Android实现下载图片并保存到SD卡中
1.java代码，下载图片的主程序
先实现显示图片，然后点击下载图片按钮，执行下载功能。
从网络上取得的图片，生成Bitmap时有两种方法，一种是先转换为byte[]，再生成bitmap；一种是直接用InputStream生成bitmap。
（1）ICS4.0及更高版本中的实现
4.0中不允许在主线程，即UI线程中操作网络，所以必须新开一个线程，在子线程中执行网络连接；然后在主线程中显示图片。
public class IcsTestActivity extends Activity { private final static String TAG = "IcsTestActivity"; private final static String ALBUM_PATH = Environment.getExternalStorageDirectory() + "/download_test/"; private ImageView mImageView; private Button mBtnSave; private ProgressDialog mSaveDialog = null; private Bitmap mBitmap; private String mFileName; private String mSaveMessage; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); mImageView = (ImageView)findViewById(R.id.imgSource); mBtnSave = (Button)findViewById(R.id.btnSave); new Thread(connectNet).start(); // 下载图片 mBtnSave.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) { mSaveDialog = ProgressDialog.show(IcsTestActivity.this, "保存图片", "图片正在保存中，请稍等...", true); new Thread(saveFileRunnable).start(); } }); } /** * Get image from newwork * @param path The path of image * @return byte[] * @throws Exception */ public byte[] getImage(String path) throws Exception{ URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); InputStream inStream = conn.getInputStream(); if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){ return readStream(inStream); } return null; } /** * Get image from newwork * @param path The path of image * @return InputStream * @throws Exception */ public InputStream getImageStream(String path) throws Exception{ URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){ return conn.getInputStream(); } return null; } /** * Get data from stream * @param inStream * @return byte[] * @throws Exception */ public static byte[] readStream(InputStream inStream) throws Exception{ ByteArrayOutputStream outStream = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = 0; while( (len=inStream.read(buffer)) != -1){ outStream.write(buffer, 0, len); } outStream.close(); inStream.close(); return outStream.toByteArray(); } /** * 保存文件 * @param bm * @param fileName * @throws IOException */ public void saveFile(Bitmap bm, String fileName) throws IOException { File dirFile = new File(ALBUM_PATH); if(!dirFile.exists()){ dirFile.mkdir(); } File myCaptureFile = new File(ALBUM_PATH + fileName); BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myCaptureFile)); bm.compress(Bitmap.CompressFormat.JPEG, 80, bos); bos.flush(); bos.close(); } private Runnable saveFileRunnable = new Runnable(){ @Override public void run() { try { saveFile(mBitmap, mFileName); mSaveMessage = "图片保存成功！"; } catch (IOException e) { mSaveMessage = "图片保存失败！"; e.printStackTrace(); } messageHandler.sendMessage(messageHandler.obtainMessage()); } }; private Handler messageHandler = new Handler() { @Override public void handleMessage(Message msg) { mSaveDialog.dismiss(); Log.d(TAG, mSaveMessage); Toast.makeText(IcsTestActivity.this, mSaveMessage, Toast.LENGTH_SHORT).show(); } }; /* * 连接网络 * 由于在4.0中不允许在主线程中访问网络，所以需要在子线程中访问 */ private Runnable connectNet = new Runnable(){ @Override public void run() { try { String filePath = "//img-my.csdn.net/uploads/201211/21/1353511891_4579.jpg"; mFileName = "test.jpg"; //以下是取得图片的两种方法 //////////////// 方法1：取得的是byte数组, 从byte数组生成bitmap byte[] data = getImage(filePath); if(data!=null){ mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);// bitmap }else{ Toast.makeText(IcsTestActivity.this, "Image error!", 1).show(); } //////////////////////////////////////////////////////// //******** 方法2：取得的是InputStream，直接从InputStream生成bitmap ***********/ mBitmap = BitmapFactory.decodeStream(getImageStream(filePath)); //********************************************************************/ // 发送消息，通知handler在主线程中更新UI connectHanlder.sendEmptyMessage(0); Log.d(TAG, "set image ..."); } catch (Exception e) { Toast.makeText(IcsTestActivity.this,"无法链接网络！", 1).show(); e.printStackTrace(); } } }; private Handler connectHanlder = new Handler() { @Override public void handleMessage(Message msg) { Log.d(TAG, "display image"); // 更新UI，显示图片 if (mBitmap != null) { mImageView.setImageBitmap(mBitmap);// display image } } }; }
（2）2.3以及以下版本可以在主线程中操作网络连接，但最好不要这样做，因为连接网络是阻塞的，如果5秒钟还没有连接上，就会引起ANR。
public class AndroidTest2_3_3 extends Activity { private final static String TAG = "AndroidTest2_3_3"; private final static String ALBUM_PATH = Environment.getExternalStorageDirectory() + "/download_test/"; private ImageView imageView; private Button btnSave; private ProgressDialog myDialog = null; private Bitmap bitmap; private String fileName; private String message; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); imageView = (ImageView)findViewById(R.id.imgSource); btnSave = (Button)findViewById(R.id.btnSave); String filePath = "http://hi.csdn.net/attachment/201105/21/134671_13059532779c5u.jpg"; fileName = "test.jpg"; try { //////////////// 取得的是byte数组, 从byte数组生成bitmap byte[] data = getImage(filePath); if(data!=null){ bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);// bitmap imageView.setImageBitmap(bitmap);// display image }else{ Toast.makeText(AndroidTest2_3_3.this, "Image error!", 1).show(); } //////////////////////////////////////////////////////// //******** 取得的是InputStream，直接从InputStream生成bitmap ***********/ bitmap = BitmapFactory.decodeStream(getImageStream(filePath)); if (bitmap != null) { imageView.setImageBitmap(bitmap);// display image } //********************************************************************/ Log.d(TAG, "set image ..."); } catch (Exception e) { Toast.makeText(AndroidTest2_3_3.this,"Newwork error!", 1).show(); e.printStackTrace(); } // 下载图片 btnSave.setOnClickListener(new Button.OnClickListener(){ public void onClick(View v) { myDialog = ProgressDialog.show(AndroidTest2_3_3.this, "保存图片", "图片正在保存中，请稍等...", true); new Thread(saveFileRunnable).start(); } }); } /** * Get image from newwork * @param path The path of image * @return byte[] * @throws Exception */ public byte[] getImage(String path) throws Exception{ URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); InputStream inStream = conn.getInputStream(); if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){ return readStream(inStream); } return null; } /** * Get image from newwork * @param path The path of image * @return InputStream * @throws Exception */ public InputStream getImageStream(String path) throws Exception{ URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setConnectTimeout(5 * 1000); conn.setRequestMethod("GET"); if(conn.getResponseCode() == HttpURLConnection.HTTP_OK){ return conn.getInputStream(); } return null; } /** * Get data from stream * @param inStream * @return byte[] * @throws Exception */ public static byte[] readStream(InputStream inStream) throws Exception{ ByteArrayOutputStream outStream = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = 0; while( (len=inStream.read(buffer)) != -1){ outStream.write(buffer, 0, len); } outStream.close(); inStream.close(); return outStream.toByteArray(); } /** * 保存文件 * @param bm * @param fileName * @throws IOException */ public void saveFile(Bitmap bm, String fileName) throws IOException { File dirFile = new File(ALBUM_PATH); if(!dirFile.exists()){ dirFile.mkdir(); } File myCaptureFile = new File(ALBUM_PATH + fileName); BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myCaptureFile)); bm.compress(Bitmap.CompressFormat.JPEG, 80, bos); bos.flush(); bos.close(); } private Runnable saveFileRunnable = new Runnable(){ @Override public void run() { try { saveFile(bitmap, fileName); message = "图片保存成功！"; } catch (IOException e) { message = "图片保存失败！"; e.printStackTrace(); } messageHandler.sendMessage(messageHandler.obtainMessage()); } }; private Handler messageHandler = new Handler() { @Override public void handleMessage(Message msg) { myDialog.dismiss(); Log.d(TAG, message); Toast.makeText(AndroidTest2_3_3.this, message, Toast.LENGTH_SHORT).show(); } }; }
下载进度条的可以参考我的另外一个帖子：Android更新下载进度条
2.main.xml文件，只有一个button和一个ImageView
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <Button android:id="@+id/btnSave" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="保存图片" /> <ImageView android:id="@+id/imgSource" android:layout_width="wrap_content" android:layout_height="wrap_content" android:adjustViewBounds="true" /> </LinearLayout>
3.在mainfest文件中增加互联网权限和写sd卡的权限
<uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
4.预览图：
