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android.widget.TabHost上的对象引用为空。setCurrentTab(int)[重复]

gesture swipe android-tabhost nullpointerexception android

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Faisal Mirza · 技术社区 · 10 年前

我正在与一个项目合作 Tabhost 在这里,我必须通过检测“手势”来实现刷卡功能。下面是我的代码

public class GameItemListActivity extends TabActivity implements ViewPager.OnPageChangeListener {
public TabHost host;
private ViewPager pager;
GestureDetectorCompat gestureDetectorCompat;
private GestureDetector gestureScanner;
public int currentTabposition;
public TabHost.TabSpec spec;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_game);
    host = (TabHost) findViewById(android.R.id.tabhost);

   // pager = (ViewPager) findViewById(R.id.pager);
    Download_Class.applicationContext=GameItemListActivity.this;
    host.setup();

    spec = host.newTabSpec("tab1");
    spec.setContent(new Intent(this, Action_Activity.class));
    spec.setIndicator("Action");
    host.addTab(spec);

    spec = host.newTabSpec("tab2");
    spec.setContent(new Intent(this, Arcade_Activity.class));
    spec.setIndicator("Arcade");
    host.addTab(spec);

    spec = host.newTabSpec("tab3");
    spec.setContent(new Intent(this, Sport_Activity.class));
    spec.setIndicator("Sports");
    host.addTab(spec);

    spec = host.newTabSpec("tab4");
    spec.setContent(new Intent(this, Cards_Activity.class));
    spec.setIndicator("Top Games");
    host.addTab(spec);

    spec = host.newTabSpec("tab5");
    spec.setContent(new Intent(this, Racing_Activity.class));
    spec.setIndicator("Racing");
    host.addTab(spec);

    spec = host.newTabSpec("tab6");
    spec.setContent(new Intent(this, GameOfTheWeek.class));
    spec.setIndicator("Game Of\nThe Week");
    host.addTab(spec);

    spec = host.newTabSpec("tab7");
    spec.setContent(new Intent(this, Puzzle_Activity.class));
    spec.setIndicator("Puzzle");
    host.addTab(spec);
    currentTabposition= getTabHost().getCurrentTab();
    Log.d("chagecurrenttab", String.valueOf(getTabHost().getCurrentTab()));}

点击选项卡可以更改选项卡。但当我想使用

host.setCurrentTab(tab position)

来自方法。它总是显示

" void android.widget.TabHost.setCurrentTab(int) 对空对象引用“

虽然我已经启动了tabhost

host = (TabHost) findViewById(android.R.id.tabhost);

详细错误如下所示。

03-06 11:53:07.717 19772-19772/com.javatechig.gridviewexample W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TabHost.setCurrentTab(int)' on a null object reference
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.javatechig.gridviewexample.Picture.GameRelated.GameItemListActivity.setTabContent(GameItemListActivity.java:159)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.javatechig.gridviewexample.Picture.GameRelated.Arcade_Activity$2.onSwipeRight(Arcade_Activity.java:118)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.javatechig.gridviewexample.Picture.SwipeListener$GestureListener.onFling(SwipeListener.java:46)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.GestureDetector.onTouchEvent(GestureDetector.java:610)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.javatechig.gridviewexample.Picture.SwipeListener.onTouch(SwipeListener.java:24)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.View.dispatchTouchEvent(View.java:8832)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2569)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2239)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2610)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1779)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.app.Activity.dispatchTouchEvent(Activity.java:2853)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2571)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.727 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2581)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
03-06 11:53:07.737 19772-19772/com.javatechig.gridviewexample W/System.err:     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2610)

请给我一个解决方案。任何解决方案都将不胜感激……提前谢谢

2 回复 | 直到 10 年前

1

0

Community Mohan Dere 5 年前

除了“TabActivity在API级别13中被弃用”和“应用程序应该使用Fragments而不是TabActivaty”这一事实之外- Android Documentation

就我个人而言,我认为你不应该使用 findViewById 因为已经有了获取TabHost的方法。

公共选项卡主机getTabHost()

返回活动用于承载其选项卡的TabHost。

如果您看到该链接的“类概述”部分,它将向您展示一个示例XML布局和您需要使用的适当XML ID。

也不清楚您在代码中调用的位置

host.setCurrentTab

因为如果 host 您问题中的代码为空,那么 host.setup() 将引发错误。

2

0

Shree Krishna 10 年前

可能是因为你正在使用 android.R 但可能不是,使用 R 只有只需更换这条线

host = (TabHost) findViewById(android.R.id.tabhost);

具有

host = (TabHost) findViewById(R.id.tabhost);

或

代替

<TabHost android:id="@+id/tabhost"

具有

<TabHost android:id="@android:id/tabhost"