嘿伙计们我正在尝试创建一个像google playstore标签的视图寻呼机指示器，我跟随这个例子
但由于某种原因，它给了我一个空指针异常。
我有一个名为NewOrder的活动，它扩展了Activity，而在setContentView上我有以下布局
我的xml布局是：
<LinearLayout 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:orientation="vertical">
<com.astuetz.PagerSlidingTabStrip
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="48dip" />
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:id="@+id/pager"
android:layout_weight="1"
android:layout_height="0px" />
</LinearLayout>
我创建了一个用于创建可滑动标签的适配器。
我的适配器：
public class TabsPagerAdapter extends FragmentPagerAdapter {
private final String[] TITLES = { "Coffees", "Sweets", "Snacks", "Drinks" };
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch (i) {
case 0:
return new CoffeesFragment();
case 1:
return new SweetsFragment();
case 2:
return new SnacksFragment();
case 3:
return new DrinksFragment();
}
return null;
}
@Override
public int getCount() {
return TITLES.length;
}
@Override
public CharSequence getPageTitle(int position) {
return TITLES[position];
}
}
对于我返回的每个片段，我都有一个具有不同布局的单独片段。
现在问题是我使用
<com.astuetz.PagerSlidingTabStrip
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="48dip" />
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:id="@+id/pager"
android:layout_weight="1"
android:layout_height="0px" />
我应该将它们放在每个片段的布局上还是放在父活动布局中？
我应该这样吗？<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:descendantFocusability="beforeDescendants"
android:focusableInTouchMode="true"
android:layout_height="match_parent"
tools:context="com.example.kostas.fragments.CoffeesFragment">
<com.astuetz.PagerSlidingTabStrip
android:id="@+id/tabs"
android:layout_width="match_parent"
android:layout_height="48dip" />
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:id="@+id/pager"
android:layout_weight="1"
android:layout_height="wrap_content" />
<LinearLayout
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Search..."
android:id="@+id/searchListCoffees" />
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/coffesListView" />
</LinearLayout>
</RelativeLayout>
这是我设置标签的地方
public class NewOrder extends FragmentActivity implements ActionBar.TabListener{
private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private PagerSlidingTabStrip tabPager;
private ActionBar actionBar;
private String[] tabs = { "Coffees", "Sweets", "Snacks", "Drinks" };
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_order);
// Initilization
viewPager = (ViewPager) findViewById(R.id.pager);
actionBar = getActionBar();
mAdapter = new TabsPagerAdapter(getSupportFragmentManager());
viewPager.setAdapter(mAdapter);
tabPager = (PagerSlidingTabStrip)findViewById(R.id.tabs);
tabPager.setViewPager(viewPager);
actionBar.setHomeButtonEnabled(false);
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Adding Tabs
for (String tab_name : tabs) {
actionBar.addTab(actionBar.newTab().setText(tab_name)
.setTabListener(this));
}
ViewPager.SimpleOnPageChangeListener mListener = new ViewPager.SimpleOnPageChangeListener(){
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
};
viewPager.setOnPageChangeListener(mListener);
}
@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}
}
我正在执行示例所说的所有操作，当我运行活动时，它会崩溃，并向我提供此错误：
Process: com.example.kostas.ordertakingsystem, PID: 1195
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.kostas.ordertakingsystem/com.example.kostas.ordertakingsystem.NewOrder}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.kostas.ordertakingsystem.NewOrder.onCreate(NewOrder.java:38)
at android.app.Activity.performCreate(Activity.java:5231)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
at android.app.ActivityThread.access$800(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5017)
at java.lang.reflect.Method.invokeNative(Native Method)
任何想法？我知道这可能是一个重复的问题，但我还没有找到正确实现它的方法。
我将不胜感激任何帮助。提前谢谢。