从Android4.0源码中提取的截图实现（在当前activity中有效，不能全局截图）

package com.kale.viewshot;


import android.app.Activity;
import android.os.Bundle;
import android.view.View;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        
        
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final GlobalScreenshot screenshot = new GlobalScreenshot(this);
        findViewById(R.id.main_btn).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                screenshot.takeScreenshot(getWindow().getDecorView(), new Runnable() {
                    @Override
                    public void run() {

                    }
                }, true, true);
                
            }
        });
    }

}

package com.kale.viewshot;

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.AnimatorSet;
import android.animation.ValueAnimator;
import android.animation.ValueAnimator.AnimatorUpdateListener;
import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.PixelFormat;
import android.graphics.PointF;
import android.media.MediaActionSound;
import android.net.Uri;
import android.util.DisplayMetrics;
import android.view.Display;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.view.animation.Interpolator;
import android.widget.ImageView;

/**
 * POD used in the AsyncTask which saves an image in the background.
 */
class SaveImageInBackgroundData {
    Context context;
    Bitmap image;
    Uri imageUri;
    Runnable finisher;
    int iconSize;
    int result;

    void clearImage() {
        image = null;
        imageUri = null;
        iconSize = 0;
    }

    void clearContext() {
        context = null;
    }
}


/**
 * TODO:
 * - Performance when over gl surfaces? Ie. Gallery
 * - what do we say in the Toast? Which icon do we get if the user uses another
 * type of gallery?
 */
class GlobalScreenshot {
    private static final String TAG = "GlobalScreenshot";

    private static final int SCREENSHOT_FLASH_TO_PEAK_DURATION = 130;
    private static final int SCREENSHOT_DROP_IN_DURATION = 430;
    private static final int SCREENSHOT_DROP_OUT_DELAY = 500;
    private static final int SCREENSHOT_DROP_OUT_DURATION = 430;
    private static final int SCREENSHOT_DROP_OUT_SCALE_DURATION = 370;
    private static final int SCREENSHOT_FAST_DROP_OUT_DURATION = 320;
    private static final float BACKGROUND_ALPHA = 0.5f;
    private static final float SCREENSHOT_SCALE = 1f;
    private static final float SCREENSHOT_DROP_IN_MIN_SCALE = SCREENSHOT_SCALE * 0.725f;
    private static final float SCREENSHOT_DROP_OUT_MIN_SCALE = SCREENSHOT_SCALE * 0.45f;
    private static final float SCREENSHOT_FAST_DROP_OUT_MIN_SCALE = SCREENSHOT_SCALE * 0.6f;
    private static final float SCREENSHOT_DROP_OUT_MIN_SCALE_OFFSET = 0f;

    private Context mContext;
    private WindowManager mWindowManager;
    private WindowManager.LayoutParams mWindowLayoutParams;
    private Display mDisplay;
    private DisplayMetrics mDisplayMetrics;

    private Bitmap mScreenBitmap;
    private View mScreenshotLayout;
    private ImageView mBackgroundView;
    private ImageView mScreenshotView;
    private ImageView mScreenshotFlash;

    private AnimatorSet mScreenshotAnimation;

    private float mBgPadding;
    private float mBgPaddingScale;

    private MediaActionSound mCameraSound;


    /**
     * @param context everything needs a context :(
     */
    public GlobalScreenshot(Context context) {
        Resources r = context.getResources();
        mContext = context;
        LayoutInflater layoutInflater = (LayoutInflater)
                context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        // Inflate the screenshot layout
        mScreenshotLayout = layoutInflater.inflate(R.layout.global_screenshot, null);
        mBackgroundView = (ImageView) mScreenshotLayout.findViewById(R.id.global_screenshot_background);
        mScreenshotView = (ImageView) mScreenshotLayout.findViewById(R.id.global_screenshot);
        mScreenshotFlash = (ImageView) mScreenshotLayout.findViewById(R.id.global_screenshot_flash);
        mScreenshotLayout.setFocusable(true);
        mScreenshotLayout.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                // Intercept and ignore all touch events
                return true;
            }
        });

        // Setup the window that we are going to use
        mWindowLayoutParams = new WindowManager.LayoutParams(
                ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT, 0, 0,
                WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
                WindowManager.LayoutParams.FLAG_FULLSCREEN
                        | WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED
                        | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                        | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED,
                PixelFormat.TRANSLUCENT);
        mWindowLayoutParams.setTitle("ScreenshotAnimation");
        mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);

        mDisplay = mWindowManager.getDefaultDisplay();
        mDisplayMetrics = new DisplayMetrics();
        mDisplay.getRealMetrics(mDisplayMetrics);

        // Scale has to account for both sides of the bg
        mBgPadding = (float) r.getDimensionPixelSize(R.dimen.global_screenshot_bg_padding);
        mBgPaddingScale = mBgPadding / mDisplayMetrics.widthPixels;

        // Setup the Camera shutter sound
        mCameraSound = new MediaActionSound();
        mCameraSound.load(MediaActionSound.SHUTTER_CLICK);
    }



    /**
     * Takes a screenshot of the current display and shows an animation.
     */
    void takeScreenshot(View view, Runnable finisher, boolean statusBarVisible, boolean navBarVisible) {
        // Take the screenshot
        mScreenBitmap = SurfaceControl.screenshot(view);
        if (mScreenBitmap == null) {
            notifyScreenshotError(mContext);
            finisher.run();
            return;
        }

        // Optimizations
        mScreenBitmap.setHasAlpha(false);
        mScreenBitmap.prepareToDraw();

        // Start the post-screenshot animation
        startAnimation(finisher, mDisplayMetrics.widthPixels, mDisplayMetrics.heightPixels,
                statusBarVisible, navBarVisible);
    }


    /**
     * Starts the animation after taking the screenshot
     */
    private void startAnimation(final Runnable finisher, int w, int h, boolean statusBarVisible,
                                boolean navBarVisible) {
        // Add the view for the animation
        mScreenshotView.setImageBitmap(mScreenBitmap);
        mScreenshotLayout.requestFocus();

        // Setup the animation with the screenshot just taken
        if (mScreenshotAnimation != null) {
            mScreenshotAnimation.end();
            mScreenshotAnimation.removeAllListeners();
        }

        mWindowManager.addView(mScreenshotLayout, mWindowLayoutParams);
        ValueAnimator screenshotDropInAnim = createScreenshotDropInAnimation();
        ValueAnimator screenshotFadeOutAnim = createScreenshotDropOutAnimation(w, h,
                statusBarVisible, navBarVisible);
        mScreenshotAnimation = new AnimatorSet();
        mScreenshotAnimation.playSequentially(screenshotDropInAnim, screenshotFadeOutAnim);
        mScreenshotAnimation.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                // Save the screenshot once we have a bit of time now
                saveScreenshotInWorkerThread(finisher);
                mWindowManager.removeView(mScreenshotLayout);

                // Clear any references to the bitmap
                mScreenBitmap = null;
                mScreenshotView.setImageBitmap(null);
            }
        });
        mScreenshotLayout.post(new Runnable() {
            @Override
            public void run() {
                // Play the shutter sound to notify that we‘ve taken a screenshot
                mCameraSound.play(MediaActionSound.SHUTTER_CLICK);

                mScreenshotView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
                mScreenshotView.buildLayer();
                mScreenshotAnimation.start();
            }
        });
    }

    private ValueAnimator createScreenshotDropInAnimation() {
        final float flashPeakDurationPct = ((float) (SCREENSHOT_FLASH_TO_PEAK_DURATION)
                / SCREENSHOT_DROP_IN_DURATION);
        final float flashDurationPct = 2f * flashPeakDurationPct;
        final Interpolator flashAlphaInterpolator = new Interpolator() {
            @Override
            public float getInterpolation(float x) {
                // Flash the flash view in and out quickly
                if (x <= flashDurationPct) {
                    return (float) Math.sin(Math.PI * (x / flashDurationPct));
                }
                return 0;
            }
        };
        final Interpolator scaleInterpolator = new Interpolator() {
            @Override
            public float getInterpolation(float x) {
                // We start scaling when the flash is at it‘s peak
                if (x < flashPeakDurationPct) {
                    return 0;
                }
                return (x - flashDurationPct) / (1f - flashDurationPct);
            }
        };
        ValueAnimator anim = ValueAnimator.ofFloat(0f, 1f);
        anim.setDuration(SCREENSHOT_DROP_IN_DURATION);
        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationStart(Animator animation) {
                mBackgroundView.setAlpha(0f);
                mBackgroundView.setVisibility(View.VISIBLE);
                mScreenshotView.setAlpha(0f);
                mScreenshotView.setTranslationX(0f);
                mScreenshotView.setTranslationY(0f);
                mScreenshotView.setScaleX(SCREENSHOT_SCALE + mBgPaddingScale);
                mScreenshotView.setScaleY(SCREENSHOT_SCALE + mBgPaddingScale);
                mScreenshotView.setVisibility(View.VISIBLE);
                mScreenshotFlash.setAlpha(0f);
                mScreenshotFlash.setVisibility(View.VISIBLE);
            }

            @Override
            public void onAnimationEnd(android.animation.Animator animation) {
                mScreenshotFlash.setVisibility(View.GONE);
            }
        });
        anim.addUpdateListener(new AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float t = (Float) animation.getAnimatedValue();
                float scaleT = (SCREENSHOT_SCALE + mBgPaddingScale)
                        - scaleInterpolator.getInterpolation(t)
                        * (SCREENSHOT_SCALE - SCREENSHOT_DROP_IN_MIN_SCALE);
                mBackgroundView.setAlpha(scaleInterpolator.getInterpolation(t) * BACKGROUND_ALPHA);
                mScreenshotView.setAlpha(t);
                mScreenshotView.setScaleX(scaleT);
                mScreenshotView.setScaleY(scaleT);
                mScreenshotFlash.setAlpha(flashAlphaInterpolator.getInterpolation(t));
            }
        });
        return anim;
    }

    private ValueAnimator createScreenshotDropOutAnimation(int w, int h, boolean statusBarVisible,
                                                           boolean navBarVisible) {
        ValueAnimator anim = ValueAnimator.ofFloat(0f, 1f);
        anim.setStartDelay(SCREENSHOT_DROP_OUT_DELAY);
        anim.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                mBackgroundView.setVisibility(View.GONE);
                mScreenshotView.setVisibility(View.GONE);
                mScreenshotView.setLayerType(View.LAYER_TYPE_NONE, null);
            }
        });

        if (!statusBarVisible || !navBarVisible) {
            // There is no status bar/nav bar, so just fade the screenshot away in place
            anim.setDuration(SCREENSHOT_FAST_DROP_OUT_DURATION);
            anim.addUpdateListener(new AnimatorUpdateListener() {
                @Override
                public void onAnimationUpdate(ValueAnimator animation) {
                    float t = (Float) animation.getAnimatedValue();
                    float scaleT = (SCREENSHOT_DROP_IN_MIN_SCALE + mBgPaddingScale)
                            - t * (SCREENSHOT_DROP_IN_MIN_SCALE - SCREENSHOT_FAST_DROP_OUT_MIN_SCALE);
                    mBackgroundView.setAlpha((1f - t) * BACKGROUND_ALPHA);
                    mScreenshotView.setAlpha(1f - t);
                    mScreenshotView.setScaleX(scaleT);
                    mScreenshotView.setScaleY(scaleT);
                }
            });
        } else {
            // In the case where there is a status bar, animate to the origin of the bar (top-left)
            final float scaleDurationPct = (float) SCREENSHOT_DROP_OUT_SCALE_DURATION
                    / SCREENSHOT_DROP_OUT_DURATION;
            final Interpolator scaleInterpolator = new Interpolator() {
                @Override
                public float getInterpolation(float x) {
                    if (x < scaleDurationPct) {
                        // Decelerate, and scale the input accordingly
                        return (float) (1f - Math.pow(1f - (x / scaleDurationPct), 2f));
                    }
                    return 1f;
                }
            };

            // Determine the bounds of how to scale
            float halfScreenWidth = (w - 2f * mBgPadding) / 2f;
            float halfScreenHeight = (h - 2f * mBgPadding) / 2f;
            final float offsetPct = SCREENSHOT_DROP_OUT_MIN_SCALE_OFFSET;
            final PointF finalPos = new PointF(
                    -halfScreenWidth + (SCREENSHOT_DROP_OUT_MIN_SCALE + offsetPct) * halfScreenWidth,
                    -halfScreenHeight + (SCREENSHOT_DROP_OUT_MIN_SCALE + offsetPct) * halfScreenHeight);

            // Animate the screenshot to the status bar
            anim.setDuration(SCREENSHOT_DROP_OUT_DURATION);
            anim.addUpdateListener(new AnimatorUpdateListener() {
                @Override
                public void onAnimationUpdate(ValueAnimator animation) {
                    float t = (Float) animation.getAnimatedValue();
                    float scaleT = (SCREENSHOT_DROP_IN_MIN_SCALE + mBgPaddingScale)
                            - scaleInterpolator.getInterpolation(t)
                            * (SCREENSHOT_DROP_IN_MIN_SCALE - SCREENSHOT_DROP_OUT_MIN_SCALE);
                    mBackgroundView.setAlpha((1f - t) * BACKGROUND_ALPHA);
                    mScreenshotView.setAlpha(1f - scaleInterpolator.getInterpolation(t));
                    mScreenshotView.setScaleX(scaleT);
                    mScreenshotView.setScaleY(scaleT);
                    mScreenshotView.setTranslationX(t * finalPos.x);
                    mScreenshotView.setTranslationY(t * finalPos.y);
                }
            });
        }
        return anim;
    }

    private void notifyScreenshotError(Context context) {

    }

    private void saveScreenshotInWorkerThread(Runnable runnable) {

    }


}

package com.kale.viewshot;

import android.graphics.Bitmap;
import android.view.View;

/**
 * Created by xf on 2014/9/14.
 */
public class SurfaceControl {

    public static Bitmap screenshot(View view) {
        view.setDrawingCacheEnabled(true);
        view.buildDrawingCache();
        Bitmap bmp = view.getDrawingCache();
        return bmp;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2011 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
-->
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView android:id="@+id/global_screenshot_background"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@android:color/black"
        android:visibility="gone" />
    <ImageView android:id="@+id/global_screenshot"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:background="@drawable/screenshot_panel"
        android:visibility="gone"
        android:adjustViewBounds="true" />
    <ImageView android:id="@+id/global_screenshot_flash"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@android:color/white"
        android:visibility="gone" />
</FrameLayout>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/main_btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Shot"
        android:layout_alignParentBottom="true"/>

</RelativeLayout>