Height and width should not be set in onSurface created. They should be set onSurfaceChanged where the values are actually passed in as a paramter to the function. It might make sense to save these to a field if you nee to access them somewhere. This can be seen in the example live wall papers that ship with the android sdk. Just search for livecube.
Here is an example:
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.livecubes.cube1;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Handler;
import android.os.SystemClock;
import android.service.wallpaper.WallpaperService;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
/*
* This animated wallpaper draws a rotating wireframe cube.
*/
public class CubeWallpaper1 extends WallpaperService {
private final Handler mHandler = new Handler();
@Override
public void onCreate() {
super.onCreate();
}
@Override
public void onDestroy() {
super.onDestroy();
}
@Override
public Engine onCreateEngine() {
return new CubeEngine();
}
class CubeEngine extends Engine {
private final Paint mPaint = new Paint();
private float mOffset;
private float mTouchX = -1;
private float mTouchY = -1;
private long mStartTime;
private float mCenterX;
private float mCenterY;
private final Runnable mDrawCube = new Runnable() {
public void run() {
drawFrame();
}
};
private boolean mVisible;
CubeEngine() {
// Create a Paint to draw the lines for our cube
final Paint paint = mPaint;
paint.setColor(0xffffffff);
paint.setAntiAlias(true);
paint.setStrokeWidth(2);
paint.setStrokeCap(Paint.Cap.ROUND);
paint.setStyle(Paint.Style.STROKE);
mStartTime = SystemClock.elapsedRealtime();
}
@Override
public void onCreate(SurfaceHolder surfaceHolder) {
super.onCreate(surfaceHolder);
// By default we don't get touch events, so enable them.
setTouchEventsEnabled(true);
}
@Override
public void onDestroy() {
super.onDestroy();
mHandler.removeCallbacks(mDrawCube);
}
@Override
public void onVisibilityChanged(boolean visible) {
mVisible = visible;
if (visible) {
drawFrame();
} else {
mHandler.removeCallbacks(mDrawCube);
}
}
@Override
public void onSurfaceChanged(SurfaceHolder holder, int format, int width, int height) {
super.onSurfaceChanged(holder, format, width, height);
// store the center of the surface, so we can draw the cube in the right spot
mCenterX = width/2.0f;
mCenterY = height/2.0f;
drawFrame();
}
@Override
public void onSurfaceCreated(SurfaceHolder holder) {
super.onSurfaceCreated(holder);
}
@Override
public void onSurfaceDestroyed(SurfaceHolder holder) {
super.onSurfaceDestroyed(holder);
mVisible = false;
mHandler.removeCallbacks(mDrawCube);
}
@Override
public void onOffsetsChanged(float xOffset, float yOffset,
float xStep, float yStep, int xPixels, int yPixels) {
mOffset = xOffset;
drawFrame();
}
/*
* Store the position of the touch event so we can use it for drawing later
*/
@Override
public void onTouchEvent(MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_MOVE) {
mTouchX = event.getX();
mTouchY = event.getY();
} else {
mTouchX = -1;
mTouchY = -1;
}
super.onTouchEvent(event);
}
/*
* Draw one frame of the animation. This method gets called repeatedly
* by posting a delayed Runnable. You can do any drawing you want in
* here. This example draws a wireframe cube.
*/
void drawFrame() {
final SurfaceHolder holder = getSurfaceHolder();
Canvas c = null;
try {
c = holder.lockCanvas();
if (c != null) {
// draw something
drawCube(c);
drawTouchPoint(c);
}
} finally {
if (c != null) holder.unlockCanvasAndPost(c);
}
// Reschedule the next redraw
mHandler.removeCallbacks(mDrawCube);
if (mVisible) {
mHandler.postDelayed(mDrawCube, 1000 / 25);
}
}
/*
* Draw a wireframe cube by drawing 12 3 dimensional lines between
* adjacent corners of the cube
*/
void drawCube(Canvas c) {
c.save();
c.translate(mCenterX, mCenterY);
c.drawColor(0xff000000);
drawLine(c, -400, -400, -400, 400, -400, -400);
drawLine(c, 400, -400, -400, 400, 400, -400);
drawLine(c, 400, 400, -400, -400, 400, -400);
drawLine(c, -400, 400, -400, -400, -400, -400);
drawLine(c, -400, -400, 400, 400, -400, 400);
drawLine(c, 400, -400, 400, 400, 400, 400);
drawLine(c, 400, 400, 400, -400, 400, 400);
drawLine(c, -400, 400, 400, -400, -400, 400);
drawLine(c, -400, -400, 400, -400, -400, -400);
drawLine(c, 400, -400, 400, 400, -400, -400);
drawLine(c, 400, 400, 400, 400, 400, -400);
drawLine(c, -400, 400, 400, -400, 400, -400);
c.restore();
}
/*
* Draw a 3 dimensional line on to the screen
*/
void drawLine(Canvas c, int x1, int y1, int z1, int x2, int y2, int z2) {
long now = SystemClock.elapsedRealtime();
float xrot = ((float)(now - mStartTime)) / 1000;
float yrot = (0.5f - mOffset) * 2.0f;
float zrot = 0;
// 3D transformations
// rotation around X-axis
float newy1 = (float)(Math.sin(xrot) * z1 + Math.cos(xrot) * y1);
float newy2 = (float)(Math.sin(xrot) * z2 + Math.cos(xrot) * y2);
float newz1 = (float)(Math.cos(xrot) * z1 - Math.sin(xrot) * y1);
float newz2 = (float)(Math.cos(xrot) * z2 - Math.sin(xrot) * y2);
// rotation around Y-axis
float newx1 = (float)(Math.sin(yrot) * newz1 + Math.cos(yrot) * x1);
float newx2 = (float)(Math.sin(yrot) * newz2 + Math.cos(yrot) * x2);
newz1 = (float)(Math.cos(yrot) * newz1 - Math.sin(yrot) * x1);
newz2 = (float)(Math.cos(yrot) * newz2 - Math.sin(yrot) * x2);
// 3D-to-2D projection
float startX = newx1 / (4 - newz1 / 400);
float startY = newy1 / (4 - newz1 / 400);
float stopX = newx2 / (4 - newz2 / 400);
float stopY = newy2 / (4 - newz2 / 400);
c.drawLine(startX, startY, stopX, stopY, mPaint);
}
/*
* Draw a circle around the current touch point, if any.
*/
void drawTouchPoint(Canvas c) {
if (mTouchX >=0 && mTouchY >= 0) {
c.drawCircle(mTouchX, mTouchY, 80, mPaint);
}
}
}
}
