ViewPager+Fragment

今天介绍一下ViewPager+fragment
使用它，需要在页面中使用RadioButton,下面给出activity_main.xml页面的代码。

<?xml version="1.0" encoding="utf-8"?>
<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="com.ice.viewpagertest.MainActivity">

    <RadioGroup
        android:id="@+id/rd_group"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:layout_alignParentBottom="true"
        android:layout_centerVertical="true"
        android:gravity="center_vertical"
        android:orientation="horizontal">


        <RadioButton
            android:id="@+id/rd_button1"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@drawable/bottom_bg"
            android:button="@null"
            android:checked="true"
            android:onClick="doclick" />


        <RadioButton
            android:id="@+id/rd_button2"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@drawable/bottom_bg2"
            android:button="@null"
            android:checked="false"
            android:onClick="doclick" />


        <RadioButton
            android:id="@+id/rd_button3"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@drawable/bottom_bg3"
            android:button="@null"
            android:checked="false"
            android:onClick="doclick" />

        <RadioButton
            android:id="@+id/rd_button4"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@drawable/bottom_bg4"
            android:button="@null"
            android:checked="false"
            android:onClick="doclick" />

    </RadioGroup>

    <android.support.v4.view.ViewPager
        android:id="@+id/vp_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/rd_group"/>
</RelativeLayout>

并且创建四个Fragment。
在MainActivity中有如下代码

public class MainActivity extends AppCompatActivity implements HelpFragment.HelpCallBack{

    private ViewPager viewpager;

    private ArrayList<Fragment> fragments;
    private RadioButton radioButton1;
    private RadioButton radioButton2;
    private RadioButton radioButton3;
    private RadioButton radioButton4;

    private String callBackStr;

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

        initView();
    }

    /**
     * 初始化界面数据
     */
    private void initView(){
        radioButton1 = (RadioButton) findViewById(R.id.rd_button1);
        radioButton2 = (RadioButton) findViewById(R.id.rd_button1);
        radioButton3 = (RadioButton) findViewById(R.id.rd_button1);
        radioButton4 = (RadioButton) findViewById(R.id.rd_button1);

        viewpager = (ViewPager) findViewById(R.id.vp_content);


        fragments = new ArrayList<Fragment>();
        fragments.add(new HelpFragment());
        fragments.add(new SpreadFragment());
        fragments.add(new ShopFragment());
        fragments.add(new MeFragment());

        FragmentManager fs = getSupportFragmentManager();
        viewpager.setAdapter(new ViewPagerAdapter(fs));
        viewpager.addOnPageChangeListener(new PageChangeListener());
    }


    public void doclick(View view){
        switch (view.getId()){
            case R.id.rd_button1:
                viewpager.setCurrentItem(0);
                break;
            case R.id.rd_button2:
                viewpager.setCurrentItem(1);
                break;
            case R.id.rd_button3:
                viewpager.setCurrentItem(2);
                break;
            case R.id.rd_button4:
                viewpager.setCurrentItem(3);
                break;
        }
    }

    @Override
    public void handlerBundle(String str) {
        callBackStr = str;
        //输出该语句，如果成功，则可以将fragment的数据传到Activity中
        System.out.println(str);
    }

    private class PageChangeListener implements ViewPager.OnPageChangeListener{
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {}

        @Override
        public void onPageSelected(int position) {
            switch (position){
                case 0:
                    radioButton1.setChecked(true);
                    break;
                case 1:
                    radioButton2.setChecked(true);
                    break;
                case 2:
                    radioButton3.setChecked(true);
                    break;
                case 3:
                    radioButton4.setChecked(true);
                    break;
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {}
    }

    /**
     * 使用ViewPager 必须要继承PagerAdapter
     */
    private class ViewPagerAdapter extends FragmentPagerAdapter{
        public ViewPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            //将数据传到各个Fragment中
            Fragment fragment = fragments.get(position);
            Bundle bundle = new Bundle();
            switch (position){
                case 0:
                    bundle.putString("ice","帮助中心");
                    break;
                case 1:
                    bundle.putString("ice","推广中心");
                    break;
                case 2:
                    bundle.putString("ice","购物中心");
                    break;
                case 3:
                    bundle.putString("ice","个人中心");
                    break;
            }
            fragment.setArguments(bundle);
            return fragment;
        }

        @Override
        public int getCount() {
            return fragments.size();
        }
    }
}
``

使用ViewPager需要调用PagerAdapter,并且可以在PagerAdapter中的
public Fragment getItem(int position)，方法中将数据传给Fragment。

下面给出Fragment代码。该代码中有将数据传到Activity中

public class HelpFragment extends Fragment{

private Context context;
private View view;
private String ice;
private TextView textView;

private HelpCallBack helpCallBack;

//该处是以进入Fragmnet就被调用的方法，在这里判断是否继承了HelpCallBack接口，并传过来的强制转型
@Override
public void onAttach(Context context) {
    super.onAttach(context);
    this.context = context;
    try {
        helpCallBack = (HelpCallBack) context;
    } catch (ClassCastException e) {
        throw new ClassCastException("Activity没有调用HelpCallBack接口");
    }
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    view = inflater.inflate(R.layout.fragment_help, null);
    ice = getArguments().getString("ice");              //获取数据
    return view;
}

//该方法是与Activity 进行数据的交流，可以在该处初始化界面
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    initView();
}

/**
 * 初始化界面
 */
private void initView(){
    textView = (TextView) view.findViewById(R.id.tv_help);
    textView.setText(ice);
    Button button = (Button) view.findViewById(R.id.bt_help);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //将数据传递给Activity
            helpCallBack.handlerBundle("我是从HelpFragmnet中传来的数据");
        }
    });
}

//声明接口，让activity调用该接口的方法
public interface HelpCallBack{
    public void handlerBundle(String str);
}

}
“`

这里有一个接口，该接口被Activity继承，在Fragment onAttach()方法中将context强转。
在button的点击事件中将数据传到Activity中。

这里给出我写的Demo
http://download.youkuaiyun.com/detail/core_ice/9520572