java - Android - 将 ImageView 设置为 URL

Question

我正在尝试将 Imageview 设置为 URL。

下面是我的代码

protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.getpic);
    ImageView i = (ImageView)findViewById(R.id.ivget);

    URL url;
    try {

        url = new URL("http://0-media-cdn.foolz.us/ffuuka/board/sp/thumb/1359/41/1359419073599s.jpg");
        Bitmap image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
        i.setImageBitmap(image);
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

但每当我尝试打开/运行该应用程序时它就会崩溃，为什么它无法运行？

06-15 00:37:20.977: E/AndroidRuntime(8579): FATAL EXCEPTION: main
06-15 00:37:20.977: E/AndroidRuntime(8579): java.lang.RuntimeException: Unable to  instantiate activity  ComponentInfo{com.OptimusApps.stayhealthy/com.OptimusApps.stayhealthy.Practice2}:  java.lang.NullPointerException
06-15 00:37:20.977: E/AndroidRuntime(8579):     at   android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1993)
 06-15 00:37:20.977: E/AndroidRuntime(8579):    at  android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2104)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.ActivityThread.access$600(ActivityThread.java:132)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1157)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.os.Looper.loop(Looper.java:137)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.ActivityThread.main(ActivityThread.java:4575)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at java.lang.reflect.Method.invokeNative(Native Method)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at  java.lang.reflect.Method.invoke(Method.java:511)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at dalvik.system.NativeStart.main(Native Method)
06-15 00:37:20.977: E/AndroidRuntime(8579): Caused by: java.lang.NullPointerException
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.Activity.findViewById(Activity.java:1794)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at com.OptimusApps.stayhealthy.Practice2.<init>(Practice2.java:17)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at java.lang.Class.newInstanceImpl(Native Method)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at java.lang.Class.newInstance(Class.java:1319)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
06-15 00:37:20.977: E/AndroidRuntime(8579):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1984)
06-15 00:37:20.977: E/AndroidRuntime(8579):     ... 11 more

上面是logcat，我不确定具体错误在哪里................................. ..................................................... ..................................................... .....................................

Answer 1

你不应该在主 ui 线程上做网络相关的操作。

您可以找到当前 View 层次结构的ViewById 设置为 Activity 。检查 ivget.xml 中是否有 imageview。还使用如下所示的异步任务并发出 http get 请求以获取图像。

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="173dp"
        android:src="@drawable/ic_launcher" />

</RelativeLayout>

主 Activity .java

    public class AndroidCustomGalleryActivity extends Activity { 
ImageView iv;
Bitmap image ;
ProgressDialog pd;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    iv = (ImageView) findViewById(R.id.imageView1);
    pd = new ProgressDialog(this);
    pd.setMessage("Loading..");
    new TheTask().execute();    
}
class TheTask extends AsyncTask<Void,Void,Void>
{

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        pd.show();
    }


    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub
        try
        {
        //URL url = new URL( "http://a3.twimg.com/profile_images/670625317/aam-logo-v3-twitter.png");


        image = downloadBitmap("http://a3.twimg.com/profile_images/670625317/aam-logo-v3-twitter.png");
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        pd.dismiss();
        if(image!=null)
        {
            iv.setImageBitmap(image);
        }

    }   
}
 private Bitmap downloadBitmap(String url) {
     // initilize the default HTTP client object
     final DefaultHttpClient client = new DefaultHttpClient();

     //forming a HttoGet request 
     final HttpGet getRequest = new HttpGet(url);
     try {

         HttpResponse response = client.execute(getRequest);

         //check 200 OK for success
         final int statusCode = response.getStatusLine().getStatusCode();

         if (statusCode != HttpStatus.SC_OK) {
             Log.w("ImageDownloader", "Error " + statusCode + 
                     " while retrieving bitmap from " + url);
             return null;

         }

         final HttpEntity entity = response.getEntity();
         if (entity != null) {
             InputStream inputStream = null;
             try {
                 // getting contents from the stream 
                 inputStream = entity.getContent();

                 // decoding stream data back into image Bitmap that android understands
                 image = BitmapFactory.decodeStream(inputStream);


             } finally {
                 if (inputStream != null) {
                     inputStream.close();
                 }
                 entity.consumeContent();
             }
         }
     } catch (Exception e) {
         // You Could provide a more explicit error message for IOException
         getRequest.abort();
         Log.e("ImageDownloader", "Something went wrong while" +
                 " retrieving bitmap from " + url + e.toString());
     } 

     return image;
 }
}