java - 位图在 Android 应用程序中加载和显示需要很长时间

Question

现在我有一个 LocationAdapter 类，它接受我的 "Location" 对象并将每个 Location 显示到 ListView。我试图将其传递到 Bitmap 图像中，并让它在 ListView 行中显示该图像。它可以工作，但是即使在加载行中的文本之后，图像也需要一段时间才能加载。我正在实际设备上进行测试。这是我的 Activity 代码:

public class MainActivity extends ActionBarActivity {

ArrayList<Location> arrayOfLocations;
LocationAdapter adapter;
private static Bitmap bitmap;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);
    setContentView(R.layout.activity_main);

    // Construct the data source
    arrayOfLocations = new ArrayList<Location>();

    // Create the adapter to convert the array to views
    adapter = new LocationAdapter(this, arrayOfLocations);

    Bitmap image = getBitmapFromID(1);

    adapter.add(new Location(image, "Place 1",
            "We have the freshest fruit in the whole world!", "2 miles",
            "8-5 mon-sat\nclosed sun"));
    adapter.add(new Location(image, "Place 2",
            "We have the freshest fruit in the whole world!", "2 miles",
            "8-5 mon-sat"));
    adapter.add(new Location(image, "Place 3",
            "We have the best cakes in the whole world!", "2 miles",
            "8-5 mon-fri\n10-1 sat\nclosed sun\nclosed Memorial Day"));
    adapter.add(new Location(image, "Fruit Stand",
            "Best place!", "2 miles",
            "8-5 mon-sat"));
    adapter.add(new Location(image, "Place 4",
            "Food!", "2 miles",
            "8-5 mon-sat"));
    adapter.add(new Location(image, "Place 5",
            "Toys!", "2 miles",
            "8-5 mon-sat"));

    // Attach the adapter to a ListView
    ListView listView = (ListView) findViewById(R.id.listView1);

    View header = (View) getLayoutInflater().inflate(
            R.layout.listview_header, null);
    listView.addHeaderView(header);

    listView.setAdapter(adapter);

}

public static Bitmap getBitmapFromID(int id) {

    //final Bitmap bitmap;

    Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {

            try {
                bitmap = BitmapFactory
                        .decodeStream((InputStream) new URL(
                                "http://icons.iconarchive.com/icons/yellowicon/game-stars/256/Mario-icon.png")
                                .getContent());

            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

        }
    });

    thread.start();
    return bitmap;
}

}

我是不是做错了什么？加载需要一段时间，这正常吗？谢谢!

Answer 1

您需要在后台线程中执行 AsyncTask 工作。然而，为了更好的方法，请看这里:

https://stackoverflow.com/a/23941258/276949

Android Volley 是 Google 推出的一个相当新的非详细库，它非常适合加载图像，并负责自动处理单独线程上的所有下载。