-2
因爲我們知道選項卡活動現在已被棄用，所以一些教程說我使用FragmentActivity代替。我正在使用這個，它給我這個空行指針異常片段活動中的空指針異常？
tabHost.addTab(spec);
我的代碼如下。
//MainActivity.java
public class MainActivity extends FragmentActivity {
public final static int HOME = 1;
public final static int CAMPUS = 2;
public final static int REPORTING = 3;
public final static int HELP = 4;
public final static int WISH = 5;
long transactionID = -1;
public static TabHost tabHost;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mytabs);
MyView view = null;
tabHost = (TabHost)findViewById(R.id.my_tabhost);
TabHost.TabSpec spec;
Intent intent;
intent = new Intent().setClass(this, TabGroup1Activity.class);
view = new MyView(this, R.drawable.home, R.drawable.home_blue, "");
view.setFocusable(true);
spec = tabHost.newTabSpec("Home").setIndicator(view).setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, TabGroup2Activity.class);
view = new MyView(this, R.drawable.home, R.drawable.home_blue, "");
view.setFocusable(true);
spec = tabHost.newTabSpec("Campus").setIndicator(view)
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, TabGroup3Activity.class);
view = new MyView(this, R.drawable.home, R.drawable.home_blue, "");
view.setFocusable(true);
spec = tabHost.newTabSpec("Reporting").setIndicator(view)
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, TabGroup4Activity.class);
view = new MyView(this, R.drawable.home, R.drawable.home_blue, "");
view.setFocusable(true);
spec = tabHost.newTabSpec("Help").setIndicator(view)
.setContent(intent);
tabHost.addTab(spec);
intent = new Intent().setClass(this, TabGroup5Activity.class);
view = new MyView(this, R.drawable.home, R.drawable.home_blue, "");
view.setFocusable(true);
spec = tabHost.newTabSpec("Wish").setIndicator(view).setContent(intent);
tabHost.addTab(spec);
tabHost.setCurrentTab(0);
tabHost.getTabWidget().getChildAt(0).getLayoutParams().height = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(1).getLayoutParams().height = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(2).getLayoutParams().height = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(3).getLayoutParams().height = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(4).getLayoutParams().height = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(0).getLayoutParams().width = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(1).getLayoutParams().width = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(2).getLayoutParams().width = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(3).getLayoutParams().width = LayoutParams.WRAP_CONTENT;
tabHost.getTabWidget().getChildAt(4).getLayoutParams().width = LayoutParams.WRAP_CONTENT;
if (MyApp.getFrom().equals("Home")) {
tabHost.setCurrentTab(0);
} else if (MyApp.getFrom().equals("Campus")) {
tabHost.setCurrentTab(1);
} else if (MyApp.getFrom().equals("Reporting")) {
tabHost.setCurrentTab(2);
} else if (MyApp.getFrom().equals("Help")) {
tabHost.setCurrentTab(3);
} else if (MyApp.getFrom().equals("Wish")) {
tabHost.setCurrentTab(4);
}
int type = 0;
if (getIntent().getExtras() != null) {
if (getIntent().getExtras().containsKey("from")) {
type = getIntent().getExtras().getInt("from");
switch (type) {
case HOME:
tabHost.setCurrentTab(0);
case CAMPUS:
tabHost.setCurrentTab(1);
case REPORTING:
tabHost.setCurrentTab(2);
case HELP:
tabHost.setCurrentTab(3);
case WISH:
tabHost.setCurrentTab(4);
default:
tabHost.setCurrentTab(0);
}
}
}
}
public long getTransactionID() {
return transactionID;
}
public void setTransactionID(long l) {
transactionID = l;
}
public void switchTabSpecial(int tab) {
tabHost.setCurrentTab(tab);
}
class ChangeTabReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
tabHost = (TabHost)findViewById(R.id.my_tabhost);
tabHost.setCurrentTab(1);
}
}
private class MyView extends LinearLayout {
ImageView iv;
public MyView(Context c, int drawable, int drawableselec, String label) {
super(c);
iv = new ImageView(c);
StateListDrawable listDrawable = new StateListDrawable();
listDrawable.addState(SELECTED_STATE_SET, this.getResources()
.getDrawable(drawable));
listDrawable.addState(ENABLED_STATE_SET, this.getResources()
.getDrawable(drawableselec));
iv.setImageDrawable(listDrawable);
iv.setBackgroundColor(Color.TRANSPARENT);
iv.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT, (float) 0.0));
setGravity(Gravity.CENTER);
addView(iv);
}
}
}
//mytabs.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" >
<TabHost
android:id="@+id/my_tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:padding="0dp" >
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:padding="0dp" >
</FrameLayout>
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
</LinearLayout>
</TabHost>
//錯誤
02-05 10:57:22.301: E/AndroidRuntime(911): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ccc.loyolacollege/com.ccc.loyolacollege.MainActivity}: java.lang.NullPointerException
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread.access$600(ActivityThread.java:123)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.os.Handler.dispatchMessage(Handler.java:99)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.os.Looper.loop(Looper.java:137)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread.main(ActivityThread.java:4424)
02-05 10:57:22.301: E/AndroidRuntime(911): at java.lang.reflect.Method.invokeNative(Native Method)
02-05 10:57:22.301: E/AndroidRuntime(911): at java.lang.reflect.Method.invoke(Method.java:511)
02-05 10:57:22.301: E/AndroidRuntime(911): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
02-05 10:57:22.301: E/AndroidRuntime(911): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
02-05 10:57:22.301: E/AndroidRuntime(911): at dalvik.system.NativeStart.main(Native Method)
02-05 10:57:22.301: E/AndroidRuntime(911): Caused by: java.lang.NullPointerException
02-05 10:57:22.301: E/AndroidRuntime(911): at android.widget.TabHost.addTab(TabHost.java:229)
02-05 10:57:22.301: E/AndroidRuntime(911): at com.ccc.loyolacollege.MainActivity.onCreate(MainActivity.java:38)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.Activity.performCreate(Activity.java:4465)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
02-05 10:57:22.301: E/AndroidRuntime(911): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
您調試了您的應用程序嗎？哪個變量是空的？ – dilix
查看我的回答，我已更新它並嘗試使用我的代碼。 – GrIsHu