问题
Recently i changed my sdk from 25 to 26 in my app in android studio, i'm getting this weird error in all my xml. At the moment the error is not afecting my app in any way i can see, but is anoying to see every time i have to edit or change something in the xml. The error here:
the following classes could not be instantiated - android.support.v7.widget.AppCompatTextView
java.lang.NullPointerException
at android.content.res.Resources_Delegate.getValue(Resources_Delegate.java:788)
at android.content.res.Resources.getValue(Resources.java:1286)
at android.support.v4.content.res.ResourcesCompat.loadFont(ResourcesCompat.java:212)
at android.support.v4.content.res.ResourcesCompat.getFont(ResourcesCompat.java:206)
at android.support.v7.widget.TintTypedArray.getFont(TintTypedArray.java:119)
at android.support.v7.widget.AppCompatTextHelper.updateTypefaceAndStyle(AppCompatTextHelper.java:208)
at android.support.v7.widget.AppCompatTextHelper.loadFromAttributes(AppCompatTextHelper.java:152)
at android.support.v7.widget.AppCompatTextHelperV17.loadFromAttributes(AppCompatTextHelperV17.java:38)
at android.support.v7.widget.AppCompatTextView.<init>(AppCompatTextView.java:81)
at android.support.v7.widget.AppCompatTextView.<init>(AppCompatTextView.java:71)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.jetbrains.android.uipreview.ViewLoader.createNewInstance(ViewLoader.java:475)
at org.jetbrains.android.uipreview.ViewLoader.loadClass(ViewLoader.java:250)
at org.jetbrains.android.uipreview.ViewLoader.loadClass(ViewLoader.java:213)
at com.android.tools.idea.rendering.LayoutlibCallbackImpl.loadClass(LayoutlibCallbackImpl.java:193)
at android.view.BridgeInflater.loadCustomView(BridgeInflater.java:333)
at android.view.BridgeInflater.onCreateView(BridgeInflater.java:152)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:717)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:785)
at android.view.BridgeInflater.createViewFromTag(BridgeInflater.java:222)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:727)
at android.view.LayoutInflater.rInflate_Original(LayoutInflater.java:858)
at android.view.LayoutInflater_Delegate.rInflate(LayoutInflater_Delegate.java:70)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:834)
at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
at com.android.layoutlib.bridge.bars.CustomBar.<init>(CustomBar.java:95)
at com.android.layoutlib.bridge.bars.StatusBar.<init>(StatusBar.java:67)
at com.android.layoutlib.bridge.impl.Layout.createStatusBar(Layout.java:224)
at com.android.layoutlib.bridge.impl.Layout.<init>(Layout.java:146)
at com.android.layoutlib.bridge.impl.RenderSessionImpl.inflate(RenderSessionImpl.java:301)
at com.android.layoutlib.bridge.Bridge.createSession(Bridge.java:429)
at com.android.ide.common.rendering.LayoutLibrary.createSession(LayoutLibrary.java:368)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:567)
at com.android.tools.idea.rendering.RenderTask$2.compute(RenderTask.java:549)
at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:863)
at com.android.tools.idea.rendering.RenderTask.createRenderSession(RenderTask.java:549)
at com.android.tools.idea.rendering.RenderTask.lambda$inflate$1(RenderTask.java:680)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
And my gradle:
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
buildToolsVersion "26.0.1"
defaultConfig {
applicationId "com.al285790.time2cook"
minSdkVersion 15
targetSdkVersion 26
multiDexEnabled true
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:26.0.1'
compile 'com.android.support:palette-v7:26.0.1'
compile 'com.android.support:design:26.0.1'
compile 'com.google.firebase:firebase-database:11.0.2'
compile 'com.google.firebase:firebase-core:9.6.1'
compile 'com.google.firebase:firebase-storage:11.0.2'
compile 'com.google.firebase:firebase-auth:11.0.2'
compile 'com.github.bumptech.glide:glide:3.7.0'
compile 'com.firebaseui:firebase-ui-storage:1.2.0'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile('com.mikepenz:materialdrawer:5.9.5@aar') {
transitive = true
}
testCompile 'junit:junit:4.12'
}
apply plugin: 'com.google.gms.google-services'
EDIT: Added some of my xml code
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"></android.support.v7.widget.Toolbar>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="android.support.design.widget.AppBarLayout$ScrollingViewBehavior">
<android.support.v4.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.al285790.time2cook.recipeInfo.RecipeInfoActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:scrollbars="none">
<TextView
android:id="@+id/recipeNameText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="24sp"
android:textStyle="bold" />
<ImageView
android:id="@+id/photoRecipe"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:scaleType="fitCenter"
app:srcCompat="@drawable/cho" />
<TextView
android:id="@+id/textView10"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Dificulty"
android:textSize="24sp"
android:textStyle="bold" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<RatingBar
android:id="@+id/ratingBarDificulty"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:isIndicator="true"
android:numStars="5"
android:stepSize="1" />
<Button
android:id="@+id/button8"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="giveLike"
android:text="LIKE!" />
</LinearLayout>
<TextView
android:id="@+id/Ingredients"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Ingredients"
android:textSize="24sp"
android:textStyle="bold" />
<android.support.v7.widget.RecyclerView
android:id="@+id/superList"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/textView9"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Steps"
android:textSize="24sp"
android:textStyle="bold" />
<android.support.v7.widget.RecyclerView
android:id="@+id/stepsList"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
</android.support.v4.widget.NestedScrollView>
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>
回答1:
I was getting this error too and tried to fix it by cleaning, rebuilding and invalidating the cache many times.
What fixed it for me was changing the parent theme in res/values/styles.xml to one with Base e.g.
<style name="AppTheme" parent="Base.Theme.AppCompat.Light.DarkActionBar">
as per the answer here.
回答2:
Two things you can try:
Cleaning/Rebuilding
Open Android Studio and go to Tools -> Clean project and let the gradle build run.
After completion, go to Tools - > Rebuild project.
- Done.
Invalidating caches
- Open Android Studio and go to File -> Invalidate Caches/Restart and click on Invalidate/Restart.
- Done.
- Open Android Studio and go to File -> Invalidate Caches/Restart and click on Invalidate/Restart.
回答3:
Its a bug in Android Studio 2.3.3 and has been reported - Preview render problem when adding maven.google.com as a maven repo
Unfortunately this bug won't be fixed in Android Studio 2.3.3 but has been fixed in Android Studio 3.0
So let us wait till stable versions are available for Android Studio 3.0
Update on 26th Oct 2017:
Android Studio 3.0 is in stable channel now. Update it and you won't see this error
来源：https://stackoverflow.com/questions/45820960/the-following-classes-could-not-be-instantiated-with-android-support-v7-widget-a