我最近开始使用 API 版本 16 (4.1) 进行 Android 开发。根据 developer.android.com 上提供的教程，我开始开发教我使用 Intents 的应用程序。问题是，一旦我的应用程序加载到模拟器上，它就会显示应用程序必须关闭的错误。我正在提供我的 xml 代码。有人可以告诉我哪里出错了吗？谢谢。
<LinearLayout 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:orientation="horizontal">
<EditText
android:id="@+id/et1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:hint="Edit text"
android:layout_weight="1"
tools:ignore="HardcodedText" />
<Button
android:id="@+id/b1"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:text="Press"
android:onClick="sendMessage"
tools:ignore="HardcodedText" />
</LinearLayout>
logcat 如下所示。
09-26 19:35:03.880: E/Trace(615): error opening trace file: No such file or directory (2)
09-26 19:35:04.430: D/AndroidRuntime(615): Shutting down VM
09-26 19:35:04.430: W/dalvikvm(615): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-26 19:35:04.471: E/AndroidRuntime(615): FATAL EXCEPTION: main
09-26 19:35:04.471: E/AndroidRuntime(615): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.learn.training1/com.learn.training1.Training1}: java.lang.NullPointerException
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.os.Looper.loop(Looper.java:137)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-26 19:35:04.471: E/AndroidRuntime(615): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 19:35:04.471: E/AndroidRuntime(615): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 19:35:04.471: E/AndroidRuntime(615): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-26 19:35:04.471: E/AndroidRuntime(615): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-26 19:35:04.471: E/AndroidRuntime(615): at dalvik.system.NativeStart.main(Native Method)
09-26 19:35:04.471: E/AndroidRuntime(615): Caused by: java.lang.NullPointerException
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.Activity.findViewById(Activity.java:1825)
09-26 19:35:04.471: E/AndroidRuntime(615): at com.learn.training1.Training1.<init>(Training1.java:15)
09-26 19:35:04.471: E/AndroidRuntime(615): at java.lang.Class.newInstanceImpl(Native Method)
09-26 19:35:04.471: E/AndroidRuntime(615): at java.lang.Class.newInstance(Class.java:1319)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-26 19:35:04.471: E/AndroidRuntime(615): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
09-26 19:35:04.471: E/AndroidRuntime(615): ... 11 more
09-26 19:35:32.352: I/Process(615): Sending signal. PID: 615 SIG: 9
09-26 19:39:22.460: E/Trace(664): error opening trace file: No such file or directory (2)
09-26 19:39:22.820: D/AndroidRuntime(664): Shutting down VM
09-26 19:39:22.820: W/dalvikvm(664): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-26 19:39:22.846: E/AndroidRuntime(664): FATAL EXCEPTION: main
09-26 19:39:22.846: E/AndroidRuntime(664): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.learn.training1/com.learn.training1.Training1}: java.lang.NullPointerException
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.os.Looper.loop(Looper.java:137)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-26 19:39:22.846: E/AndroidRuntime(664): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 19:39:22.846: E/AndroidRuntime(664): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 19:39:22.846: E/AndroidRuntime(664): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-26 19:39:22.846: E/AndroidRuntime(664): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-26 19:39:22.846: E/AndroidRuntime(664): at dalvik.system.NativeStart.main(Native Method)
09-26 19:39:22.846: E/AndroidRuntime(664): Caused by: java.lang.NullPointerException
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.Activity.findViewById(Activity.java:1825)
09-26 19:39:22.846: E/AndroidRuntime(664): at com.learn.training1.Training1.<init>(Training1.java:15)
09-26 19:39:22.846: E/AndroidRuntime(664): at java.lang.Class.newInstanceImpl(Native Method)
09-26 19:39:22.846: E/AndroidRuntime(664): at java.lang.Class.newInstance(Class.java:1319)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-26 19:39:22.846: E/AndroidRuntime(664): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
09-26 19:39:22.846: E/AndroidRuntime(664): ... 11 more
09-26 19:40:29.130: E/Trace(712): error opening trace file: No such file or directory (2)
09-26 19:40:29.431: D/dalvikvm(712): newInstance failed: Lcom/learn/training1/Training1; not accessible to Landroid/app/Instrumentation;
09-26 19:40:29.431: D/AndroidRuntime(712): Shutting down VM
09-26 19:40:29.431: W/dalvikvm(712): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-26 19:40:29.461: E/AndroidRuntime(712): FATAL EXCEPTION: main
09-26 19:40:29.461: E/AndroidRuntime(712): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.learn.training1/com.learn.training1.Training1}: java.lang.IllegalAccessException: access to class not allowed
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.os.Looper.loop(Looper.java:137)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-26 19:40:29.461: E/AndroidRuntime(712): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 19:40:29.461: E/AndroidRuntime(712): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 19:40:29.461: E/AndroidRuntime(712): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-26 19:40:29.461: E/AndroidRuntime(712): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-26 19:40:29.461: E/AndroidRuntime(712): at dalvik.system.NativeStart.main(Native Method)
09-26 19:40:29.461: E/AndroidRuntime(712): Caused by: java.lang.IllegalAccessException: access to class not allowed
09-26 19:40:29.461: E/AndroidRuntime(712): at java.lang.Class.newInstanceImpl(Native Method)
09-26 19:40:29.461: E/AndroidRuntime(712): at java.lang.Class.newInstance(Class.java:1319)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-26 19:40:29.461: E/AndroidRuntime(712): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
09-26 19:40:29.461: E/AndroidRuntime(712): ... 11 more
09-26 19:43:52.020: E/Trace(760): error opening trace file: No such file or directory (2)
09-26 19:43:52.110: D/dalvikvm(760): newInstance failed: Lcom/learn/training1/Training1; not accessible to Landroid/app/Instrumentation;
09-26 19:43:52.110: D/AndroidRuntime(760): Shutting down VM
09-26 19:43:52.110: W/dalvikvm(760): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
09-26 19:43:52.190: E/AndroidRuntime(760): FATAL EXCEPTION: main
09-26 19:43:52.190: E/AndroidRuntime(760): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.learn.training1/com.learn.training1.Training1}: java.lang.IllegalAccessException: access to class not allowed
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1983)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.os.Handler.dispatchMessage(Handler.java:99)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.os.Looper.loop(Looper.java:137)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread.main(ActivityThread.java:4745)
09-26 19:43:52.190: E/AndroidRuntime(760): at java.lang.reflect.Method.invokeNative(Native Method)
09-26 19:43:52.190: E/AndroidRuntime(760): at java.lang.reflect.Method.invoke(Method.java:511)
09-26 19:43:52.190: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-26 19:43:52.190: E/AndroidRuntime(760): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-26 19:43:52.190: E/AndroidRuntime(760): at dalvik.system.NativeStart.main(Native Method)
09-26 19:43:52.190: E/AndroidRuntime(760): Caused by: java.lang.IllegalAccessException: access to class not allowed
09-26 19:43:52.190: E/AndroidRuntime(760): at java.lang.Class.newInstanceImpl(Native Method)
09-26 19:43:52.190: E/AndroidRuntime(760): at java.lang.Class.newInstance(Class.java:1319)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
09-26 19:43:52.190: E/AndroidRuntime(760): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1974)
09-26 19:43:52.190: E/AndroidRuntime(760): ... 11 more
09-26 19:47:20.550: I/Process(810): Sending signal. PID: 810 SIG: 9
最佳答案
看起来您的 Activity 没有正确声明(也许您没有将其设为public？)。你应该有一个名为 Training1.java 的文件，在这个文件中你应该有类似的东西
public class Training1 extends Activity {
...your activity code here...
}
参见 https://groups.google.com/forum/?fromgroups=#!topic/android-developers/0Gw5WHc1J6g
编辑:添加注释
注意:此外，您不应该有任何构造函数。 Android 框架会为您处理这件事。
关于java - Android 开发- Intent ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12604707/