Android中使用SDcard读取文件

<!-- 在SDCard中创建与删除文件权限 -->
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<!-- 往SDCard写入数据权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />
<EditText
android:id="@+id/et1"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<Button
android:id="@+id/bt1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="使用SDcard写操作" />
<EditText
android:id="@+id/et2"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<Button
android:id="@+id/bt2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="使用SDcard读操作" />
</LinearLayout> 

import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import org.apache.http.util.EncodingUtils;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import android.app.Activity;
import android.content.Context;
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.Toast;
public class MainActivity extends AppCompatActivity {
private Button bt1, bt2;
private EditText et1, et2;
private static final String FILENAME = "temp_file.txt";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bt1 = (Button) this.findViewById(R.id.bt1);
bt2 = (Button) this.findViewById(R.id.bt2);
et1 = (EditText) this.findViewById(R.id.et1);
et2 = (EditText) this.findViewById(R.id.et2);
bt1.setOnClickListener(new MySetOnClickListener());
bt2.setOnClickListener(new MySetOnClickListener());
}
private class MySetOnClickListener implements OnClickListener {
@Override
public void onClick(View v) {
File file = new File(Environment.getExternalStorageDirectory(),
FILENAME);
switch (v.getId()) {
case R.id.bt1:// 使用SDcard写操作
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
try {
FileOutputStream fos = new FileOutputStream(file);
fos.write(et1.getText().toString().getBytes());
fos.close();
Toast.makeText(MainActivity.this, "写入文件成功",
Toast.LENGTH_LONG).show();
} catch (Exception e) {
Toast.makeText(MainActivity.this, "写入文件失败",
Toast.LENGTH_SHORT).show();
}
} else {
// 此时SDcard不存在或者不能进行读写操作的
Toast.makeText(MainActivity.this,
"此时SDcard不存在或者不能进行读写操作", Toast.LENGTH_SHORT).show();
}
break;
case R.id.bt2:// 使用SDcard读操作
if (Environment.getExternalStorageState().equals(
Environment.MEDIA_MOUNTED)) {
try {
FileInputStream inputStream = new FileInputStream(file);
byte[] b = new byte[inputStream.available()];
inputStream.read(b);
et2.setText(new String(b));
Toast.makeText(MainActivity.this, "读取文件成功",
Toast.LENGTH_LONG).show();
} catch (Exception e) {
Toast.makeText(MainActivity.this, "读取失败",
Toast.LENGTH_SHORT).show();
}
} else {
// 此时SDcard不存在或者不能进行读写操作的
Toast.makeText(MainActivity.this,
"此时SDcard不存在或者不能进行读写操作", Toast.LENGTH_SHORT).show();
}
break;
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}