如何将选项卡添加到ActionBar for Swipe Tabs？

Question

我想用import android.app.ActionBar; import android.app.FragmentTransaction; import android.os.Bundle; import android.support.v4.app.FragmentActivity; import com.rastari.salar.mymetarialbank.R; /** * Created by Salar on 9/5/2015. */ public class AccountsActivityChart extends FragmentActivity implements ActionBar.TabListener { ActionBar actionBar; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_chart); actionBar=getActionBar(); actionBar.setNavigationMode(actionBar.NAVIGATION_MODE_TABS); //Add the Action Bar Tabs actionBar.addTab(actionBar.newTab().setText("Accounts Activity"+"Chart Activity").setTabListener(this)); } @Override public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) { } @Override public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) { } @Override public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) { } } 创建两个滑动标签。

这是我的代码：

> 05-11 06:09:28.013    2371-2371/? E/AndroidRuntime﹕ FATAL EXCEPTION:
> main
>     Process: com.rastari.salar.mymetarialbank, PID: 2371
>     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rastari.salar.mymetarialbank/com.rastari.salar.mymetarialbank.activity.AccountsActivityChart}:
> java.lang.NullPointerException: Attempt to invoke virtual method 'void
> android.app.ActionBar.setNavigationMode(int)' on a null object
> reference
>             at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
>             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
>             at android.app.ActivityThread.access$800(ActivityThread.java:151)
>             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
>             at android.os.Handler.dispatchMessage(Handler.java:102)
>             at android.os.Looper.loop(Looper.java:135)
>             at android.app.ActivityThread.main(ActivityThread.java:5254)
>             at java.lang.reflect.Method.invoke(Native Method)
>             at java.lang.reflect.Method.invoke(Method.java:372)
>             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
>             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
>      Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setNavigationMode(int)' on
> a null object reference
>             at com.rastari.salar.mymetarialbank.activity.AccountsActivityChart.onCreate(AccountsActivityChart.java:21)
>             at android.app.Activity.performCreate(Activity.java:5990)
>             at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
>             at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
>             at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
>             at android.app.ActivityThread.access$800(ActivityThread.java:151)
>             at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
>             at android.os.Handler.dispatchMessage(Handler.java:102)
>             at android.os.Looper.loop(Looper.java:135)
>             at android.app.ActivityThread.main(ActivityThread.java:5254)
>             at java.lang.reflect.Method.invoke(Native Method)
>             at java.lang.reflect.Method.invoke(Method.java:372)
>             at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
>             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 05-11
> 06:09:30.037      444-504/? E/InputDispatcher﹕ channel '155e1fbc
> com.rastari.salar.mymetarialbank/com.rastari.salar.mymetarialbank.activity.MainActivity
> (server)' ~ Channel is unrecoverably broken and will be disposed!
> 05-11 06:09:30.037      444-504/? E/InputDispatcher﹕ channel '2f2170b7
> com.rastari.salar.mymetarialbank/com.rastari.salar.mymetarialbank.activity.Login
> (server)' ~ Channel is unrecoverably broken and will be disposed!

当我运行应用程序时会发生此错误：

import android.support.v7.app.ActionBar
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import com.rastari.salar.mymetarialbank.R;

public class AccountsActivityChart extends ActionBarActivity implements ActionBar.TabListener {

    ActionBar actionBar;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chart);

        actionBar = getSupportActionBar();
        actionBar.setNavigationMode(actionBar.NAVIGATION_MODE_TABS);

        //Add the Action Bar Tabs
        actionBar.addTab(actionBar.newTab().setText("Accounts Activity"+"Chart Activity").setTabListener(this));
    }

    @Override
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {

    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }

    @Override
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {

    }
}

我真的不知道该怎么办！ 你们能指导我吗？ 非常感谢你。

最新代码：

df2 <- expand.grid(ind_2=levels(my.df$individual), ind_1=levels(my.df$individual))[, 2:1]

Answer 1

首先，您正在创建一个FragmentActivity并希望看到一个不会发生的ActionBar。

替换

AccountsActivityChart extends FragmentActivity

与

AccountsActivityChart extends ActionBarActivity

其次，你需要打电话

actionBar = getSupportActionBar();

而不是

actionBar = getActionBar();

因为ActionBarActivity是appcompat-v7库的一部分。这就是您致电actionBar.setNavigationMode()时应用崩溃的原因，因为getActionBar()与null一起使用时会返回FragmentActivity。

完成此操作后，您应该可以使用

actionBar.setNavigationMode(actionBar.NAVIGATION_MODE_TABS);

成功并查看ActionBar下的可滑动标签。

修改

替换

import android.app.ActionBar

与

import android.support.v7.app.ActionBar