痞客興的部落格

寫入資料

FileOutputStream fout = openFileOutput("myfile.txt",MODE_PRIVATE);
BufferedOutputStream buffout = new BufferedOutputStream(fout);
buffout.write("這是測試".getBytes());
buffout.close();

讀取資料

FileInputStream fin = openFileInput("myfile.txt");
BufferedInputStream buffin = new BufferedInputStream(fin);
byte[] buffbyte = new byte[20];
int length = buffin.read(buffbyte);
buffin.close();

清空資料

FileOutputStream fout = openFileOutput("myfile.txt", MODE_PRIVATE);
fout.close();

一個簡單的範例

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
    <EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/edt_write"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
    <Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Write to File"
android:id="@+id/btn_write"
android:layout_below="@+id/edt_write"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
    <Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Refresh display"
android:id="@+id/btn_display"
android:layout_alignTop="@+id/btn_write"
android:layout_toRightOf="@+id/btn_write"
android:layout_toEndOf="@+id/btn_write" />
    <TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:id="@+id/tv_display"
android:layout_below="@+id/btn_clear"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
    <Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="clear File"
android:id="@+id/btn_clear"
android:layout_below="@+id/btn_write"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</RelativeLayout>

MainActivity.java

package tw.idv.charleslin74.filereadwritetest;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    EditText edt_write;
    TextView tv_display;
    Button btn_write,btn_display,btn_clear;

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

        edt_write = (EditText)findViewById(R.id.edt_write);
        tv_display = (TextView)findViewById(R.id.tv_display);
        btn_write = (Button)findViewById(R.id.btn_write);
        btn_display = (Button)findViewById(R.id.btn_display);
        btn_clear = (Button)findViewById(R.id.btn_clear);

        btn_write.setOnClickListener(btnClickListener);
        btn_display.setOnClickListener(btnClickListener);
        btn_clear.setOnClickListener(btnClickListener);
    }

    private Button.OnClickListener btnClickListener = new Button.OnClickListener() {
        @Override
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.btn_write:
                    try {
                        String strout = String.valueOf(edt_write.getText());
                        FileOutputStream fout = openFileOutput("myfile.txt", MODE_APPEND);
                        BufferedOutputStream buffout = new BufferedOutputStream(fout);
                        buffout.write(strout.getBytes());
                        buffout.write("\n".getBytes());
                        buffout.close();
                        edt_write.setText("");
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    break;
                case R.id.btn_display:
                    try {
                        FileInputStream fin = openFileInput("myfile.txt");
                        BufferedInputStream buffin = new BufferedInputStream(fin);
                        byte[] buffbyte = new byte[30];
                        buffin.read(buffbyte);
                        tv_display.setText(new String(buffbyte));
                        buffin.close();
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    break;
                case R.id.btn_clear:
                    try {
                        FileOutputStream fout = openFileOutput("myfile.txt", MODE_PRIVATE);
                        fout.close();
                        tv_display.setText("");
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }

            }
        }
    };
}