读取外部存储的文件数据Environment.getExternalStorageDirectory()

MainActivity .java

package com.example.debug;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.io.UnsupportedEncodingException;

import android.os.Bundle;

import android.os.Environment;

import android.app.Activity;

import android.content.Context;

import android.util.Log;

import android.view.Menu;

import android.view.View;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends Activity {

String filename="test";

private EditText et;

private TextView show;

File sdcard=Environment.getExternalStorageDirectory();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
et=(EditText) findViewById(R.id.et);
show=(TextView) findViewById(R.id.show);
findViewById(R.id.readBtn).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
File myfile=new  File(sdcard, "Thismyfile.txt");
   if(myfile.exists()){
   try {
FileInputStream fis=new FileInputStream(myfile);
InputStreamReader isr=new InputStreamReader(fis,"utf-8");
char []input=new char[fis.available()];
isr.read(input);
isr.close();
fis.close();
String inString=new String(input);
show.setText(inString);
} catch (FileNotFoundException e) {
} catch (UnsupportedEncodingException e) {
} catch (IOException e) {
}
   }
}
});
findViewById(R.id.writeBtn).setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
   File myfile=new  File(sdcard, "Thismyfile.txt");
   if(!sdcard.exists()){
    Toast.makeText(MainActivity.this, "当前设备不存在sd卡", Toast.LENGTH_LONG).show();
       return;
   }
   try {
myfile.createNewFile();
Toast.makeText(MainActivity.this, "文件创建完成", Toast.LENGTH_LONG).show();
   FileOutputStream fos=new FileOutputStream(myfile);
   OutputStreamWriter osw=new OutputStreamWriter(fos);
   osw.write(et.getText().toString());
   osw.flush();
   osw.close();
   fos.close();
   Toast.makeText(MainActivity.this, "文件已经写入完成", Toast.LENGTH_LONG).show();
   } catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

});
}

}

activity_main.xml:

<LinearLayout 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:orientation="vertical"

    tools:context=".MainActivity" >

<EditText 

    android:id="@+id/et"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:hint="在这里输入要保存的数据"

    />

<Button

    android:id="@+id/writeBtn"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="写入数据" />

<Button

    android:id="@+id/readBtn"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="读取数据" />

<TextView 

    android:id="@+id/show"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:hint="这里显示读到的内容"

    />

</LinearLayout>

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