File文件存储

文件存储的核心是Context提供了一个openFileOutput()与openFileInput()俩个方法

课程demo

 1 public class MainActivity extends AppCompatActivity {
 2 private EditText edit;
 3     private TextView tx;
 4     @Override
 5     protected void onCreate(Bundle savedInstanceState) {
 6         super.onCreate(savedInstanceState);
 7         setContentView(R.layout.activity_main);
 8         edit= (EditText) findViewById(R.id.edit);
 9         tx= (TextView) findViewById(R.id.tx);
10     }
11     @Override
12     protected void onDestroy() {
13         super.onDestroy();
14      String input=edit.getText().toString();
15         save(input);
16     }

//保存数据
思想：通过openFileOutput方法，得到一个FileOutputStream对象，将其包裹在
OutputStreamWriter上，也生成一个对象，继续包裹在BufferedWriter上，得到一个对象
调用write()方法，把数据传入

 1  private void save(String input) {
 2         FileOutputStream fileout=null;
 3         BufferedWriter writer=null;
 4         try {
 5    //data:文件名 Context.MODE_PRIVATE:访问权限
 6             fileout=openFileOutput("data", Context.MODE_PRIVATE);
 7             writer=new BufferedWriter(new OutputStreamWriter(fileout));
 8             writer.write(input);
 9         } catch (FileNotFoundException e) {
10             e.printStackTrace();
11         } catch (IOException e) {
12             e.printStackTrace();
13         }
14         finally {
15             if(writer!=null)
16                 try {
17                     writer.close();
18                 } catch (IOException e) {
19                     e.printStackTrace();
20                 }
21         }
22     }
23     public void doclick(View v) {
24         switch (v.getId()) {
25             case R.id.bt:
26             String text = load();
27             tx.setText(text);
28         }
29     }
30 //取出数据
31     public String load()
32     {
33         FileInputStream input=null;
34         BufferedReader read=null;
35 //StringBuilder的对象的append方法可以将字符连接起来
36         StringBuilder content=new StringBuilder();
37         try {
38             input=openFileInput("data");
39             read=new BufferedReader(new InputStreamReader(input));
40             String line="";
41             while((line=read.readLine())!=null){
42                 content.append(line);
43             }
44         } catch (FileNotFoundException e) {
45             e.printStackTrace();
46         } catch (IOException e) {
47             e.printStackTrace();
48         }
49         return content.toString();
50     }
51 }