来自 URL 的 Android 图像不起作用

Question

我有一个 JSON 文件想要从中检索 url 并显示它的图像视图。我使用 JSON PARSER ASYNC TASK 来做到这一点，在执行后我运行一个任务来显示不工作的图像视图

我的 Java 代码

    @Override
    protected JSONObject doInBackground(String... args) {
        JSONParser jParser = new JSONParser();

        // Getting JSON from URL
        JSONObject json = jParser.getJSONFromUrl(url);
        return json;
    }
     @Override
     protected void onPostExecute(JSONObject json) {
        try {
                // Getting JSON Array

                // Storing  JSON item in a Variable
                Url = http://icons.iconarchive.com/icons/benjigarner/softdimension/48/
                String icon = json.getString("icon"); //URL String
                String ImageUrl = Url + Icon;

                //Function to get image from URL - First method
                Drawable MyImage = loadloadImageFromURL(ImageUrl);

                //Function to get image from URL - Second method
                Bitmap MyImage = getBitmapFromURL(ImageUrl);
                //Third Method
                new ImageDownload().execute(ImageUrl);

                ImageView Image = (ImageView) rootView.findViewById(R.id.imgMainWeather);   Image.setImageBitmap(MainActivity.WeatherImage);

                } catch (JSONException e) {
            e.printStackTrace();
        }
     }
    //Function First Method
    public static Drawable loadImageFromURL(String url) {
    try {
        InputStream is = (InputStream) new URL(url).getContent();  // While Debugging After this line Error occurs
        Drawable d = Drawable.createFromStream(is, "src name");
        return d;
    } catch (Exception e) {
        Log.i("Image", "No Image");
        return null;
    }
}
//Second Method
public static Bitmap getBitmapFromURL(String src){
    try {
        URL url = new URL(src);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream(); // While Debugging After this line Error occurs
        Bitmap MyBitmap = BitmapFactory.decodeStream(input);
        return MyBitmap;

    } catch (Exception e) {
        e.printStackTrace();
        Log.i("Image", "No Image");
        return null;
    }
}
//Async Task even tried this
private class ImageDownload extends AsyncTask<String, String, Drawable>{

    @Override
    protected Drawable doInBackground(String... str) {

        Drawable image = loadImageFromURL(str[0]);

        return image;
    }

}

我将上述 3 种方法用于第 2 种方法我得到以下错误并且没有图像视图和异步任务显示没有错误并且没有图像

我的错误

01-09 18:08:15.294: I/Image(1221): Image Null
01-09 18:08:15.315: W/System.err(1221): android.os.NetworkOnMainThreadException
01-09 18:08:15.315: W/System.err(1221):at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
01-09 18:08:15.315: W/System.err(1221):     at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
01-09 18:08:15.315: W/System.err(1221):     at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
01-09 18:08:15.324: W/System.err(1221):     at java.net.InetAddress.getAllByName(InetAddress.java:214)
01-09 18:08:15.324: W/System.err(1221):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70)
01-09 18:08:15.324: W/System.err(1221):     at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50)
01-09 18:08:15.324: W/System.err(1221):     at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:341)
01-09 18:08:15.334: W/System.err(1221):     at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87)
01-09 18:08:15.334: W/System.err(1221):     at libcore.net.http.HttpConnection.connect(HttpConnection.java:128)
01-09 18:08:15.345: W/System.err(1221):     at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:315)
01-09 18:08:15.345: W/System.err(1221):     at libcore.net.http.HttpEngine.connect(HttpEngine.java:310)
01-09 18:08:15.345: W/System.err(1221):     at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:289)
01-09 18:08:15.354: W/System.err(1221):     at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:239)
01-09 18:08:15.364: W/System.err(1221):     at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
01-09 18:08:15.364: W/System.err(1221):     at in.datumdata.weather.MainActivity.getBitmapFromURL(MainActivity.java:109)
01-09 18:08:15.364: W/System.err(1221):     at in.datumdata.weather.MainActivity$JSONParse.onPostExecute(MainActivity.java:187)
01-09 18:08:15.374: W/System.err(1221):     at in.datumdata.weather.MainActivity$JSONParse.onPostExecute(MainActivity.java:1)
01-09 18:08:15.374: W/System.err(1221):     at android.os.AsyncTask.finish(AsyncTask.java:631)
01-09 18:08:15.374: W/System.err(1221):     at android.os.AsyncTask.access$600(AsyncTask.java:177)
01-09 18:08:15.384: W/System.err(1221):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
01-09 18:08:15.384: W/System.err(1221):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-09 18:08:15.384: W/System.err(1221):     at android.os.Looper.loop(Looper.java:137)
01-09 18:08:15.397: W/System.err(1221):     at android.app.ActivityThread.main(ActivityThread.java:4745)
01-09 18:08:15.404: W/System.err(1221):     at java.lang.reflect.Method.invokeNative(Native Method)
01-09 18:08:15.404: W/System.err(1221):     at java.lang.reflect.Method.invoke(Method.java:511)
01-09 18:08:15.414: W/System.err(1221):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-09 18:08:15.414: W/System.err(1221):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-09 18:08:15.414: W/System.err(1221):     at dalvik.system.NativeStart.main(Native Method)

我想从 json 文件中检索 3 张图像 帮我解决这个问题提前谢谢

Answer 1

AsyncTask - 执行一个长时间运行的任务并防止 ui 被这个长时间运行的进程阻塞。

doInBackground - 无法在 UI 中进行任何更改的后台工作方法

OnPostExecute - 在 UI 中进行任何更改的方法

网络 OnMainThread 异常：

您在 onPostExecute 中获取图像，该图像应该在 doInBackground 中

并从 doInBackground 将图像传递给 onPostExecute 或将下载的位图保存在静态位图变量中，该变量可用于 onPostExecute 并使用该位图。