Question

我在listview项目中缩放并显示自定义视图的位图图像时遇到问题。我使用延迟加载来显示我的图像，在下载和显示图像时，我的自定义视图显示加载的gif。我在this tutorial中为lazyload定制了类，它可以工作。我认为我的问题是将下载的位图绘制到我的自定义视图的画布上。我想列出我的问题和我的代码到目前为止。

自定义视图中显示的图像质量下降。我不知道为什么。
当我向下滚动或向上滚动列表视图时，可以感觉到它没有正确滚动。
我的图片＆＃39;如果匹配父和高度应按宽度的变化比例缩放。

真的这对我来说是一个大问题，我无法处理它。任何帮助和建议将不胜感激。

我的适配器中的getView方法

ImagePrevLoader imgLoader = new ImagePrevLoader(context); // actually it is initilized in constructor of adapter

public View getView(final int position, final View convertView, ViewGroup parent) {
    ArtItemHolder holder;
    View view = convertView;

    if (view == null) {
        LayoutInflater inflater = ((Activity) this.context).getLayoutInflater();
        holder = new ArtItemHolder();
        view = inflater.inflate(R.layout.feed_list_item, parent, false);

        holder.image = view.findViewById(R.id.img_Image);
        holder.pubDate = (TextView) view.findViewById(R.id.txt_puslishDate);
        holder.arTitle = (TextView) view.findViewById(R.id.txt_arTitle);

        view.setTag(holder);
    } else {
        holder = (AdvItemHolder) view.getTag();
    }
    Article ar= articles.get(position);

    imgLoader.DisplayImage(ar.getImages().get(0).getUrl(), (ImagePreView) holder.image);    

    return view;
}

private static class ArtItemHolder{
    View image;
    TextView pubDate;
    TextView arTitle;
}

我的自定义视图

public class ImagePreView extends View{
    private static String TAG = "ImagePreView";
    private Movie gifImage;
    private Bitmap myImage;
    Context context;

    public ImagePreView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        this.context = context;
        if (!isInEditMode()) {
            new ImagePreView(context, attrs, defStyleAttr);
        }
        init();
    }
    public ImagePreView(Context context, AttributeSet attrs) {
        super(context, attrs, 0);
        this.context = context;

        init();
    }
    public ImagePreView(Context context) {
        super(context, null, 0);
        this.context = context;

        init();
    }

    private void init(){
        setLayerType(View.LAYER_TYPE_SOFTWARE, null);// yada manifeste android:hardwareAccelerated="false" ekle
        //setFocusable(true);
        InputStream is;
        try {
            is = context.getResources().getAssets().open("dialogbox_loader.gif");
            gifImage = Movie.decodeStream(is);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    @Override
    protected void onDraw(Canvas canvas) {
        //canvas.drawColor(0xFFD8D8D8);
        canvas.drawColor(Color.TRANSPARENT);
        Paint paint = new Paint();
        paint.setColor(0xFFA4A4A4);
        paint.setStrokeWidth( 2.4f );
        paint.setStyle( Style.STROKE );
        canvas.drawRect( 0, 0, getWidth(), getHeight(), paint );
        super.onDraw(canvas);

        if(getWidth() < 1 || getHeight()<1)
            requestLayout();
        //Log.d(TAG, "WIDTH : " + getWidth()+ ", HEIGHT : " + getHeight());
        if(myImage != null){
            int width = (getWidth() - myImage.getWidth())/2;
            int height = (getHeight() - myImage.getHeight())/2;

            canvas.drawBitmap(myImage, width, height, new Paint());
        } else if(gifImage != null){
            //canvas.drawColor(0, Mode.CLEAR);
            //Bitmap b = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
            //canvas.drawBitmap(b, 0, 0, new Paint());
            showLoadingGif(canvas);
        }

    }

    long movieStart ;
    private void showLoadingGif(Canvas canvas){
        long now = android.os.SystemClock.uptimeMillis();
        if (movieStart == 0)
            movieStart = now;

        int relTime = (int) ((now - movieStart) % gifImage.duration());
        gifImage.setTime(relTime);
        int width = getWidth()/2 - gifImage.width()/2;
        int height = getHeight()/2 - gifImage.height()/2;

        gifImage.draw(canvas, width, height);
        this.invalidate();
    }


    public void display(Bitmap bitmap){
        this.myImage = getScaledBitmap(bitmap);
        invalidate();
    }

    private Bitmap getScaledBitmap(Bitmap bitmap) {
        int viewWidth = getWidth();
        int viewHeight = getHeight();
        // Get current dimensions
        int width = bitmap.getWidth();
        int height = bitmap.getHeight();

        int boundBoxInDp = viewWidth;
        if(viewHeight>viewWidth)
            boundBoxInDp = viewHeight;

        float xScale = ((float) boundBoxInDp) / width;
        float yScale = ((float) boundBoxInDp) / height;
        float scale = (xScale <= yScale) ? xScale : yScale;

        Matrix matrix = new Matrix();
        matrix.postScale(scale, scale);

        try {
            Bitmap scaledBitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
            return scaledBitmap;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return bitmap;
    }
}

Listview项目布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" 
    android:gravity="center"
    android:id="@+id/feed_item_parent">

           <TextView
                android:id="@+id/txt_arTitle"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="TextView" 
                android:textColor="@color/main_text_color"
                android:textSize="15sp"
                android:textStyle="bold"/>
           <com.mobile.zenex.component.ImagePreView
                android:id="@+id/img_Image"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"/>
            <TextView
                android:id="@+id/txt_puslishDate"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="TextView" 
                android:textColor="@color/grey_text_color"
                android:textSize="15sp"
                android:textStyle="bold"/>
</LinearLayout>

Answer 1

尝试使用Picasso进行下载/缓存，它可以提高质量/下载速度：

http://square.github.io/picasso/

在自定义视图列表视图项中缩放位图图像

1 个答案: