文件存储---内部存储/外部存储

一个简单的记事本   

外部存储需要内存卡读取写入权限

activity_main.xml

MainActivity.java

public class MainActivity extends AppCompatActivity {
    EditText content;
    Button save_btn;
    //File file=; 外部存储代码
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        content = (EditText) findViewById(R.id.content);
        save_btn = (Button) findViewById(R.id.save_btn);
        //file=new File(Environment.getExternalStorageDirectory(),"text.text");
        byte buffer[]=null;
        FileInputStream fi = null;
        save_btn.setOnClickListener(new myClick());
        try {
            fi = openFileInput("Demo");//外部存储改为 fi = new FileInputStream(file);
            buffer = new byte[fi.available()];
            fi.read(buffer);

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (fi != null) {
                try {
                    fi.close();
                    String cont=new String(buffer);
                    content.setText(cont);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

    //保存按钮监听事件
    public class myClick implements View.OnClickListener {

        @Override
        public void onClick(View v) {
            String con = content.getText().toString();
            FileOutputStream fileOutputStream = null;
            //保存文件
            try {
                fileOutputStream = openFileOutput("Demo", MODE_PRIVATE);//外部存储改为  fileOutputStream = new FileOutputStream(file);
                fileOutputStream.write(con.getBytes());
                fileOutputStream.flush();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    if (fileOutputStream != null) {
                        fileOutputStream.close();
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }


}