android内存文件读写

public class MainActivity extends Activity implements OnClickListener {
    private Button fileSave;
    private Button fileRead;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fileSave = (Button) findViewById(R.id.button1);
        fileRead = (Button) findViewById(R.id.button2);
        fileSave.setOnClickListener(this);
        fileRead.setOnClickListener(this);

    }

    @Override
    public void onClick(View v) {
        int id = v.getId();
        switch (id) {
        case R.id.button1:
            FileOutputStream fos = null;
            try {
                fos = openFileOutput("out.txt", Context.MODE_PRIVATE);
                fos.write("text...".getBytes());
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (fos != null) {
                    try {
                        fos.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

            break;
        case R.id.button2:
            FileInputStream fis = null;
            try {
                fis = openFileInput("out.txt");
                byte[] b = new byte[1024];
                int len = 0;
                StringBuilder sb = new StringBuilder();
                while ((len = fis.read(b)) != -1) {
                    String string = new String(b, 0, len);
                    sb.append(string);
                }
                Toast.makeText(this, sb.toString(), Toast.LENGTH_SHORT).show();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (fis != null) {
                    try {
                        fis.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
            break;
        default:
            break;
        }
    }
}