WebView本来自带capturePicture截图方法，但是在L后该方法被标记为废弃，虽然还能用，官方建议用onDraw去替代实现。
WebView的长截图是从顶部开始到页面的最底部，即使是当前没有展示出来的地方也会算进去，所以页面越长，截图也越长，占用内存也会越大，而且不能指定缩放度来减小内容占用。对于一些页面的特殊布局效果可能有所偏差，比如底部悬浮块，在截图中不会放在最底部，而是直接在第一屏高度的底部位置，所以需要2端特殊处理。
// API 21+ 截长图需要设置,必须在WebView初始化之前调用
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
WebView.enableSlowWholeDocumentDraw();
}
public class WebUtils {
/**
* 注意getContentHeight,capturePicture只能在UI线程调用，而绘制Bitmap是耗时操作
*/
public static Bitmap captureWebView(WebView webView) {
Bitmap bitmap;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
int height = (int) (webView.getContentHeight() * webView.getScale());
int width = webView.getMeasuredWidth();
bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
webView.draw(canvas);
} else {
Picture picture = webView.capturePicture();
bitmap = Bitmap.createBitmap(picture.getWidth(), picture.getHeight(), Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
picture.draw(canvas);
}
return bitmap;
}
/**
* WebView长截图：
* 必须在UI线程调用，返回结果在子线程操作，绘制Bitmap是耗时操作
*
* 这里不限制图片大小，因为在有些手机全屏大小，有些手机会压缩大小。
* 用完图片需要回收，占用内存较大。
*/
@UiThread
public static Callable capture(final WebView webView) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
final int height = (int) (webView.getContentHeight() * webView.getScale());
final int width = webView.getMeasuredWidth();
return new Callable() {
@WorkerThread
@Override
public Bitmap call() throws Exception {
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
//noinspection WrongThread
webView.draw(canvas);
return bitmap;
}
};
} else {
final Picture picture = webView.capturePicture();
final int width = picture.getWidth();
final int height = picture.getHeight();
return new Callable() {
@WorkerThread
@Override
public Bitmap call() throws Exception {
Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.RGB_565);
Canvas canvas = new Canvas(bitmap);
picture.draw(canvas);
return bitmap;
}
};
}
}
}
// 在主线程执行
final Callable capture = WebUtils.capture(mWebView);
Callable callable = new Callable() {
@Override
public File call() throws Exception {
File dir = StorageUtils.getAppImagesDir(getContext());
File file = FileUtils.createJpegImage(dir, "Capture");
FileUtils.saveBitmap(capture.call(), file);
return file;
}
// 在子线程调用callable.call
因为是耗时操作，所以最好在操作时加个loading效果。
具体例子
这里除了对WebView页面进行长截图后，还要对这个图片进行处理，比如在头部拼接头部内容，在尾部再拼接尾部内容，还有图片压缩等等。
public void captureWebView() {
final Callable captureCallable = WebUtils.capture(mWebView);
Observable.fromCallable(captureCallable)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.map(new Function() {
@Override
public File apply(@NonNull Bitmap bitmap) throws Exception {
// 1.先保存压缩体积后的文件
File dir = StorageUtils.getAppImagesDir(getContext());
File file = FileUtils.createJpegImage(dir, "Capture-Origin-");
FileUtils.saveBitmapToFile(file, bitmap, 5000); // max size 5Mb
return file;
}
})
.map(new Function() {
@Override
public Bitmap apply(@NonNull File file) throws Exception {
// 2.压缩宽高大小，减少内存占用
Bitmap contentBmp = BitmapUtils.compress(file.getAbsolutePath(), 1080, 1920 * 8);
// 拼接图片，不先保存文件再解码才拼接
Rect outRect = new Rect();
Bitmap headerBmp = generateHeader(getContext(), outRect, title);
Bitmap footerBmp = BitmapFactory.decodeResource(getResources(), R.mipmap.img_footer);
Bitmap composedBmp = ShareImageUtils.composeImage(contentBmp, headerBmp, footerBmp);
contentBmp.recycle();
headerBmp.recycle();
footerBmp.recycle();
return composedBmp;
}
})
.map(new Function() {
@Override
public File apply(@NonNull Bitmap bitmap) throws Exception {
// 3.保存合成压缩后的文件
File dir = StorageUtils.getAppImagesDir(getContext());
File file = FileUtils.createJpegImage(dir, "Capture-composed-");
FileUtils.saveBitmapToFile(file, bitmap, 5000);
return file;
}
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new DisposableObserver() {
@Override
protected void onStart() {
showLoadingView();
}
@Override
public void onNext(@NonNull File file) {
if (file != null) {
CaptureShareDialog.showDialog(getFragmentManager(), file);
}
}
@Override
public void onComplete() {
hideLoadingView();
}
@Override
public void onError(@NonNull Throwable e) {
hideLoadingView();
}
});
}
参考文章
https://stackoverflow.com/questions/20942623/which-can-replace-capturepicture-function/20963109#20963109