的工具提示，这会在 

perfromLongClick()
中实现 
OnClickListener
。我正在尝试稍微改变他的方式。我计划在其 
init{}
块内执行此操作，如下所示：

init {
        // so we can click and show its tooltip; a long-click still does
        setOnClickListener { performLongClick() }
    }

它适用于扩展 

TextView
的类。请帮忙，谢谢。

我已经列出了我在那里尝试过的内容。我找不到任何相关的帖子或教程来扩展

SwitchMaterial
。也许没有必要这样做？

编辑：添加build.gradle文件

我的

build.gradle
文件如下：

plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id 'kotlin-android-extensions'
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "xxx"
        minSdk 26
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

        ndk {
            abiFilters "armeabi", "armeabi-v7a", "x86", "mips"
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    packagingOptions {
        exclude 'AndroidManifest.xml'
    }
}


dependencies {
    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.5.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
    implementation project(path: ':opencv')
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.4'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4'
    implementation 'com.google.code.gson:gson:2.10'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
    implementation 'androidx.core:core-ktx:1.3.2'
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation group: 'commons-io', name: 'commons-io', version: '2.6'
    implementation group: 'org.javatuples', name: 'javatuples', version: '1.2'
    implementation('com.squareup.okhttp3:okhttp:4.9.3')
    implementation('org.apache.commons:commons-csv:1.5')
    implementation files('libs/openCVLibrary330-v1.1-release.aar')

    //firebase, choose for kotlin and java or Both.
    implementation 'com.google.firebase:firebase-crashlytics-ktx:18.3.0'
    implementation 'com.google.firebase:firebase-crashlytics'
}
android kotlin material-ui android-constraintlayout android-scrollview
2个回答
0
投票

系统/库代码中发生的这些类型的错误可能很难追踪。

我只能通过 1）强制 

defStyleAttr
为零，或者 2）强制布局文件中的 
textOn
属性为空（
android:textOn="@null"
）来重现您的错误。这告诉我，您正在丢失属性或修改样式，使得 
textOn
以及可能的 
textOff
出现空值。通过在 XML 布局中设置 
android:textOn="On"
和 
android:textOff="Off"
，您也许可以确信这就是问题的根源。 （但这不是解决办法。）

那么，我为什么这么说呢？如果我们以相反的顺序获取堆栈跟踪中顶部的程序参考行，我们可以看到崩溃中涉及的代码。

    at androidx.appcompat.widget.SwitchCompat.onMeasure(SwitchCompat.java:905)
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        ...
        if (mOnLayout == null) {
            mOnLayout = makeLayout(mTextOnTransformed); // Line 905
        }
        ...
    }

    at androidx.appcompat.widget.SwitchCompat.makeLayout(SwitchCompat.java:982)
    private Layout makeLayout(CharSequence transformedText) {
        return new StaticLayout(transformedText, mTextPaint,
                transformedText != null
                        ? (int) Math.ceil(Layout.getDesiredWidth(transformedText, mTextPaint)) : 0, // Line 982
                Layout.Alignment.ALIGN_NORMAL, 1.f, 0, true);
    }



    at android.text.StaticLayout.<init>(StaticLayout.java:455)
            this(source, 0, source.length(), paint, width, align, // Line 455
         spacingmult, spacingadd, includepad);

如果我们在StaticLayout.java的第455行设置断点，我们可以看到

source
为空，直接导致崩溃。

java.lang.NullPointerException：尝试在空对象引用上调用接口方法“int java.lang.CharSequence.length()”

追溯到

source
变量的来源，我们看到它来自
mTextOnTransformed
（
SwitchCompat.java
的第905行。）唯一设置
mTextOnTransformed
的地方是在以下代码中：

    In SwtichCompat.hava:
    private void setTextOnInternal(CharSequence textOn) {
        ...
        mTextOnTransformed = doTransformForOnOffText(textOn);
        ...
    }

并且 

textOn
是开关“打开”时显示的文本，为空。

我无法具体告诉您如何纠正此错误，但请仔细查看与开关及其属性（包括样式）相关的所有内容，以尝试找出问题所在。

0
投票

你可以发布你的themes.xml文件（或styles.xml）吗？

我遇到了类似的问题，经过调查，我发现我的主要应用程序主题是扩展 Material 2 样式。我的主要应用程序主题如下：

<!-- Base application theme. -->
<style name="Theme.AppTheme" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
    ...
</style>

更改为扩展 Material 3 样式后，我能够修复它。

<!-- Base application theme. -->
<style name="Theme.AppTheme" parent="Theme.Material3.DayNight.NoActionBar">
    ...
</style>
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