Question

我的 MainActivity 类 - 我想要实现固定标签

package com.nikhil.tabs;


import android.app.ActionBar;
import android.support.v4.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;

public class MainActivity extends FragmentActivity {


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

        ViewPager pager  = (ViewPager) findViewById(R.id.pager);

        pager.setAdapter(new TabsPagerAdapter(getSupportFragmentManager()));

        // How to add tabs here
       // What more is missing?

            } 

    //Do I need any listeners for tabs here?

}

以下是我的适配器类的代码。最初我使用了FragmentPagerAdapter，但我在MainActivity中遇到了ActionBar的一些问题。所以，现在我正在使用FragmentStatePagerAdapter。

我的适配器类

package com.nikhil.tabs;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.FragmentStatePagerAdapter;

public class TabsPagerAdapter extends FragmentStatePagerAdapter {

    public TabsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    // Tab titles
    private String[] tabs = { "Top Rated", "Games"};

    @Override
    public Fragment getItem(int index) {

        switch (index) {
            case 0:
                // Top Rated fragment activity
                return new TopRatedFragment();
            case 1:
                // Games fragment activity
                return new GamesFragment();
        }

        return null;
    }

    @Override
    public int getCount() {
        // get item count - equal to number of tabs
        return tabs.length;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return tabs[position];
    }

}

如果我运行我的应用。我没有得到任何标签。有什么遗漏？

如果我尝试添加

viewPager.setAdapter(mAdapter);
        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));
        }

在我的班级中，NAVIGATION_MODE_TABS正在逐渐被删除，因为它已被弃用。不过，如果我尝试运行应用程序，它就会崩溃。

编辑：

我的Logcat：

03-07 23:03:02.350    2970-2970/com.nikhil.tabs E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.nikhil.tabs, PID: 2970
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.nikhil.tabs/com.nikhil.tabs.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object reference
            at com.nikhil.tabs.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

使用API 21时，不推荐使用方法setNavigationMode(ActionBar.NAVIGATION_MODE_TABS)。请参阅this。

如果您希望使用Google Play商店风格的标签，则可以使用PagerSlidingTabStrip library。

SlidingTabsBasic

的Google示例

我在这里缺少什么 - 在我的活动中实施标签？

1 个答案: