Question

当按下一个按钮来切换意图时，我得到了芝加哥火车追踪器意外停止和一个logcat：

09-02 19:54:15.745: D/AndroidRuntime(20681): Shutting down VM
09-02 19:54:15.745: W/dalvikvm(20681): threadid=1: thread exiting with uncaught exception (group=0x41ab6700)
09-02 19:54:15.755: E/AndroidRuntime(20681): FATAL EXCEPTION: main
09-02 19:54:15.755: E/AndroidRuntime(20681): java.lang.IllegalStateException: Could not find a method sendMessage(View) in the activity class com.dev.chicagotraintracker.MainActivity for onClick handler on view class android.widget.ImageButton with id 'Button'
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.view.View$1.onClick(View.java:3620)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.view.View.performClick(View.java:4240)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.view.View$PerformClick.run(View.java:17721)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.os.Handler.handleCallback(Handler.java:730)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.os.Handler.dispatchMessage(Handler.java:92)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.os.Looper.loop(Looper.java:137)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.app.ActivityThread.main(ActivityThread.java:5103)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at java.lang.reflect.Method.invokeNative(Native Method)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at java.lang.reflect.Method.invoke(Method.java:525)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at dalvik.system.NativeStart.main(Native Method)
09-02 19:54:15.755: E/AndroidRuntime(20681): Caused by: java.lang.NoSuchMethodException: sendMessage [class android.view.View]
09-02 19:54:15.755: E/AndroidRuntime(20681):    at java.lang.Class.getConstructorOrMethod(Class.java:423)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at java.lang.Class.getMethod(Class.java:787)
09-02 19:54:15.755: E/AndroidRuntime(20681):    at android.view.View$1.onClick(View.java:3613)
09-02 19:54:15.755: E/AndroidRuntime(20681):    ... 11 more
09-02 19:54:16.875: I/Process(20681): Sending signal. PID: 20681 SIG: 9

我的代码是：

MainActivity.java

package com.dev.chicagotraintracker;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {


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


    public void login_Click(View v) {;
Intent myIntent = new Intent(MainActivity.this, Screenmap.class);
startActivityForResult(myIntent, 0);


    }

    public void onClick(View v) {
        // TODO Auto-generated method stub

    }

;

}

Screenmap.java

package com.dev.chicagotraintracker;

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


public class Screenmap extends Activity {

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

和AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.dev.chicagotraintracker"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="17" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.dev.chicagotraintracker.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity android:name="Screenmap" android:label="Screenmap"></activity>
</application>

</manifest>

Answer 1

异常似乎很清楚：

java.lang.IllegalStateException：在活动类com.dev.chicagotraintracker.MainActivity中找不到方法sendMessage（View）`

错误是因为您在android:onClick="sendMessage"中定义的ImageButton中提到了activity_main.xml，但您的sendMessage()中没有任何MainActivity功能。这就是你得到错误的原因。您需要在MainActivity中定义该函数，告诉它在单击ImageButton时应该发生什么。所以在该函数内部按钮点击时应执行的代码。

例如：如果您想在按钮上开始新活动，请执行以下操作：

public void sendMessage(View v){ 

    Intent myIntent = new Intent(MainActivity.this, Screenmap.class);   
    startActivityForResult(myIntent, 0); 

}

将这段代码放在onCreate()之外，作为一个不同的函数。

Answer 2

您必须在名为sendMessage的活动中实施一种方法，因为logcat说

您MainActivity.java

中的类似内容

public void sendMessage(View)
{
\\ do your stuff
}

以及下一个错误也是因为这个

 <activity android:name="Screenmap" android:label="Screenmap"></activity>

应该是这样的

 <activity android:name=".Screenmap" android:label="Screenmap"></activity>

或者

<activity android:name="com.dev.chicagotraintracker.Screenmap" android:label="Screenmap">
</activity>

不要忘记android:name=".Screenmap"“。”在活动名称之前创建类的完整路径

Answer 3

您的activity_main.xml指定在单击ImageButton时，它应调用sendMessage方法，但是，您尚未在活动中创建sentMessage方法。

在主活动中将方法实现为public void sendMessage(View view){ // code }时，同样重要的是要注意View参数是对单击的ImageButton的引用。

按下按钮切换视图时出错

3 个答案:

或者