我正在尝试在我的应用中实施3标签系统。
Index.java（应该找到3个标签）
public class Index extends FragmentActivity{
private FragmentTabHost mTabHost;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_index);
mTabHost = (FragmentTabHost) findViewById(android.R.id.tabhost);
mTabHost.setup(this, getSupportFragmentManager(), android.R.id.tabcontent);
mTabHost.addTab(
mTabHost.newTabSpec("tab1").setIndicator("Tab 1", null),
FragmentTab.class, null);
mTabHost.addTab(
mTabHost.newTabSpec("tab2").setIndicator("Tab 2", null),
FragmentTab.class, null);
mTabHost.addTab(
mTabHost.newTabSpec("tab3").setIndicator("Tab 3", null),
FragmentTab.class, null);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_index,menu);
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
INDEX.XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.vincent.tennispartner2.Index">
<android.support.v4.app.FragmentTabHost
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"/>
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" />
</LinearLayout>
</android.support.v4.app.FragmentTabHost>
</RelativeLayout>
FragmentTab.java
/**
* Created by Vincent on 2015-08-25.
*/
public class FragmentTab extends Fragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_layout, container, false);
TextView tv = (TextView) v.findViewById(R.id.text);
tv.setText(this.getTag() + " Content");
return v;
}
}
我已经被困在这个部分好几个小时，从动作栏到碎片到工具栏到其他东西，但我找不到任何适合我的东西。看到我刚刚开始在java / android中编码，我真的可以使用一些帮助。
完全错误：
08-25 15:41:22.085 13008-13008/com.example.vincent.tennispartner2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.vincent.tennispartner2, PID: 13008
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.vincent.tennispartner2/com.example.vincent.tennispartn er2.Index}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentTabHost.setup(android.content.Context, android.support.v4.app.FragmentManager, int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2760)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5944)
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:1389)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentTabHost.setup(android.content.Context, android.support.v4.app.FragmentManager, int)' on a null object reference
at com.example.vincent.tennispartner2.Index.onCreate(Index.java:25)
at android.app.Activity.performCreate(Activity.java:6289)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2760)
at android.app.ActivityThread.access$900(ActivityThread.java:177)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5944)
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:1389)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1184)
非常感谢任何提示！
答案 0 :(得分：0)
更改：
mTabHost = (FragmentTabHost) findViewById(R.id.tabhost);
致：
.interview-patient {
width: 100vw * $interview-patient-scalar;
height: 281.9vw * $interview-patient-scalar;
max-height: 100vh * $interview-patient-scalar;
max-width: 36.75vh * $interview-patient-scalar;
margin: auto;
position: absolute;
top:0;bottom:0; /* vertical center */
left:0;right:0; /* horizontal center */
}
答案 1 :(得分：0)
变化：
setContentView(R.layout.activity_index);
要：
setContentView(R.layout.index);