Facebook開源了一款加載效果工具Shimmer,可以實現字體的閃閃發光效果,效果如下
鏈接地址在這裏https://github.com/facebook/Shimmer,不過是針對iOS開發實現的,看了下沒看懂(還沒搞過object-c,囧ZR),所以隨手搜了Shimmer android,居然真有人做了,在這裏https://github.com/RomainPiel/Shimmer-android,下面是效果圖
實現的核心部分是使用線性漸變LinearGradient,然後繪圖的時候不斷將漸變平移來達到閃動的效果,平移量的控制使用了屬性動畫,想了一下這部分也可以自己來控制,下面就來做個簡單改造:
public class MyTextView extends TextView {
private LinearGradient mLinearGradient;
private Matrix mGradientMatrix;
private Paint mPaint;
private int mViewWidth = 0;
private int mTranslate = 0;
private boolean mAnimating = true;
public MyTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (mViewWidth == 0) {
mViewWidth = getMeasuredWidth();
if (mViewWidth > 0) {
mPaint = getPaint();
mLinearGradient = new LinearGradient(-mViewWidth, 0, 0, 0,
new int[] { 0x33ffffff, 0xffffffff, 0x33ffffff },
new float[] { 0, 0.5f, 1 }, Shader.TileMode.CLAMP);
mPaint.setShader(mLinearGradient);
mGradientMatrix = new Matrix();
}
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mAnimating && mGradientMatrix != null) {
mTranslate += mViewWidth / 10;
if (mTranslate > 2 * mViewWidth) {
mTranslate = -mViewWidth;
}
mGradientMatrix.setTranslate(mTranslate, 0);
mLinearGradient.setLocalMatrix(mGradientMatrix);
postInvalidateDelayed(50);
}
}
}
繼承一個TextView,因爲漸變的平移需要view的寬度,所以在onSizeChanged裏將各個需要的元素初始化,在linearGradient裏定義了漸變的顏色和顏色的變化位置,然後設置給繪圖使用的paint。onDraw()方法裏控制偏移量的計算,這裏每次移動寬度的1/10,postInvalidateDelay()裏設置每一幀繪製的時間,也就是控制閃動的快慢。效果如下
評論裏建議的從中間到兩邊的效果
從中間到兩邊需要對稱的變換,這裏是將中間的光斑逐漸擴大覆蓋到整個文字,還是使用LinearGradient,只是動作從平移變成了縮放。一開始想到的是兩個光斑從中間開始分別左右移動,但因爲繪製的時候使用一個paint,在paint裏設置相應的shader,用這種思路實現兩邊對稱的變換,試了一下沒有達到好的效果,暫時還沒想到更好的辦法,歡迎給出各種建議。下面修改的代碼
public class MyTextView extends TextView {
private LinearGradient mLinearGradient;
private Matrix mGradientMatrix;
private Paint mPaint;
private int mViewWidth = 0;
private float mScale = 0.1f;
private boolean mAnimating = true;
public MyTextView(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
if (mViewWidth == 0) {
mViewWidth = getMeasuredWidth();
if (mViewWidth > 0) {
mPaint = getPaint();
mLinearGradient = new LinearGradient(0, 0, mViewWidth, 0,
new int[] { 0x33ffffff, 0xffffffff, 0x33ffffff },
new float[] { 0.0f, 0.5f, 1.0f }, Shader.TileMode.CLAMP);
mPaint.setShader(mLinearGradient);
mGradientMatrix = new Matrix();
}
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mAnimating && mGradientMatrix != null) {
mScale += 0.1f;
if (mScale > 1.2f) {
mScale = 0.1f;
}
mGradientMatrix.setScale(mScale, mScale, mViewWidth / 2, 0);
mLinearGradient.setLocalMatrix(mGradientMatrix);
postInvalidateDelayed(100);
}
}
}
示例下載:http://download.csdn.net/detail/xu_fu/7254849
2015.03.10 更新:
Facebook在Android上也實現了Shimmer效果,可以針對所有的View,地址:http://facebook.github.io/shimmer-android/