应用程序正在强制关闭，但我不知道为什么

Question

I can't get an emulator working on my slow computer so I have to go through the process of loading my app into a physical device. Well it compiles all fine and I can't notice any obvious error but it doesn't want to run. It started happening after I followed a tutorial on how to go from page to another. Everything looks good in comparison to the Tutorial.

Manifest File

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

    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" android:hardwareAccelerated="false">
        <activity
            android:name="com.example.mcesfireassist.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:label="@string/app_name"
                android:name=".App2Activity" >
            </activity>

  </application>

</manifest>

Main XML

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@layout/activity_main"
    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" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/home_intro" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="54dp"
        android:ems="10"
        android:inputType="number"
        android:singleLine="true"
        android:text="@string/Unit_num" >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:ems="10"
        android:inputType="textNoSuggestions|textShortMessage"
        android:text="@string/asn" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/editText2"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="38dp"
        android:text="@string/start_button" />

</RelativeLayout>

Main Java File

package com.example.mcesfireassist;

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

public class MainActivity extends Activity {
    Button button;

    @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; 
        }


    public void addListenerOnButton() {
        final Context context = this;
        button = (Button) findViewById (R.id.button1);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {

                Intent intent = new Intent(context, App2Activity.class);
                            startActivity(intent);   

        }
        });

}

}

If you would like to see the java and xml of the second page I can add it, I just didn't wanna make the post any longer then necessary.

Answer 1

You code is not functioning because you never call the addListenerOnButton() method. An OnClickListener is never attached to the Button . In fact, a reference to the button doesn't even exist in your activity.

You can either call addListenerOnButton() after setContentView(R.layout.activity_main) or try the following code that includes a few changes:

package com.example.mcesfireassist;

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

public class MainActivity extends Activity {
    Button button;

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

        button = (Button) findViewById (R.id.button1);
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0) {

                Intent intent = new Intent(MainActivity.this, App2Activity.class);
                startActivity(intent);   

            }
        });
    }


    @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; 
    }

}

Edit 1:

Please change the following code:

<activity
    android:label="@string/app_name"
    android:name=".App2Activity" >
</activity>

to:

<activity
    android:label="@string/app_name"
    android:name="com.example.mcesfireassist.App2Activity" >
</activity>