android 讀取, 寫入及刪除檔案 (internal storage)

版面要加入一個editView, 一個textView及三個 Button (editView, textView, btnRead, btnWrite, btnDel)

MainActivity.java

import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.view.View.OnClickListener;
import android.widget.Toast;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;


public class MainActivity extends ActionBarActivity {
    private Button btnTxtRead;
    private Button btnTxtWrite;
    private Button btnFileDel;
    private EditText txtWrite;
    private TextView txtRead;
    String fileName = "dateRec.dat";


    @Override     

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtWrite = (EditText) findViewById(R.id.editText);
        txtRead = (TextView) findViewById(R.id.textView);

        btnTxtRead = (Button) findViewById(R.id.btnRead);
        btnTxtWrite = (Button) findViewById(R.id.btnWrite);
        btnFileDel = (Button) findViewById(R.id.btnDel);

        btnTxtRead.setOnClickListener(btnListener);
        btnTxtWrite.setOnClickListener(btnListener);
        btnFileDel.setOnClickListener(btnListener);


    }


    private void writer() {
        FileOutputStream fos = null;
        
        try {
            fos = openFileOutput(fileName, Context.MODE_PRIVATE);
            fos.write(txtWrite.getText().toString().getBytes());
            fos.close();

            File file = new File(getFilesDir() + "/" + fos);
            Toast.makeText(getApplicationContext(), file.getAbsolutePath(), Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    private void reader() {
        FileInputStream fos = null;
        BufferedInputStream buffered = null;
        txtRead.setText("");

        try {
            fos = openFileInput(fileName);
            buffered = new BufferedInputStream(fos);
            byte[] buffbyte = new byte[200];
            txtRead.setText("");
            do {
                int flag = buffered.read(buffbyte);
                if (flag == -1) {
                    break;
                } else {
                    txtRead.append(new String(buffbyte), 0, flag);
                }
            }while (true);
            buffered.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void fileDel() {
        File file = new File(getFilesDir() + "/" + fileName);
        if (file.exists()){
            file.delete();
            Toast.makeText(getBaseContext(),
                    "File deleted",
                    Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(getBaseContext(),
                    "File doesn't exist",
                    Toast.LENGTH_SHORT).show();
        }
    }

    private OnClickListener btnListener = new OnClickListener() {
            public void onClick(View v) {
                switch (v.getId()) {
                    case R.id.btnRead:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Read button pressed", Toast.LENGTH_SHORT).show();
                            reader();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                    case R.id.btnWrite:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Write button pressed", Toast.LENGTH_SHORT).show();
                            writer();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                    case R.id.btnDel:
                        try {
                            Toast.makeText(getApplicationContext(),
                                    "Del button pressed", Toast.LENGTH_SHORT).show();
                            fileDel();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        break;
                }


            }


        };
    }