以下代码引发 NullPointerException，我不知道为什么。问题似乎是我没有正确引用 EditText 对象。但我不知道如何使它正确。
这是我的代码中有趣的部分：
private static ArrayList<String> roomList = new ArrayList<String>();
private static ArrayList<String> deviceList = new ArrayList<String>();
private static String project_name;
private static String router_ip;
private static String port;
private static String device_name;
private static String room_name;
private static String datatype;
private static String grpaddr;
private static boolean status;
private EditText et_project_name;
private EditText et_router_ip;
private EditText et_port;
private Spinner spinner_dpt;
private CheckBox cb_checkStatus;
private EditText et_device_name;
private EditText et_groupaddress;
private View textEntryView;
private static final String[] items={"1.001 (Lichtschalter)", "5.001 (Dimmer/Jalousien)",
"9.001 (Temperaturanzeige)", "1.008 (Jalousien)"};
private SectionsPagerAdapter mSectionsPagerAdapter;
private ViewPager mViewPager;
private static ManualConfigDBAdapter dbHelper;
/**
* OnCreate
* */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_create_project_manually);
setup();
}
/**
* Setup
* */
public void setup(){
//DATABASE
// Add project to Database
dbHelper = new ManualConfigDBAdapter(this);
dbHelper.open();
// Create the adapter that will return a fragment for each of the three primary sections
// of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the action bar.
final ActionBar actionBar = getActionBar();
// set the app icon as an action to go home
actionBar.setDisplayHomeAsUpEnabled(true);
//enable tabs in actionbar
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding tab.
// We can also use ActionBar.Tab#select() to do this if we have a reference to the
// Tab.
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by the adapter.
// Also specify this Activity object, which implements the TabListener interface, as the
// listener for when this tab is selected.
actionBar.addTab(
actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
//get the controls from the layout
et_project_name = (EditText) mViewPager.findViewById(R.id.project_name);
et_router_ip = (EditText) mViewPager.findViewById(R.id.router_ip);
et_port = (EditText) mViewPager.findViewById(R.id.port);
//Use a input filter for the input of the IP adress
InputFilter[] filters = new InputFilter[1];
filters[0] = new InputFilter() {
public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
if (end > start) {
String destTxt = dest.toString();
String resultingTxt = destTxt.substring(0, dstart) + source.subSequence(start, end) + destTxt.substring(dend);
if (!resultingTxt.matches ("^\\d{1,3}(\\.(\\d{1,3}(\\.(\\d{1,3}(\\.(\\d{1,3})?)?)?)?)?)?")) {
return "";
} else {
String[] splits = resultingTxt.split("\\.");
for (int i=0; i<splits.length; i++) {
if (Integer.valueOf(splits[i]) > 255) {
return "";
}
}
}
}
return null;
}
};
et_router_ip.setFilters(filters);
}
和 LogCat：
02-16 20:09:25.755: E/AndroidRuntime(26658): FATAL EXCEPTION: main
02-16 20:09:25.755: E/AndroidRuntime(26658): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.bertrandt.bertrandtknx/de.bertrandt.bertrandtknx.CreateProjectManually}: java.lang.NullPointerException
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1970)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread.access$600(ActivityThread.java:128)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.os.Handler.dispatchMessage(Handler.java:99)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.os.Looper.loop(Looper.java:137)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread.main(ActivityThread.java:4514)
02-16 20:09:25.755: E/AndroidRuntime(26658): at java.lang.reflect.Method.invokeNative(Native Method)
02-16 20:09:25.755: E/AndroidRuntime(26658): at java.lang.reflect.Method.invoke(Method.java:511)
02-16 20:09:25.755: E/AndroidRuntime(26658): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
02-16 20:09:25.755: E/AndroidRuntime(26658): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
02-16 20:09:25.755: E/AndroidRuntime(26658): at dalvik.system.NativeStart.main(Native Method)
02-16 20:09:25.755: E/AndroidRuntime(26658): Caused by: java.lang.NullPointerException
02-16 20:09:25.755: E/AndroidRuntime(26658): at de.bertrandt.bertrandtknx.CreateProjectManually.setup(CreateProjectManually.java:152)
02-16 20:09:25.755: E/AndroidRuntime(26658): at de.bertrandt.bertrandtknx.CreateProjectManually.onCreate(CreateProjectManually.java:75)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.Activity.performCreate(Activity.java:4562)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053)
02-16 20:09:25.755: E/AndroidRuntime(26658): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934)
02-16 20:09:25.755: E/AndroidRuntime(26658): ... 11 more
02-16 20:09:25.770: D/dalvikvm(26658): GC_CONCURRENT freed 396K, 4% free 14704K/15303K, paused 2ms+3ms
使用的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" >
<RelativeLayout
android:id="@+id/project_save_text"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:background="@color/black"
android:orientation="vertical" >
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginTop="10dp"
android:text="@string/project_name"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/project_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView2"
android:ems="10"
android:hint="@string/project_name_hint" >
</EditText>
<TextView
android:id="@+id/textView4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/project_name"
android:layout_marginTop="10dp"
android:text="@string/router_ip"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/router_ip"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView4"
android:digits="0123456789."
android:ems="10"
android:hint="@string/router_adress_info"
android:inputType="numberDecimal|phone" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:contentDescription="@string/placeholder"
android:src="@drawable/bertrandtlogoinv" />
<TextView
android:id="@+id/info_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/imageView1"
android:layout_alignParentLeft="true"
android:gravity="center"
android:text="@string/info_settings"
android:textAppearance="?android:attr/textAppearanceSmall"
android:textSize="16dp" />
<ImageView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ImageView1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_above="@+id/info_text"
android:layout_alignParentLeft="true"
android:contentDescription="@string/placeholder"
android:paddingBottom="2dp"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:paddingTop="2dp"
android:scaleType="fitXY"
android:src="@color/ics_blue" />
<ImageView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/ImageView01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignTop="@+id/imageView1"
android:contentDescription="@string/placeholder"
android:paddingBottom="2dp"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:paddingTop="2dp"
android:scaleType="fitXY"
android:src="@color/ics_blue" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/router_ip"
android:layout_marginTop="10dp"
android:text="@string/Port"
android:textAppearance="?android:attr/textAppearanceMedium" />
<EditText
android:id="@+id/port"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/textView3"
android:digits="0123456789"
android:ems="10"
android:hint="@string/port_hint"
android:inputType="number"
android:maxLength="5" />
</RelativeLayout>
</RelativeLayout>
以下行引发错误：
et_router_ip.setFilters(filters);
解决方案
要使用视图寻呼机创建 3 个不同的片段，您应该：
1）使用视图寻呼机和视图寻呼机适配器创建 FragmentActivity。
2）用静态实例创建3个片段
public final class Fragment1 extends Fragment
{
public static Fragment1 newInstance() {
return new Fragment1();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
LinearLayout layout = new LinearLayout(getActivity());
// your fragment xml view
return view;
}
}
3）用它填充视图寻呼机适配器；
public class FragmentAdapter extends FragmentPagerAdapter
{
public InstallFragmentAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return Fragment1.newInstance();
case 1:
return Fragment2.newInstance();
case 2:
return Fragment3.newInstance();
}
return null;
}
}