Android基础--创建模块化接口笔记

         这是一个简单的复用Fragment的小案例，比较基础，需要熟练，我们常常使用Fragment来显示一些UI控件，但是Fragment 不必像Activity一样一定要拥有一个UI控件。如果不复写onCreateView(),Fragment可以作为一个纯粹的数据源或者其他模块而存在。这种机制可以很好地将应用程序中的模型部分进行模块化处理，因为FragmentManager会使得Fragment之间的访问变得简单。

          案例描述：用三个fragmeng演示一个简单的概要-详情类的应用程序，宿主Fragment显示一个用户可以访问的网站列表，详情Fragment则通过一个WebView来显示选中网站列表条目后的详细URL信息。第三个Fragment是没有UI界面的，它用来为其他Fragment提供模型数据。

       

DataFragment.java

       

** * 封装应用程序的数据逻辑 */public class DataFragment extends Fragment {    public static String TAG= DataFragment.class.getSimpleName();    public static class DataItem{        private String mName;        private String mUrl;        public DataItem(String mName, String mUrl) {            this.mName = mName;            this.mUrl = mUrl;        }        public String getmName() {            return mName;        }        public String getmUrl() {            return mUrl;        }    }    //用来创建新的实例    public static DataFragment newInstance(){        return new DataFragment();    }    private ArrayList<DataItem>  mDataSet;    @Override    public void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //构建初始化数据        mDataSet = new ArrayList<DataItem>();        mDataSet.add(new DataItem("Baidu", "https://www.baidu.com"));        mDataSet.add(new DataItem("CSDN", "http://www.csdn.net"));        mDataSet.add(new DataItem("Android", "http://www.android.com"));    }        public ArrayList<DataItem> getLatestData(){            return mDataSet;        }}

      宿主MasterFragment.java

 

/** * 宿主视图Fragment */public class MasterFragment extends DialogFragment implements AdapterView.OnItemClickListener {public static String TAG= MasterFragment.class.getSimpleName();   /*   * 回调接口，用来将选择的数据反馈给父Activity   * */    public interface  OnItemSelectedListener{        void onDataItemSelected(DataFragment.DataItem selected);   }    //用来创建实例   public static MasterFragment newInstance(){       return new MasterFragment();   }    private ArrayAdapter<DataFragment.DataItem> mAdapter;    private OnItemSelectedListener mItemSelectedListener;/** 连接监听器接口，并且确保我们要关联的Activity支持该接口* */    @Override    public void onAttach(Activity activity) {        super.onAttach(activity);        try {            mItemSelectedListener= (OnItemSelectedListener) activity;        }catch (ClassCastException e){            throw new IllegalArgumentException("Activity must implement OnItemSelectedListener");        }    }    /*    * 构建一个自定义适配器来显示数据模型中的name字段    * */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mAdapter=new ArrayAdapter<DataFragment.DataItem>(getActivity(),                android.R.layout.simple_list_item_1){            @Override            public View getView(int position, View convertView, ViewGroup parent) {                View row=convertView;                if(row==null){                    row=LayoutInflater.from(getContext()).inflate(android.R.layout.simple_list_item_1,                            parent,false);                }                DataFragment.DataItem item = getItem(position);                TextView tv = (TextView) row.findViewById(android.R.id.text1);                tv.setText(item.getmName());                return row;            }        };    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        ListView list = new ListView(getActivity());        list.setOnItemClickListener(this);        list.setAdapter(mAdapter);        return list;    }    /*    * 可以直接访问要显示的对话框，设置对话框的标题    * */    @Override    public Dialog onCreateDialog(Bundle savedInstanceState) {        Dialog dialog = super.onCreateDialog(savedInstanceState);        dialog.setTitle("Select a title");        return dialog;    }    /*    * 从DataFrament中得到最新的数据信息    * */    @Override    public void onResume() {        super.onResume();        //获得最新数据列表        DataFragment fragment= (DataFragment) getFragmentManager()                .findFragmentByTag(DataFragment.TAG);        if(fragment!=null){            mAdapter.clear();            for(DataFragment.DataItem item:fragment.getLatestData()){                mAdapter.add(item);            }            mAdapter.notifyDataSetChanged();        }    }    @Override    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        //通知Activity        mItemSelectedListener.onDataItemSelected(mAdapter.getItem(position));        //如果对话框显示的，则隐藏它        //在fragment嵌入到某个视图的情况下，这个方法返回false;        boolean showsDialog = getShowsDialog();        if(showsDialog){            dismiss();        }    }}

DetailFragment.java

   
       

/** * 详情视图. */public class DetailFragment extends Fragment {    private WebView mWebView;    /*    *自定义web客户端启用进度显示。    * */    private WebViewClient mWebViewClient=new WebViewClient(){        @Override        public void onPageStarted(WebView view, String url, Bitmap favicon) {            getActivity().setProgressBarVisibility(true);        }        @Override        public void onPageFinished(WebView view, String url) {            getActivity().setProgressBarIndeterminateVisibility(false);        }    };    //设置一个显示的WebView    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        setRetainInstance(true);        mWebView=new WebView(getActivity());        mWebView.getSettings().setJavaScriptEnabled(true);        mWebView.setWebViewClient(mWebViewClient);        return mWebView;    }    //外部方法，用来将一个新的网站内容加载到视图    public void loadUrl(String url){       mWebView.loadUrl(url);    }}

MainActivity.java

public class MainActivity extends FragmentActivity implements MasterFragment.OnItemSelectedListener {    public static String TAG= MainActivity.class.getSimpleName();    private MasterFragment mMaster;    private DetailFragment mDetail;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //窗口上启用一个进度条        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);        setContentView(R.layout.activity_main);        setProgressBarIndeterminateVisibility(false);        //加载数据Fragment        DataFragment fragment = (DataFragment) getSupportFragmentManager()                .findFragmentByTag(DataFragment.TAG);        if(fragment==null){            fragment=DataFragment.newInstance();            //保存这个实例            fragment.setRetainInstance(true);            //通过一个tag而不是一个容器id关联fragment            FragmentTransaction ft=                    getSupportFragmentManager().beginTransaction();            ft.add(fragment,DataFragment.TAG);            ft.commit();        }        mDetail= (DetailFragment) getSupportFragmentManager()                .findFragmentById(R.id.fragment_detail);        mDetail.setRetainInstance(true);        //或者嵌入到宿主fragment,直接作为dialog显示。        mMaster=MasterFragment.newInstance();        //如果存在容器视图，嵌入fragment        View container=findViewById(R.id.fragment_master);        if(container !=null){            FragmentTransaction ft = getSupportFragmentManager().beginTransaction();            ft.add(R.id.fragment_master,mMaster);            ft.commit();        }    }    @Override    public void onDataItemSelected(DataFragment.DataItem selected) {        String s = selected.getmUrl();         //显示详情信息        mDetail.loadUrl(selected.getmUrl());    }    //Button点击事件    public void onShowClick(View v){        mMaster.show(getSupportFragmentManager(),null);    }}