android(安卓)sd卡写入 读取文件的例子

首先将图片写入到SDcard中，然后再把它读取出来显示到到imageView上。

用到的图片

xml文件代码：

    <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>

java文件：

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;
		}
	}


}

运行效果图：

点击读取图片后显示如下：

最后需要提醒的是需要加入SD卡的权限哦

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