Android在SD卡上的文件读写

该程序实现将字符串保存到文件，读取文件。

首先要获取外部存储写权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

MainActivity.java

package com.example.sdfiledemo;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import android.app.Activity;import android.os.Bundle;import android.os.Environment;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.TextView;import android.widget.Toast;import com.example.sdfiledemo.R.id;public class MainActivity extends Activity {Button write, read;EditText text;TextView lable;File dir, file;FileOutputStream fos;FileInputStream fis;ByteArrayOutputStream baos;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);write = (Button) findViewById(id.button1);read = (Button) findViewById(id.button2);text = (EditText) findViewById(id.editText1);lable = (TextView) findViewById(id.textView1);if (Environment.getExternalStorageState().equals(//查看SD卡是否挂载Environment.MEDIA_MOUNTED)) {Toast.makeText(MainActivity.this, "SD卡已挂载!", Toast.LENGTH_SHORT).show();}dir = new File("/mnt/sdcard/mydir");file = new File(dir.toString() + "/file.txt");if (!dir.exists()) {// 若文件夹不存在，则创建目录dir.mkdirs();Toast.makeText(MainActivity.this, "mydir文件夹已经创建!",Toast.LENGTH_SHORT).show();}write.setOnClickListener(new OnClickListener() {public void onClick(View v) {try {fos = new FileOutputStream(file, false);// 不追加String str = text.getText().toString();// 直接将字节数组写到文件中，文件若不存在会自动创建fos.write(str.getBytes());fos.close();// 关闭文件输出流Toast.makeText(MainActivity.this, "文件已经写入!",Toast.LENGTH_SHORT).show();} catch (Exception e) {e.printStackTrace();}}});read.setOnClickListener(new OnClickListener() {// 将文件字节读取到字节数组输出流中，以一个字节数组作缓冲public void onClick(View v) {try {fis = new FileInputStream(file);byte[] buff = new byte[1024];// 设置一个缓冲baos = new ByteArrayOutputStream();int len;while ((len = fis.read(buff)) != -1) {// 如果buff没有读完baos.write(buff, 0, len);// 就将buff内容保存到字节数组输出流中}byte[] data = baos.toByteArray();// 得到字节数组输出流的数据baos.close();// 关闭字节数组输出流fis.close();// 关闭文件输出流lable.setText(new String(data));// 将读出的内容显示Toast.makeText(MainActivity.this, "文件已经读出!",Toast.LENGTH_SHORT).show();} catch (Exception e) {e.printStackTrace();}}});}}

布局文件

<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" >    <LinearLayout        android:id="@+id/linearLayout1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentRight="true"        android:layout_alignParentTop="true"        android:orientation="vertical" >        <EditText            android:id="@+id/editText1"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_alignParentLeft="true"            android:layout_alignParentRight="true"            android:layout_alignParentTop="true"            android:ems="10" >            <requestFocus />        </EditText>        <Button            android:id="@+id/button1"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_alignParentLeft="true"            android:layout_alignParentRight="true"            android:layout_below="@+id/editText1"            android:text="Button" />        <TextView            android:id="@+id/textView1"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_alignParentLeft="true"            android:layout_alignParentRight="true"            android:layout_below="@+id/linearLayout1"            android:text="Large Text"            android:textAppearance="?android:attr/textAppearanceLarge" />        <Button            android:id="@+id/button2"            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:text="Button" />    </LinearLayout></RelativeLayout>

更多相关文章

随机推荐