Android4.2.2 Gallery2源码分析(4)——GLCanvas.java

首先申明，找到这个类是在GLRootView.java中发现的线索。这是一个接口，源码中对该接口作了详细的说明：

[java]
view plaincopyprint?

//
// <SPAN style="COLOR: #ff6666">GLCanvas gives a convenient interface to draw using OpenGL.</SPAN>

//
// When a rectangle is specified in this interface, it means the region

// [x, x+width) * [y, y+height)

//
public interface GLCanvas {
<SPAN style="COLOR: #ff6666"> // Tells GLCanvas the size of the underlying GL surface. This should be

// called before first drawing and when the size of GL surface is changed.

// This is called by GLRoot and should not be called by the clients

// who only want to draw on the GLCanvas. Both width and height must be

// nonnegative.</SPAN>
public void setSize(int width, int height);

public void setSize(int x, int y, int width, int height);

public void clearBuffer();
public void clearBuffer(float[] argb);

public void setAlpha(float alpha);
public float getAlpha();

public void multiplyAlpha(float alpha);

public void translate(float x, float y, float z);
public void translate(float x, float y);
public void scale(float sx, float sy, float sz);
public void rotate(float angle, float x, float y, float z);
public void multiplyMatrix(float[] mMatrix, int offset);

public void save();

public void save(int saveFlags);

public static final int SAVE_FLAG_ALL = 0xFFFFFFFF;
public static final int SAVE_FLAG_ALPHA = 0x01;
public static final int SAVE_FLAG_MATRIX = 0x02;

public void restore();

<SPAN style="COLOR: #ff6666"> // Draws a line using the specified paint from (x1, y1) to (x2, y2).

// (Both end points are included).

</SPAN> public void drawLine(float x1, float y1, float x2, float y2, GLPaint paint);

<SPAN style="COLOR: #ff6666"> // Draws a rectangle using the specified paint from (x1, y1) to (x2, y2).

// (Both end points are included).</SPAN>

public void drawRect(float x1, float y1, float x2, float y2, GLPaint paint);

// Fills the specified rectangle with the specified color.

public void fillRect(float x, float y, float width, float height, int color);

<SPAN style="COLOR: #ff6666"> // Draws a texture to the specified rectangle.</SPAN>

public void drawTexture(
BasicTexture texture, int x, int y, int width, int height);
public void drawMesh(BasicTexture tex, int x, int y, int xyBuffer,
int uvBuffer, int indexBuffer, int indexCount);

<SPAN style="COLOR: #ff6666"> // Draws the source rectangle part of the texture to the target rectangle.</SPAN>

public void drawTexture(BasicTexture texture, RectF source, RectF target);

// Draw a texture with a specified texture transform.

public void drawTexture(BasicTexture texture, float[] mTextureTransform,
int x, int y, int w, int h);

<SPAN style="COLOR: #ff6666"> // Draw two textures to the specified rectangle. The actual texture used is

// from * (1 - ratio) + to * ratio

// The two textures must have the same size.</SPAN>

public void drawMixed(BasicTexture from, int toColor,
float ratio, int x, int y, int w, int h);

// Draw a region of a texture and a specified color to the specified

// rectangle. The actual color used is from * (1 - ratio) + to * ratio.

// The region of the texture is defined by parameter "src". The target

// rectangle is specified by parameter "target".

public void drawMixed(BasicTexture from, int toColor,
float ratio, RectF src, RectF target);

public GL11 getGLInstance();

public boolean unloadTexture(BasicTexture texture);

public void deleteBuffer(int bufferId);

public void deleteRecycledResources();

public void dumpStatisticsAndClear();

public void beginRenderTarget(RawTexture texture);

public void endRenderTarget();
}

//
// GLCanvas gives a convenient interface to draw using OpenGL.
//
// When a rectangle is specified in this interface, it means the region
// [x, x+width) * [y, y+height)
//
public interface GLCanvas {
// Tells GLCanvas the size of the underlying GL surface. This should be
// called before first drawing and when the size of GL surface is changed.
// This is called by GLRoot and should not be called by the clients
// who only want to draw on the GLCanvas. Both width and height must be
// nonnegative.
public void setSize(int width, int height);

public void setSize(int x, int y, int width, int height);

public void clearBuffer();
public void clearBuffer(float[] argb);

public void setAlpha(float alpha);
public float getAlpha();

public void multiplyAlpha(float alpha);

public void translate(float x, float y, float z);
public void translate(float x, float y);
public void scale(float sx, float sy, float sz);
public void rotate(float angle, float x, float y, float z);
public void multiplyMatrix(float[] mMatrix, int offset);

public void save();

public void save(int saveFlags);

public static final int SAVE_FLAG_ALL = 0xFFFFFFFF;
public static final int SAVE_FLAG_ALPHA = 0x01;
public static final int SAVE_FLAG_MATRIX = 0x02;

public void restore();

// Draws a line using the specified paint from (x1, y1) to (x2, y2).
// (Both end points are included).
public void drawLine(float x1, float y1, float x2, float y2, GLPaint paint);

// Draws a rectangle using the specified paint from (x1, y1) to (x2, y2).
// (Both end points are included).
public void drawRect(float x1, float y1, float x2, float y2, GLPaint paint);

// Fills the specified rectangle with the specified color.
public void fillRect(float x, float y, float width, float height, int color);

// Draws a texture to the specified rectangle.
public void drawTexture(
BasicTexture texture, int x, int y, int width, int height);
public void drawMesh(BasicTexture tex, int x, int y, int xyBuffer,
int uvBuffer, int indexBuffer, int indexCount);

// Draws the source rectangle part of the texture to the target rectangle.
public void drawTexture(BasicTexture texture, RectF source, RectF target);

// Draw a texture with a specified texture transform.
public void drawTexture(BasicTexture texture, float[] mTextureTransform,
int x, int y, int w, int h);

// Draw two textures to the specified rectangle. The actual texture used is
// from * (1 - ratio) + to * ratio
// The two textures must have the same size.
public void drawMixed(BasicTexture from, int toColor,
float ratio, int x, int y, int w, int h);

// Draw a region of a texture and a specified color to the specified
// rectangle. The actual color used is from * (1 - ratio) + to * ratio.
// The region of the texture is defined by parameter "src". The target
// rectangle is specified by parameter "target".
public void drawMixed(BasicTexture from, int toColor,
float ratio, RectF src, RectF target);

public GL11 getGLInstance();

public boolean unloadTexture(BasicTexture texture);

public void deleteBuffer(int bufferId);

public void deleteRecycledResources();

public void dumpStatisticsAndClear();

public void beginRenderTarget(RawTexture texture);

public void endRenderTarget();
}

这里留下了我觉得与最终布局形成有比较直接关系的地方的注释(完整内容可查看源码)，从这些注释中，我意识到Gallery的布局之所以不同我之前所见的那些布局视图，是因为这里使用了OpenGL，并且使用了OpenGL材质渲染，那么不能根据以往的经验直接找到视图也就不足为奇了，因为OpenGL是在代码中一点一点画出来的，因此所有的布局视图都要到代码中去发现和寻找。