Android的suiface类源码深度剖析

surface用来处理一段单独的缓冲区，这段缓冲区是由屏幕合成器来管理的。

surface 包含安全的内容，使用一些特殊的措施来阻止在其他的进程中复制surface内容。尤其是截屏和VNC服务。surface不能被硬件加速。它创建的缓冲区有几种：BUFFERS，NORMAL，BLUR，DIM。

当surface不能被创建或更改大小时候，系统会抛出异常。surface创建过程中，创建了一个画布，并且在之后的程序设计中我们可以使用。我们可以锁定或解锁一个surface，但解锁时，只有调用post()或postAll() 是才会更新屏幕。

源码：

package android.view;

import android.graphics.*;
import android.os.Parcelable;
import android.os.Parcel;
import android.util.Log;

public class Surface implements Parcelable {
private static final String LOG_TAG = "Surface";


public static final int HIDDEN = 0x00000004;

public static final int HARDWARE = 0x00000010;

public static final int GPU = 0x00000028;

public static final int SECURE = 0x00000080;


public static final int NON_PREMULTIPLIED = 0x00000100;


public static final int PUSH_BUFFERS = 0x00000200;


public static final int FX_SURFACE_NORMAL = 0x00000000;


public static final int FX_SURFACE_BLUR = 0x00010000;


public static final int FX_SURFACE_DIM = 0x00020000;

public static final int FX_SURFACE_MASK = 0x000F0000;

public static final int SURFACE_HIDDEN = 0x01;


public static final int SURACE_FROZEN = 0x02;

public static final int SURFACE_DITHER = 0x04;

public static final int SURFACE_BLUR_FREEZE= 0x10;

public static final int ROTATION_0 = 0;
public static final int ROTATION_90 = 1;
public static final int ROTATION_180 = 2;
public static final int ROTATION_270 = 3;


public static final int FLAGS_ORIENTATION_ANIMATION_DISABLE = 0x000000001;

@SuppressWarnings("unused")
private int mSurface;
@SuppressWarnings("unused")
private int mSaveCount;
@SuppressWarnings("unused")
private Canvas mCanvas;

/**
* Exception thrown when a surface couldn't be created or resized
*/
public static class OutOfResourcesException extends Exception {
public OutOfResourcesException() {
}
public OutOfResourcesException(String name) {
super(name);
}
}

native private static void nativeClassInit();
static { nativeClassInit(); }

public Surface(SurfaceSession s,
int pid, int display, int w, int h, int format, int flags)
throws OutOfResourcesException {
mCanvas = new Canvas();
init(s,pid,display,w,h,format,flags);
}

public Surface() {
mCanvas = new Canvas();
}

public native void copyFrom(Surface o);


public native boolean isValid();

public native void clear();

public Canvas lockCanvas(Rect dirty) throws OutOfResourcesException {

return lockCanvasNative(dirty);
}

private native Canvas lockCanvasNative(Rect dirty);

public native void unlockCanvasAndPost(Canvas canvas);

public native void unlockCanvas(Canvas canvas);

public static native void openTransaction();

public static native void closeTransaction();

public static native void freezeDisplay(int display);

public static native void unfreezeDisplay(int display);

public static native void setOrientation(int display, int orientation, int flags);

public static void setOrientation(int display, int orientation) {
setOrientation(display, orientation, 0);
}


public native void setLayer(int zorder);
public native void setPosition(int x, int y);
public native void setSize(int w, int h);

public native void hide();
public native void show();
public native void setTransparentRegionHint(Region region);
public native void setAlpha(float alpha);
public native void setMatrix(float dsdx, float dtdx,
float dsdy, float dtdy);

public native void freeze();
public native void unfreeze();

public native void setFreezeTint(int tint);

public native void setFlags(int flags, int mask);

@Override
public String toString() {
return "Surface(native-token=" + mSurface + ")";
}

private Surface(Parcel source) throws OutOfResourcesException {
init(source);
}

public int describeContents() {
return 0;
}

public native void readFromParcel(Parcel source);
public native void writeToParcel(Parcel dest, int flags);

public static final Parcelable.Creator<Surface> CREATOR
= new Parcelable.Creator<Surface>()
{
public Surface createFromParcel(Parcel source) {
try {
return new Surface(source);
} catch (Exception e) {
Log.e(LOG_TAG, "Exception creating surface from parcel", e);
}
return null;
}

public Surface[] newArray(int size) {
return new Surface[size];
}
};

/* no user serviceable parts here ... */
@Override
protected void finalize() throws Throwable {
clear();
}

private native void init(SurfaceSession s,
int pid, int display, int w, int h, int format, int flags)
throws OutOfResourcesException;

private native void init(Parcel source);
}