系统自带的截屏方法

/**
     * Request a screenshot be taken.
     *
     * @param screenshotType The type of screenshot, for example either
     *                       {@link android.view.WindowManager.TAKE_SCREENSHOT_FULLSCREEN}
     *                       or {@link android.view.WindowManager.TAKE_SCREENSHOT_SELECTED_REGION}
     * @param hasStatus {@code true} if the status bar is currently showing. {@code false} if not.
     * @param hasNav {@code true} if the navigation bar is currently showing. {@code false} if not.
     * @param handler A handler used in case the screenshot times out
     */
        public void takeScreenshot(final int screenshotType, final boolean hasStatus,
            final boolean hasNav, @NonNull Handler handler) {
        synchronized (mScreenshotLock) {
            if (mScreenshotConnection != null) {
                return;
            }
            final ComponentName serviceComponent = new ComponentName(SYSUI_PACKAGE,
                    SYSUI_SCREENSHOT_SERVICE);
            final Intent serviceIntent = new Intent();

            final Runnable mScreenshotTimeout = new Runnable() {
                @Override public void run() {
                    synchronized (mScreenshotLock) {
                        if (mScreenshotConnection != null) {
                            mContext.unbindService(mScreenshotConnection);
                            mScreenshotConnection = null;
                            notifyScreenshotError();
                        }
                    }
                }
            };

            serviceIntent.setComponent(serviceComponent);
            ServiceConnection conn = new ServiceConnection() {
                @Override
                public void onServiceConnected(ComponentName name, IBinder service) {
                    synchronized (mScreenshotLock) {
                        if (mScreenshotConnection != this) {
                            return;
                        }
                        Messenger messenger = new Messenger(service);
                        Message msg = Message.obtain(null, screenshotType);
                        final ServiceConnection myConn = this;
                        Handler h = new Handler(handler.getLooper()) {
                            @Override
                            public void handleMessage(Message msg) {
                                synchronized (mScreenshotLock) {
                                    if (mScreenshotConnection == myConn) {
                                        mContext.unbindService(mScreenshotConnection);
                                        mScreenshotConnection = null;
                                        handler.removeCallbacks(mScreenshotTimeout);
                                    }
                                }
                            }
                        };
                        msg.replyTo = new Messenger(h);
                        msg.arg1 = hasStatus ? 1: 0;
                        msg.arg2 = hasNav ? 1: 0;
                        try {
                            messenger.send(msg);
                        } catch (RemoteException e) {
                            Log.e(TAG, "Couldn't take screenshot: " + e);
                        }
                    }
                }

                @Override
                public void onServiceDisconnected(ComponentName name) {
                    synchronized (mScreenshotLock) {
                        if (mScreenshotConnection != null) {
                            mContext.unbindService(mScreenshotConnection);
                            mScreenshotConnection = null;
                            handler.removeCallbacks(mScreenshotTimeout);
                            notifyScreenshotError();
                        }
                    }
                }
            };
            if (mContext.bindServiceAsUser(serviceIntent, conn,
                    Context.BIND_AUTO_CREATE | Context.BIND_FOREGROUND_SERVICE_WHILE_AWAKE,
                    UserHandle.CURRENT)) {
                mScreenshotConnection = conn;
                handler.postDelayed(mScreenshotTimeout, SCREENSHOT_TIMEOUT_MS);
            }
        }
    }

参数说明：第一个参数screenshot，传入WindowManager.TAKE_SCREENSHOT_FULLSCREEN可以截取全屏，传入WindowManager.TAKE_SCREENSHOT_SELECTED_REGION可以选择截屏的区域。hasStatus，是否有状态栏，hasNav是否有导航栏，最后一个可以传入一个new Handler()。

可以通过反射来调用

  private void takeScreenshot(Context context, int screenshotType, boolean hasStatus, boolean hasNav, @NonNull Handler handler){
        try {
            Class clazz = Class.forName("com.android.internal.util.ScreenshotHelper");
            Constructor c = clazz.getConstructor(Context.class);
            Object p = c.newInstance(context);
            @SuppressLint("BlockedPrivateApi") Method takeScreenshot = clazz.getDeclaredMethod("takeScreenshot", int.class,boolean.class,boolean.class, Handler.class);
            takeScreenshot.setAccessible(true);
            takeScreenshot.invoke(p,screenshotType,hasStatus,hasNav,handler);
        }catch (Exception e){
            Log.d(TAG, "takeScreenshot: Exception "+e.toString());
        }
    }

调用

 takeScreenshot(getApplicationContext(),1,true,true,new Handler());

必须要申明权限

<uses-permission android:name="android.permission.INTERACT_ACROSS_USERS_FULL" />
<uses-permission android:name="android.permission.INTERACT_ACROSS_USERS" />

而且必须要系统的签名

android:sharedUserId="android.uid.system"