Android实现下载图片并保存到SD卡中

拼搏现实的明天。 2024-02-17 17:31 18阅读 0赞

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。

![复制代码][copycode.gif]

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 = "https://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
                }
            }
        };
    
    }

![复制代码][copycode.gif]

（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。

![复制代码][copycode.gif]

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();
            }
        };
    }

![复制代码][copycode.gif]

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][Android]

2.main.xml文件，只有一个button和一个ImageView

![复制代码][copycode.gif]

<?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>

![复制代码][copycode.gif]

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：

![18160827-9be92bf5d3da4843a7803b610cd97930.gif][]

转：[http://blog.csdn.net/ameyume/article/details/6528205][http_blog.csdn.net_ameyume_article_details_6528205]

[copycode.gif]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/58962e69e6a24962a48ca22b3e63eec1.png
[Android]: http://blog.csdn.net/ameyume/archive/2011/02/14/6183462.aspx
[18160827-9be92bf5d3da4843a7803b610cd97930.gif]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/30/651b4e6610f1494994f4b27c903126d3.png
[http_blog.csdn.net_ameyume_article_details_6528205]: http://blog.csdn.net/ameyume/article/details/6528205