Mega Code Archive
Demonstrates the handling of touch screen and trackball events to implement a simple painting app
<![CDATA[
/*
* Copyright (C) 2007 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 app.test;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Picture;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
//Need the following import to get access to the app resources, since this
//class is in a sub-package.
/**
* Demonstrates the handling of touch screen and trackball events to
* implement a simple painting app.
*/
public class Test extends GraphicsActivity {
/** Used as a pulse to gradually fade the contents of the window. */
private static final int FADE_MSG = 1;
/** Menu ID for the command to clear the window. */
private static final int CLEAR_ID = Menu.FIRST;
/** Menu ID for the command to toggle fading. */
private static final int FADE_ID = Menu.FIRST+1;
/** How often to fade the contents of the window (in ms). */
private static final int FADE_DELAY = 100;
/** The view responsible for drawing the window. */
MyView mView;
/** Is fading mode enabled? */
boolean mFading;
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Create and attach the view that is responsible for painting.
mView = new MyView(this);
setContentView(mView);
mView.requestFocus();
// Restore the fading option if we are being thawed from a
// previously saved state. Note that we are not currently remembering
// the contents of the bitmap.
mFading = savedInstanceState != null ? savedInstanceState.getBoolean("fading", true) : true;
}
@Override public boolean onCreateOptionsMenu(Menu menu) {
menu.add(0, CLEAR_ID, 0, "Clear");
menu.add(0, FADE_ID, 0, "Fade").setCheckable(true);
return super.onCreateOptionsMenu(menu);
}
@Override public boolean onPrepareOptionsMenu(Menu menu) {
menu.findItem(FADE_ID).setChecked(mFading);
return super.onPrepareOptionsMenu(menu);
}
@Override public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case CLEAR_ID:
mView.clear();
return true;
case FADE_ID:
mFading = !mFading;
if (mFading) {
startFading();
} else {
stopFading();
}
return true;
default:
return super.onOptionsItemSelected(item);
}
}
@Override protected void onResume() {
super.onResume();
// If fading mode is enabled, then as long as we are resumed we want
// to run pulse to fade the contents.
if (mFading) {
startFading();
}
}
@Override protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// Save away the fading state to restore if needed later. Note that
// we do not currently save the contents of the display.
outState.putBoolean("fading", mFading);
}
@Override protected void onPause() {
super.onPause();
// Make sure to never run the fading pulse while we are paused or
// stopped.
stopFading();
}
/**
* Start up the pulse to fade the screen, clearing any existing pulse to
* ensure that we don't have multiple pulses running at a time.
*/
void startFading() {
mHandler.removeMessages(FADE_MSG);
mHandler.sendMessageDelayed(
mHandler.obtainMessage(FADE_MSG), FADE_DELAY);
}
/**
* Stop the pulse to fade the screen.
*/
void stopFading() {
mHandler.removeMessages(FADE_MSG);
}
private Handler mHandler = new Handler() {
@Override public void handleMessage(Message msg) {
switch (msg.what) {
// Upon receiving the fade pulse, we have the view perform a
// fade and then enqueue a new message to pulse at the desired
// next time.
case FADE_MSG: {
mView.fade();
mHandler.sendMessageDelayed(
mHandler.obtainMessage(FADE_MSG), FADE_DELAY);
break;
}
default:
super.handleMessage(msg);
}
}
};
public class MyView extends View {
private static final int FADE_ALPHA = 0x06;
private static final int MAX_FADE_STEPS = 256/FADE_ALPHA + 4;
private static final int TRACKBALL_SCALE = 10;
private Bitmap mBitmap;
private Canvas mCanvas;
private final Rect mRect = new Rect();
private final Paint mPaint;
private final Paint mFadePaint;
private float mCurX;
private float mCurY;
private int mFadeSteps = MAX_FADE_STEPS;
public MyView(Context c) {
super(c);
setFocusable(true);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setARGB(255, 255, 255, 255);
mFadePaint = new Paint();
mFadePaint.setDither(true);
mFadePaint.setARGB(FADE_ALPHA, 0, 0, 0);
}
public void clear() {
if (mCanvas != null) {
mPaint.setARGB(0xff, 0, 0, 0);
mCanvas.drawPaint(mPaint);
invalidate();
mFadeSteps = MAX_FADE_STEPS;
}
}
public void fade() {
if (mCanvas != null && mFadeSteps < MAX_FADE_STEPS) {
mCanvas.drawPaint(mFadePaint);
invalidate();
mFadeSteps++;
}
}
@Override protected void onSizeChanged(int w, int h, int oldw,
int oldh) {
int curW = mBitmap != null ? mBitmap.getWidth() : 0;
int curH = mBitmap != null ? mBitmap.getHeight() : 0;
if (curW >= w && curH >= h) {
return;
}
if (curW < w) curW = w;
if (curH < h) curH = h;
Bitmap newBitmap = Bitmap.createBitmap(curW, curH,
Bitmap.Config.RGB_565);
Canvas newCanvas = new Canvas();
newCanvas.setBitmap(newBitmap);
if (mBitmap != null) {
newCanvas.drawBitmap(mBitmap, 0, 0, null);
}
mBitmap = newBitmap;
mCanvas = newCanvas;
mFadeSteps = MAX_FADE_STEPS;
}
@Override protected void onDraw(Canvas canvas) {
if (mBitmap != null) {
canvas.drawBitmap(mBitmap, 0, 0, null);
}
}
@Override public boolean onTrackballEvent(MotionEvent event) {
int N = event.getHistorySize();
final float scaleX = event.getXPrecision() * TRACKBALL_SCALE;
final float scaleY = event.getYPrecision() * TRACKBALL_SCALE;
for (int i=0; i<N; i++) {
//Log.i("TouchPaint", "Intermediate trackball #" + i
// + ": x=" + event.getHistoricalX(i)
// + ", y=" + event.getHistoricalY(i));
mCurX += event.getHistoricalX(i) * scaleX;
mCurY += event.getHistoricalY(i) * scaleY;
drawPoint(mCurX, mCurY, 1.0f, 16.0f);
}
//Log.i("TouchPaint", "Trackball: x=" + event.getX()
// + ", y=" + event.getY());
mCurX += event.getX() * scaleX;
mCurY += event.getY() * scaleY;
drawPoint(mCurX, mCurY, 1.0f, 16.0f);
return true;
}
@Override public boolean onTouchEvent(MotionEvent event) {
int action = event.getActionMasked();
if (action != MotionEvent.ACTION_UP && action != MotionEvent.ACTION_CANCEL) {
int N = event.getHistorySize();
int P = event.getPointerCount();
for (int i = 0; i < N; i++) {
for (int j = 0; j < P; j++) {
mCurX = event.getHistoricalX(j, i);
mCurY = event.getHistoricalY(j, i);
drawPoint(mCurX, mCurY,
event.getHistoricalPressure(j, i),
event.getHistoricalTouchMajor(j, i));
}
}
for (int j = 0; j < P; j++) {
mCurX = event.getX(j);
mCurY = event.getY(j);
drawPoint(mCurX, mCurY, event.getPressure(j), event.getTouchMajor(j));
}
}
return true;
}
private void drawPoint(float x, float y, float pressure, float width) {
//Log.i("TouchPaint", "Drawing: " + x + "x" + y + " p="
// + pressure + " width=" + width);
if (width < 1) width = 1;
if (mBitmap != null) {
float radius = width / 2;
int pressureLevel = (int)(pressure * 255);
mPaint.setARGB(pressureLevel, 255, 255, 255);
mCanvas.drawCircle(x, y, radius, mPaint);
mRect.set((int) (x - radius - 2), (int) (y - radius - 2),
(int) (x + radius + 2), (int) (y + radius + 2));
invalidate(mRect);
}
mFadeSteps = 0;
}
}
}
class GraphicsActivity extends Activity {
// set to true to test Picture
private static final boolean TEST_PICTURE = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public void setContentView(View view) {
if (TEST_PICTURE) {
ViewGroup vg = new PictureLayout(this);
vg.addView(view);
view = vg;
}
super.setContentView(view);
}
}
class PictureLayout extends ViewGroup {
private final Picture mPicture = new Picture();
public PictureLayout(Context context) {
super(context);
}
public PictureLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public void addView(View child) {
if (getChildCount() > 1) {
throw new IllegalStateException(
"PictureLayout can host only one direct child");
}
super.addView(child);
}
@Override
public void addView(View child, int index) {
if (getChildCount() > 1) {
throw new IllegalStateException(
"PictureLayout can host only one direct child");
}
super.addView(child, index);
}
@Override
public void addView(View child, LayoutParams params) {
if (getChildCount() > 1) {
throw new IllegalStateException(
"PictureLayout can host only one direct child");
}
super.addView(child, params);
}
@Override
public void addView(View child, int index, LayoutParams params) {
if (getChildCount() > 1) {
throw new IllegalStateException(
"PictureLayout can host only one direct child");
}
super.addView(child, index, params);
}
@Override
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.MATCH_PARENT,
LayoutParams.MATCH_PARENT);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
final int count = getChildCount();
int maxHeight = 0;
int maxWidth = 0;
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
measureChild(child, widthMeasureSpec, heightMeasureSpec);
}
}
maxWidth += getPaddingLeft() + getPaddingRight();
maxHeight += getPaddingTop() + getPaddingBottom();
Drawable drawable = getBackground();
if (drawable != null) {
maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());
maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());
}
setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),
resolveSize(maxHeight, heightMeasureSpec));
}
private void drawPict(Canvas canvas, int x, int y, int w, int h, float sx,
float sy) {
canvas.save();
canvas.translate(x, y);
canvas.clipRect(0, 0, w, h);
canvas.scale(0.5f, 0.5f);
canvas.scale(sx, sy, w, h);
canvas.drawPicture(mPicture);
canvas.restore();
}
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(mPicture.beginRecording(getWidth(), getHeight()));
mPicture.endRecording();
int x = getWidth() / 2;
int y = getHeight() / 2;
if (false) {
canvas.drawPicture(mPicture);
} else {
drawPict(canvas, 0, 0, x, y, 1, 1);
drawPict(canvas, x, 0, x, y, -1, 1);
drawPict(canvas, 0, y, x, y, 1, -1);
drawPict(canvas, x, y, x, y, -1, -1);
}
}
@Override
public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
location[0] = getLeft();
location[1] = getTop();
dirty.set(0, 0, getWidth(), getHeight());
return getParent();
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
final int count = super.getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final int childLeft = getPaddingLeft();
final int childTop = getPaddingTop();
child.layout(childLeft, childTop,
childLeft + child.getMeasuredWidth(),
childTop + child.getMeasuredHeight());
}
}
}
}
]]>