TabHost的自定义

使用自定义的TabHost可以不用继承TabActicity，但是要注意的是如果使用Activity作为Content的话，有两处代码是一定要加的。不然就会出现RuntimeError，还有在XML布局中使用自定义的TabHost时除了TabHost的id自定义外，LinearLayout和TabWidget的id必须使用系统默认。具体可参考下面的Demo。
使用TabWidget的效果（左）和自定义View的效果图（右）：
       
MainActivity加载的XML布局：

<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"
    tools:context=".MainActivity" >

    <TabHost
        android:id="@+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="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="0" />

            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="match_parent"
                android:layout_height="0dip"
                android:layout_weight="1" />
        </LinearLayout>
    </TabHost>

</RelativeLayout>

MainActivity的Java代码（注意红色代码）：

package com.hitech.tabhostdemo;

import android.app.Activity;
import android.app.LocalActivityManager;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;

@SuppressWarnings("deprecation")
public class MainActivity extends Activity {

    private LocalActivityManager lam;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TabHost tabHost = (TabHost) findViewById(R.id.tabhost);

        // Intent对象
        Intent intent1 = new Intent(this, TabSpecActivity1.class);
        Intent intent2 = new Intent(this, TabSpecActivity2.class);
        Intent intent3 = new Intent(this, TabSpecActivity3.class);

        // TabSpec对象
        TabSpec tabSpec1 = tabHost.newTabSpec("first");
        tabSpec1.setIndicator("第一页",
                getResources().getDrawable(android.R.drawable.ic_dialog_email));
        tabSpec1.setContent(intent1);

        TabSpec tabSpec2 = tabHost.newTabSpec("second");
        tabSpec2.setIndicator("第二页",
                getResources().getDrawable(android.R.drawable.ic_btn_speak_now));
        tabSpec2.setContent(intent2);

        TabSpec tabSpec3 = tabHost.newTabSpec("third");
        tabSpec3.setIndicator("第三页",
                getResources().getDrawable(android.R.drawable.ic_dialog_dialer));
        tabSpec3.setContent(intent3);

        lam = new LocalActivityManager(this, false);
        lam.dispatchCreate(savedInstanceState);
        tabHost.setup(lam);

        tabHost.addTab(tabSpec1);
        tabHost.addTab(tabSpec2);
        tabHost.addTab(tabSpec3);

        // TabActivity
    }

    @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_main, menu);
        return true;
    }

    @Override
    protected void onPause() {
        super.onPause();
        lam.dispatchPause(isFinishing());
    }
}

自定义View代替TabWidget效果的实现原理：隐藏TabWidget，然后在线性布局中加入自定义View，如上图中即为LinearLayout中添加三个TextView，再分别对TextView设置点击事件来模拟TabWidget的效果。
同样，MainActivity加载的XML布局如下：

<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"
    tools:context=".MainActivity" >

    <TabHost
        android:id="@+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="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="0"
                android:orientation="horizontal"android:visibility="gone" />

            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="match_parent"
                android:layout_height="0dip"
                android:layout_weight="1" />

            <View
                android:layout_width="match_parent"
                android:layout_height="1dp"
                android:layout_marginBottom="1dp"
                android:background="@android:color/background_light" />

            <LinearLayout
android:layout_width="match_parent"
                android:layout_height="wrap_content" >

                <TextView
                    android:id="@+id/tab_convst"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:drawablePadding="-10dp"
                    android:drawableTop="@drawable/ic_widget_conversation"
                    android:gravity="center"
                    android:paddingBottom="5dp"
                    android:text="@string/conversation" />

                <TextView
                    android:id="@+id/tab_folder"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:drawablePadding="-10dp"
                    android:drawableTop="@drawable/ic_widget_folder"
                    android:gravity="center"
                    android:paddingBottom="5dp"
                    android:text="@string/folder" />

                <TextView
                    android:id="@+id/tab_group"
                    android:layout_width="0dp"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:drawablePadding="-10dp"
                    android:drawableTop="@drawable/ic_widget_group"
                    android:gravity="center"
                    android:paddingBottom="5dp"
                    android:text="@string/group" />
            </LinearLayout>
        </LinearLayout>
    </TabHost>

</RelativeLayout>

注意和以往不同之处已做标记，分别是TabWidget和自定义的LinearLayout。
MainActivity中的处理：

package com.hitech.capacitymessage;

import android.app.Activity;
import android.app.LocalActivityManager;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TabHost;
import android.widget.TabHost.TabSpec;
import android.widget.TextView;

@SuppressWarnings("deprecation")
public class MainActivity extends Activity implements OnClickListener {

    private static final String TAG = "MainActivity";
    private LocalActivityManager lam;
    private TabHost tabHost;
    private Bundle state;
    private TabSpec tab1;
    private TabSpec tab2;
    private TabSpec tab3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.state = savedInstanceState;
        activityInitializer();
    }

    private void activityInitializer() {
        tabHost = (TabHost) findViewById(R.id.tabhost);
        tab1 = tabHost.newTabSpec("tab1");
        tab1.setIndicator("会话",
                getResources().getDrawable(R.drawable.ic_widget_conversation));
        tab1.setContent(new Intent(this, TabActivity1.class));

        tab2 = tabHost.newTabSpec("tab2");
        tab2.setIndicator("文件夹",
                getResources().getDrawable(R.drawable.ic_widget_folder));
        tab2.setContent(new Intent(this, TabActivity2.class));

        tab3 = tabHost.newTabSpec("tab3");
        tab3.setIndicator("群组",
                getResources().getDrawable(R.drawable.ic_widget_group));
        tab3.setContent(new Intent(this, TabActivity3.class));

        lam = new LocalActivityManager(this, true);
        lam.dispatchCreate(state);
        tabHost.setup(lam);

        tabHost.addTab(tab1);
        tabHost.addTab(tab2);
        tabHost.addTab(tab3);

        TextView block1 = (TextView) findViewById(R.id.tab_convst);
        TextView block2 = (TextView) findViewById(R.id.tab_folder);
        TextView block3 = (TextView) findViewById(R.id.tab_group);

        block1.setOnClickListener(this);
        block2.setOnClickListener(this);
        block3.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        String tabTag = tabHost.getCurrentTabTag();
        switch (v.getId()) {
        case R.id.tab_convst:
            if (!tabTag.equals("tab1")) {
                tabHost.setCurrentTabByTag("tab1");
            }
            Log.e(TAG, tabHost.getCurrentTabTag());
            break;
        case R.id.tab_folder:
            if (!tabTag.equals("tab2")) {
                tabHost.setCurrentTabByTag("tab2");
            }
            Log.e(TAG, tabHost.getCurrentTabTag());
            break;
        case R.id.tab_group:
            if (!tabTag.equals("tab3")) {
                tabHost.setCurrentTabByTag("tab3");
            }
            Log.e(TAG, tabHost.getCurrentTabTag());
            break;
        default:
            break;
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        lam.dispatchPause(isFinishing());
    }
}