Android之雪花飄落的動畫特效
阿新 • • 發佈:2019-01-24
之前有搜尋過相關的資訊,但是都不是最全的,下面我們來直接瞭解這個特效吧:
下面我們來看一看程式碼的實現吧:
三個工具類:其中主函式中不需要寫程式碼,只需佈局有相應的控制元件即可,雪花的大小、顏色和數量等可以自己設定
1.***********************************SnowFlake.java*************************************
import android.graphics.Canvas; import android.graphics.Paint; import android.graphics.Point; import me.chunyu.spike.wcl_snowfall_demo.RandomGenerator; /** * 雪花的類, 移動, 移出螢幕會重新設定位置. * <p/> * Created by wangchenlong on 16/1/24. */ public class SnowFlake { // 雪花的角度 private static final float ANGE_RANGE = 0.1f; // 角度範圍 private static final float HALF_ANGLE_RANGE = ANGE_RANGE / 2f; // 一般的角度 private static final float HALF_PI = (float) Math.PI / 2f; // 半PI private static final float ANGLE_SEED = 25f; // 角度隨機種子 private static final float ANGLE_DIVISOR = 10000f; // 角度的分母 // 雪花的移動速度 private static final float INCREMENT_LOWER = 2f; private static final float INCREMENT_UPPER = 4f; // 雪花的大小 private static final float FLAKE_SIZE_LOWER = 7f; private static final float FLAKE_SIZE_UPPER = 20f; private final RandomGenerator mRandom; // 隨機控制器 private final Point mPosition; // 雪花位置 private float mAngle; // 角度 private final float mIncrement; // 雪花的速度 private final float mFlakeSize; // 雪花的大小 private final Paint mPaint; // 畫筆 private SnowFlake(RandomGenerator random, Point position, float angle, float increment, float flakeSize, Paint paint) { mRandom = random; mPosition = position; mIncrement = increment; mFlakeSize = flakeSize; mPaint = paint; mAngle = angle; } public static SnowFlake create(int width, int height, Paint paint) { RandomGenerator random = new RandomGenerator(); int x = random.getRandom(width); int y = random.getRandom(height); Point position = new Point(x, y); float angle = random.getRandom(ANGLE_SEED) / ANGLE_SEED * ANGE_RANGE + HALF_PI - HALF_ANGLE_RANGE; float increment = random.getRandom(INCREMENT_LOWER, INCREMENT_UPPER); float flakeSize = random.getRandom(FLAKE_SIZE_LOWER, FLAKE_SIZE_UPPER); return new SnowFlake(random, position, angle, increment, flakeSize, paint); } // 繪製雪花 public void draw(Canvas canvas) { int width = canvas.getWidth(); int height = canvas.getHeight(); move(width, height); canvas.drawCircle(mPosition.x, mPosition.y, mFlakeSize, mPaint); } // 移動雪花 private void move(int width, int height) { double x = mPosition.x + (mIncrement * Math.cos(mAngle)); double y = mPosition.y + (mIncrement * Math.sin(mAngle)); mAngle += mRandom.getRandom(-ANGLE_SEED, ANGLE_SEED) / ANGLE_DIVISOR; // 隨機晃動 mPosition.set((int) x, (int) y); // 移除螢幕, 重新開始 if (!isInside(width, height)) { reset(width); } } // 判斷是否在其中 private boolean isInside(int width, int height) { int x = mPosition.x; int y = mPosition.y; return x >= -mFlakeSize - 1 && x + mFlakeSize <= width && y >= -mFlakeSize - 1 && y - mFlakeSize < height; } // 重置雪花 private void reset(int width) { mPosition.x = mRandom.getRandom(width); mPosition.y = (int) (-mFlakeSize - 1); // 最上面 mAngle = mRandom.getRandom(ANGLE_SEED) / ANGLE_SEED * ANGE_RANGE + HALF_PI - HALF_ANGLE_RANGE; } }
2.***********************************SnowView.java*************************************
import android.annotation.TargetApi; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.view.View; /** * 雪花檢視, DELAY時間重繪, 繪製NUM_SNOWFLAKES個雪花 * <p/> * Created by wangchenlong on 16/1/24. */ public class SnowView extends View { private static final int NUM_SNOWFLAKES = 150; // 雪花數量 private static final int DELAY = 5; // 延遲 private SnowFlake[] mSnowFlakes; // 雪花 public SnowView(Context context) { super(context); } public SnowView(Context context, AttributeSet attrs) { super(context, attrs); } public SnowView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); if (w != oldw || h != oldh) { initSnow(w, h); } } private void initSnow(int width, int height) { Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG); // 抗鋸齒 paint.setColor(Color.WHITE); // 白色雪花 paint.setStyle(Paint.Style.FILL); // 填充; mSnowFlakes = new SnowFlake[NUM_SNOWFLAKES]; for (int i = 0; i < NUM_SNOWFLAKES; ++i) { mSnowFlakes[i] = SnowFlake.create(width, height, paint); } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); for (SnowFlake s : mSnowFlakes) { s.draw(canvas); } // 隔一段時間重繪一次, 動畫效果 getHandler().postDelayed(runnable, DELAY); } // 重繪執行緒 private Runnable runnable = new Runnable() { @Override public void run() { invalidate(); } }; }
3.*******************************RandomGenerator.java*****************************************
import java.util.Random; /** * 隨機生成器 * <p/> * Created by wangchenlong on 16/1/24. */ public class RandomGenerator { private static final Random RANDOM = new Random(); // 區間隨機 public float getRandom(float lower, float upper) { float min = Math.min(lower, upper); float max = Math.max(lower, upper); return getRandom(max - min) + min; } // 上界隨機 public float getRandom(float upper) { return RANDOM.nextFloat() * upper; } // 上界隨機 public int getRandom(int upper) { return RANDOM.nextInt(upper); } }
一個佈局:
4.*******************************activity_main.xml*****************************************
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:contentDescription="@null"
android:scaleType="centerCrop"
android:src="@drawable/christmas"/>
<me.chunyu.spike.wcl_snowfall_demo.views.SnowView
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</FrameLayout>
</RelativeLayout>
OK