Question

我在Android中创建多个activities，这是我的logcat错误输出。

log.txt的

05-03 03:17:23.295: E/PhonePolicy(1854): Could not preload class for phone policy: com.android.internal.policy.impl.PhoneWindow$ContextMenuCallback
05-03 03:17:37.044: W/dalvikvm(1854): threadid=1: thread exiting with uncaught exception (group=0x409db1f8)
05-03 03:17:37.044: E/AndroidRuntime(1854): FATAL EXCEPTION: main
05-03 03:17:37.044: E/AndroidRuntime(1854): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jumoun.itemp/com.jumoun.itemp.Converter}: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.os.Looper.loop(Looper.java:137)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread.main(ActivityThread.java:4427)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at java.lang.reflect.Method.invokeNative(Native Method)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at java.lang.reflect.Method.invoke(Method.java:511)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at dalvik.system.NativeStart.main(Native Method)
05-03 03:17:37.044: E/AndroidRuntime(1854): Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button
05-03 03:17:37.044: E/AndroidRuntime(1854):     at com.jumoun.itemp.Converter.onCreate(Converter.java:41)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.Activity.performCreate(Activity.java:4465)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
05-03 03:17:37.044: E/AndroidRuntime(1854):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
05-03 03:17:37.044: E/AndroidRuntime(1854):     ... 11 more
05-03 03:17:38.704: I/Process(1854): Sending signal. PID: 1854 SIG: 9

这是我的java文件Converter.java http://pastebin.com/VNNPy7D5

谢谢你们：）

Answer 1

如果我算上这个

ibHome3 = (Button) findViewById(R.id.ibHome3);

导致您的问题。你在xml中将它作为ImageButton但在java声明中作为Button。只需将其更改为

即可

ImageButton ibHome3;

关于Logcat

另外，关于logcat的一点建议。如果您在Caused By之后找到第Fatal Exception行，则可以更轻松地追踪问题。这是

 Caused by: java.lang.ClassCastException: android.widget.ImageButton cannot be cast to android.widget.Button

这给出了异常

java.lang.ClassCastException

然后找到引用你的包之后的第一行。在这里

at com.jumoun.itemp.Converter.onCreate(Converter.java:41)

这告诉我们问题从第41行的Converter.java开始

Answer 2

布局文件中有两个按钮，对吗？它们看起来在XML文件中被定义为ImageButton。在您的Activity中，您将其声明为Button并尝试使用强制转换转换为（Button）。在Activity文件中将类型更改为ImageButton。它可以解决你的问题。

Answer 3

在第41行，您必须将按钮投射到ImageButton而不是按钮：

ibHome3 = (ImageButton) findViewById(R.id.ibHome3);

Android中有3项活动的多项活动

3 个答案: