android底部菜单栏实现原理与代码

<?xml version="1.0" encoding="UTF-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@color/bg_gray"
android:orientation="vertical" >
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="fill_parent"
android:layout_height="0.0dip"
android:layout_weight="1.0" />
<TabWidget
android:id="@android:id/tabs"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="0.0"
android:visibility="gone" />
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
<RadioGroup
android:id="@+id/main_tab_group"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="@drawable/bottom1"
android:gravity="bottom"
android:orientation="horizontal"
>
<RadioButton
android:id="@+id/main_tab_addExam"
style="@style/MMTabButton"
android:layout_weight="1.0"
android:drawableTop="@drawable/bg_checkbox_icon_menu_0"
android:text="添加考试" />
<RadioButton
android:id="@+id/main_tab_myExam"
style="@style/MMTabButton"
android:layout_weight="1.0"
android:checked="true"
android:drawableTop="@drawable/bg_checkbox_icon_menu_1"
android:text="我的考试" />
<RadioButton
android:id="@+id/main_tab_message"
style="@style/MMTabButton"
android:layout_weight="1.0"
android:drawableTop="@drawable/bg_checkbox_icon_menu_2"
android:text="我的通知" />
<RadioButton
android:id="@+id/main_tab_settings"
style="@style/MMTabButton"
android:layout_weight="1.0"
android:drawableTop="@drawable/bg_checkbox_icon_menu_3"
android:text="设置" />
</RadioGroup>
<TextView
android:id="@+id/main_tab_new_message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal|top"
android:layout_marginLeft="60dip"
android:layout_marginTop="1dip"
android:background="@drawable/tips"
android:gravity="center"
android:text="1"
android:textColor="#ffffff"
android:textSize="10sp"
android:visibility="gone" />
</FrameLayout>
</LinearLayout>
</TabHost>

<style name="MMTabButton">
<item name="android:textSize">12.0dip</item>
<item name="android:gravity">center_horizontal</item>
<item name="android:background">@drawable/bg_checkbox_menus</item>
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:button">@null</item>
<item name="android:textColor">@color/white</item>
<item name="android:layout_weight">1.0</item>
<item name="android:paddingBottom">2.0dip</item>
<item name="android:paddingTop">2.0dip</item>
</style>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item
android:state_checked="false"
android:drawable="@drawable/mm_trans" />
<item
android:state_checked="true"
android:drawable="@drawable/home_btn_bg" />
</selector>

package cn.com.karl.test;
import android.app.TabActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.Window;
import android.widget.RadioGroup;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.widget.TabHost;
import android.widget.TextView;
public class MainActivity extends TabActivity {
/** Called when the activity is first created. */
private TabHost tabHost;
private TextView main_tab_new_message;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
main_tab_new_message=(TextView) findViewById(R.id.main_tab_new_message);
main_tab_new_message.setVisibility(View.VISIBLE);
main_tab_new_message.setText("10");
tabHost=this.getTabHost();
TabHost.TabSpec spec;
Intent intent;
intent=new Intent().setClass(this, AddExamActivity.class);
spec=tabHost.newTabSpec("添加考试").setIndicator("添加考试").setContent(intent);
tabHost.addTab(spec);
intent=new Intent().setClass(this,MyExamActivity.class);
spec=tabHost.newTabSpec("我的考试").setIndicator("我的考试").setContent(intent);
tabHost.addTab(spec);
intent=new Intent().setClass(this, MyMessageActivity.class);
spec=tabHost.newTabSpec("我的通知").setIndicator("我的通知").setContent(intent);
tabHost.addTab(spec);
intent=new Intent().setClass(this, SettingActivity.class);
spec=tabHost.newTabSpec("设置").setIndicator("设置").setContent(intent);
tabHost.addTab(spec);
tabHost.setCurrentTab(1);
RadioGroup radioGroup=(RadioGroup) this.findViewById(R.id.main_tab_group);
radioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {

@Override
public void onCheckedChanged(RadioGroup group, int checkedId) {
// TODO Auto-generated method stub
switch (checkedId) {
case R.id.main_tab_addExam://添加考试
tabHost.setCurrentTabByTag("添加考试");
break;
case R.id.main_tab_myExam://我的考试
tabHost.setCurrentTabByTag("我的考试");
break;
case R.id.main_tab_message://我的通知
tabHost.setCurrentTabByTag("我的通知");
break;
case R.id.main_tab_settings://设置
tabHost.setCurrentTabByTag("设置");
break;
default:
//tabHost.setCurrentTabByTag("我的考试");
break;
}
}
});
}
}