Android开发:使用Fragment改造TabActivity
TabActivity在API 13(Android 3.2)被标记为过期,需要使用Fragment来实现,Fragment是Android 3.0引入的一个概念,主要就是为了适应各种不同的屏幕大小(手机、平板电脑)。Android 4.1发布时,google还发布了一个Android Support v4的包,用于Android 1.6以上的系统兼容新的特性,其中包括Fragment。为了在低于Android 3.0的平台上使用Fragment,我们需要在项目的libs中加入android-support-v4.jar这个包,一般现在的开发都需要兼顾3.0以下的平台,所以基本上都是使用这个包里的Fragment,而不是直接使用Android内置的Fragment。
在最新的Android文档里面,关于TabActivity,只讲到了它已经过期,并且贴了两个代码片段,但是点开其中的Sample链接,只是链接到了Sample的首页,还是不能看到完整的代码,要看完整的代码,就要在SDK Manager里面把Sample下载下来,然后用Eclipse打开才能看到。但是,即使看了Sample,要想弄明白怎么把自己的TabActivity转过去,也要耗费不少的功夫,因为那个Sample比较复杂。
我也是搞了两三天才弄明白Fragment的基本概念,实际上就是为了适应不同的屏幕分辨率,有的屏幕在一个Activity中可以包含一个Fragment,有的则可以包含多个,所以需要根据不同的配置调整显示方式,例如在同一个Activity里面显示两个Fragment,或者在一个Activity里面显示其中一个Fragment,另外一个Activity里面显示另外一个Fragment,实际上就是把显示内容划分成多块,每一块都有各自的生命周期,但是每一块又是跟它所在的Activity分不开的,Fragment的生命周期依赖Activity的生命周期而存在。
下图是Fragment在不同屏幕上的显示以及Fragment与所在Activity的关系:
下图是Fragment的生命周期:
下图是Fragment的生命周期与Activity的对应关系:
以上图片都来自Android的官方开发指南。
从最后一幅图可以看出,Activity的生命周期中的每个回调函数,在Fragment里都有对应的回调函数,这个在TabActivity的改造中很重要。
好了,这些基本的东西都了解之后,就可以开工了,如果你不打算深入理解Fragment,只是为了去掉横跨在TabActivity上难看的删除线,在你的Activity都是基本的Activity的情况下,那么按照以下的步骤来做就行了:
首先,使用Tab的应用都有一个入口的主Activity,我们把它叫做MainActivity,它包含了多个Tab,每个Tab又对应一个Activity,这个MainActivity的改造如下:
不要改动 TabManager这个静态内部类,只修改OnCreate里面的内容即可,当然,如果你原来的Activity里面的其他回调函数重写了的话,也可以继续保留,这里只是把原来继承Activity改为了继承FragmentActivity。
而OnCreate里面的
第二步,把原来包含的两个tab对应的Activity分别改造成FragmentActivity,这个改造起来也很简单,由于Activity生命周期里的Start,Resume,Pause,Stop,Destroy在Fragment中都有对应的生命周期,所以在Activity里的回调函数,直接复制到Fragment里就可以了,而Activity里的OnCreate,则对应Fragment的多个回调函数,但是我们可以把它对应到Fragment里的OnReateView里面,不过需要修改一些东西,先看代码:
public class Tab1FragmentActivity extends FragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
FragmentManager fm = getSupportFragmentManager();
if (fm.findFragmentById(android.R.id.content) == null ) {
Tab1Fragment tab1Fragment = new Tab1Fragment();
fm.beginTransaction().add(android.R.id.content, tab1Fragment).commit();
}
}
public static class Tab1Fragment extends Fragment {
private TextView textView1 = null ;
private TextView textView2 = null ;
private tab1BroadcastReceiver receiver;
private IntentFilter intentFilter;
@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.tab1, container, false );
textView1 = (TextView) v.findViewById(R.id.textView1);
textView1.setText( "TextView1 " );
return v;
}
@Override
public void onPause() {
super .onPause();
getActivity().unregisterReceiver(receiver);
}
@Override
public void onResume() {
super .onResume();
receiver = new tab1BroadcastReceiver();
getActivity().registerReceiver(receiver, getIntentFilter());
}
private IntentFilter getIntentFilter() {
if (intentFilter == null ) {
intentFilter = new IntentFilter();
intentFilter.addAction("TAB1_ACTION");
}
return intentFilter;
}
class Tab1BroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals("TAB1_ACTION")) {
}
}
}
}
以上代码演示了一个包含两个TextView的Activity,为了演示getActivity()函数,还加了一个BroadcastReceiver。
这个类包含了一个静态内部类,主类继承了FragmentActivity,这是使用Fragment的必要条件,但是这个FragmentActivity的OnCreate回调函数内容非常简单,只有下面几行:
后面的 Tab1Fragment静态内部类,OnPause,OnResume等回调函数的内容都直接把原来Activity里面的对应内容复制过来就行了,如果遇到原来使用了this(表示当前Activity,或者所在的Context)的地方,就用getActivity()来代替即可,该函数就是返回Fragment所在的Activity对象。如果原来的控件是Activity的私有成员,就把它们复制到Fragment里面,作为Fragment的私有成员,然后在Fragment的 onCreateView回调函数获取,该函数实际对应了Activity的OnCreate回调函数,但是里面的代码要稍作修改。
一般来说,Activity里设置布局的语句是
SetContentView(R.layout.tab1);
在Fragment的OnCreateView里需要改成:
完工之后,你的程序运行起来没有任何改变,唯一的好处就是看不到TabActivity上的删除线了,但是代价却是在libs目录里多了android-support-v4.jar文件,并且代码变得更复杂。另外,假如你用到了地图控件,例如百度地图,你还不能改造,因为百度地图需要放在一个MapActivity里面,这个Activity不能再继承FragmentActivity。Google地图已经在最新的API里解决了这个问题,不过用google地图的风险就是很多行货手机安装不了,因为缺了GMS。
在最新的Android文档里面,关于TabActivity,只讲到了它已经过期,并且贴了两个代码片段,但是点开其中的Sample链接,只是链接到了Sample的首页,还是不能看到完整的代码,要看完整的代码,就要在SDK Manager里面把Sample下载下来,然后用Eclipse打开才能看到。但是,即使看了Sample,要想弄明白怎么把自己的TabActivity转过去,也要耗费不少的功夫,因为那个Sample比较复杂。
我也是搞了两三天才弄明白Fragment的基本概念,实际上就是为了适应不同的屏幕分辨率,有的屏幕在一个Activity中可以包含一个Fragment,有的则可以包含多个,所以需要根据不同的配置调整显示方式,例如在同一个Activity里面显示两个Fragment,或者在一个Activity里面显示其中一个Fragment,另外一个Activity里面显示另外一个Fragment,实际上就是把显示内容划分成多块,每一块都有各自的生命周期,但是每一块又是跟它所在的Activity分不开的,Fragment的生命周期依赖Activity的生命周期而存在。
下图是Fragment在不同屏幕上的显示以及Fragment与所在Activity的关系:
下图是Fragment的生命周期:
下图是Fragment的生命周期与Activity的对应关系:
以上图片都来自Android的官方开发指南。
从最后一幅图可以看出,Activity的生命周期中的每个回调函数,在Fragment里都有对应的回调函数,这个在TabActivity的改造中很重要。
好了,这些基本的东西都了解之后,就可以开工了,如果你不打算深入理解Fragment,只是为了去掉横跨在TabActivity上难看的删除线,在你的Activity都是基本的Activity的情况下,那么按照以下的步骤来做就行了:
首先,使用Tab的应用都有一个入口的主Activity,我们把它叫做MainActivity,它包含了多个Tab,每个Tab又对应一个Activity,这个MainActivity的改造如下:
/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Demonstrates combining a TabHost with a ViewPager to implement a tab UI
* that switches between tabs and also allows the user to perform horizontal
* flicks to move between the tabs.
*/
public class MainActivity extends FragmentActivity {
TabHost mTabHost;
TabManager mTabManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
setContentView(R.layout.fragment_tabs);
Resources res = getResources();
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mTabManager = new TabManager( this , mTabHost, R.id.realtabcontent);
mTabManager.addTab(mTabHost.newTabSpec( "tab1 " ).setIndicator("tab1"),
Tab1FragmentActivity.Tab1Fragment. 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();
}
}
}
}
以上代码基本上是从Sample里面copy过来的,但是里面的Tab改成了两个,分别加载
Tab1FragmentActivity和
Tab2FragmentActivity(实际上是加载依附在这两个Activity上的Fragment),后面讲到。
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Demonstrates combining a TabHost with a ViewPager to implement a tab UI
* that switches between tabs and also allows the user to perform horizontal
* flicks to move between the tabs.
*/
public class MainActivity extends FragmentActivity {
TabHost mTabHost;
TabManager mTabManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
setContentView(R.layout.fragment_tabs);
Resources res = getResources();
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
mTabManager = new TabManager( this , mTabHost, R.id.realtabcontent);
mTabManager.addTab(mTabHost.newTabSpec( "tab1 " ).setIndicator("tab1"),
Tab1FragmentActivity.Tab1Fragment. class , null );
mTabManager.addTab(mTabHost.newTabSpec(
"tab2
"
).setIndicator("tab2"),
Tab1FragmentActivity.Tab2Fragment. class , null );
Tab1FragmentActivity.Tab2Fragment. 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();
}
}
}
}
不要改动 TabManager这个静态内部类,只修改OnCreate里面的内容即可,当然,如果你原来的Activity里面的其他回调函数重写了的话,也可以继续保留,这里只是把原来继承Activity改为了继承FragmentActivity。
而OnCreate里面的
setContentView(R.layout.fragment_tabs);
这句,表示Activity的布局,这个布局文件fragment_tabs.xml如下:
<?
xml version="1.0" encoding="utf-8"
?>
<!--
/* //device/apps/common/assets/res/layout/tab_content.xml
**
** Copyright 2011, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
-->
< 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:orientation ="vertical"
android:layout_width ="fill_parent"
android:layout_height ="fill_parent" >
< TabWidget
android:id ="@android:id/tabs"
android:orientation ="horizontal"
android:layout_width ="fill_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 ="fill_parent"
android:layout_height ="0dp"
android:layout_weight ="1" />
</ LinearLayout >
</ TabHost >
请不要改动这个xml文件。
<!--
/* //device/apps/common/assets/res/layout/tab_content.xml
**
** Copyright 2011, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
-->
< 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:orientation ="vertical"
android:layout_width ="fill_parent"
android:layout_height ="fill_parent" >
< TabWidget
android:id ="@android:id/tabs"
android:orientation ="horizontal"
android:layout_width ="fill_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 ="fill_parent"
android:layout_height ="0dp"
android:layout_weight ="1" />
</ LinearLayout >
</ TabHost >
第二步,把原来包含的两个tab对应的Activity分别改造成FragmentActivity,这个改造起来也很简单,由于Activity生命周期里的Start,Resume,Pause,Stop,Destroy在Fragment中都有对应的生命周期,所以在Activity里的回调函数,直接复制到Fragment里就可以了,而Activity里的OnCreate,则对应Fragment的多个回调函数,但是我们可以把它对应到Fragment里的OnReateView里面,不过需要修改一些东西,先看代码:
public class Tab1FragmentActivity extends FragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super .onCreate(savedInstanceState);
FragmentManager fm = getSupportFragmentManager();
if (fm.findFragmentById(android.R.id.content) == null ) {
Tab1Fragment tab1Fragment = new Tab1Fragment();
fm.beginTransaction().add(android.R.id.content, tab1Fragment).commit();
}
}
public static class Tab1Fragment extends Fragment {
private TextView textView1 = null ;
private TextView textView2 = null ;
private tab1BroadcastReceiver receiver;
private IntentFilter intentFilter;
@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.tab1, container, false );
textView1 = (TextView) v.findViewById(R.id.textView1);
textView1.setText( "TextView1 " );
textView2
=
(TextView) v.findViewById(R.id.textView2);
textView2.setText( "TextView2 " );
textView2.setText( "TextView2 " );
return v;
}
@Override
public void onPause() {
super .onPause();
getActivity().unregisterReceiver(receiver);
}
@Override
public void onResume() {
super .onResume();
receiver = new tab1BroadcastReceiver();
getActivity().registerReceiver(receiver, getIntentFilter());
}
private IntentFilter getIntentFilter() {
if (intentFilter == null ) {
intentFilter = new IntentFilter();
intentFilter.addAction("TAB1_ACTION");
}
return intentFilter;
}
class Tab1BroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
if (intent.getAction().equals("TAB1_ACTION")) {
textView1.setText(
"Received!
"
);
}}
}
}
}
这个类包含了一个静态内部类,主类继承了FragmentActivity,这是使用Fragment的必要条件,但是这个FragmentActivity的OnCreate回调函数内容非常简单,只有下面几行:
FragmentManager fm
=
getSupportFragmentManager();
if (fm.findFragmentById(android.R.id.content) == null ) {
Tab1Fragment tab1Fragment = new Tab1Fragment();
fm.beginTransaction().add(android.R.id.content, tab1Fragment).commit();
}
一般Activity里面的SetContentView都没有了,也没有了各种控件的成员变量,因为所有这一切,都被包含在静态内部类
Tab1Fragment里面,在Activity里,只需要包含上面的代码,这段代码的意思是,如果在这个Activity里面没有Fragment,就新建一个,并加入到后台堆栈中,以便程序控制Fragment的显示顺序。android.R.id.content是个系统自带的常量,这个常量表示“根”内容,也就是说,这个Activity的根内容就是一个Fragment,下面的东西都由Fragment来构造和完成。这里只需要修改Fragment的类名和变量名,其他东西都不要改。
if (fm.findFragmentById(android.R.id.content) == null ) {
Tab1Fragment tab1Fragment = new Tab1Fragment();
fm.beginTransaction().add(android.R.id.content, tab1Fragment).commit();
}
后面的 Tab1Fragment静态内部类,OnPause,OnResume等回调函数的内容都直接把原来Activity里面的对应内容复制过来就行了,如果遇到原来使用了this(表示当前Activity,或者所在的Context)的地方,就用getActivity()来代替即可,该函数就是返回Fragment所在的Activity对象。如果原来的控件是Activity的私有成员,就把它们复制到Fragment里面,作为Fragment的私有成员,然后在Fragment的 onCreateView回调函数获取,该函数实际对应了Activity的OnCreate回调函数,但是里面的代码要稍作修改。
一般来说,Activity里设置布局的语句是
SetContentView(R.layout.tab1);
在Fragment的OnCreateView里需要改成:
View v
=
inflater.inflate(R.layout.tab1, container,
false
);
这里获取了根View后,是为了后面获取各控件。
在Activity里的findViewById,需要改成Fragment的
v.findViewById
这个v就是通过上面的语句来取得。这个回调函数的最后就是返回v。其他东西跟Activity的OnCreate基本相同。当然,由于Activity的OnCreate对应了Fragment的多个回调函数,也许有些东西放在其他回调函数里面会更适合。
以下是Tab1对应的布局文件tab1.xml:
第三步,按照第二步的样子修改Tab2,这里省略。
这里获取了根View后,是为了后面获取各控件。
在Activity里的findViewById,需要改成Fragment的
v.findViewById
这个v就是通过上面的语句来取得。这个回调函数的最后就是返回v。其他东西跟Activity的OnCreate基本相同。当然,由于Activity的OnCreate对应了Fragment的多个回调函数,也许有些东西放在其他回调函数里面会更适合。
以下是Tab1对应的布局文件tab1.xml:
<?
xml version="1.0" encoding="utf-8"
?>
< RelativeLayout
xmlns:android ="http://schemas.android.com/apk/res/android"
android:id ="@+id/tab1_layout"
android:layout_width ="fill_parent"
android:layout_height ="fill_parent"
>
< TextView
android:id ="@+id/textView1"
android:layout_width ="fill_parent"
android:layout_height ="wrap_content"
android:gravity ="left"
/>
< TextView
android:id ="@+id/textView2"
android:layout_width ="fill_parent"
android:layout_height ="wrap_content"
android:gravity ="left"
android:layout_below ="@id/textView1"
/>
</ RelativeLayout >
< RelativeLayout
xmlns:android ="http://schemas.android.com/apk/res/android"
android:id ="@+id/tab1_layout"
android:layout_width ="fill_parent"
android:layout_height ="fill_parent"
>
< TextView
android:id ="@+id/textView1"
android:layout_width ="fill_parent"
android:layout_height ="wrap_content"
android:gravity ="left"
/>
< TextView
android:id ="@+id/textView2"
android:layout_width ="fill_parent"
android:layout_height ="wrap_content"
android:gravity ="left"
android:layout_below ="@id/textView1"
/>
</ RelativeLayout >
完工之后,你的程序运行起来没有任何改变,唯一的好处就是看不到TabActivity上的删除线了,但是代价却是在libs目录里多了android-support-v4.jar文件,并且代码变得更复杂。另外,假如你用到了地图控件,例如百度地图,你还不能改造,因为百度地图需要放在一个MapActivity里面,这个Activity不能再继承FragmentActivity。Google地图已经在最新的API里解决了这个问题,不过用google地图的风险就是很多行货手机安装不了,因为缺了GMS。