Question

我使用了开发人员指南中的Loading Bitmaps Efficiently，并按照教程中的指示点进行操作。

您可能知道，这是我使用的代码：

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth,int reqHeight){
    //Raw height and width of the Image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height>reqHeight || width>reqWidth) {
        final int heightratio = Math.round((float)height / (float)reqHeight);
        final int widthRatio = Math.round((float)width / (float)reqWidth);

        inSampleSize = heightratio < widthRatio ? heightratio : widthRatio;
    }
    return inSampleSize;
}
public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,int reqWidth,int reqHeight){
    //first decode with inJustdecodeBounds = true to check dimensions.

    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeResource(res, resId, options);
    //Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

    //Decode bitmap with inSampleSize
    options.inJustDecodeBounds = false;

    return BitmapFactory.decodeResource(res, resId, options);
}

我在切换案例中将此方法称为：

handler.postDelayed(new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            learn_full_iv.setVisibility(View.VISIBLE);
            learn_full_iv.startAnimation(anim);

            switch (id) {
            case R.id.a:
                //learn_full_iv.setImageResource(R.drawable.aeroplane);
                learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                        getResources(), R.drawable.aeroplane, learn_full_iv.getWidth(), learn_full_iv.getWidth()));
                Toast.makeText(getApplicationContext(), "Width : " + learn_full_iv.getWidth() + "Height : " + learn_full_iv.getHeight(), Toast.LENGTH_SHORT).show();
                playSound(1, 2);
                break;
            case R.id.b:
                //learn_full_iv.setImageResource(R.drawable.ball);
                learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                        getResources(), R.drawable.ball, learn_full_iv.getWidth(), learn_full_iv.getWidth()));
                Toast.makeText(getApplicationContext(), "Width : " + learn_full_iv.getWidth() + "Height : " + learn_full_iv.getHeight(), Toast.LENGTH_SHORT).show();
                playSound(3, 4);
                break;
            case R.id.c:
                //learn_full_iv.setImageResource(R.drawable.camel);
                learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                        getResources(), R.drawable.camel, learn_full_iv.getWidth(), learn_full_iv.getWidth()));
                Toast.makeText(getApplicationContext(), "Width : " + learn_full_iv.getWidth() + "Height : " + learn_full_iv.getHeight(), Toast.LENGTH_SHORT).show();
                playSound(5, 6);
                break;
            case R.id.d:
                //learn_full_iv.setImageResource(R.drawable.drum);
                learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                        getResources(), R.drawable.drum, learn_full_iv.getWidth(), learn_full_iv.getWidth()));
                Toast.makeText(getApplicationContext(), "Width : " + learn_full_iv.getWidth() + "Height : " + learn_full_iv.getHeight(), Toast.LENGTH_SHORT).show();
                playSound(7, 8);
                break;
                    default:
                    break;     
}

现在问题是每次加载onCreate（）时，首先单击的图像将仅显示图像的纯色而不显示整个图像，如下所示：

Image View Without Width & Height

从下次点击开始，无论是在同一图片还是下一张图片上，代码都可以正常工作： ImageView with desired width & Height!

其他一切正常，直到Activity重新启动。如果我们重新启动或恢复此活动，则会发生同样的事情。

那么，出了什么问题？

Answer 1

我刚解决了它＆amp;想出了我的自己，实际上它是一个小的看看Android的图像加载：

  @Override
    public void run() {
        // TODO Auto-generated method stub
        learn_full_iv.setVisibility(View.VISIBLE);
        learn_full_iv.startAnimation(anim);

        switch (id) {
        case R.id.a:
            //learn_full_iv.setImageResource(R.drawable.aeroplane);
            learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                    getResources(), R.drawable.aeroplane, learn_full_iv.getWidth(), learn_full_iv.getWidth()));
            Toast.makeText(getApplicationContext(), "Width : " + learn_full_iv.getWidth() + "Height : " + learn_full_iv.getHeight(), Toast.LENGTH_SHORT).show();
            playSound(1, 2);
            break;
    ...........

上面代码中的问题是我只是在run方法的开头启用ImageView“learn_full_iv”，它将具有宽度＆amp;高度为“0”默认情况下，因为图像仍未在ImageView上设置

所以，如果我们打电话：

 learn_full_iv.setImageBitmap(decodeSampledBitmapFromResource(
                getResources(), R.drawable.aeroplane, learn_full_iv.getWidth(), learn_full_iv.getWidth()));

宽度和宽度在这种情况下，高度将为零，因此，只显示该图像的固体颜色。所以，我使用方法来获得宽度和宽度。屏幕高度为整数值＆amp;将它们传递到相应的宽度和宽度。上面的BITMAP DECODE方法中的高度部分。

多数民众赞成，因为现在我们有宽度和宽度。高度为值，现在将显示位图。

简单!!!

Answer 2

请澄清：

你为什么要在runnable中调用switch cod？
你在哪里调用处理程序来运行??

确保不在onresume / onstart方法中调用处理程序启动方法也确保在方向更改时不再调用oncreate

有效加载位图 - 开始时显示纯色

2 个答案: