如何在 Android 中完全加载 ImageView

How to get when an ImageView is completely loaded in Android(如何在 Android 中完全加载 ImageView)

问题描述

我正在开发一个在一堆图像上画线的应用程序.为了选择这些图像，我有一个单选组，每当用户单击单选按钮时，图像都会加载所有自己的绘图.

I'm developing an App which draws lines over a bunch of Images. To choose these images, I have a radio group and, whenever the user clicks in a radio button, the image is load with all its own drawings.

在我的收音机监听器中，我有以下代码:

In my radio listenner I have the following code:

bitmap = BitmapUtils.decodeSampledBitmapFromResource(root + DefinesAndroid.CAMINHO_SHOPPINGS_SDCARD + nomeImagemAtual, size.x, size.y);
mImage.setImageBitmap(bitmap);

mImage.setDrawLines(true);
mImage.setImageBitmap(loadBitmapFromView(mImage));

decodeSampledBitmapFromResource 方法我从这个关于 android 开发者的链接获得(它更有效地加载位图)http://developer.android.com/training/displaying-bitmaps/load-bitmap.html

the decodeSampledBitmapFromResource method I got from this link on android developers (it loads bitmaps more effitiently) http://developer.android.com/training/displaying-bitmaps/load-bitmap.html

这是我用来获取视图位图的方法

And here's the method I call to get a Bitmap of a View

    public static Bitmap loadBitmapFromView(View v) {
        Bitmap b = Bitmap.createBitmap( v.getLayoutParams().width, v.getLayoutParams().height, Bitmap.Config.ARGB_8888);                
        Canvas c = new Canvas(b);
        v.layout(0, 0, v.getLayoutParams().width, v.getLayoutParams().height);
        v.draw(c);
        return b;
}

我正在设置 mImage 的图像位图，因为我正在使用 ImageViewTouch 库(它可以在 ImageView 上进行缩放)，如果我不这样做，所有的画布绘图都会被删除与图像的任何交互(如放大/缩小).

I'm setting the image Bitmap of mImage because I'm using ImageViewTouch library (which enables pinch zooming over an ImageView) and if I don't do it, all the canvas drawing is deleted with any interaction over the image (like zooming in/out).

错误日志如下

07-11 21:13:41.567: E/AndroidRuntime(20056): java.lang.IllegalArgumentException: width and height must be > 0
07-11 21:13:41.567: E/AndroidRuntime(20056):    at android.graphics.Bitmap.createBitmap(Bitmap.java:638)
07-11 21:13:41.567: E/AndroidRuntime(20056):    at android.graphics.Bitmap.createBitmap(Bitmap.java:620)

我几乎可以肯定这个错误的发生是因为当我调用 getBitmapFromView 方法时图像位图没有完全加载.

I'm almost sure that this error is occuring cause the image bitmap is not completely loaded when I call getBitmapFromView method.

我如何知道视图何时完全加载?

How can I know when the view is loaded completely?

推荐答案

这样调用loadBitmapFromView:

mImage.post(new Runnable() {
    @Override
    public void run() {
        loadBitmapFromView(mImage);
    }
});

Runnable 提供给 post() 方法将在视图测量和布局后执行，因此 getWidth() 和 getHeight() 将返回实际的宽度和高度.

Runnable provided to post() method will be executed after view measuring and layouting, so getWidth() and getHeight() will return actual width and height.

您还能做什么，通过调用 measure 手动测量 View，然后从 getMeasuredWidth() 和 获取结果>getMeasuredHeight().但我不推荐这种方式.

What else can you do, is measuring View manually, by invoking measure, and then taking result from getMeasuredWidth() and getMeasuredHeight(). But I do not recommend this way.

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