如何以编程方式将图像添加到我的 android 应用程序

Question

我希望能够使用 url 作为图像源。我找到了以下转换为位图的函数。但是，我得到一个“NetworkOnMainThreadException”。使用日志我发现

conn.connect();

，是函数崩溃的地方。

我还发现由于异常我应该使用 AsyncTask 类扩展。所以我在下面的第二段代码中使用了它。我仍然以同样的例外告终。我不完全理解错误的含义，只是我试图同时在同一个地方做太多事情。

有没有更简单的方法可以将网址转换为我可以使用的图片？如何修复我现在拥有的功能？

 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;
        }   

非常感谢您抽出宝贵时间阅读本文。

Answer 1

首先，不要忘记清单中的互联网权限

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

其次是你的实现错误..

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
}
}

调用方式是：

new BitmapTaks().execute(url);

应该是这样的，希望对你有帮助

编辑：

AsyncTask - 这是异步结构..

在这种情况下，参数是 ImageView，并且您还想为 url 传递字符串。 结果将是位图，并将在 OnPostExecute 方法上设置。

我把上面的例子写下来以便理解..你可以看下一个链接：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