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
一、Activity截屏
1、截Activity界面（包含空白的状态栏）
/**
* 根据指定的Activity截图（带空白的状态栏）
*
* @param context 要截图的Activity
* @return Bitmap
*/
public static Bitmap shotActivity(Activity context) {
View view = context.getWindow().getDecorView();
view.setDrawingCacheEnabled(true);
view.buildDrawingCache();
Bitmap bitmap = Bitmap.createBitmap(view.getDrawingCache(), 0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
view.setDrawingCacheEnabled(false);
view.destroyDrawingCache();
return bitmap;
}
2、截Activity界面（去除状态栏）
/**
* 根据指定的Activity截图（去除状态栏）
*
* @param activity 要截图的Activity
* @return Bitmap
*/
public Bitmap shotActivityNoStatusBar(Activity activity) {
// 获取windows中最顶层的view
View view = activity.getWindow().getDecorView();
view.buildDrawingCache();
// 获取状态栏高度
Rect rect = new Rect();
view.getWindowVisibleDisplayFrame(rect);
int statusBarHeights = rect.top;
Display display = activity.getWindowManager().getDefaultDisplay();
// 获取屏幕宽和高
int widths = display.getWidth();
int heights = display.getHeight();
// 允许当前窗口保存缓存信息
view.setDrawingCacheEnabled(true);
// 去掉状态栏
Bitmap bmp = Bitmap.createBitmap(view.getDrawingCache(), 0,
statusBarHeights, widths, heights - statusBarHeights);
// 销毁缓存信息
view.destroyDrawingCache();
return bmp;
}
二、View截屏
/**
* 根据指定的view截图
*
* @param v 要截图的view
* @return Bitmap
*/
public static Bitmap getViewBitmap(View v) {
if (null == v) {
return null;
}
v.setDrawingCacheEnabled(true);
v.buildDrawingCache();
if (Build.VERSION.SDK_INT >= 11) {
v.measure(View.MeasureSpec.makeMeasureSpec(v.getWidth(), View.MeasureSpec.EXACTLY),
View.MeasureSpec.makeMeasureSpec(v.getHeight(), View.MeasureSpec.EXACTLY));
v.layout((int) v.getX(), (int) v.getY(), (int) v.getX() + v.getMeasuredWidth(), (int) v.getY() + v.getMeasuredHeight());
} else {
v.measure(View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED),
View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
}
Bitmap bitmap = Bitmap.createBitmap(v.getDrawingCache(), 0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
v.setDrawingCacheEnabled(false);
v.destroyDrawingCache();
return bitmap;
}
三、ScrollView截屏
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
/**
* Scrollview截屏
*
* @param scrollView 要截图的ScrollView
* @return Bitmap
*/
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;
}
四、ListView截屏
ListView是会回收与重用Item，并且只会绘制在屏幕上显示的ItemView，下面的方法采用一个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。
/**
* ListView截图
*
* @param listView 要截图的ListView
* @return Bitmap
*/
public static Bitmap shotListView(ListView listView) {
ListAdapter adapter = listView.getAdapter();
int itemsCount = adapter.getCount();
int allItemsHeight = 0;
ArrayList<Bitmap> bmps = new ArrayList<>();
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;
}
五、RecyclerView截屏
/**
* RecyclerView截屏
*
* @param view 要截图的RecyclerView
* @return Bitmap
*/
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;
}
六、WebView截屏
1、截取webView可视区域的截图
/**
* 截取webView可视区域的截图
* @param webView 前提：WebView要设置webView.setDrawingCacheEnabled(true);
* @return
*/
private Bitmap captureWebViewVisibleSize(WebView webView){
Bitmap bmp = webView.getDrawingCache();
return bmp;
}
2、截取webView的整个页面
/**
* 截取webView快照(webView加载的整个内容的大小)
* @param webView
* @return
*/
private Bitmap captureWebView(WebView webView){
Picture snapShot = webView.capturePicture();
Bitmap bmp = Bitmap.createBitmap(snapShot.getWidth(),snapShot.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bmp);
snapShot.draw(canvas);
return bmp;
}
3、截取手机屏幕，获取界面展示的webview
/**
* 截屏
*
* @param context
* @return
*/
private Bitmap captureScreen(Activity context) {
View cv = context.getWindow().getDecorView();
Bitmap bmp = Bitmap.createBitmap(cv.getWidth(), cv.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bmp);
cv.draw(canvas);
return bmp;
}
