用Fragment实现tabhost的切换效果

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要达到切换效果有几种方式：
1、可以在布局使用FragmentTabHost,TabWidget这种办法；
2、也可以只在Activity中布局下面的页卡按钮，切换的内容用fragment来替换，替换的时候如果调用replace()方法，则fragment的状态在切换后是不能保存的，例如：如果有输入框，输入了一段字符，再切换到其他fragment，再切换回来，则原来输入的字符没有了。因为replace()方法是先remove掉原来的fragment，再add一个fragment，所以不能保存fragment原来的状态。如果要保存原来的状态，就用add()方法来添加fragment，再用FragmentTransaction来隐藏和显示fragment。

（一）Activity的布局

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent">    <RadioGroup        android:id="@+id/fragment_hide_radiogroup"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_alignParentBottom="true"        android:orientation="horizontal">        <RadioButton            android:id="@+id/fragment_hide_radiobtn_one"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="tab1"            android:checked="true"            android:layout_weight="1"            android:button="@null"            android:layout_marginLeft="60dp"            android:layout_marginTop="10dp"            android:layout_marginBottom="10dp"            android:textSize="20sp"/>        <RadioButton            android:id="@+id/fragment_hide_radiobtn_two"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="tab2"            android:layout_weight="1"            android:button="@null"            android:layout_marginTop="10dp"            android:layout_marginBottom="10dp"            android:textSize="20sp"/>        <RadioButton            android:id="@+id/fragment_hide_radiobtn_three"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="tab3"            android:layout_weight="1"            android:button="@null"            android:layout_marginTop="10dp"            android:layout_marginBottom="10dp"            android:textSize="20sp"/>    </RadioGroup>    <FrameLayout        android:id="@+id/fragment_hide_framelayout"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:layout_above="@id/fragment_hide_radiogroup"></FrameLayout></RelativeLayout>

（二）随意创建三个fragment类，布局也随意。

（三）Activity中的代码

public class TabFragment_hide_show_Activity extends AppCompatActivity {    private RadioGroup mRadioGroup;    private FirstHideFragment firstHideFragment;//声明自定义的fragment    private SecondHideFragment secondHideFragment;    private ThirdHideFragment thirdHideFragment;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_tab_fragment_hide_show_);        mRadioGroup = (RadioGroup) findViewById(R.id.fragment_hide_radiogroup);        if (firstHideFragment == null) {            firstHideFragment = FirstHideFragment.newInstance();//实例化fragment        }        getSupportFragmentManager().beginTransaction().add(R.id.fragment_hide_framelayout, firstHideFragment).commit();//监听页卡选项按钮        mRadioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {            @Override            public void onCheckedChanged(RadioGroup group, int checkedId) {                FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();                hideFragment(fragmentTransaction);//调用此方法来隐藏所有的fragment                switch (checkedId) {                    case R.id.fragment_hide_radiobtn_one:                        fragmentTransaction.show(firstHideFragment);                        break;                    case R.id.fragment_hide_radiobtn_two:                        if (secondHideFragment == null) {                            secondHideFragment = SecondHideFragment.newInstance();//实例化fragment                            fragmentTransaction.add(R.id.fragment_hide_framelayout, secondHideFragment);                        }else{                            fragmentTransaction.show(secondHideFragment);                        }                        break;                    case R.id.fragment_hide_radiobtn_three:                        if (thirdHideFragment == null) {                            thirdHideFragment = ThirdHideFragment.newInstance();                            fragmentTransaction.add(R.id.fragment_hide_framelayout, thirdHideFragment);                        }else{                            fragmentTransaction.show(thirdHideFragment);                        }                        break;                }                fragmentTransaction.commit();            }        });    }    /**     * 隐藏所有的fragment     * @param fragmentTransaction     */    public void hideFragment(FragmentTransaction fragmentTransaction) {        if (firstHideFragment != null) {            fragmentTransaction.hide(firstHideFragment);        }        if (secondHideFragment != null) {            fragmentTransaction.hide(secondHideFragment);        }        if (thirdHideFragment != null) {            fragmentTransaction.hide(thirdHideFragment);        }    }}

这里写图片描述

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