<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
  package="com.sdcardread"
  android:versionCode="1"
  android:versionName="1.0" >

  <uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="18" />

  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> <!-- 向SDCard写入数据权限 -->

  <application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
      android:name="com.sdcardread.MainActivity"
      android:label="@string/app_name" >
      <intent-filter>
        <action android:name="android.intent.action.MAIN" />

        <category android:name="android.intent.category.LAUNCHER" />
      </intent-filter>
    </activity>
  </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>
<resources>

  <string name="app_name">图片读取</string>
  <string name="action_settings">Settings</string>

</resources>

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

  <TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="24sp" />

  <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="24sp" />

  <LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >
  </LinearLayout>

</LinearLayout>

package com.sdcardread;

import java.io.File;

import android.os.Bundle;
import android.os.Environment;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

public class MainActivity extends Activity {
 private TextView textView1;
 private LinearLayout linearLayout1;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textView1 = (TextView) findViewById(R.id.textView1);
  linearLayout1 = (LinearLayout) findViewById(R.id.linearLayout1);
  boolean isSdCardExist = Environment.getExternalStorageState().equals(
    Environment.MEDIA_MOUNTED);// 判断sdcard是否存在
  if (isSdCardExist) {
   String sdpath = Environment.getExternalStorageDirectory()
     .getAbsolutePath();// 获取sdcard的根路径
   textView1.setText("sd卡是存在的。以下是sdcard下的img25.jpg！");
   String filepath = sdpath + File.separator + "img25.jpg";
   File file = new File(filepath);
   ImageView imageView = new ImageView(this);//创建一个imageView对象
   if (file.exists()) {
    Bitmap bm = BitmapFactory.decodeFile(filepath);
    // 将图片显示到ImageView中
    imageView.setImageBitmap(bm);
    linearLayout1.addView(imageView);
   }
  } else {
   textView1.setText("sd卡不存在！");
  }

 }

}