Android example source code file (WindowSurface.java)

This example Android source code file (WindowSurface.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" ^TM.

Java - Android tags/keywords

activity, android, canvas, drawing, drawingthread, failure, graphics, interruptedexception, movingpoint, num_old, num_old*2, os, override, paint, surfaceholder, ui, view, windowsurface

The WindowSurface.java Android example source code

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);
                }
            }
        }
    }
}