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

 public class MainActivity extends AppCompatActivity {
 private EditText edit;
     private TextView tx;
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         edit= (EditText) findViewById(R.id.edit);
         tx= (TextView) findViewById(R.id.tx);
     }
     @Override
     protected void onDestroy() {
         super.onDestroy();
      String input=edit.getText().toString();
         save(input);
     }

//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

  private void save(String input) {
         FileOutputStream fileout=null;
         BufferedWriter writer=null;
         try {
    //data:文件名 Context.MODE_PRIVATE:访问权限
             fileout=openFileOutput("data", Context.MODE_PRIVATE);
             writer=new BufferedWriter(new OutputStreamWriter(fileout));
             writer.write(input);
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         finally {
             if(writer!=null)
                 try {
                     writer.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
         }
     }
     public void doclick(View v) {
         switch (v.getId()) {
             case R.id.bt:
             String text = load();
             tx.setText(text);
         }
     }
 //取出数据
     public String load()
     {
         FileInputStream input=null;
         BufferedReader read=null;
 //StringBuilder的对象的append方法可以将字符连接起来
         StringBuilder content=new StringBuilder();
         try {
             input=openFileInput("data");
             read=new BufferedReader(new InputStreamReader(input));
             String line="";
             while((line=read.readLine())!=null){
                 content.append(line);
             }
         } catch (FileNotFoundException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
         return content.toString();
     }
 }