Android建立demo时一种实用的管理方法

package com.majunzhe.demos.te_customeview; /** * Created by mjz on 15-1-8. */ import android.content.Context; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Rect; import android.graphics.RectF; import android.util.AttributeSet; import android.view.Menu; import android.view.MotionEvent; import android.view.View; import java.util.Random; /** * This view implements the drawing canvas. * * It handles all of the input events and drawing functions. */ public class PaintView extends View { private static final int MSG_FADE = 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; /** Colors to cycle through. */ static final int[] COLORS = new int[] { Color.WHITE, Color.RED, Color.YELLOW, Color.GREEN, Color.CYAN, Color.BLUE, Color.MAGENTA, }; /** Background color. */ static final int BACKGROUND_COLOR = Color.BLACK; private static final int FADE_ALPHA = 0x06; private static final int MAX_FADE_STEPS = 256 / (FADE_ALPHA/2) + 4; private static final int TRACKBALL_SCALE = 10; private static final int SPLAT_VECTORS = 40; private final Random mRandom = new Random(); private Bitmap mBitmap; private Canvas mCanvas; private final Paint mPaint = new Paint(); private final Paint mFadePaint = new Paint(); private float mCurX; private float mCurY; private int mOldButtonState; private int mFadeSteps = MAX_FADE_STEPS; /** The index of the current color to use. */ int mColorIndex; public PaintView(Context c) { super(c); init(); } public PaintView(Context c, AttributeSet attrs) { super(c, attrs); init(); } private void init() { setFocusable(true); mPaint.setAntiAlias(true); mFadePaint.setColor(BACKGROUND_COLOR); mFadePaint.setAlpha(FADE_ALPHA); } public void clear() { if (mCanvas != null) { mPaint.setColor(BACKGROUND_COLOR); mCanvas.drawPaint(mPaint); invalidate(); mFadeSteps = MAX_FADE_STEPS; } } public void fade() { if (mCanvas != null && mFadeSteps < MAX_FADE_STEPS) { mCanvas.drawPaint(mFadePaint); invalidate(); mFadeSteps++; } } public void text(String text) { if (mBitmap != null) { final int width = mBitmap.getWidth(); final int height = mBitmap.getHeight(); mPaint.setColor(COLORS[mColorIndex]); mPaint.setAlpha(255); int size = height; mPaint.setTextSize(size); Rect bounds = new Rect(); mPaint.getTextBounds(text, 0, text.length(), bounds); int twidth = bounds.width(); twidth += (twidth/4); if (twidth > width) { size = (size*width)/twidth; mPaint.setTextSize(size); mPaint.getTextBounds(text, 0, text.length(), bounds); } Paint.FontMetrics fm = mPaint.getFontMetrics(); mCanvas.drawText(text, (width-bounds.width())/2, ((height-size)/2) - fm.ascent, mPaint); mFadeSteps = 0; invalidate(); } } @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.ARGB_8888); 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) { final int action = event.getActionMasked(); if (action == MotionEvent.ACTION_DOWN) { // Advance color when the trackball button is pressed. advanceColor(); } if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_MOVE) { final 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++) { moveTrackball(event.getHistoricalX(i) * scaleX, event.getHistoricalY(i) * scaleY); } moveTrackball(event.getX() * scaleX, event.getY() * scaleY); } return true; } private void moveTrackball(float deltaX, float deltaY) { final int curW = mBitmap != null ? mBitmap.getWidth() : 0; final int curH = mBitmap != null ? mBitmap.getHeight() : 0; mCurX = Math.max(Math.min(mCurX + deltaX, curW - 1), 0); mCurY = Math.max(Math.min(mCurY + deltaY, curH - 1), 0); paint(PaintMode.Draw, mCurX, mCurY); } @Override public boolean onTouchEvent(MotionEvent event) { return onTouchOrHoverEvent(event, true /*isTouch*/); } @Override public boolean onHoverEvent(MotionEvent event) { return onTouchOrHoverEvent(event, false /*isTouch*/); } private boolean onTouchOrHoverEvent(MotionEvent event, boolean isTouch) { final int buttonState = event.getButtonState(); int pressedButtons = buttonState & ~mOldButtonState; mOldButtonState = buttonState; if ((pressedButtons & MotionEvent.BUTTON_SECONDARY) != 0) { // Advance color when the right mouse button or first stylus button // is pressed. advanceColor(); } PaintMode mode; if ((buttonState & MotionEvent.BUTTON_TERTIARY) != 0) { // Splat paint when the middle mouse button or second stylus button is pressed. mode = PaintMode.Splat; } else if (isTouch || (buttonState & MotionEvent.BUTTON_PRIMARY) != 0) { // Draw paint when touching or if the primary button is pressed. mode = PaintMode.Draw; } else { // Otherwise, do not paint anything. return false; } final int action = event.getActionMasked(); if (action == MotionEvent.ACTION_DOWN || action == MotionEvent.ACTION_MOVE || action == MotionEvent.ACTION_HOVER_MOVE) { final int N = event.getHistorySize(); final int P = event.getPointerCount(); for (int i = 0; i < N; i++) { for (int j = 0; j < P; j++) { paint(getPaintModeForTool(event.getToolType(j), mode), event.getHistoricalX(j, i), event.getHistoricalY(j, i), event.getHistoricalPressure(j, i), event.getHistoricalTouchMajor(j, i), event.getHistoricalTouchMinor(j, i), event.getHistoricalOrientation(j, i), event.getHistoricalAxisValue(MotionEvent.AXIS_DISTANCE, j, i), event.getHistoricalAxisValue(MotionEvent.AXIS_TILT, j, i)); } }