三指截屏

来源：互联网发布：阿里云怎么监控编辑：程序博客网时间：2024/06/18 06:21

这里写图片描述

根据上一篇文章Android 4.4系统原生截图解析 ,我们知道系统截屏是调用了TakeScreenshotService，为实现在任何界面都能实现三指截屏，我们就得在PhoneWindow(frameworks/base/policy/src/com/Android/internal/policy/impl/PhoneWindow.Java)中，对其进行触摸监听。即在dispatchTouchEvent中，监听触摸事件。监听完后，触发截屏，大致的思路就是这样了，来看下我们在代码中的具体实现。首先，我们来实现三指触摸事件响应

@Overridepublic boolean dispatchTouchEvent(MotionEvent ev) {    //add by steven zhang    //监听三指滑动事件    parse3PointerScreenShot(ev);    final Callback cb = getCallback();    return cb != null && !isDestroyed() && mFeatureId < 0 ? cb.dispatchTouchEvent(ev)            : super.dispatchTouchEvent(ev);}private static final int MAX_POINTER = 10;//最大手指头个数 private static final float Y_OFFSET = 180;//Y轴滑动的最大值 private boolean is3Pointer = false;//是否是三指滑动private float downY[] = new float[MAX_POINTER];//手指按下时Y轴坐标private float upY[] = new float[MAX_POINTER];//手指松开时Y轴坐标private float matchY[] = new float[MAX_POINTER];//手指滑动间距private void clearArrayData(float[] data) {    for (int i = 0; i < data.length; i++) {        data[i] = 0;    }}private void parse3PointerScreenShot(MotionEvent ev) {    int actionMasked = ev.getActionMasked();    int pointerCount = ev.getPointerCount();    //获取Settings中是否允许三指截屏，1为允许，非1为不允许    int value = Settings.System.getInt(mContext.getContentResolver(), "screenshot_pointer", 1);    if (value != 1) {        return ;    }    if (pointerCount == 3) {        switch (actionMasked) {        case MotionEvent.ACTION_POINTER_DOWN:            for (int i = 0; i < pointerCount; i++) {                int pointerId = ev.getPointerId(i);                downY[pointerId] = ev.getY(i);            }            is3Pointer = true;            break;        case MotionEvent.ACTION_POINTER_UP:            if (is3Pointer) { //如果是三个手指，就获取每个手指的滑动间距，否则就清空数据                for (int i = 0; i < pointerCount; i++) {                    int pointerId = ev.getPointerId(i);                    upY[pointerId] = ev.getY(i);                    matchY[pointerId] = Math.abs(upY[pointerId] - downY[pointerId]);                }            } else {                clearArrayData(downY);                clearArrayData(upY);                clearArrayData(matchY);            }            break;        default:            break;        }        boolean[] flag = new boolean[] {                false, false, false,        };        for (int i = 0; i < pointerCount; i++) {            int pointerId = ev.getPointerId(i);            //三个手指划过的距离是否大于最大预定值            if (matchY[pointerId] > Y_OFFSET) {                flag[i] = true;                matchY[pointerId] = 0;            }        }        //如果三个指头都划过了最大预定值，就开始截屏        if (flag[0] && flag[1] && flag[2]) {            Handler mHandler = new Handler();            mHandler.post(mScreenshotRunnable);        }    } else {        is3Pointer = false;    }}1
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上面我们在dispatchTouchEvent中接收了触摸事件，如果是我们想要的三指触摸就触摸截屏mHandler.post(mScreenshotRunnable);这里的mScreenshotRunnable就是和Android 4.4系统原生截图解析里的PhoneWindowManager(frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java)中的mScreenshotRunnable是一样的，我们把它从PhoneWindowManager移植到了PhoneWindow，具体来看代码实现。

private final Runnable mScreenshotRunnable = new Runnable() {    @Override    public void run() {        takeScreenshot();    }};final Object mScreenshotLock = new Object();ServiceConnection mScreenshotConnection = null;final Runnable mScreenshotTimeout = new Runnable() {    @Override public void run() {        synchronized (mScreenshotLock) {            if (mScreenshotConnection != null) {                mContext.unbindService(mScreenshotConnection);                mScreenshotConnection = null;            }        }    }};private void takeScreenshot() {    synchronized (mScreenshotLock) {        if (mScreenshotConnection != null) {            return;        }        //初始化要绑定的服务，从这里可以看出要绑定的服务是SystemUI里的TakeScreenshotService        ComponentName cn = new ComponentName("com.android.systemui",                "com.android.systemui.screenshot.TakeScreenshotService");        Intent intent = new Intent();        intent.setComponent(cn);        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, 1);                    final ServiceConnection myConn = this;                    Handler h = new Handler() {                        @Override                        public void handleMessage(Message msg) {                            synchronized (mScreenshotLock) {                                if (mScreenshotConnection == myConn) {                                    mContext.unbindService(mScreenshotConnection);                                    mScreenshotConnection = null;                                    removeCallbacks(mScreenshotTimeout);                                }                            }                        }                    };                    msg.replyTo = new Messenger(h);                    msg.arg1 = msg.arg2 = 0;                    try {                        messenger.send(msg);                    } catch (RemoteException e) {                    }                }            }            @Override            public void onServiceDisconnected(ComponentName name) {}        };        //绑定Service        if (mContext.bindService(                intent, conn, Context.BIND_AUTO_CREATE)) {            mScreenshotConnection = conn;            //设置超时机制，若超时就解除绑定            postDelayed(mScreenshotTimeout, 10000);        }    }}1
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private final Runnable mScreenshotRunnable = new Runnable() {    @Override    public void run() {        takeScreenshot();    }};final Object mScreenshotLock = new Object();ServiceConnection mScreenshotConnection = null;final Runnable mScreenshotTimeout = new Runnable() {    @Override public void run() {        synchronized (mScreenshotLock) {            if (mScreenshotConnection != null) {                mContext.unbindService(mScreenshotConnection);                mScreenshotConnection = null;            }        }    }};private void takeScreenshot() {    synchronized (mScreenshotLock) {        if (mScreenshotConnection != null) {            return;        }        //初始化要绑定的服务，从这里可以看出要绑定的服务是SystemUI里的TakeScreenshotService        ComponentName cn = new ComponentName("com.android.systemui",                "com.android.systemui.screenshot.TakeScreenshotService");        Intent intent = new Intent();        intent.setComponent(cn);        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, 1);                    final ServiceConnection myConn = this;                    Handler h = new Handler() {                        @Override                        public void handleMessage(Message msg) {                            synchronized (mScreenshotLock) {                                if (mScreenshotConnection == myConn) {                                    mContext.unbindService(mScreenshotConnection);                                    mScreenshotConnection = null;                                    removeCallbacks(mScreenshotTimeout);                                }                            }                        }                    };                    msg.replyTo = new Messenger(h);                    msg.arg1 = msg.arg2 = 0;                    try {                        messenger.send(msg);                    } catch (RemoteException e) {                    }                }            }            @Override            public void onServiceDisconnected(ComponentName name) {}        };        //绑定Service        if (mContext.bindService(                intent, conn, Context.BIND_AUTO_CREATE)) {            mScreenshotConnection = conn;            //设置超时机制，若超时就解除绑定            postDelayed(mScreenshotTimeout, 10000);        }    }}1
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从上面的代码可以看出，我只是把PhoneWindowManager中，截图部分的代码，单独移植到了PhoneWindow中。即可实现，三指截屏了。等等，这样我们真的可以实现截屏了吗？触摸监听、截屏两个都实现了，应该可以实现三指截屏了吧？？？我们再来看看截屏的实现，它是通过绑定TakeScreenshotService实现的截屏，bindService我们都知道，如果我们的应用跟service不在同一个进程，进行绑定的话会报错，所以，当我们完成上面的步骤后实现三指截屏，系统会报如下的错误。

E/AndroidRuntime(3282): java.lang.SecurityException: Not allowed to bind to service Intent { cmp=com.android.systemui/.screenshot.TakeScreenshotService }

E/AndroidRuntime(3282): at android.app.ContextImpl.bindServiceCommon(ContextImpl.java:1676)E/AndroidRuntime(3282): at android.app.ContextImpl.bindService(ContextImpl.java:1640)

E/AndroidRuntime(3282): at android.content.ContextWrapper.bindService(ContextWrapper.java:517)E/AndroidRuntime(3282): at com.android.internal.policy.impl.PhoneWindow$DecorView.takeScreenshot(PhoneWindow.java:2205)

E/AndroidRuntime(3282): at com.android.internal.policy.impl.PhoneWindow$DecorView.access$1000(PhoneWindow.java:1950)

E/AndroidRuntime(3282): at com.android.internal.policy.impl.PhoneWindow$DecorView$1.run(PhoneWindow.java:2142)

E/AndroidRuntime(3282): at android.os.Handler.handleCallback(Handler.java:808)

E/AndroidRuntime(3282): at android.os.Handler.dispatchMessage(Handler.java:103)

E/AndroidRuntime(3282): at android.os.Looper.loop(Looper.java:193)

E/AndroidRuntime(3282): at android.app.ActivityThread.main(ActivityThread.java:5292)

E/AndroidRuntime(3282): at java.lang.reflect.Method.invokeNative(Native Method)

E/AndroidRuntime(3282): at java.lang.reflect.Method.invoke(Method.java:515)

E/AndroidRuntime(3282): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)

E/AndroidRuntime(3282): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)

E/AndroidRuntime(3282): at dalvik.system.NativeStart.main(Native Method)

因此，我们还需要在SystemUI的AndroidManifest.xml中的修改TakeScreenshotService的export为true。

<service android:name=".screenshot.TakeScreenshotService"             android:process=":screenshot"             android:exported="true" />1
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这样我们就可以真正的实现三指截屏了。同时，还要注意在PhoneWindow中导入相应的java包。

import android.content.ServiceConnection;import android.content.ComponentName;import android.os.Message;import android.os.Messenger;import android.content.Intent;import android.os.IBinder;import android.os.UserHandle;import android.provider.Settings;1
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三指截屏的功能，差不多就分析完了。这里给出一个patch文件，感兴趣的同学可以直接看这个文件，就更能明白，我在哪些地方做了系统的修改。

参考文章

android系统怎么实现三指截屏

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