Andriod新手，出现小问题，求解答~~

[lckankan]

public class FragmentTabActivity extends Activity implements OnClickListener {
private FragmentManager fragmentManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_fragment_tab);
setTabSelection(0); //显示这行有错
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.login1_layout:
setTabSelection(0);
break;
case R.id.login2_layout:
setTabSelection(1);
break;
default:
break;
}
}

private void setTabSelection(int index) {
FragmentTransaction transaction = this.fragmentManager.beginTransaction(); //显示这行有错
hideFragments(transaction);
switch (index) {
case 0:
login1Text.setTextColor(Color.WHITE);
if (login1Fragment == null) {
login1Fragment = new AFragment();
transaction.add(R.id.content, login1Fragment);
} else {
transaction.show(login1Fragment);
}
break;
case 1:
default:
login2Text.setTextColor(Color.WHITE);
if (login2Fragment == null) {
login2Fragment = new BFragment();
transaction.add(R.id.content, login2Fragment);
} else {
transaction.show(login2Fragment);
}
break;
}
transaction.commit();
}
private void hideFragments(FragmentTransaction transaction) {
if (login1Fragment != null) {
transaction.hide(login1Fragment);
}
if (login2Fragment != null) {
transaction.hide(login2Fragment);
}
}
}
LogCat中显示：
04-16 09:05:05.148: E/AndroidRuntime(1642): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.FragmentTransaction android.app.FragmentManager.beginTransaction()' on a null object reference
04-16 09:05:05.148: E/AndroidRuntime(1642): at lc.bishe.pingjiao.FragmentTabActivity.setTabSelection(FragmentTabActivity.java:91)
04-16 09:05:05.148: E/AndroidRuntime(1642): at lc.bishe.pingjiao.FragmentTabActivity.onCreate(FragmentTabActivity.java:44)

[u013892510]

fragmentManager 这个需要初始化 fragmentManager = getSupportFragmentManager();