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)

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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()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() 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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