10天学安卓-第九天-白红宇

原文:

接着昨天的任务，我们今天实现左右滑动可以切换城市的功能。

这里就需要引入新的控件了，Android给我们提供了ViewPager，我们就使用这个，同时，显示天气的界面我们也不再使用Activity，而改为Fragment。

Fragment

Fragment可以认为是可复用的UI组件，有自己的布局和完整的生命周期，可以处理本身的事件，但是必须依存于Activity，不能脱离Activity而存在。

可以看出来，Fragment的生命周期跟Activity非常相似，并且会随着Activity的销毁而销毁。

下面，我们来战。

首先，新建一个Fragment的子类，取名为WeatherFragment。

public class WeatherFragment extends Fragment{    @Override    public void onCreate( Bundle savedInstanceState )    {        super.onCreate( savedInstanceState );    }    @Override    public View onCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState )    {        return super.onCreateView( inflater, container, savedInstanceState );    }}

这是用来显示天气的界面，而我们之前是直接在Activity中显示的，需要把这部分代码给移植到Fragment中。

这是个麻烦的过程，不过不要紧，慢慢来。

新建一个Layout，取名为frag_weather.xml，然后把activity_main.xml中的代码给复制过来，

我们让WeatherFragment使用新的Layout，再把MainActivity中关于天气的代码移植到WeatherFragment中，

public class WeatherFragment extends Fragment{    @ViewInject( R.id.weather_list )    private ListView lstWeather;    private WeatherAdapter adapter;    private BaiduData data;    private List
    
      datas;    private String city;    public void setCity( String city )    {        this.city = city;    }    @Override    public void onCreate( Bundle savedInstanceState )    {        super.onCreate( savedInstanceState );        datas = new ArrayList
     
      ();        adapter = new WeatherAdapter( getActivity(), datas );    }    @Override    public View onCreateView( LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState )    {        View view = inflater.inflate( R.layout.frag_weather, null );        ViewUtils.inject( this, view );        lstWeather.setAdapter( adapter );        getWeather();        return view;    }    private void getWeather()    {        HttpUtils http = new HttpUtils();        RequestParams params = new RequestParams();        params.addQueryStringParameter( "location", city );        params.addQueryStringParameter( "output", "json" );        params.addQueryStringParameter( "ak", "YknGmxIoPugT7YrNrG955YLS" );        http.send( HttpMethod.GET, "http://api.map.baidu.com/telematics/v3/weather", params, new RequestCallBack
      
       ()        {            @Override            public void onSuccess( ResponseInfo
       
         responseInfo )            {                String weather = responseInfo.result;                Gson gson = new Gson();                data = gson.fromJson( weather, BaiduData.class );                datas.clear();                datas.addAll( data.getResults().get( 0 ).getWeather_data() );                adapter.notifyDataSetChanged();                Log.v( "onSuccess", data.toString() );            }            @Override            public void onFailure( HttpException arg0, String arg1 )            {                Log.v( "onFailure", arg1 );            }        } );    }}

然后，修改主页面activity_main.xml为：

这里我们引入了ViewPager，并且还有一个LinearLayout，其中ViewPager我们用来显示天气，Linearlayout用来作为指示器，表示我们当前所选城市的次序。

之后，修改我们主页面的代码，主界面现在的作用主要是两个：

1. 初次启动的时候，获取所在地城市

2. 处理切换Fragment的逻辑

3. 处理页面跳转/返回的逻辑

public class MainActivity extends FragmentActivity{    @ViewInject( R.id.viewPager )    private ViewPager pager;    @ViewInject( R.id.viewGroup )    private LinearLayout layout;    private MyAdapter mAdapter;    private List
    
      citys;    private LocationClient mLocationClient;    private BDLocationListener myListener;    private List
     
       imageViews;    @Override    protected void onCreate( Bundle savedInstanceState )    {        super.onCreate( savedInstanceState );        setContentView( R.layout.activity_main );        Log.v( "WeatherAPP", "onCreate" );        ViewUtils.inject( this );        imageViews = new ArrayList
      
       ();        citys = readCity();        mAdapter = new MyAdapter( getSupportFragmentManager() );        pager.setAdapter( mAdapter );        pager.setOnPageChangeListener( new OnPageChangeListener()        {            @Override            public void onPageSelected( int arg0 )            {                setTitle( citys.get( arg0 ).getCityName() + "天气" );                setImageBackground( arg0 );            }            @Override            public void onPageScrolled( int arg0, float arg1, int arg2 )            {            }            @Override            public void onPageScrollStateChanged( int arg0 )            {            }        } );        if( citys == null || citys.size() == 0 )        {            citys = new ArrayList
       
        ();            initLocationClient();            mLocationClient.start();        }        showIndicator( 0 );    }    private void showIndicator( int position )    {        layout.removeAllViews();        imageViews = new ArrayList
        
         ();        pager.setCurrentItem( position );        for( int i = 0; i < citys.size(); i++ )        {            ImageView imageView = new ImageView( this );            LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams( 20, 20 );            lp.leftMargin = 5;            imageView.setLayoutParams( lp );            imageViews.add( imageView );            if( i == position )            {                setTitle( citys.get( position ).getCityName() + "天气" );                imageView.setBackgroundResource( R.drawable.page_indicator_focused );            }            else            {                imageView.setBackgroundResource( R.drawable.page_indicator_unfocused );            }            layout.addView( imageView );        }    }    private void setImageBackground( int selectItems )    {        for( int i = 0; i < imageViews.size(); i++ )        {            if( i == selectItems )            {                imageViews.get( i ).setBackgroundResource( R.drawable.page_indicator_focused );            }            else            {                imageViews.get( i ).setBackgroundResource( R.drawable.page_indicator_unfocused );            }        }    }    @Override    public boolean onCreateOptionsMenu( Menu menu )    {        super.onCreateOptionsMenu( menu );        menu.add( Menu.NONE, Menu.FIRST + 1, 0, "添加城市" ).setShowAsAction( MenuItem.SHOW_AS_ACTION_ALWAYS );        return true;    }    @Override    public boolean onOptionsItemSelected( MenuItem item )    {        if( item.getItemId() == Menu.FIRST + 1 )        {            Intent intent = new Intent( getApplicationContext(), ChooseCityActivity.class );            intent.putExtra( "key", "value" );            startActivityForResult( intent, 99 );        }        return super.onOptionsItemSelected( item );    }    @Override    protected void onActivityResult( int requestCode, int resultCode, Intent data )    {        super.onActivityResult( requestCode, resultCode, data );        if( resultCode == RESULT_OK )        {            String city = data.getStringExtra( "selectedCity" );            addCity( city );        }    }    private void initLocationClient()    {        mLocationClient = new LocationClient( getApplicationContext() ); // 声明LocationClient类        myListener = new MyLocationListener();        LocationClientOption option = new LocationClientOption();        option.setLocationMode( LocationMode.Hight_Accuracy );        option.setIsNeedAddress( true );        mLocationClient.setLocOption( option );        mLocationClient.registerLocationListener( myListener );    }    @Override    protected void onStop()    {        Log.v( "WeatherAPP", "onStop" );        super.onStop();        if( mLocationClient != null ) mLocationClient.stop();    }    @Override    protected void onPause()    {        Log.v( "WeatherAPP", "onPause" );        super.onPause();    }    @Override    protected void onRestart()    {        Log.v( "WeatherAPP", "onRestart" );        super.onRestart();    }    @Override    protected void onResume()    {        Log.v( "WeatherAPP", "onResume" );        super.onResume();    }    @Override    protected void onStart()    {        Log.v( "WeatherAPP", "onStart" );        super.onStart();    }    @Override    protected void onDestroy()    {        Log.v( "WeatherAPP", "onDestroy" );        super.onDestroy();    }    public class MyLocationListener implements BDLocationListener    {        @Override        public void onReceiveLocation( BDLocation location )        {            String city = location.getCity();            addCity( city );        }    }    private void addCity( String city )    {        SelectCityBean cityBean = new SelectCityBean();        cityBean.setCityName( city );        saveCity( cityBean );        if( citys == null ) citys = new ArrayList
         
          (); citys.add( cityBean ); mAdapter.notifyDataSetChanged(); showIndicator( citys.size() - 1 ); } private void saveCity( SelectCityBean city ) { DbUtils dbUtils = WeatherApplication.getInstance().getDbUtil(); try { dbUtils.save( city ); } catch( DbException e ) { } } private List
          
            readCity() { DbUtils dbUtils = WeatherApplication.getInstance().getDbUtil(); try { return dbUtils.findAll( SelectCityBean.class ); } catch( DbException e ) { return null; } } public class MyAdapter extends FragmentStatePagerAdapter { public MyAdapter( FragmentManager fm ) { super( fm ); } @Override public Fragment getItem( int arg0 ) { WeatherFragment fragment = new WeatherFragment(); fragment.setCity( citys.get( arg0 ).getCityName() ); return fragment; } @Override public int getItemPosition( Object object ) { return POSITION_NONE; } @Override public int getCount() { if( citys == null ) return 0; return citys.size(); } }}

基本上面目全非了，跟之前的代码完全不一样了，这里面的主要变动为：

1. saveCity、readCity不再从Preference中获取数据了，而改为从数据库获取

2. 增加了MyAdapter以及相关的ViewPager的逻辑

这里还用到了一个新的SelectCityBean以及两个图片资源，

public class SelectCityBean{    private int id;    private String cityName;    public int getId()    {        return id;    }    public void setId( int id )    {        this.id = id;    }    public String getCityName()    {        return cityName;    }    public void setCityName( String cityName )    {        this.cityName = cityName;    }}

两个图片资源分别代表了当前城市以及其他城市，

完成之后，运行来看看，我这边的效果是这样的：

你可以试着添加城市看看，是不是这样的效果。

今天的内容比较少，代码比较多，大家多多练习一下。

附件是本次的工程文件， http://pan.baidu.com/s/1sj2V5fB 。

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