我正在按照教程
https://www.youtube.com/watch?v=VVahIc8yENk进行操作,我收到了错误消息
java.lang.NullPointerException: Attempt to invoke virtual method ‘void
android.app.ActionBar.setNavigationMode(int)’ on a null object
reference
我正在使用Android Studio编写这个程序,我已经尝试从API 11到21,但没有一个工作.
public class Tabtest extends FragmentActivity implements ActionBar.TabListener {
ActionBar actionBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tab_test);
actionBar=getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.Tab tab1=actionBar.newTab();
tab1.setText("tab1");
tab1.setTabListener(this);
ActionBar.Tab tab2=actionBar.newTab();
tab2.setText("tab2");
tab2.setTabListener(this);
ActionBar.Tab tab3=actionBar.newTab();
tab3.setText("tab3");
tab3.setTabListener(this);
ActionBar.Tab tab4=actionBar.newTab();
tab4.setText("tab4");
tab4.setTabListener(this);
actionBar.addTab(tab1);
actionBar.addTab(tab2);
actionBar.addTab(tab3);
actionBar.addTab(tab4);
}
@Override
public void onTabSelected(ActionBar.Tab tab,FragmentTransaction ft) {
Log.d("VIVZ","onTabReselected at "+" position "+tab.getPosition()+" name "+tab.getText());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,"onTabReselected at "+" position "+tab.getPosition()+" name "+tab.getText());
}
@Override
public void onTabReselected(ActionBar.Tab tab,"onTabReselected at "+" position "+tab.getPosition()+" name "+tab.getText());
}
}
解决方法
我在youtube上关注Vivz示例,但是当该方法被弃用时,我必须找到另一种方法.尝试：而不是向操作栏添加标签：
修改你的适配器：
public class CollectionPagerAdapter extends FragmentStatePagerAdapter {
private String[] titles = {"Item 1","Item 2","Item 3" };
public CollectionPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int i) {
switch(i){
case 0:
return new FragmentA();
case 1:
return new FragmentB();
case 2:
return new FragmentC();
}
return null;
}
@Override
public int getCount() {
return titles.length;
}
@Override
public CharSequence getPageTitle(int position) {
return titles[position];
}
}
在您想要实现选项卡的活动中尝试
public class Tabtest extends ActionBarActivity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_tab_test);
ViewPager pager = (ViewPager) findViewById(R.id.your_view_pager);
pager.setAdapter(new CollectionPagerAdapter(getSupportFragmentManager()));
PagerSlidingTabStrip tabs = (PagerSlidingTabStrip) findViewById(R.id.tabs);
tabs.setViewPager(pager);
}
现在,如果您想在选项卡名称下设置带有移动指示器的Google Play商店标签,并在用户滚动时移动,请编译此库
compile 'com.astuetz:pagerslidingtabstrip:1.0.1'
<LinearLayout //obvIoUsly add width and height and other necessery stuff android:orientation="vertical"> <com.astuetz.PagerSlidingTabStrip android:id="@+id/tabs" android:layout_width="match_parent" android:layout_height="48dip" /> <android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/pager" android:layout_width="match_parent" android:layout_height="match_parent" /> </LinearLayout>
然后你将获得预期的效果.
希望能帮助到你！！！
