拿到Samsung的7寸平板，是3.x系统，在状态栏上多了个截屏按钮，拿到Galaxy Notes 10.1，该功能更是不可删除的添加在状态栏，既然如此，我们今天在我们平板上也添加上该按键，实现简单的快捷截屏功能，而不是按POWER和VOL-进行。
在Android4.0源码的frameworks/base/packages/SystemUI/res/drawable-mdpi/目录下添加ic_sysbar_screenshot.png文件，图片如下：
该图片的背景是透明的PNG文件。
接下来修改frameworks/base/packages/SystemUI/res/layout-sw600dp/status_bar.xml文件，在
android:layout_width="80dip"
android:layout_height="match_parent"
android:src="@drawable/ic_sysbar_screenshot"
android:contentDescription="@string/accessibility_screenshot"
systemui:glowBackground="@drawable/ic_sysbar_highlight"
/>
接下来修改frameworks/base/packages/SystemUI/res/values/strings.xml文件，添加如下内容：
ScreenShot
至此，重新编译烧录源码，在状态栏上会多出截屏图标，接下来需要继续实现截屏功能，查看了frameworks里的源码，找到了frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java文件里有可参考的片断，故继续修改frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java文件，相应的添加如下内容：
import android.os.Messenger;
import android.content.ComponentName;
import android.content.ServiceConnection;
在View mRecentButton;后面添加View mScreenshotButton;语句。
在mRecentButton.setOnClickListener(mOnClickListener);后添加如下内容：
mScreenshotButton = mNavigationArea.findViewById(R.id.my_screenshot);
mScreenshotButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
mHandler.postDelayed(mScreenshotChordLongPress,
ViewConfiguration.getGlobalActionKeyTimeout());
}
});
接下来在public int getStatusBarHeight() {前添加如下内容：
private final Runnable mScreenshotChordLongPress = new Runnable() {
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;
}
}
}
};
// Assume this is called from the Handler thread.
private void takeScreenshot() {
synchronized (mScreenshotLock) {
if (mScreenshotConnection != null) {
return;
}
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(mHandler.getLooper()) {
@Override
public void handleMessage(Message msg) {
synchronized (mScreenshotLock) {
if (mScreenshotConnection == myConn) {
mContext.unbindService(mScreenshotConnection);
mScreenshotConnection = null;
mHandler.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) {}
};
if (mContext.bindService(intent, conn, Context.BIND_AUTO_CREATE)) {
mScreenshotConnection = conn;
mHandler.postDelayed(mScreenshotTimeout, 10000);
}
}
}
至此，再次编译源码并烧录，截屏功能实现了，现在还存有的是图标的状态处理了，这部分就不说明了。
实现截屏功能时，4.0上既然已实现该功能，那么就直接找源码，确认哪儿有实现，直接拿过来使用，尽量拿来主义，但又不失学习性。
