Android 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。