我试图在一个 Fragment 的布局中动态添加一个TextView,但是一直无法成功。应用程序启动后立即关闭。
我认为问题与TextView Paper = new TextView(this);
这一部分有关。由于我正在使用 Fragments,所以不知道如何获取正确的Context。也许我的假设是错误的,但我真的不知道错误可能在哪里。
public class PageFragment extends Fragment {
private int fragmentNR;
public PageFragment(int nr) {
this.fragmentNR = nr;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = new View(getActivity());
if (fragmentNR == 0)
v = inflater.inflate(R.layout.page1, container, false);
else if (fragmentNR == 1)
v = inflater.inflate(R.layout.page2, container, false);
else if (fragmentNR == 2)
v = inflater.inflate(R.layout.page3, container, false);
return v;
}
}
public class MainActivity extends FragmentActivity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
PageAdapter mPageAdapter = new PageAdapter(getSupportFragmentManager());
ViewPager mViewPager = (ViewPager) findViewById(R.id.viewpager);
mViewPager.setAdapter(mPageAdapter);
//This is where i try to add my TextView into my Layout
LinearLayout PaperLayout = (LinearLayout) findViewById(R.id.PaperLayout);//PaperLayout is a LinearLayout within the Page2-Fragment(R.layout.page2)
TextView Paper = new TextView(this);
Paper.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT));
Paper.setText("Paper2");
PaperLayout.addView(Paper);
}
}
日志记录器
07-18 16:32:58.330: E/AndroidRuntime(614): FATAL EXCEPTION: main
07-18 16:32:58.330: E/AndroidRuntime(614): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.loni.math_prime/com.loni.math_prime.MainActivity}: java.lang.NullPointerException
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.access$600(ActivityThread.java:130)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.os.Handler.dispatchMessage(Handler.java:99)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.os.Looper.loop(Looper.java:137)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.main(ActivityThread.java:4745)
07-18 16:32:58.330: E/AndroidRuntime(614): at java.lang.reflect.Method.invokeNative(Native Method)
07-18 16:32:58.330: E/AndroidRuntime(614): at java.lang.reflect.Method.invoke(Method.java:511)
07-18 16:32:58.330: E/AndroidRuntime(614): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
07-18 16:32:58.330: E/AndroidRuntime(614): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
07-18 16:32:58.330: E/AndroidRuntime(614): at dalvik.system.NativeStart.main(Native Method)
07-18 16:32:58.330: E/AndroidRuntime(614): Caused by: java.lang.NullPointerException
07-18 16:32:58.330: E/AndroidRuntime(614): at com.loni.math_prime.MainActivity.onCreate(MainActivity.java:30)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.Activity.performCreate(Activity.java:5008)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
07-18 16:32:58.330: E/AndroidRuntime(614): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
07-18 16:32:58.330: E/AndroidRuntime(614): ... 11 more
XML
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<android.support.v4.view.PagerTitleStrip
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="32dp"
android:textStyle="bold"
android:textColor="#fff5ee"
android:layout_gravity="top" />
</android.support.v4.view.ViewPager>
</LinearLayout>