android(安卓)sd卡写入 读取文件的例子

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">

<Button
android:id="@+id/copy"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="复制到SD卡" />

<Button
android:id="@+id/read"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="读取图片" />

<ImageView
android:id="@+id/img"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

</LinearLayout>

MainActivity .java

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity implements OnClickListener {

private Button copy;
private Button read;
private ImageView img;
private String path;
private static final String DATABASE_PATH = Environment.getExternalStorageDirectory()+"/Fover";//文件存放目录
private static final String DATABASE_FILENAME = "i.png";//文件名称以及后缀

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

initView();
}

private void initView() {
copy=(Button)findViewById(R.id.copy);
read=(Button)findViewById(R.id.read);
img=(ImageView)findViewById(R.id.img);

copy.setOnClickListener(this);
read.setOnClickListener(this);
}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.copy:
path=DATABASE_PATH+"/"+DATABASE_FILENAME;
File dir=new File(DATABASE_PATH);
if(!dir.exists()){
dir.mkdir();
}
if(!(new File(path)).exists()){
Log.v("Fover", "执行写入代码，写入路径为"+path);
InputStream is = MainActivity.class.getResourceAsStream("/assets/ico.png");
try{
FileOutputStream fos = new FileOutputStream(path);
byte[] buffer = new byte[1024];
int count = 0;
while ((count = is.read(buffer)) > 0)
{
fos.write(buffer, 0, count);
}
fos.close();
is.close();
}catch (Exception e) {
e.printStackTrace();
}
}

break;
case R.id.read:
File file = new File(path);
if (file.exists()) {
Bitmap bm = BitmapFactory.decodeFile(path);
//将图片显示到ImageView中
img.setImageBitmap(bm);
}

break;

default:
break;
}
}

}

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