我想从网址中获取多张图片，并且必须在我的图片视图中使用它们

Question

我的应用程序在执行时崩溃，我已经使用位图array来存储图像。任何人都可以帮助我，特别感谢事先未提供url，但是我正在使用图像的有效url，所以没有问题。

谢谢。

    package abc.expandable;
    import java.io.IOException;
    import java.io.InputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.net.URLConnection;
    import java.util.ArrayList;

    import android.app.Activity;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.os.AsyncTask;
    import android.os.Bundle;
    import android.util.Log;
    import android.widget.ImageView;
    import android.widget.Toast;

    public class MainActivity extends Activity {

        public static final String URL =
                " some url";
        public static final String URL1="some url";
        ImageView imageView;
        ImageView imageView1;
        ArrayList<Bitmap> bitmapArray=new ArrayList<Bitmap>(4);
        /** Called when the activity is first created. */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            imageView = (ImageView) findViewById(R.id.imageView);
            imageView1=(ImageView)findViewById(R.id.imageView1);
            // Create an object for subclass of AsyncTask
            GetXMLTask task = new GetXMLTask();
            // Execute the task
            int a=0;
            task.execute(new String[]{URL});
            imageView.setImageBitmap(bitmapArray.get(0));

            Toast.makeText(MainActivity.this, "downloading image please wait ", Toast.LENGTH_SHORT).show();


           // task.execute(new String[]{URL1});
            //imageView1.setImageBitmap(bitmapArray.get(a));
        }

        private class GetXMLTask extends AsyncTask<String, Void, Bitmap> {
            @Override
            protected Bitmap doInBackground(String... urls) {
                Bitmap map = null;
                for (String url : urls) {
                    map = downloadImage(url);
                }
                return map;
            }

            // Sets the Bitmap returned by doInBackground
            @Override
            protected void onPostExecute(Bitmap result)
            {

    //            imageView.setImageBitmap(bitmapArray.get(0));
                Toast.makeText(MainActivity.this, "downloaded", Toast.LENGTH_SHORT).show();
                Log.i("bitmap", "bitmap ");
            }

            // Creates Bitmap from InputStream and returns it
            private Bitmap downloadImage(String url) {
                Bitmap bitmap = null;
                InputStream stream = null;
                BitmapFactory.Options bmOptions = new BitmapFactory.Options();
                bmOptions.inSampleSize = 1;

                try {
                    stream = getHttpConnection(url);
                    bitmap = BitmapFactory.
                            decodeStream(stream, null, bmOptions);
                    stream.close();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                bitmapArray.add(bitmap);
                return bitmap;

            }

            // Makes HttpURLConnection and returns InputStream
            private InputStream getHttpConnection(String urlString)
                    throws IOException {
                InputStream stream = null;
                URL url = new URL(urlString);
                URLConnection connection = url.openConnection();

                try {
                    HttpURLConnection httpConnection = (HttpURLConnection) connection;
                    httpConnection.setRequestMethod("GET");
                    httpConnection.connect();

                    if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
                        stream = httpConnection.getInputStream();
                    }
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                return stream;
            }

        }
    }

这是原木猫

03-04 18:59:24.307 18588-18588/abc.expandable E/AndroidRuntime: FATAL EXCEPTION: main
                                                                Process: abc.expandable, PID: 18588
                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{abc.expandable/abc.expandable.MainActivity}: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339)
                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
                                                                    at android.app.ActivityThread.access$800(ActivityThread.java:155)
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                    at android.os.Looper.loop(Looper.java:135)
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5343)
                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                    at java.lang.reflect.Method.invoke(Method.java:372)
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905)
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700)
                                                                 Caused by: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
                                                                    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
                                                                    at java.util.ArrayList.get(ArrayList.java:308)
                                                                    at abc.expandable.MainActivity.onCreate(MainActivity.java:38)
                                                                    at android.app.Activity.performCreate(Activity.java:6010)
                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129)
                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413) 
                                                                    at android.app.ActivityThread.access$800(ActivityThread.java:155) 
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317) 
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                    at android.os.Looper.loop(Looper.java:135) 
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5343) 
                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                    at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:905) 
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:700) 

Answer 1

删除此行，它应该可以工作：

imageView.setImageBitmap(bitmapArray.get(0));

您正在访问一个空数组，这会导致异常，因为您的数组成员被添加到一个比UI线程慢的线程中。 您应该在ASyncTask的onPostExecute中设置imageview。 这样，在尝试访问成员之前，请确保ASyncTask已完成并将成员添加到阵列中。