java如何以编程方式将图像添加到安卓应用程序

Question

我想能够使用url的图像源。我找到了以下转换为位图的函数。然而，我得到了一个“NetworkOnMainThreadException”用日志我发现了

conn.connect();

，是函数崩溃的地方

我还发现，由于这个异常，我应该使用AsyncTask类扩展。所以我在下面代码的第二部分中使用了它。我还是以同样的例外告终。我不完全明白这个错误意味着什么，只是我试图在同一时间在同一个地方做太多的事情

有没有更简单的方法将url转换为我可以使用的图像？如何修复我现在的功能

 public static Bitmap getImageBitmap(String url) {
            Log.i("bitmap","here?");
            Bitmap bm = null;
            Log.i("bitmap","here?");
            try {
                Log.i("bitmap","here?");
                URL aURL = new URL(url);
                Log.i("bitmap","here?");
                URLConnection conn = aURL.openConnection();
                Log.i("bitmap","last ?");
                conn.connect();
                Log.i("bitmap","here?");
                InputStream is = conn.getInputStream();
                Log.i("bitmap","here?");
                BufferedInputStream bis = new BufferedInputStream(is);
                Log.i("bitmap","here?");
                bm = BitmapFactory.decodeStream(bis);
                bis.close();
                Log.i("bitmap","here?");
                is.close();
                Log.i("bitmap","here?");
           } catch (IOException e) {
               Log.e("img", "Error getting bitmap", e);
           }
           return bm;
        }   

使用异步任务：

class taskRunner extends AsyncTask<String, URL, Bitmap>{

     public static Bitmap getImageBitmap(String url) {
            Log.i("bitmap","here?");
            Bitmap bm = null;
            Log.i("bitmap","here?");
            try {
                Log.i("bitmap","here?");
                URL aURL = new URL(url);
                Log.i("bitmap","here?");
                URLConnection conn = aURL.openConnection();
                Log.i("bitmap","last ?");
                conn.connect();
                Log.i("bitmap","here?");
                InputStream is = conn.getInputStream();
                Log.i("bitmap","here?");
                BufferedInputStream bis = new BufferedInputStream(is);
                Log.i("bitmap","here?");
                bm = BitmapFactory.decodeStream(bis);
                bis.close();
                Log.i("bitmap","here?");
                is.close();
                Log.i("bitmap","here?");
           } catch (IOException e) {
               Log.e("img", "Error getting bitmap", e);
           }
           return bm;
        }   

非常感谢您抽出时间阅读本文

Answer 1

首先，不要忘记清单中的互联网许可

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

第二个问题是你的实现是错误的

class BitmapTaks extends AsyncTask<ImageView, Void, Bitmap> {

protected Bitmap doInBackground(ImageView... imageview) {
   Log.i("bitmap","here?");
        Bitmap bm = null;
        Log.i("bitmap","here?");
        try {
            Log.i("bitmap","here?");
            URL aURL = new URL(urls[0]);
            Log.i("bitmap","here?");
            URLConnection conn = aURL.openConnection();
            Log.i("bitmap","last ?");
            conn.connect();
            Log.i("bitmap","here?");
            InputStream is = conn.getInputStream();
            Log.i("bitmap","here?");
            BufferedInputStream bis = new BufferedInputStream(is);
            Log.i("bitmap","here?");
            bm = BitmapFactory.decodeStream(bis);
            bis.close();
            Log.i("bitmap","here?");
            is.close();
            Log.i("bitmap","here?");
       } catch (IOException e) {
           Log.e("img", "Error getting bitmap", e);
       }
       return bm;
}

protected void onPostExecute(Bitmap b) {
   //do something after execute
}
}

这种说法是：

new BitmapTaks().execute(url);

应该是这样的，希望有帮助

编辑：

AsyncTask-这是异步结构

在本例中，参数是ImageView，您还希望传递url的字符串。 结果将是位图，并将在OnPostExecute方法上设置

为了理解，我写下了上面的例子。。您可以查看下一个链接：http://chrisharrington1.wordpress.com/2012/01/24/android-setting-a-downloaded-image-to-an-imageview/

如果你还需要什么，请告诉我