将 Android webview 渲染为位图、html5 javascript、回调问题 [英] Rendering Android webview to bitmap, html5 javascript , callback issue
问题描述
我有一个带有按钮、图像和网络视图的活动.我的目标是加载一个页面,然后在其上执行 javascript 以使用 HTML5 等绘制图形.
I have an activity with a button and an image and a webview. My goal is to load a page, then execute javascript on it to draw graphics using HTML5 etc.
html5 绘制的图片高度为 unknown/variable ,但宽度应始终与手机的宽度/或浏览器窗口相同.
The height of the image drawn by the html5 is unknown/variable , but the width should always be the same as the phone's width/or browser window.
我有一个 javascript 接口来获取一个回调,其中包含它现在已经完成调用绘图函数的信息,它给了我高度.
I have a javascript interface to get a callback containing info that it has now finished calling the drawing function, and it is giving me the height.
这里是网络视图的设置
mWeb = (WebView) findViewById(R.id.webView1);
mWeb.clearCache(true);
mWeb.addJavascriptInterface(new IJavascriptHandler(), "cpjs");
mWeb.getSettings().setJavaScriptEnabled(true);
mWeb.loadUrl(" http://theURL.com ");
mWeb.setInitialScale(100);
mWeb.getSettings().setDefaultZoom(WebSettings.ZoomDensity.FAR);
mWeb.setWebViewClient(new WebViewClient() {
public void onPageFinished(WebView view, String url){
mWidth = mWeb.getWidth();
mHeight = mWeb.getHeight();
view.loadUrl("javascript: Tools.adjustWidth(" + mWidth + " )");
String javaCouponRender = "renderCoupon(" + kupongJson + ", 0); void(0)";
view.loadUrl("javascript: " + javaCouponRender);
}
});
}
我的视图中的按钮,我曾经使用此功能将我的 webview 渲染为纹理:
And the button I have in my view, I have used to initiate render my webview to a texture with this function:
void renderCoupon(int width,int height){
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
final Canvas c =new Canvas(bitmap);
mWeb.draw(c);
imgView.setMinimumWidth(width);
imgView.setMinimumHeight(height);
imgView.setImageBitmap(bitmap);
imgView.setVisibility(View.VISIBLE);
}
这有效.按下按钮,将绘制的内容渲染到纹理并且图像视图具有正确的结果.唯一的警告是我必须等到页面加载/绘制后才能按下按钮.
This works. Pressing the button, renders the drawn content to the texture and the imageview has a correct result. The only cavaet is I have to wait until the page has loaded/drawn before pressing the button.
现在,我已经实现了从 javascript 获得的回调,如下所示:
Now, I have implemented the callback I get from javascript like this:
final class IJavascriptHandler {
IJavascriptHandler() {
}
public void couponRenderedCallback(final int height){
mHasGotRenderCallback = true;
mHeight = height;
Toast t = Toast.makeText(getApplicationContext(), "see if it helps sleeping", 2000);
t.show();
try{
Thread.sleep(5000);
}
catch(InterruptedException ex){
}
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast t2 = Toast.makeText(getApplicationContext(), "and now we render to texture", 2000);
t2.show();
renderCoupon(mWidth, mHeight);
}
});
}
}
而且每次,这个回调函数都会渲染一个白页.有趣的是,如果我在看到这个回调被调用时立即按下渲染到纹理按钮,它会显示预期的结果.是 runOnUiThread 以某种方式失败了吗?
And every time, this callback function renders a white page. The funny thing is that if I physically press the render-to-texture button as soon as I see this callback is called, it shows the expected result. Is it runOnUiThread that is failing somehow?
睡眠是我添加的内容,目的是查看 webview 渲染和我从 javascript 获得的回调是否存在某种有趣的延迟.
The sleep is something I added to see if there was some sort of funny delay of the webview rendering and the callback I get from javascript.
我也尝试将 sleep 移动到 runOnUiThread 中,这也没有帮助.
I have also tried moving the sleep into the runOnUiThread , which also did not help.
我希望有人知道我应该朝哪个方向解决这个问题.任何帮助表示赞赏.
I hope someone knows in what direction I should look to solve this problem. Any help is appreciated.
推荐答案
找到了解决办法,就是把renderCoupon改成这样:
Found a solution, which was to change the renderCoupon to this:
void renderCoupon(final int width,final int height){
mWeb.postDelayed(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
final Canvas c =new Canvas(bitmap);
mWeb.draw(c);
imgView.setMinimumWidth(width);
imgView.setMinimumHeight(height);
imgView.setImageBitmap(bitmap);
imgView.setVisibility(View.VISIBLE);
}
}, 100);
}
当然,我在回调中删除了 Sleep 内容.感谢我的同事给我提示了这一点.:)
And of course I removed the Sleep stuff in my callback. Thanks to my collegue who tipped me about this. :)
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