Question

这是LogCat，希望它有所帮助：

> 01-15 04:10:50.154: E/AndroidRuntime(369): FATAL EXCEPTION: main
>         01-15 04:10:50.154: E/AndroidRuntime(369): java.lang.RuntimeException: Unable to start activity
> ComponentInfo{com.guzi.uyproductions/com.guzi.uyproductions.MainActivity}:
> java.lang.ClassCastException: android.widget.ImageButton
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.os.Handler.dispatchMessage(Handler.java:99)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.os.Looper.loop(Looper.java:130)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread.main(ActivityThread.java:3683)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at java.lang.reflect.Method.invokeNative(Native Method)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at java.lang.reflect.Method.invoke(Method.java:507)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at dalvik.system.NativeStart.main(Native Method)
>         01-15 04:10:50.154: E/AndroidRuntime(369): Caused by: java.lang.ClassCastException: android.widget.ImageButton
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at com.guzi.uyproductions.MainActivity.onCreate(MainActivity.java:21)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
>         01-15 04:10:50.154: E/AndroidRuntime(369):    ... 11 more
>         01-15 04:10:52.874: I/Process(369): Sending signal. PID: 369 SIG: 9

这是.java：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Button button = (Button)findViewById(R.id.imageButton2);

    button.setOnClickListener(new OnClickListener() {
      public void onClick(View arg0) {
        Intent viewIntent =
          new Intent("android.intent.action.VIEW",
            Uri.parse("https://www.google.com"));
          startActivity(viewIntent);
      }
    });

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Answer 1

你好删除这一行Button button = (Button)findViewById(R.id.imageButton2);

并使用

ImageButton button = (ImageButton )findViewById(R.id.imageButton2);

您需要使用ImageButton，但使用的是Button

Answer 2

正如Jitesh已经解释过的那样，我只想补充一点，以消除一些混淆。

从ImageButton的名称我们可能认为它是Button类的子类（就像textview是View类）。这就是误解可能导致这个问题的原因。我们知道我们可以将子类强制转换为它的超类。

但是ImageButton不是Button类的子类（既不是直接也不是间接）所以你不能像你那样进行转换。这里发生了ClassCastException。

为什么我的应用程序不断崩溃

2 个答案: