膨胀自定义按钮类时出错.NoSuchMethodException

Question

我正在尝试创建一个包含两个文本字段的自定义按钮.当我从代码创建实例时,它可以工作.当我尝试从XML充气时,它会崩溃.

到目前为止我尝试解决这个问题:

• 遵循并理解SDK中的LabelView代码示例.
• 接下来,了解这个优秀的Devoxx自定义FlowLayout演示文稿.
• 跟随并理解了关于该主题的大量教程.
• 花了不少时间审查stackoverflow上的类似问题.
• 将代码剥离回简单地将属性集传递给超类的基础知识.

从我读过的问题来看,最常见的原因是没有定义获取属性集所需的构造函数即

MyClass(Context context, AttributeSet attrs) {
    super(context, attrs);
}

在LogCat的错误列表的末尾附近,我有:

Caused by: java.lang.NoSuchMethodException: <init> [class android.content.Context, interface android.util.AttributeSet]

这可能会导致我得出与其他许多人一样的错误的结论,但是当你查看下面的代码时,你可以看到我已经定义了这个表单的构造函数.

我似乎完全像所有消息来源所说的那样做.我只是看不到我错过的东西.

SRC/com.soundconception.custombuttontest2/TitledValueButton.java

package com.soundconception.custombuttontest2;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.Button;

public class TitledValueButton extends Button {

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

    protected TitledValueButton(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
}

RES /值/ attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="TitledValueButton">
        <attr name="titleText" format="string" />
    </declare-styleable>

</resources>

RES /布局/ activity_main.xml中

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res/com.soundconception.custombuttontest2"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

        <com.soundconception.custombuttontest2.TitledValueButton 
            android:id="@+id/test_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="1..2..3.."
            app:titleText="Testing" />

</RelativeLayout>

SRC/com.soundconception.custombuttontest2/MainActivity.java

package com.soundconception.custombuttontest2;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

logcat的

threadid=1: thread exiting with uncaught exception (group=0x41a5a700)
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.soundconception.custombuttontest2/com.soundconception.custombuttontest2.MainActivity}: android.view.InflateException: Binary XML file line #13: Error inflating class com.soundconception.custombuttontest2.TitledValueButton
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class com.soundconception.custombuttontest2.TitledValueButton
at android.view.LayoutInflater.createView(LayoutInflater.java:603)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:696)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:755)
at android.view.LayoutInflater.inflate(LayoutInflater.java:492)
at android.view.LayoutInflater.inflate(LayoutInflater.java:397)
at android.view.LayoutInflater.inflate(LayoutInflater.java:353)
at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:267)
at android.app.Activity.setContentView(Activity.java:1895)
at com.soundconception.custombuttontest2.MainActivity.onCreate(MainActivity.java:12)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
... 11 more
Caused by: java.lang.NoSuchMethodException: <init> [class android.content.Context, interface android.util.AttributeSet]
at java.lang.Class.getConstructorOrMethod(Class.java:423)
at java.lang.Class.getConstructor(Class.java:397)
at android.view.LayoutInflater.createView(LayoutInflater.java:568)
... 22 more

Answer 1

缺少此构造函数:

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

    }

将此构造函数添加到自定义按钮类.

Answer 2

缺少一个构造函数.添加此项以删除崩溃.

记住构造函数必须处于公共模式.

public TitledValueButton(Context context, AttributeSet attrs) {

    super(context, attrs); // This should be first line of constructor 
}

和

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

}

记住构造函数必须处于公共模式.

Answer 3

尝试在布局中声明非静态内部类时（使用美元符号），我遇到了相同的错误消息。只需在static我的班级中添加键盘密码即可使其工作。