android：ClassCastException：android.widget.spinner

Question

以下是我收到此错误的代码段：

final PatchedSpinner spinner = (PatchedSpinner) findViewById(R.id.ActivitySpinner);

这是xml：

<Spinner
    android:id="@+id/ActivitySpinner"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="33dp" />

而且在活动类中我实现了这个：

public class PatchedSpinner extends Spinner {

    public PatchedSpinner(Context context, AttributeSet attrs, int defStyle) { 
        super(context, attrs, defStyle); 
    } 

    public PatchedSpinner(Context context) { 
        super(context); 
    } 

    public PatchedSpinner(Context context, AttributeSet attrs) { 
        super(context, attrs); 
    }

    @Override 
    public boolean performClick() {
        // this line removed, we do not want to delegate the click to the spinner.
        // boolean handled = super.performClick(); 

        Context context = getContext();

        final DropDownAdapter adapter = new DropDownAdapter(getAdapter());

        CharSequence mPrompt = getPrompt();

        AlertDialog.Builder builder = new AlertDialog.Builder(context); 
        if (mPrompt != null) { 
            builder.setTitle(mPrompt); 
        } 
        builder.setSingleChoiceItems(adapter, getSelectedItemPosition(), this).show();

        return true; 
    }
}

我究竟做错了什么？ 我将微调器投射到PatchedSpinner，它扩展了Spinner ......

堆栈跟踪：

05-05 23:56:11.149: E/AndroidRuntime(368): FATAL EXCEPTION: main
05-05 23:56:11.149: E/AndroidRuntime(368): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.biohouse/com.example.biohouse.CalculateWatt}: android.view.InflateException: Binary XML file line #74: Error inflating class com.example.biohouse.PatchedSpinner
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.os.Looper.loop(Looper.java:123)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread.main(ActivityThread.java:4627)
05-05 23:56:11.149: E/AndroidRuntime(368):  at java.lang.reflect.Method.invokeNative(Native Method)
05-05 23:56:11.149: E/AndroidRuntime(368):  at java.lang.reflect.Method.invoke(Method.java:521)
05-05 23:56:11.149: E/AndroidRuntime(368):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-05 23:56:11.149: E/AndroidRuntime(368):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-05 23:56:11.149: E/AndroidRuntime(368):  at dalvik.system.NativeStart.main(Native Method)
05-05 23:56:11.149: E/AndroidRuntime(368): Caused by: android.view.InflateException: Binary XML file line #74: Error inflating class com.example.biohouse.PatchedSpinner
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:576)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.rInflate(LayoutInflater.java:618)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.inflate(LayoutInflater.java:407)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.inflate(LayoutInflater.java:320)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.inflate(LayoutInflater.java:276)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.support.v7.app.ActionBarActivityDelegateBase.setContentView(ActionBarActivityDelegateBase.java:128)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.support.v7.app.ActionBarActivity.setContentView(ActionBarActivity.java:76)
05-05 23:56:11.149: E/AndroidRuntime(368):  at com.example.biohouse.CalculateWatt.onCreate(CalculateWatt.java:41)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
05-05 23:56:11.149: E/AndroidRuntime(368):  ... 11 more
05-05 23:56:11.149: E/AndroidRuntime(368): Caused by: java.lang.ClassNotFoundException: com.example.biohouse.PatchedSpinner in loader dalvik.system.PathClassLoader[/data/app/com.example.biohouse-1.apk]
05-05 23:56:11.149: E/AndroidRuntime(368):  at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:243)
05-05 23:56:11.149: E/AndroidRuntime(368):  at java.lang.ClassLoader.loadClass(ClassLoader.java:573)
05-05 23:56:11.149: E/AndroidRuntime(368):  at java.lang.ClassLoader.loadClass(ClassLoader.java:532)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.createView(LayoutInflater.java:466)
05-05 23:56:11.149: E/AndroidRuntime(368):  at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:565)
05-05 23:56:11.149: E/AndroidRuntime(368):  ... 20 more

Answer 1

我认为您需要将相关的类名称调用为com.package.name.CustomWidget而不是视图中的默认窗口小部件Spinner ，如下所示：

<com.package.name.PatchedSpinner
    android:id="@+id/ActivitySpinner"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_below="@+id/textView1"
    android:layout_marginTop="33dp" />  

如果没有提到，活动会尝试找到默认的android.widget.Spinner而你用PatchedSpinner声明了这个。 它可能是ClassCastException的原因。

另外，请确保自定义类具有正确的构造函数：

public class PatchedSpinner extends Spinner {
    public PatchedSpinner(Context context) {
        super(context);
    }
    public PatchedSpinner(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    public PatchedSpinner(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }
}