我的应用程序的所有页面中都有一个“菜单”图像视图，如果单击菜单，所有菜单项（如登录、主页、工作、关于）都会打开，如果我单击“关于”菜单项，应用程序会强制关闭并获取“菜单的 OnClicklistener”出现空指针异常，但其他菜单项没有此问题，请问有人可以解决这个问题吗？
public class About extends Activity {
LinearLayout line1, line2;
ImageView menu;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_about);
menu.setOnClickListener(new View.OnClickListener() {
ImageView menu = (ImageView)findViewById(R.id.menu);
public void onClick(View v) {
menu.setVisibility(View.VISIBLE);
// TODO Auto-generated method stub
line1.setVisibility(View.VISIBLE);
if (line2.getVisibility() == View.INVISIBLE || line2.getVisibility() == View.GONE) {
line2.setVisibility(View.VISIBLE); }
else {
line2.setVisibility(View.INVISIBLE);
}
}
});
ImageView home = (ImageView) findViewById(R.id.home);
home.setOnClickListener(new View.OnClickListener() {
public void onClick(View v){
startActivity(new Intent(About.this, Home.class));
}
});
ImageView jobs = (ImageView) findViewById(R.id.jobs);
jobs.setOnClickListener(new View.OnClickListener() {
public void onClick(View v){
startActivity(new Intent(About.this, Jobs.class));
}
});
ImageView log = (ImageView) findViewById(R.id.log);
log.setOnClickListener(new View.OnClickListener() {
public void onClick(View v){
startActivity(new Intent(About.this, Login.class));
}
});
ImageView about = (ImageView) findViewById(R.id.about);
about.setOnClickListener(new View.OnClickListener() {
public void onClick(View v){
startActivity(new Intent(getApplicationContext(), About.class));
}
});
}
XML 文件
<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="@color/black" >
<LinearLayout
android:id="@+id/ll1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="@color/black"
android:layout_alignParentTop="true"
android:layout_alignParentRight="true">
<ImageView
android:id="@+id/menu"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/menu" />
</LinearLayout>
<LinearLayout
android:id="@+id/ll2"
android:layout_width="199dp"
android:layout_height="wrap_content"
android:background="@color/black"
android:layout_toRightOf="@+id/ll1"
android:visibility="gone"
>
<ImageView
android:id="@+id/about"
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_above="@+id/textView1"
android:layout_toLeftOf="@+id/jobs"
android:src="@drawable/about" />
<ImageView
android:id="@+id/jobs"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/jobs" />
<ImageView
android:id="@+id/log"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/log" />
<ImageView
android:id="@+id/home"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/home" />
</LinearLayout>
<TextView
android:id="@+id/textView3"
android:layout_width="match_parent"
android:layout_height="50dip"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:background="@color/white"
android:textColor="@color/white"/>
<TextView
android:id="@+id/textView4"
android:layout_width="match_parent"
android:layout_height="710dp"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView1"
android:layout_marginTop="46dp"
android:text="@string/AboutPage"
android:textColor="@color/white" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/ll1"
android:layout_centerHorizontal="true"
android:layout_marginTop="26dp"
android:text="@string/WelcometoRebuixcom"
android:textAppearance="?android:attr/textAppearanceLarge"
android:textColor="@color/white" />