使用自定义视图即时崩溃
Instant crash with the use of a custom view
我以前从未使用过自定义视图，所以很可能我做错了什么。
下面是我的 SmartTabLayout class 的 Java 代码，它应该根据其所有内容的总组合宽度在 MODE_FIXED 和 MODE_SCROLLABLE 之间切换选项卡。
import android.content.Context;
import android.util.AttributeSet;
import android.view.ViewGroup;
public class SmartTabLayout extends android.support.design.widget.TabLayout {
public SmartTabLayout(Context context) {
super(context);
}
public SmartTabLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
public SmartTabLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (getTabCount() == 0) return;
try {
ViewGroup tabLayout = (ViewGroup)getChildAt(0);
int combinedWidth = 0;
for (int i = 0; i < tabLayout.getChildCount(); i++)
combinedWidth += tabLayout.getChildAt(i).getMeasuredWidth();
setTabMode(combinedWidth <= getMeasuredWidth() ? MODE_FIXED : MODE_SCROLLABLE);
} catch (Exception e) {
// e.printStackTrace();
}
}
}
我的布局 XML 文件包含以下部分：
<SmartTabLayout
android:id="@+id/tabLayout"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabGravity="fill"
app:tabMode="scrollable"
android:layout_gravity="center_horizontal">
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Left" />
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Center" />
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Right" />
</SmartTabLayout>
当（在我的 XML 文件中）我将 SmartTabLayout 更改为 android.support.design.widget.TabLayout 时，一切正常，但没有所需的 "smart" 功能。所以我假设 XML 代码没问题。但是当我在 XML 文件中使用我的 SmartTabLayout 时，应用程序在启动后立即崩溃。调试器甚至不调用我的自定义代码的一行。我错过了什么？
日志（下方）包含以下消息：
Didn't find class "android.view.SmartTabLayout" on path...
我是否应该在某处明确指向我的自定义视图 class？
02-16 15:56:14.328 24316-24316/? E/Zygote: v2
02-16 15:56:14.328 24316-24316/? I/libpersona: KNOX_SDCARD checking this for 10327
02-16 15:56:14.328 24316-24316/? I/libpersona: KNOX_SDCARD not a persona
02-16 15:56:14.330 24316-24316/? E/Zygote: accessInfo : 0
02-16 15:56:14.331 24316-24316/? W/SELinux: SELinux selinux_android_compute_policy_index : Policy Index[2], Con:u:r:zygote:s0 SPD:SEPF_SECMOBILE_7.0_0006 RAM:SEPF_SECMOBILE_7.0_0010, [-1 -1 -9 -1 0 1]
02-16 15:56:14.332 24316-24316/? I/SELinux: SELinux: seapp_context_lookup: seinfo=untrusted, level=s0:c512,c768, pkgname=com.example.android
02-16 15:56:14.339 24316-24316/? I/art: Late-enabling -Xcheck:jni
02-16 15:56:14.381 24316-24316/? D/TimaKeyStoreProvider: TimaSignature is unavailable
02-16 15:56:14.381 24316-24316/? D/ActivityThread: Added TimaKeyStore provider
02-16 15:56:14.406 24316-24316/com.example.android W/ActivityThread: Application com.example.android is waiting for the debugger on port 8100...
02-16 15:56:14.409 24316-24316/com.example.android I/System.out: Sending WAIT chunk
02-16 15:56:15.420 24316-24323/com.example.android I/art: Debugger is active
02-16 15:56:15.611 24316-24316/com.example.android I/System.out: Debugger has connected
02-16 15:56:15.611 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:15.811 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.012 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.212 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.412 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.613 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.813 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:17.013 24316-24316/com.example.android I/System.out: debugger has settled (1370)
02-16 15:56:17.112 24316-24316/com.example.android W/System: ClassLoader referenced unknown path: /data/app/com.example.android-2/lib/arm64
02-16 15:56:17.129 24316-24316/com.example.android D/ContextRelationMgrBrdg: loadKlass() : caller=com.samsung.android.bridge.multiscreen.common.ContextRelationManagerBridge.<clinit>:28 com.samsung.android.bridge.multiscreen.common.ContextRelationManagerBridge.getInstance:-1
02-16 15:56:17.139 24316-24316/com.example.android I/InstantRun: starting instant run server: is main process
02-16 15:56:17.210 24316-24316/com.example.android W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
02-16 15:56:17.315 24316-24316/com.example.android D/TextView: setTypeface with style : 0
02-16 15:56:17.316 24316-24316/com.example.android D/TextView: setTypeface with style : 0
02-16 15:56:17.348 24316-24316/com.example.android D/AndroidRuntime: Shutting down VM
02-16 15:56:17.354 24316-24316/com.example.android E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android, PID: 24316
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android/com.example.android.Main}: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class SmartTabLayout
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2947)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3008)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1650)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6688)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
Caused by: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class SmartTabLayout
Caused by: android.view.InflateException: Binary XML file line #0: Error inflating class SmartTabLayout
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.SmartTabLayout" on path: DexPathList[[zip file "/data/app/com.example.android-2/base.apk", zip file "/data/app/com.example.android-2/split_lib_dependencies_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.android-2/lib/arm64, /system/lib64, /vendor/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:380)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at android.view.LayoutInflater.createView(LayoutInflater.java:616)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:707)
at com.android.internal.policy.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:68)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:724)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:792)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:734)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:865)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:828)
at android.view.LayoutInflater.inflate(LayoutInflater.java:525)
at android.view.LayoutInflater.inflate(LayoutInflater.java:427)
at android.view.LayoutInflater.inflate(LayoutInflater.java:378)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:287)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
at com.example.android.Main.onCreate(Main.java:52)
at android.app.Activity.performCreate(Activity.java:6912)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2900)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3008)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1650)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6688)
at java.lang.reflect.Method.invoke(Native Method)02-16 15:56:17.355 24316-24316/com.example.android E/AndroidRuntime:
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
尝试对前两个构造函数的超级调用进行以下更改：
public SmartTabLayout(Context context) {
super(context, null);
}
public SmartTabLayout(Context context, AttributeSet attrs) {
super(context, attrs, 0);
}
public SmartTabLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
日志指向一个
java.lang.ClassNotFoundException: Didn't find class "android.view.SmartTabLayout"
错误，尝试将布局更改为
<<package_name>.SmartTabLayout
android:id="@+id/tabLayout"
.../>
正如我们许多人所想的那样，将 <SmartTabLayout> 更改为 <com.example.android.SmartTabLayout> 会很有趣。
但这还不足以使其发挥作用。我必须添加：
package com.example.android;
在我的 SmartTabLayout class 文件的开头。现在可以使用了，但是显示警告
Package name 'com.example.android' does not correspond to the file
path ''
所以我必须将 Java class 源代码从 ...\java 目录移动到 ...\java\com.example.android 文件夹，现在它可以正常工作了。
文件的移动是有道理的，因为我添加了package com.example.android;。
但为什么我必须将此自定义视图作为我的包的一部分才能使其正常工作？那不应该在包裹之外工作吗？诡异的。但正如我所写，这是我第一次使用自定义视图，所以我学到了一些东西。is/was
希望对遇到同样问题的其他人有所帮助。
我以前从未使用过自定义视图，所以很可能我做错了什么。
下面是我的 SmartTabLayout class 的 Java 代码，它应该根据其所有内容的总组合宽度在 MODE_FIXED 和 MODE_SCROLLABLE 之间切换选项卡。
import android.content.Context;
import android.util.AttributeSet;
import android.view.ViewGroup;
public class SmartTabLayout extends android.support.design.widget.TabLayout {
public SmartTabLayout(Context context) {
super(context);
}
public SmartTabLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
public SmartTabLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (getTabCount() == 0) return;
try {
ViewGroup tabLayout = (ViewGroup)getChildAt(0);
int combinedWidth = 0;
for (int i = 0; i < tabLayout.getChildCount(); i++)
combinedWidth += tabLayout.getChildAt(i).getMeasuredWidth();
setTabMode(combinedWidth <= getMeasuredWidth() ? MODE_FIXED : MODE_SCROLLABLE);
} catch (Exception e) {
// e.printStackTrace();
}
}
}
我的布局 XML 文件包含以下部分：
<SmartTabLayout
android:id="@+id/tabLayout"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabGravity="fill"
app:tabMode="scrollable"
android:layout_gravity="center_horizontal">
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Left" />
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Center" />
<android.support.design.widget.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Right" />
</SmartTabLayout>
当（在我的 XML 文件中）我将 SmartTabLayout 更改为 android.support.design.widget.TabLayout 时，一切正常，但没有所需的 "smart" 功能。所以我假设 XML 代码没问题。但是当我在 XML 文件中使用我的 SmartTabLayout 时，应用程序在启动后立即崩溃。调试器甚至不调用我的自定义代码的一行。我错过了什么？
日志（下方）包含以下消息：
Didn't find class "android.view.SmartTabLayout" on path...
我是否应该在某处明确指向我的自定义视图 class？
02-16 15:56:14.328 24316-24316/? E/Zygote: v2
02-16 15:56:14.328 24316-24316/? I/libpersona: KNOX_SDCARD checking this for 10327
02-16 15:56:14.328 24316-24316/? I/libpersona: KNOX_SDCARD not a persona
02-16 15:56:14.330 24316-24316/? E/Zygote: accessInfo : 0
02-16 15:56:14.331 24316-24316/? W/SELinux: SELinux selinux_android_compute_policy_index : Policy Index[2], Con:u:r:zygote:s0 SPD:SEPF_SECMOBILE_7.0_0006 RAM:SEPF_SECMOBILE_7.0_0010, [-1 -1 -9 -1 0 1]
02-16 15:56:14.332 24316-24316/? I/SELinux: SELinux: seapp_context_lookup: seinfo=untrusted, level=s0:c512,c768, pkgname=com.example.android
02-16 15:56:14.339 24316-24316/? I/art: Late-enabling -Xcheck:jni
02-16 15:56:14.381 24316-24316/? D/TimaKeyStoreProvider: TimaSignature is unavailable
02-16 15:56:14.381 24316-24316/? D/ActivityThread: Added TimaKeyStore provider
02-16 15:56:14.406 24316-24316/com.example.android W/ActivityThread: Application com.example.android is waiting for the debugger on port 8100...
02-16 15:56:14.409 24316-24316/com.example.android I/System.out: Sending WAIT chunk
02-16 15:56:15.420 24316-24323/com.example.android I/art: Debugger is active
02-16 15:56:15.611 24316-24316/com.example.android I/System.out: Debugger has connected
02-16 15:56:15.611 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:15.811 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.012 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.212 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.412 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.613 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:16.813 24316-24316/com.example.android I/System.out: waiting for debugger to settle...
02-16 15:56:17.013 24316-24316/com.example.android I/System.out: debugger has settled (1370)
02-16 15:56:17.112 24316-24316/com.example.android W/System: ClassLoader referenced unknown path: /data/app/com.example.android-2/lib/arm64
02-16 15:56:17.129 24316-24316/com.example.android D/ContextRelationMgrBrdg: loadKlass() : caller=com.samsung.android.bridge.multiscreen.common.ContextRelationManagerBridge.<clinit>:28 com.samsung.android.bridge.multiscreen.common.ContextRelationManagerBridge.getInstance:-1
02-16 15:56:17.139 24316-24316/com.example.android I/InstantRun: starting instant run server: is main process
02-16 15:56:17.210 24316-24316/com.example.android W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
02-16 15:56:17.315 24316-24316/com.example.android D/TextView: setTypeface with style : 0
02-16 15:56:17.316 24316-24316/com.example.android D/TextView: setTypeface with style : 0
02-16 15:56:17.348 24316-24316/com.example.android D/AndroidRuntime: Shutting down VM
02-16 15:56:17.354 24316-24316/com.example.android E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android, PID: 24316
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android/com.example.android.Main}: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class SmartTabLayout
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2947)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3008)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1650)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6688)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
Caused by: android.view.InflateException: Binary XML file line #0: Binary XML file line #0: Error inflating class SmartTabLayout
Caused by: android.view.InflateException: Binary XML file line #0: Error inflating class SmartTabLayout
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.SmartTabLayout" on path: DexPathList[[zip file "/data/app/com.example.android-2/base.apk", zip file "/data/app/com.example.android-2/split_lib_dependencies_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_0_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_1_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_2_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_3_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_4_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_5_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_6_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_7_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_8_apk.apk", zip file "/data/app/com.example.android-2/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.example.android-2/lib/arm64, /system/lib64, /vendor/lib64]]
at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
at java.lang.ClassLoader.loadClass(ClassLoader.java:380)
at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
at android.view.LayoutInflater.createView(LayoutInflater.java:616)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:707)
at com.android.internal.policy.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:68)
at android.view.LayoutInflater.onCreateView(LayoutInflater.java:724)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:792)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:734)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:865)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:828)
at android.view.LayoutInflater.inflate(LayoutInflater.java:525)
at android.view.LayoutInflater.inflate(LayoutInflater.java:427)
at android.view.LayoutInflater.inflate(LayoutInflater.java:378)
at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:287)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
at com.example.android.Main.onCreate(Main.java:52)
at android.app.Activity.performCreate(Activity.java:6912)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2900)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3008)
at android.app.ActivityThread.-wrap14(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1650)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6688)
at java.lang.reflect.Method.invoke(Native Method)02-16 15:56:17.355 24316-24316/com.example.android E/AndroidRuntime:
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358)
尝试对前两个构造函数的超级调用进行以下更改：
public SmartTabLayout(Context context) {
super(context, null);
}
public SmartTabLayout(Context context, AttributeSet attrs) {
super(context, attrs, 0);
}
public SmartTabLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
日志指向一个
java.lang.ClassNotFoundException: Didn't find class "android.view.SmartTabLayout"
错误，尝试将布局更改为
<<package_name>.SmartTabLayout
android:id="@+id/tabLayout"
.../>
正如我们许多人所想的那样，将 <SmartTabLayout> 更改为 <com.example.android.SmartTabLayout> 会很有趣。
但这还不足以使其发挥作用。我必须添加：
package com.example.android;
在我的 SmartTabLayout class 文件的开头。现在可以使用了，但是显示警告
Package name 'com.example.android' does not correspond to the file path ''
所以我必须将 Java class 源代码从 ...\java 目录移动到 ...\java\com.example.android 文件夹，现在它可以正常工作了。
文件的移动是有道理的，因为我添加了package com.example.android;。
但为什么我必须将此自定义视图作为我的包的一部分才能使其正常工作？那不应该在包裹之外工作吗？诡异的。但正如我所写，这是我第一次使用自定义视图，所以我学到了一些东西。is/was
希望对遇到同样问题的其他人有所帮助。