The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
package com.example.android.apis.graphics;
import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
/**
* Demonstrates how to take over the Surface from a window to do direct
* drawing to it (without going through the view hierarchy).
*/
public class WindowSurface extends Activity implements SurfaceHolder.Callback2 {
DrawingThread mDrawingThread;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Tell the activity's window that we want to do our own drawing
// to its surface. This prevents the view hierarchy from drawing to
// it, though we can still add views to capture input if desired.
getWindow().takeSurface(this);
// This is the thread that will be drawing to our surface.
mDrawingThread = new DrawingThread();
mDrawingThread.start();
}
@Override
protected void onPause() {
super.onPause();
// Make sure the drawing thread is not running while we are paused.
synchronized (mDrawingThread) {
mDrawingThread.mRunning = false;
mDrawingThread.notify();
}
}
@Override
protected void onResume() {
super.onResume();
// Let the drawing thread resume running.
synchronized (mDrawingThread) {
mDrawingThread.mRunning = true;
mDrawingThread.notify();
}
}
@Override
protected void onDestroy() {
super.onDestroy();
// Make sure the drawing thread goes away.
synchronized (mDrawingThread) {
mDrawingThread.mQuit = true;
mDrawingThread.notify();
}
}
public void surfaceCreated(SurfaceHolder holder) {
// Tell the drawing thread that a surface is available.
synchronized (mDrawingThread) {
mDrawingThread.mSurface = holder;
mDrawingThread.notify();
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
// Don't need to do anything here; the drawing thread will pick up
// new sizes from the canvas.
}
public void surfaceRedrawNeeded(SurfaceHolder holder) {
}
public void surfaceDestroyed(SurfaceHolder holder) {
// We need to tell the drawing thread to stop, and block until
// it has done so.
synchronized (mDrawingThread) {
mDrawingThread.mSurface = holder;
mDrawingThread.notify();
while (mDrawingThread.mActive) {
try {
mDrawingThread.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
// Tracking of a single point that is moving on the screen.
static final class MovingPoint {
float x, y, dx, dy;
void init(int width, int height, float minStep) {
x = (float)((width-1)*Math.random());
y = (float)((height-1)*Math.random());
dx = (float)(Math.random()*minStep*2) + 1;
dy = (float)(Math.random()*minStep*2) + 1;
}
float adjDelta(float cur, float minStep, float maxStep) {
cur += (Math.random()*minStep) - (minStep/2);
if (cur < 0 && cur > -minStep) cur = -minStep;
if (cur >= 0 && cur < minStep) cur = minStep;
if (cur > maxStep) cur = maxStep;
if (cur < -maxStep) cur = -maxStep;
return cur;
}
void step(int width, int height, float minStep, float maxStep) {
x += dx;
if (x <= 0 || x >= (width-1)) {
if (x <= 0) x = 0;
else if (x >= (width-1)) x = width-1;
dx = adjDelta(-dx, minStep, maxStep);
}
y += dy;
if (y <= 0 || y >= (height-1)) {
if (y <= 0) y = 0;
else if (y >= (height-1)) y = height-1;
dy = adjDelta(-dy, minStep, maxStep);
}
}
}
/**
* This is a thread that will be running a loop, drawing into the
* window's surface.
*/
class DrawingThread extends Thread {
// These are protected by the Thread's lock.
SurfaceHolder mSurface;
boolean mRunning;
boolean mActive;
boolean mQuit;
// Internal state.
int mLineWidth;
float mMinStep;
float mMaxStep;
boolean mInitialized;
final MovingPoint mPoint1 = new MovingPoint();
final MovingPoint mPoint2 = new MovingPoint();
static final int NUM_OLD = 100;
int mNumOld = 0;
final float[] mOld = new float[NUM_OLD*4];
final int[] mOldColor = new int[NUM_OLD];
int mBrightLine = 0;
// X is red, Y is blue.
final MovingPoint mColor = new MovingPoint();
final Paint mBackground = new Paint();
final Paint mForeground = new Paint();
int makeGreen(int index) {
int dist = Math.abs(mBrightLine-index);
if (dist > 10) return 0;
return (255-(dist*(255/10))) << 8;
}
@Override
public void run() {
mLineWidth = (int)(getResources().getDisplayMetrics().density * 1.5);
if (mLineWidth < 1) mLineWidth = 1;
mMinStep = mLineWidth * 2;
mMaxStep = mMinStep * 3;
mBackground.setColor(0xff000000);
mForeground.setColor(0xff00ffff);
mForeground.setAntiAlias(false);
mForeground.setStrokeWidth(mLineWidth);
while (true) {
// Synchronize with activity: block until the activity is ready
// and we have a surface; report whether we are active or inactive
// at this point; exit thread when asked to quit.
synchronized (this) {
while (mSurface == null || !mRunning) {
if (mActive) {
mActive = false;
notify();
}
if (mQuit) {
return;
}
try {
wait();
} catch (InterruptedException e) {
}
}
if (!mActive) {
mActive = true;
notify();
}
// Lock the canvas for drawing.
Canvas canvas = mSurface.lockCanvas();
if (canvas == null) {
Log.i("WindowSurface", "Failure locking canvas");
continue;
}
// Update graphics.
if (!mInitialized) {
mInitialized = true;
mPoint1.init(canvas.getWidth(), canvas.getHeight(), mMinStep);
mPoint2.init(canvas.getWidth(), canvas.getHeight(), mMinStep);
mColor.init(127, 127, 1);
} else {
mPoint1.step(canvas.getWidth(), canvas.getHeight(),
mMinStep, mMaxStep);
mPoint2.step(canvas.getWidth(), canvas.getHeight(),
mMinStep, mMaxStep);
mColor.step(127, 127, 1, 3);
}
mBrightLine+=2;
if (mBrightLine > (NUM_OLD*2)) {
mBrightLine = -2;
}
// Clear background.
canvas.drawColor(mBackground.getColor());
// Draw old lines.
for (int i=mNumOld-1; i>=0; i--) {
mForeground.setColor(mOldColor[i] | makeGreen(i));
mForeground.setAlpha(((NUM_OLD-i) * 255) / NUM_OLD);
int p = i*4;
canvas.drawLine(mOld[p], mOld[p+1], mOld[p+2], mOld[p+3], mForeground);
}
// Draw new line.
int red = (int)mColor.x + 128;
if (red > 255) red = 255;
int blue = (int)mColor.y + 128;
if (blue > 255) blue = 255;
int color = 0xff000000 | (red<<16) | blue;
mForeground.setColor(color | makeGreen(-2));
canvas.drawLine(mPoint1.x, mPoint1.y, mPoint2.x, mPoint2.y, mForeground);
// Add in the new line.
if (mNumOld > 1) {
System.arraycopy(mOld, 0, mOld, 4, (mNumOld-1)*4);
System.arraycopy(mOldColor, 0, mOldColor, 1, mNumOld-1);
}
if (mNumOld < NUM_OLD) mNumOld++;
mOld[0] = mPoint1.x;
mOld[1] = mPoint1.y;
mOld[2] = mPoint2.x;
mOld[3] = mPoint2.y;
mOldColor[0] = color;
// All done!
mSurface.unlockCanvasAndPost(canvas);
}
}
}
}
}