Android(安卓)将从网络获取的数据缓存到私有文件

1：activity_main.xml

<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">    <Button         android:id="@+id/btn_get_titles"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Get Titles"/>    <ListView            android:id="@+id/lv_show"        android:layout_below="@id/btn_get_titles"        android:layout_width="match_parent"        android:layout_height="wrap_content"/></RelativeLayout>

2：MainActivity.java

public class MainActivity extends Activity implements OnClickListener {    private Button btnGetTitles=null;    private ListView lvShow=null;    private List<String> titleList=null;        @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                initUI();                btnGetTitles.setOnClickListener(this);    }    private void initUI(){        btnGetTitles=(Button)findViewById(R.id.btn_get_titles);        lvShow=(ListView)findViewById(R.id.lv_show);    }    @Override    public void onClick(View arg0) {        new Thread(new GetTitlesThread()).start();    }        Handler getTitlesHandler=new Handler(){        public void handleMessage(Message msg){            if(msg.what==100){                ArrayAdapter<String> adapter=new ArrayAdapter<String>(                        MainActivity.this,                        android.R.layout.simple_list_item_1,                        titleList);                lvShow.setAdapter(adapter);            }        }    };    class GetTitlesThread implements Runnable{        @Override        public void run() {            //1：判断缓存文件是否存在。/data/data/com.yan.example/jsontest/files/titles.txt            String path=getFilesDir().getPath()+"//" ;            File file=new File(path+"titles.txt");            if(file.exists()){                //2：如果缓存文件存在，就从文件取数据。                readFile("titles.txt");                getTitlesHandler.obtainMessage(100).sendToTarget();            }else{                //3：如果缓存文件不存在，就从网络取数据 ，然后将数据保存到缓存文件。                String url="http://www.zhihuiqd.com/wsht/server/selectTitle2json.php";                String res=getStringFromeNet(url);                                        saveFile("titles.txt",res);//////将内容缓存起来                                try{                    JSONArray json=new JSONArray(res);                    int len=json.length();                    String title="";                    titleList=new ArrayList<String>();                                                for(int i=0;i<len;i++){                        JSONObject temp=(JSONObject)json.get(i);                        title=temp.getString("title");                        titleList.add(title);                    }                }catch(Exception e){                    e.printStackTrace();                }                getTitlesHandler.obtainMessage(100).sendToTarget();            }        }    }        //保存文件    private void saveFile(String filename,String str){        try{            FileOutputStream fos=openFileOutput(filename,Activity.MODE_PRIVATE);            byte[]bytes=str.getBytes();            fos.write(bytes);            fos.flush();            fos.close();        }catch(Exception e){            e.printStackTrace();        }    }        //读取文件    private void readFile(String filename){        String res="";        try{            FileInputStream fis=openFileInput(filename);            int length=fis.available();            byte[]buffer=new byte[length];            fis.read(buffer);            res=EncodingUtils.getString(buffer, "UTF-8");            fis.close();            JSONArray json=new JSONArray(res);            int len=json.length();            String title="";            titleList=new ArrayList<String>();            for(int i=0;i<len;i++){                JSONObject temp=(JSONObject)json.get(i);                title=temp.getString("title");                titleList.add(title);            }        }catch(Exception e){            e.printStackTrace();        }    }        //从网络服务端取数据    private String getStringFromeNet(String url){        StringBuilder builder=new StringBuilder();        HttpClient client=new DefaultHttpClient();        HttpGet get=new HttpGet(url);        try{            HttpResponse response=client.execute(get);            if(response.getStatusLine().getStatusCode()==200){                BufferedReader reader=new BufferedReader(                        new InputStreamReader(response.getEntity().getContent()));                for(String s=reader.readLine();s!=null;s=reader.readLine()){                    builder.append(s);                }            }        }catch(Exception e){            e.printStackTrace();        }        return builder.toString();    }}

3：运行结果。

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