为自定义对话框扩展视图时出现 ClassCastException

Question

我正在尝试向 Android 应用程序添加自定义对话框类型，但每当我按下应该打开对话框的按钮时，我都会强制关闭。

强制关闭的日志输出如下：

06-05 22:53:28.413: ERROR/AndroidRuntime(187): Uncaught handler: thread main exiting due to uncaught exception
06-05 22:53:28.453: ERROR/AndroidRuntime(187): java.lang.IllegalStateException: Could not execute method of the activity
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.View$1.onClick(View.java:2027)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.View.performClick(View.java:2344)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.View.onTouchEvent(View.java:4133)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.widget.TextView.onTouchEvent(TextView.java:6510)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.View.dispatchTouchEvent(View.java:3672)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:882)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1712)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1202)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.app.Activity.dispatchTouchEvent(Activity.java:1987)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1696)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1658)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.os.Looper.loop(Looper.java:123)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.app.ActivityThread.main(ActivityThread.java:4203)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at java.lang.reflect.Method.invokeNative(Native Method)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at java.lang.reflect.Method.invoke(Method.java:521)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at dalvik.system.NativeStart.main(Native Method)
06-05 22:53:28.453: ERROR/AndroidRuntime(187): Caused by: java.lang.reflect.InvocationTargetException
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at nocom.autophage.bikecalc.BikeCalcMainMenu.showAddMeasurementDialog(BikeCalcMainMenu.java:69)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at java.lang.reflect.Method.invokeNative(Native Method)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at java.lang.reflect.Method.invoke(Method.java:521)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.view.View$1.onClick(View.java:2022)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     ... 21 more
06-05 22:53:28.453: ERROR/AndroidRuntime(187): Caused by: java.lang.ClassCastException: android.widget.Button
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at nocom.autophage.bikecalc.BikeCalcMainMenu.onCreateDialog(BikeCalcMainMenu.java:48)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.app.Activity.createDialog(Activity.java:867)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     at android.app.Activity.showDialog(Activity.java:2408)
06-05 22:53:28.453: ERROR/AndroidRuntime(187):     ... 25 more

创建对话框的代码如下所示： 案例 DIALOG_ADD_MEASUREMENT： AlertDialog.Builder addMeasurementBuilder；

        Context mContext = getApplicationContext();
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
        View layout = inflater.inflate(R.layout.add_measurement_dialog,
                                       (ViewGroup) findViewById(R.id.add_measurement_dialog));
        addMeasurementBuilder = new AlertDialog.Builder(mContext);
        addMeasurementBuilder.setView(layout);
        dialog = addMeasurementBuilder.create();
        break;

对话框的 XML（这是我最有信心的部分）是：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:id="@+id/add_measurement_dialog">

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/add_measurement_dialog_title" />

<Spinner
android:id="@+id/add_measurement_spinner"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:prompt="@string/add_measurement_prompt" />

<EditText
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/add_measurement_value" />

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:text="@string/calc"
android:onClick="showFeatureNotYetImplementedToast" />

<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal">

    <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:text="@string/cancel"
    android:onClick="showFeatureNotYetImplementedToast" />

    <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:text="@string/add"
    android:onClick="showFeatureNotYetImplementedToast" />  

</LinearLayout>

</LinearLayout>

我唯一能想到的是，也许我不应该使用对话框的 xml 根元素的 id 作为viewgroup...但我不知道我还要在充气器调用中添加什么内容。

编辑：以及 BikeCalcMainMenu.java 的完整内容： 包 nocom.autophage.bikecalc；

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

public class BikeCalcMainMenu extends Activity {
    /** Called when the activity is first created. */

    static final int DIALOG_HELP = 0;
    static final int DIALOG_ADD_MEASUREMENT = 1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }

    protected Dialog onCreateDialog(int id) {
        Dialog dialog;
        switch(id) {
        case DIALOG_HELP:
            AlertDialog.Builder helpBuilder = new AlertDialog.Builder(this);
            helpBuilder.setMessage(getText(R.string.h_help_text))
                   .setCancelable(false)
                   .setNeutralButton("OK", new DialogInterface.OnClickListener() {
                       public void onClick(DialogInterface dialog, int id) {
                            dismissDialog(DIALOG_HELP);
                       }
                   });
            AlertDialog helpAlert = helpBuilder.create();
            dialog = helpAlert;
            break;
        case DIALOG_ADD_MEASUREMENT:
            AlertDialog.Builder addMeasurementBuilder;
 //         AlertDialog dialog;

            Context mContext = getApplicationContext();
            LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
            View layout = inflater.inflate(R.layout.add_measurement_dialog, (ViewGroup) findViewById(R.id.add_measurement_dialog));
            addMeasurementBuilder = new AlertDialog.Builder(mContext);
            addMeasurementBuilder.setView(layout);
            dialog = addMeasurementBuilder.create();
            break;
        default:
            dialog = null;
        }
        return dialog;
    }

    public void showHelpScreenDialog(View v) {
        showDialog(DIALOG_HELP);
    }

    public void showNotYetImplementedToast(View v) {
        Toast not_yet_implemented_toast = Toast.makeText(getApplicationContext(), getText(R.string.feature_not_implemented), Toast.LENGTH_SHORT);
        not_yet_implemented_toast.show();
    }

    public void showAddMeasurementDialog(View v) {
        showDialog(DIALOG_ADD_MEASUREMENT);
    }
}

Answer 1

您是否尝试过删除 XML 中的 onClick 属性？

当它尝试绑定它们时可能会出现问题，因为它们不存在

（另外，您使用应用程序上下文有什么特殊原因吗？）

Answer 2

我还没有测试过这一点，但我相信这条线会导致你的问题

View layout = inflater.inflate(R.layout.add_measurement_dialog, (ViewGroup) findViewById(R.id.add_measurement_dialog));

如果你提供第二个参数来膨胀，那么你实际上会得到那个父组。考虑在这里传递 null 。

授予 http://developer .android.com/reference/android/view/LayoutInflater.html#inflate%28int,%20android.view.ViewGroup%29 了解详细信息

Answer 3

在解决类似的问题时，我刚刚用头撞了一两堵墙。

尝试调用 addMeasurementBuilder = new AlertDialog.Builder(this); （而不是使用 mContext）并查看是否有效。

Android 开发人员的对话框教程传递了 getApplicationContext() 的结果，但我测试了代码（复制和粘贴），它也崩溃了！非常糟糕的形式，谷歌。

我在这个问题中找到了答案。