来自 imageurl 的图像视图图像给出异常

Question

我正在使用 image-URL 来表示 imageView 中的图像，但我的 android 应用程序抛出了以下异常。 我正在使用异步任务来获取图像 URL 并将其放在 onpostexecute() 方法中的 imageview 中。

我的代码

protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            ImageView i=(ImageView)findViewById(R.id.imageView1);
            Bitmap bitmap;
            Drawable d;
            try {
                bitmap = BitmapFactory.decodeStream((InputStream)new URL(logo.get(0)).getContent());
                 i.setImageBitmap(bitmap); 


            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

logcat 异常

03-05 06:34:25.148: E/AndroidRuntime(1653): FATAL EXCEPTION: main
03-05 06:34:25.148: E/AndroidRuntime(1653): android.os.NetworkOnMainThreadException
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.net.InetAddress.getAllByName(InetAddress.java:214)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpEngine.connect(HttpEngine.java:311)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:81)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.net.URLConnection.getContent(URLConnection.java:190)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.net.URL.getContent(URL.java:447)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at com.example.slideoutmenu.LayerStack$logo.onPostExecute(LayerStack.java:249)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at com.example.slideoutmenu.LayerStack$logo.onPostExecute(LayerStack.java:1)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.AsyncTask.finish(AsyncTask.java:631)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.os.Looper.loop(Looper.java:137)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at android.app.ActivityThread.main(ActivityThread.java:5039)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.lang.reflect.Method.invokeNative(Native Method)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at java.lang.reflect.Method.invoke(Method.java:511)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-05 06:34:25.148: E/AndroidRuntime(1653):     at dalvik.system.NativeStart.main(Native Method)

如何显示来自 imageurl 的图像。

Answer 1

onPostExecute() 方法在 UI 线程上运行。您应该将以下行移至 doInBackground() 方法。

bitmap = BitmapFactory.decodeStream((InputStream)new URL(logo.get(0)).getContent());

Answer 2

尝试下面的代码，它可以有效地用于网络任务。

class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap> {
    private final WeakReference<ImageView> imageViewReference;
    private String data;

    public BitmapWorkerTask(ImageView imageView) {
        // Use a WeakReference to ensure the ImageView can be garbage
        // collected
        imageViewReference = new WeakReference<ImageView>(imageView);
    }

    // Decode image in background.
    @Override
    protected Bitmap doInBackground(String... params) {
        data = params[0];
        try {
            return BitmapFactory.decodeStream((InputStream) new URL(data)
                    .getContent());
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    // Once complete, see if ImageView is still around and set bitmap.
    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (imageViewReference != null && bitmap != null) {
            final ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                imageView.setImageBitmap(bitmap);
            }
        }
    }
}

要使用该类，请使用以下语句。

ImageView img = (ImageView) findViewById(R.id.imageView1);
BitmapWorkerTask task = new BitmapWorkerTask(img);
task.execute("your image url");

Answer 3

NetworkOnMainThreadException。

您正在对在主线程上运行的此方法 onPostExecute() 进行网络操作。阅读here。

在doInBackground()这个方法中做这个网络操作。