在app中强制关闭错误

Question

我在运行我的应用时遇到问题，但我无法找出问题所在！我创建了第一个有两个按钮的屏幕。这个“主页”屏幕是chordsApp.java。如果我按下第一个按钮，我想去track1.java，如果按第二个按钮，我想去track2.java！该程序运行，但当我试图按下第一个或第二个按钮时，它会弹出一个错误并告诉我强制关闭!!这是代码：

ChordApp.java

package com.example.ChordsApp;

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

public class ChordsApp extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Button next = (Button) findViewById(R.id.button);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), track1.class);
                startActivityForResult(myIntent,0);
            }

        });
        Button next1 = (Button) findViewById(R.id.button1);
        next1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), track2.class);
                startActivityForResult(myIntent, 0);
            }

        });

    }

}

track1.java

package com.example.ChordsApp;

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

public class track1 extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main2);

        Button next = (Button) findViewById(R.id.button3);
        next.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
                Intent intent = new Intent();
                setResult(RESULT_OK, intent);
                finish();
           }

       });

    }
}

track2.java

package com.example.ChordsApp;

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

public class track2 extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main3);

        Button next1 = (Button) findViewById(R.id.button4);
        next1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
                Intent intent = new Intent();
                setResult(RESULT_OK, intent);
                finish();
           }

       });

    }
}

main.xml中

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout 
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        >
        <ImageView 
            android:id="@+id/pic"
            android:adjustViewBounds="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/guitar"
            android:layout_gravity="center"
       />
        <TextView  
            android:layout_width="fill_parent" 
            android:layout_height="wrap_content" 
            android:text="@string/hello"
            />  
    <LinearLayout
       android:orientation="vertical"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal" >
            <Button
                android:text="track1"
                android:id="@+id/button"
                android:layout_width="250px"
                android:textSize="18px"
                android:layout_height="55px" />    
       <Button 
                android:text="track2"
                android:id="@+id/button1"
                android:layout_width="250px"
                android:textSize="18px"
                android:layout_height="55px" /> 
    </LinearLayout>
</LinearLayout>

main2.xml

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="hi"/>

<Button android:text="Home"
    android:id="@+id/button3"
    android:layout_width="250px"
        android:textSize="18px"
    android:layout_height="55px"
    android:layout_gravity="center_horizontal"
    > 

   </Button>  
</LinearLayout>

main3.xml

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:text="hi"/>

<Button android:text="Home"
    android:id="@+id/button4"
    android:layout_width="250px"
        android:textSize="18px"
    android:layout_height="55px"
    android:layout_gravity="center_horizontal"
    > 

</Button>  
</LinearLayout>