代码不起作用

Question

我正在使用android studio，我正在尝试实现这里提到的代码 http://developer.android.com/guide/topics/ui/actionbar.html 但它不起作用。我正在尝试使用制表符和片段设置操作栏。但每次我尝试运行应用程序崩溃。我的代码如下。

MainActivity

int i;
for(i=0; i<len_arr; i++)
    if(arr[i] == some_num){
        printf("The idx of %d is: %d\n", some_num, i);
        break;
    }
if(i == len_arr)
    printf("Number not found.\n");

清单文件：

for(int i=0; (i<len_arr) && (printf("Number not found.\n")); i++)
    if(arr[i] == some_num){
        printf("The idx of %d is: %d\n", some_num, i);
        break;
    }

标签监听器：

public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Notice that setContentView() is not used, because we use the root
    // android.R.id.content as the container for each fragment

    // setup action bar for tabs
    ActionBar actionBar = getActionBar();

    actionBar.setDisplayShowTitleEnabled(false);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    Tab tab = actionBar.newTab()
            .setText(R.string.artist)
            .setTabListener(new TabListener<keyPad>(
                    this, "artist", keyPad.class));
    actionBar.addTab(tab);

    tab = actionBar.newTab()
            .setText(R.string.album)
            .setTabListener(new TabListener<CallLog>(
                    this, "album",CallLog.class));
    actionBar.addTab(tab);
}

Style.xml文件：

  <?xml version="1.0" encoding="utf-8"?>
  <manifest
     xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.example.iahmed.actionbarandroidstudio" >

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:theme="@style/AppTheme"

    android:label="@string/app_name">
    <activity
        android:name="MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
       </activity>
   </application>

 </manifest>

键盘（CallLog是相同的）：

   import android.app.ActionBar;
   import android.app.Activity;
   import android.app.Fragment;
   import android.app.FragmentTransaction;
   import android.os.Bundle;
   import android.widget.Toast;

   public  class TabListener<T extends Fragment> implements   ActionBar.TabListener {
private final Activity mActivity;
private final String mTag;
private final Class<T> mClass;
private final Bundle mArgs;
private Fragment mFragment;

public TabListener(Activity activity, String tag, Class<T> clz) {
    this(activity, tag, clz, null);
}

public TabListener(Activity activity, String tag, Class<T> clz, Bundle args) {
    mActivity = activity;
    mTag = tag;
    mClass = clz;
    mArgs = args;


    mFragment = mActivity.getFragmentManager().findFragmentByTag(mTag);
    if (mFragment != null && !mFragment.isDetached()) {
        FragmentTransaction ft = mActivity.getFragmentManager().beginTransaction();
        ft.detach(mFragment);
        ft.commit();
    }
}

public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
    if (mFragment == null) {
        mFragment = Fragment.instantiate(mActivity, mClass.getName(), mArgs);
        ft.add(android.R.id.content, mFragment, mTag);
    } else {
        ft.attach(mFragment);
    }
}

public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
    if (mFragment != null) {
        ft.detach(mFragment);
    }
}

public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
    Toast.makeText(mActivity, "Reselected!", Toast.LENGTH_SHORT).show();
}
}

activity_main.xml中：

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

<!-- Customize your theme here. -->
</style>

logcat的：

public class keyPad extends Fragment {

@Override

public View onCreateView(LayoutInflater inflater, ViewGroup container,

                         Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.keypad, container, false);

    return rootView;

}
}

（日志猫的一部分）

Answer 1

添加操作栏的活动代码中缺少

setContentView（）。