java - android 尝试在空对象引用上调用虚拟方法 'void android.app.ActionBar.setHomeButtonEnabled(boolean)'

Question

我有代码，我正在通过导入项目及其运行在 Eclipse 上尝试

但是当我在 android studio 上尝试时遇到问题，这是:

Attempt to invoke virtual method 'void android.app.ActionBar.setHomeButtonEnabled(boolean)' on a null object referenc

我使用 android.support.v4 ，这是代码:

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

public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Top Rated", "Games", "Movies" };

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

    // Initilization
    viewPager = (ViewPager) findViewById(R.id.pager);
    actionBar = getActionBar();
    mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

    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));
    }

    /**
     * on swiping the viewpager make respective tab selected
     * */
    viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            // on changing the page
            // make respected tab selected
            actionBar.setSelectedNavigationItem(position);
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
        }

        @Override
        public void onPageScrollStateChanged(int arg0) {
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    super.onCreateOptionsMenu(menu);
    return true;
}

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

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    // on tab selected
    // show respected fragment view
    viewPager.setCurrentItem(tab.getPosition());
}

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

}

我现在能做什么？我是 Android 编程新手吗？

请评估我并编辑我的代码以在我的项目中运行

Answer 1

将 getActionBar() 替换为 getSupportActionBar()。 将 import android.app.ActionBar; 替换为 import android.support.v7.app.ActionBar; 您遇到的另一个错误:您将 android.support.v4.app.FragmentActivity 与 android.app.FragmentTransaction; 您应该将 import android.app.FragmentTransaction; 替换为 import android.support.v4.app.FragmentTransaction; 相同import android.app.ActionBar.Tab;

的东西