即使AppCompatImageButton不是ImageButton，也无法将其强制转换为android.widget.Button

时间：2018-07-19 20:18:51

标签： android

我遇到了我无法理解的错误：

07-19 22:14:50.750 23192-23192/com.example.shun.zeatbeta E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.shun.zeatbeta, PID: 23192
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.shun.zeatbeta/com.example.shun.zeatbeta.ReauthenticateActivity}: java.lang.ClassCastException: android.support.v7.widget.AppCompatImageButton cannot be cast to android.widget.Button
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988)
        at android.app.ActivityThread.-wrap14(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1631)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6682)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
     Caused by: java.lang.ClassCastException: android.support.v7.widget.AppCompatImageButton cannot be cast to android.widget.Button
        at com.example.shun.zeatbeta.ReauthenticateActivity.onCreate(ReauthenticateActivity.java:59)
        at android.app.Activity.performCreate(Activity.java:6942)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2880)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988) 
        at android.app.ActivityThread.-wrap14(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1631) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6682) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410) 

在活动中使程序崩溃的行：

private Button loginButton;

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

activity_reauthenticate2.xml： 

<com.example.shun.zeatbeta.ComfortaaButton
    android:id="@+id/loginButton"
    android:layout_width="match_parent"
    android:layout_height="@dimen/button_height"
    android:layout_marginTop="20dp"
    android:background="@drawable/round_button_blue"
    android:text="@string/login"
    android:textColor="@color/white"
    android:textSize="15dp"
    app:layout_constraintBottom_toTopOf="@id/facebookWrapper"
    app:layout_constraintTop_toBottomOf="@id/textFields" />

ComfortaaButton.java 

package com.example.shun.zeatbeta;

import android.content.Context;
import android.graphics.Typeface;
import android.support.v7.widget.AppCompatButton;
import android.util.AttributeSet;

public class ComfortaaButton extends AppCompatButton {
    public ComfortaaButton(Context context) {
        super(context);
        init();
    }
    public ComfortaaButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    public ComfortaaButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }
    public void init() {
        Typeface tf = Typeface.createFromAsset(getContext().getAssets(), "font/Comfortaa-Regular.ttf");
        setTypeface(tf, 1);
    }

}

为什么会出现此错误？该按钮显然是Button，而不是ImageButton。我尝试清理项目，重新启动，清除缓存等。甚至尝试创建新的活动和布局文件，错误再次出现！

更新：我在活动中获得了该行崩溃的代码的信息：

Unexpected cast to AppCompatButton: layout tag was ImageButton (Id bound to an ImageButton in activity_landing_page.xml) less... (⌘F1) 
Keeps track of the view types associated with ids and if it finds a usage of the id in the Java code it ensures that it is treated as the same type.

因此，似乎它在activity_landing_page.xml中而不是activity_reauthenticate2.xml中按ID查找活动。为什么？我该如何更改？

应用程序gradle： 

apply plugin: 'com.android.application'

android {
    compileSdkVersion 27
    buildToolsVersion '27.0.3'
    defaultConfig {
        applicationId "com.example.s.company"
        minSdkVersion 17
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        vectorDrawables.useSupportLibrary = true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation 'com.android.support:support-v4:27.1.1'
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    implementation 'com.facebook.android:facebook-android-sdk:4.33.0'
    implementation 'com.android.support:design:27.1.1'
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.github.bumptech.glide:glide:4.7.1'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.7.1'
    implementation 'com.stripe:stripe-android:6.1.2'
    compile 'com.google.firebase:firebase-auth:15.0.0'
    compile 'com.google.firebase:firebase-core:15.0.0'
    compile 'com.google.firebase:firebase-database:15.0.0'
    compile 'com.google.firebase:firebase-storage:15.0.0'
    compile 'com.firebaseui:firebase-ui-storage:3.3.1'
    compile 'com.android.volley:volley:1.1.0'
    compile 'com.felipecsl.asymmetricgridview:library:2.0.1'
    compile 'com.google.android.gms:play-services-maps:15.0.1'
    compile 'com.nostra13.universalimageloader:universal-image-loader:1.9.5'
    compile 'com.github.ittianyu:BottomNavigationViewEx:1.2.1'
    compile 'com.squareup.picasso:picasso:2.5.2'
    compile 'com.android.support.constraint:constraint-layout:1.1.0'
    compile 'com.github.arimorty:floatingsearchview:2.1.1'
    implementation 'info.hoang8f:android-segmented:1.0.6'
    testCompile 'junit:junit:4.12'

}

apply plugin: 'com.google.gms.google-services'

3 个答案:

答案 0 :(得分：1)

您的loginButton必须有其他重复ID。只要确保您从R.id.loginButton中输入loginButton = (Button) findViewById(R.id.loginButton);作为目标Activity或xml即可正确导入。

答案 1 :(得分：0)

更新： 按钮也应该可以正常工作。

以AppCompatButton初始化视图，

private AppCompatButton mLoginButton;

mLoginButton=findViewById(R.id.loginButton);

答案 2 :(得分：-1)

//我错误编码时出现这个错误 val deleteButton = itemView.findViewById<(Button)>(R.id.item_delete_button) //实际上在 XML 文件中，我使用了图像视图而不是按钮来使该图像 // 可点击。 // 所以我把 <(Button)> 改成了 <(ImageView)>。然后这个问题就解决了。

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