Android截屏
Android截屏的原理：获取具体需要截屏的区域的Bitmap，然后绘制在画布上，保存为图片后进行分享或者其它用途
在截屏功能中，有时需要截取全屏的内容，有时需要截取超过一屏的内容（比如：Listview，Scrollview，RecyclerView）。下面介绍各种场景获取Bitmap的方法
普通截屏的实现
获取当前Window的DrawingCache的方式，即decorView的DrawingCache
/**
* shot the current screen ,with the status but the status is trans *
*
* @param ctx current activity
*/
public static Bitmap shotActivity(Activity ctx) {
View view = ctx.getWindow().getDecorView();
view.setDrawingCacheEnabled(true);
view.buildDrawingCache();
Bitmap bp = Bitmap.createBitmap(view.getDrawingCache(), 0, 0, view.getMeasuredWidth(),
view.getMeasuredHeight());
view.setDrawingCacheEnabled(false);
view.destroyDrawingCache(); return bp;
}获取当前View的DrawingCache
public static Bitmap getViewBp(View v) { if (null == v) { return null;
}
v.setDrawingCacheEnabled(true);
v.buildDrawingCache(); if (Build.VERSION.SDK_INT >= 11) {
v.measure(MeasureSpec.makeMeasureSpec(v.getWidth(),
MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(
v.getHeight(), MeasureSpec.EXACTLY));
v.layout((int) v.getX(), (int) v.getY(),
(int) v.getX() + v.getMeasuredWidth(),
(int) v.getY() + v.getMeasuredHeight());
} else {
v.measure(MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED),
MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
}
Bitmap b = Bitmap.createBitmap(v.getDrawingCache(), 0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
v.setDrawingCacheEnabled(false);
v.destroyDrawingCache(); return b;
}开源方案
在滚动视图中，如果当前View并没有在视图中全部绘制出来，我们可以利用View的ScrollTo()和ScrollBy()方法来移动画布，同时获取当前View的可视部分的DrawingCache，最后进行拼接得到其Bitmap，参考:[PGSSoft/scrollscreenshot@[Github]](https://github.com/PGSSoft/scrollscreenshot)。
Scrollview截屏
三个截屏中，ScrollView最简单，因为ScrollView只有一个childView，虽然没有全部显示在界面上，但是已经全部渲染绘制，因此可以直接 调用scrollView.draw(canvas)来完成截图
public static Bitmap shotScrollView(ScrollView scrollView) { int h = 0;
Bitmap bitmap = null; for (int i = 0; i < scrollView.getChildCount(); i++) {
h += scrollView.getChildAt(i).getHeight();
scrollView.getChildAt(i).setBackgroundColor(Color.parseColor("#ffffff"));
}
bitmap = Bitmap.createBitmap(scrollView.getWidth(), h, Bitmap.Config.RGB_565); final Canvas canvas = new Canvas(bitmap);
scrollView.draw(canvas); return bitmap;
}listview截屏
而ListView就是会回收与重用Item，并且只会绘制在屏幕上显示的ItemView，根据stackoverflow上大神的建议，采用一个List来存储Item的视图，这种方案依然不够好，当Item足够多的时候，可能会发生oom。
public static Bitmap shotListView(ListView listview) {
ListAdapter adapter = listview.getAdapter(); int itemscount = adapter.getCount(); int allitemsheight = 0;
List<Bitmap> bmps = new ArrayList<Bitmap>(); for (int i = 0; i < itemscount; i++) {
View childView = adapter.getView(i, null, listview);
childView.measure(
View.MeasureSpec.makeMeasureSpec(listview.getWidth(), View.MeasureSpec.EXACTLY),
View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
childView.layout(0, 0, childView.getMeasuredWidth(), childView.getMeasuredHeight());
childView.setDrawingCacheEnabled(true);
childView.buildDrawingCache();
bmps.add(childView.getDrawingCache());
allitemsheight += childView.getMeasuredHeight();
}
Bitmap bigbitmap =
Bitmap.createBitmap(listview.getMeasuredWidth(), allitemsheight, Bitmap.Config.ARGB_8888);
Canvas bigcanvas = new Canvas(bigbitmap);
Paint paint = new Paint(); int iHeight = 0; for (int i = 0; i < bmps.size(); i++) {
Bitmap bmp = bmps.get(i);
bigcanvas.drawBitmap(bmp, 0, iHeight, paint);
iHeight += bmp.getHeight();
bmp.recycle();
bmp = null;
} return bigbitmap;
}RecyclerView截屏
我们都知道，在新的Android版本中，已经可以用RecyclerView来代替使用ListView的场景，相比较ListView，RecyclerView对Item View的缓存支持的更好。可以采用和ListView相同的方案，这里也是在stackoverflow上看到的方案。
public static Bitmap shotRecyclerView(RecyclerView view) {
RecyclerView.Adapter adapter = view.getAdapter();
Bitmap bigBitmap = null; if (adapter != null) { int size = adapter.getItemCount(); int height = 0;
Paint paint = new Paint(); int iHeight = 0; final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024); // Use 1/8th of the available memory for this memory cache.
final int cacheSize = maxMemory / 8;
LruCache<String, Bitmap> bitmaCache = new LruCache<>(cacheSize); for (int i = 0; i < size; i++) {
RecyclerView.ViewHolder holder = adapter.createViewHolder(view, adapter.getItemViewType(i));
adapter.onBindViewHolder(holder, i);
holder.itemView.measure(
View.MeasureSpec.makeMeasureSpec(view.getWidth(), View.MeasureSpec.EXACTLY),
View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
holder.itemView.layout(0, 0, holder.itemView.getMeasuredWidth(),
holder.itemView.getMeasuredHeight());
holder.itemView.setDrawingCacheEnabled(true);
holder.itemView.buildDrawingCache();
Bitmap drawingCache = holder.itemView.getDrawingCache(); if (drawingCache != null) {
bitmaCache.put(String.valueOf(i), drawingCache);
}
height += holder.itemView.getMeasuredHeight();
}
bigBitmap = Bitmap.createBitmap(view.getMeasuredWidth(), height, Bitmap.Config.ARGB_8888);
Canvas bigCanvas = new Canvas(bigBitmap);
Drawable lBackground = view.getBackground(); if (lBackground instanceof ColorDrawable) {
ColorDrawable lColorDrawable = (ColorDrawable) lBackground; int lColor = lColorDrawable.getColor();
bigCanvas.drawColor(lColor);
} for (int i = 0; i < size; i++) {
Bitmap bitmap = bitmaCache.get(String.valueOf(i));
bigCanvas.drawBitmap(bitmap, 0f, iHeight, paint);
iHeight += bitmap.getHeight();
bitmap.recycle();
}
} return bigBitmap;
}相信有不少小伙伴用BRVH第三方库来做recycleview的适配器的。使用这个库的话再用上面的方法会报角标越界的错误，看了BRVH的源码
public void onBindViewHolder(ViewHolder holder, int positions) { int viewType = holder.getItemViewType(); switch(viewType) { case 0: this.convert((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount())); case 273: case 819: case 1365: break; case 546: this.addLoadMore(holder); break; default: this.convert((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount())); this.onBindDefViewHolder((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount()));
}
}在调用adapter.onBindViewHolder时，因为里面的position参数未使用，里面用的计算holder.getLayoutPosition() - this.getHeaderLayoutCount()的值一直是-1导致角标越界报错。
本人理解，RecyclerView的截屏原理是，首先构造每个item的ViewHolder，然后调用具体设置数据到每个item的方法，此时cache中就存有item的内容，此时绘制就能获取到完整的内容。采用v7包中的onBindViewHolder方法即可，或者是BRVH的convert方法，可以看到BRVH中没有暴露出这个方法，而且唯一暴露出的onBindViewHolder还会报角标越界错误，此时我们就需要在BRVH的基础上暴露出convert即可，代码如下
public class MyAdapter extends BaseQuickAdapter<T> { public MyAdapter() { super(getItemLayoutResId(), datas);
} /**
* 用于对外暴露convert方法,构造缓存视图(截屏用)
* @param viewHolder
* @param t
*/
public void startConvert(BaseViewHolder viewHolder, T t){
convert(viewHolder,t);
} @Override
protected void convert(BaseViewHolder viewHolder, T t) {
bindView(viewHolder, t);
}
}然后将上面所述的获取Bitmap方法修改一下
/**
* 截取recycler view
*/
public static Bitmap getRecyclerViewScreenshot(RecyclerView view) {
BaseListFragment.MyAdapter adapter = (BaseListFragment.MyAdapter) view.getAdapter();
Bitmap bigBitmap = null; if (adapter != null) { int size = adapter.getData().size(); int height = 0;
Paint paint = new Paint(); int iHeight = 0; final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024); // Use 1/8th of the available memory for this memory cache.
final int cacheSize = maxMemory / 8;
LruCache<String, Bitmap> bitmaCache = new LruCache<>(cacheSize); for (int i = 0; i < size; i++) {
BaseViewHolder holder = (BaseViewHolder) adapter.createViewHolder(view, adapter.getItemViewType(i)); //此处需要调用convert方法，否则绘制出来的都是空的item
adapter.startConvert(holder, adapter.getData().get(i));
holder.itemView.measure(
View.MeasureSpec.makeMeasureSpec(view.getWidth(), View.MeasureSpec.EXACTLY),
View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
holder.itemView.layout(0, 0, holder.itemView.getMeasuredWidth(),
holder.itemView.getMeasuredHeight());
holder.itemView.setDrawingCacheEnabled(true);
holder.itemView.buildDrawingCache();
Bitmap drawingCache = holder.itemView.getDrawingCache(); if (drawingCache != null) {
bitmaCache.put(String.valueOf(i), drawingCache);
}
height += holder.itemView.getMeasuredHeight();
}
bigBitmap = Bitmap.createBitmap(view.getMeasuredWidth(), height, Bitmap.Config.ARGB_8888);
Canvas bigCanvas = new Canvas(bigBitmap);
Drawable lBackground = view.getBackground(); if (lBackground instanceof ColorDrawable) {
ColorDrawable lColorDrawable = (ColorDrawable) lBackground; int lColor = lColorDrawable.getColor();
bigCanvas.drawColor(lColor);
} for (int i = 0; i < size; i++) {
Bitmap bitmap = bitmaCache.get(String.valueOf(i));
bigCanvas.drawBitmap(bitmap, 0f, iHeight, paint);
iHeight += bitmap.getHeight();
bitmap.recycle();
}
} return bigBitmap;
}合成Bitmap
比如四张合成一张
/**
* 将四张图拼成一张
*
* @param pic1 图一
* @param pic2 图二
* @param pic3 图三
* @param pic4 图四
* @return only_bitmap
* 详情见说明：{@link com.bertadata.qxb.util.ScreenShotUtils}
*/
public static Bitmap combineBitmapsIntoOnlyOne(Bitmap pic1, Bitmap pic2, Bitmap pic3, Bitmap pic4, Activity context) { int w_total = pic2.getWidth(); int h_total = pic1.getHeight() + pic2.getHeight() + pic3.getHeight() + pic4.getHeight(); int h_pic1 = pic1.getHeight(); int h_pic4 = pic4.getHeight(); int h_pic12 = pic1.getHeight() + pic2.getHeight(); //此处为防止OOM需要对高度做限制
if (h_total > HEIGHTLIMIT) { return null;
}
Bitmap only_bitmap = Bitmap.createBitmap(w_total, h_total, Bitmap.Config.ARGB_4444);
Canvas canvas = new Canvas(only_bitmap);
canvas.drawColor(ContextCompat.getColor(context, R.color.color_content_bg));
canvas.drawBitmap(pic1, 0, 0, null);
canvas.drawBitmap(pic2, 0, h_pic1, null);
canvas.drawBitmap(pic3, 0, h_pic12, null);
canvas.drawBitmap(pic4, 0, h_total - h_pic4, null); return only_bitmap;
}图片后期处理
/**
* 将传入的Bitmap合理压缩后输出到系统截屏目录下
* 命名格式为：Screenshot+时间戳+启信宝报名.jpg
* 同时通知系统重新扫描系统文件
*
* @param pic1 图一 标题栏截图
* @param pic2 图二 scrollview截图
* @param context 用于通知重新扫描文件系统，为提升性能可去掉
* 详情见说明：{@link com.bertadata.qxb.util.ScreenShotUtils}
*/
public static void savingBitmapIntoFile(final Bitmap pic1, final Bitmap pic2, final Activity context, final BitmapAndFileCallBack callBack) { if (context == null || context.isFinishing()) { return;
}
Thread thread = new Thread(new Runnable() { @Override
public void run() {
String fileReturnPath = ""; int w = pic1.getWidth();
Bitmap bottom = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_picture_combine_bottom);
Bitmap top_banner = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_picture_combine_top);
Bitmap bitmap_bottom = anyRatioCompressing(bottom, (float) w / bottom.getWidth(), (float) w / bottom.getWidth());
Bitmap bitmap_top = anyRatioCompressing(top_banner, (float) w / bottom.getWidth(), (float) w / bottom.getWidth()); final Bitmap only_bitmap = combineBitmapsIntoOnlyOne(bitmap_top, pic1, pic2, bitmap_bottom, context); // 获取当前时间
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss-ms", Locale.getDefault());
String data = sdf.format(new Date()); // 获取内存路径
// 设置图片路径+命名规范
// 声明输出文件
String storagePath = Environment.getExternalStorageDirectory().getAbsolutePath();
String fileTitle = "Screenshot_" + data + "_com.bertadata.qxb.biz_info.jpg";
String filePath = storagePath + "/DCIM/"; final String fileAbsolutePath = filePath + fileTitle;
File file = new File(fileAbsolutePath); /**
* 质压与比压结合
* 分级压缩
* 输出文件
*/
if (only_bitmap != null) { try { // 首先，对原图进行一步质量压缩,形成初步文件
FileOutputStream fos = new FileOutputStream(file);
only_bitmap.compress(Bitmap.CompressFormat.JPEG, 50, fos); // 另建一个文件other_file预备输出
String other_fileTitle = "Screenshot_" + data + "_com.bertadata.qxb.jpg";
String other_fileAbsolutePath = filePath + other_fileTitle;
File other_file = new File(other_fileAbsolutePath);
FileOutputStream other_fos = new FileOutputStream(other_file); // 其次，要判断质压之后的文件大小，按文件大小分级进行处理
long file_size = file.length() / 1024; // size of file(KB)
if (file_size < 0 || !(file.exists())) { // 零级： 文件判空
throw new NullPointerException();
} else if (file_size > 0 && file_size <= 256) { // 一级： 直接输出
deleteFile(other_file); // 通知刷新文件系统，显示最新截取的图文件
fileReturnPath = fileAbsolutePath;
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + fileAbsolutePath)));
} else if (file_size > 256 && file_size <= 768) { // 二级： 简单压缩:压缩为原比例的3/4，质压为50%
anyRatioCompressing(only_bitmap, (float) 3 / 4, (float) 3 / 4).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
deleteFile(file); // 通知刷新文件系统，显示最新截取的图文件
fileReturnPath = other_fileAbsolutePath;
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
} else if (file_size > 768 && file_size <= 1280) { // 三级： 中度压缩：压缩为原比例的1/2，质压为40%
anyRatioCompressing(only_bitmap, (float) 1 / 2, (float) 1 / 2).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
deleteFile(file); // 通知刷新文件系统，显示最新截取的图文件
fileReturnPath = other_fileAbsolutePath;
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
} else if (file_size > 1280 && file_size <= 2048) { // 四级： 大幅压缩：压缩为原比例的1/3，质压为40%
anyRatioCompressing(only_bitmap, (float) 1 / 3, (float) 1 / 3).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
deleteFile(file); // 通知刷新文件系统，显示最新截取的图文件
fileReturnPath = other_fileAbsolutePath;
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
} else if (file_size > 2048) { // 五级： 中度压缩：压缩为原比例的1/2，质压为40%
anyRatioCompressing(only_bitmap, (float) 1 / 2, (float) 1 / 2).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
deleteFile(file); // 通知刷新文件系统，显示最新截取的图文件
fileReturnPath = other_fileAbsolutePath;
context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
} // 注销fos;
fos.flush();
other_fos.flush();
other_fos.close();
fos.close(); //callback用于回传保存成功的路径以及Bitmap
callBack.onSuccess(only_bitmap, fileReturnPath);
} catch (Exception e) {
e.printStackTrace();
}
} else callBack.onSuccess(null, "");
}
});
thread.start();
}
/**
* 可实现任意宽高比例压缩（宽高压比可不同）的压缩方法（主要用于微压）
*
* @param bitmap 源图
* @param width_ratio 宽压比（float）（0<&&<1)
* @param height_ratio 高压比（float）（0<&&<1)
* @return 目标图片
* <p>
*/
public static Bitmap anyRatioCompressing(Bitmap bitmap, float width_ratio, float height_ratio) {
Matrix matrix = new Matrix();
matrix.postScale(width_ratio, height_ratio); return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
}本文参考http://www.cnblogs.com/BoBoMEe/p/4556917.html，并结合自己实际项目操作完成
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