1

这是我的选项卡式屏幕代码：

CareActivity.xml

import java.util.HashMap;

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.view.Menu;
import android.view.View;
import android.widget.TabHost;

public class CareActivity extends FragmentActivity {

    TabHost mTabHost;
    TabManager mTabManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_care);
        mTabHost = (TabHost)findViewById(android.R.id.tabhost);
        mTabHost.setup();

        mTabManager = new TabManager(this, mTabHost, R.id.realtabcontent);

        /*TabSpec spec = mTabHost.newTabSpec("ARTICLES").setIndicator("ARTICLES").setContent(new Intent().setClass(this, ListingActivity.class).putExtra("tabId", 0));
        mTabHost.addTab(spec);

        spec = mTabHost.newTabSpec("PRODUCTS").setIndicator("PRODUCTS").setContent(new Intent().setClass(this, ListingActivity.class).putExtra("tabId", 1));
        mTabHost.addTab(spec);*/

        mTabManager.addTab(mTabHost.newTabSpec("articles").setIndicator("ARTICLES"),
                Listing411Activity.class, null);

        mTabManager.addTab(mTabHost.newTabSpec("products").setIndicator("PRODUCTS"),
                Listing411Activity.class, null);

        if (savedInstanceState != null) {
            mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putString("tab", mTabHost.getCurrentTabTag());
    }

    /**
     * This is a helper class that implements a generic mechanism for
     * associating fragments with the tabs in a tab host.  It relies on a
     * trick.  Normally a tab host has a simple API for supplying a View or
     * Intent that each tab will show.  This is not sufficient for switching
     * between fragments.  So instead we make the content part of the tab host
     * 0dp high (it is not shown) and the TabManager supplies its own dummy
     * view to show as the tab content.  It listens to changes in tabs, and takes
     * care of switch to the correct fragment shown in a separate content area
     * whenever the selected tab changes.
     */
    public static class TabManager implements TabHost.OnTabChangeListener {
        private final FragmentActivity mActivity;
        private final TabHost mTabHost;
        private final int mContainerId;
        private final HashMap<String, TabInfo> mTabs = new HashMap<String, TabInfo>();
        TabInfo mLastTab;

        static final class TabInfo {
            private final String tag;
            private final Class<?> clss;
            private final Bundle args;
            private Fragment fragment;

            TabInfo(String _tag, Class<?> _class, Bundle _args) {
                tag = _tag;
                clss = _class;
                args = _args;
            }
        }

        static class DummyTabFactory implements TabHost.TabContentFactory {
            private final Context mContext;

            public DummyTabFactory(Context context) {
                mContext = context;
            }

            @Override
            public View createTabContent(String tag) {
                View v = new View(mContext);
                v.setMinimumWidth(0);
                v.setMinimumHeight(0);
                return v;
            }
        }

        public TabManager(FragmentActivity activity, TabHost tabHost, int containerId) {
            mActivity = activity;
            mTabHost = tabHost;
            mContainerId = containerId;
            mTabHost.setOnTabChangedListener(this);
        }

        public void addTab(TabHost.TabSpec tabSpec, Class<?> clss, Bundle args) {
            tabSpec.setContent(new DummyTabFactory(mActivity));
            String tag = tabSpec.getTag();

            TabInfo info = new TabInfo(tag, clss, args);

            // Check to see if we already have a fragment for this tab, probably
            // from a previously saved state.  If so, deactivate it, because our
            // initial state is that a tab isn't shown.
            info.fragment = mActivity.getSupportFragmentManager().findFragmentByTag(tag);
            if (info.fragment != null && !info.fragment.isDetached()) {
                FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
                ft.detach(info.fragment);
                ft.commit();
            }

            mTabs.put(tag, info);
            mTabHost.addTab(tabSpec);
        }

        @Override
        public void onTabChanged(String tabId) {
            TabInfo newTab = mTabs.get(tabId);
            if (mLastTab != newTab) {
                FragmentTransaction ft = mActivity.getSupportFragmentManager().beginTransaction();
                if (mLastTab != null) {
                    if (mLastTab.fragment != null) {
                        ft.detach(mLastTab.fragment);
                    }
                }
                if (newTab != null) {
                    if (newTab.fragment == null) {
                        newTab.fragment = Fragment.instantiate(mActivity,
                                newTab.clss.getName(), newTab.args);
                        ft.add(mContainerId, newTab.fragment, newTab.tag);
                    } else {
                        ft.attach(newTab.fragment);
                    }
                }

                mLastTab = newTab;
                ft.commit();
                mActivity.getSupportFragmentManager().executePendingTransactions();
            }
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_care411, menu);
        return true;
    }

}

active_care.xml

<TabHost
    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:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TabWidget
            android:id="@android:id/tabs"
            android:orientation="horizontal"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0"/>

        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_weight="0"/>

        <FrameLayout
            android:id="@+android:id/realtabcontent"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"/>

    </LinearLayout>
</TabHost>

清单活动.java

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;

public class ListingActivity extends FragmentActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_listing411);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_listing411, menu);
        return true;
    }

}

它给出了 ClassCastException。这是日志猫：

10-29 17:52:18.706: E/AndroidRuntime(495): FATAL EXCEPTION: main
10-29 17:52:18.706: E/AndroidRuntime(495): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jjwoundcare.main/com.jjwoundcare.main.CareActivity}: java.lang.ClassCastException: com.jjwoundcare.main.ListingActivity
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.os.Looper.loop(Looper.java:123)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread.main(ActivityThread.java:3683)
10-29 17:52:18.706: E/AndroidRuntime(495):  at java.lang.reflect.Method.invokeNative(Native Method)
10-29 17:52:18.706: E/AndroidRuntime(495):  at java.lang.reflect.Method.invoke(Method.java:507)
10-29 17:52:18.706: E/AndroidRuntime(495):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-29 17:52:18.706: E/AndroidRuntime(495):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-29 17:52:18.706: E/AndroidRuntime(495):  at dalvik.system.NativeStart.main(Native Method)
10-29 17:52:18.706: E/AndroidRuntime(495): Caused by: java.lang.ClassCastException: com.jjwoundcare.main.ListingActivity
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.support.v4.app.Fragment.instantiate(Fragment.java:388)
10-29 17:52:18.706: E/AndroidRuntime(495):  at com.jjwoundcare.main.CareActivity$TabManager.onTabChanged(CareActivity.java:138)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.widget.TabHost.invokeOnTabChangeListener(TabHost.java:359)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.widget.TabHost.setCurrentTab(TabHost.java:344)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.widget.TabHost.addTab(TabHost.java:216)
10-29 17:52:18.706: E/AndroidRuntime(495):  at com.jjwoundcare.main.CareActivity$TabManager.addTab(CareActivity.java:123)
10-29 17:52:18.706: E/AndroidRuntime(495):  at com.jjwoundcare.main.CareActivity.onCreate(CareActivity.java:35)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-29 17:52:18.706: E/AndroidRuntime(495):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)

我的代码中的问题在哪里？

4

1 回答 1

1

ListingActivity.java应该由Fragment扩展

public class FirstFragment extends Fragment{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
         return inflater.inflate(R.layout.fragment1, container,false);
    }
}

片段1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <Button
        android:id="@+id/button1"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="fregment2" />

</LinearLayout>
于 2013-01-01T21:31:31.147 回答